Veterinary Echocardiography - [1989] Bonagura

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Veterinary Echocardiography 
JOHN D. BONAGURA, D.V.M.* and MATTHEW W. MILLER, D.V.M.** 
*The Ohio State University College of Veterinary Medicine, Columbus, Ohio and the 
**Department of Small Animal Medicine and Surgery, Texas A&M University 
College of Veterinary Medicine, College Station, Texas 
Echocardiography is used increasingly in the 
medical care of domesticated animals with 
spontaneous cardiovascular disease. Although 
the number of veterinarians engaged in clinical 
cardiology is comparatively small, veterinary 
application of echocardiography had a parallel 
development to the clinical experience of the 
medical cardiologist. Veterinary echocardiogra- 
phy has also benefited from laboratory investi- 
gations of experimentally induced cardiovascu- 
lar disease, most notably from studies con- 
ducted in dogs. There are hundreds of 
publications related to echocardiography in an- 
imal research and veterinary care. 
This article will illustrate the clinical value of 
echocardiography in veterinary medicine by de- 
scribing two-dimensional and M-mode imaging 
in animals, and initial experiences with Doppler 
echocardiography and color flow imaging. Our 
perspective is that of the veterinary clinician; 
thus, we will emphasize the value of Doppler 
echocardiography in the identification of com- 
parative spontaneous cardiovascular diseases in 
animals. There is a large amount of information 
available regarding Doppler echocardiography 
in the evaluation of induced heart disease in 
laboratory dogs. We will limit our discussion to 
data that are clinically relevant to veterinary 
practice, thereby disregarding the otherwise 
important information about induced myocar- 
Note: color illustrations do not appear in numerical order. 
Dr. Bonagura is currently the Visiting Research Fellow, 
Royal (William Dick) School of Veterinary Studies, Univer- 
sity of Edinburgh, Summerhall Square, Edinburgh, Scot- 
land. 
Address for correspondence: Matthew W. Miller, D.V.M., 
Diplomate A.C.V.I.M., Assistant Professor, Dept. of Small 
Animal Medicine and Surgery, Texas A&M University Col- 
lege of Veterinary Medicine, College Station, TX 77843- 
4474. 
dial ischemia in dogs. Some practical sugges- 
tions for the recording of echocardiograms in 
animals are included for those who may not be 
experienced in performing Doppler echocardi- 
ography in the closed-chest animal. It is hoped 
that this information will be valuable and inter- 
esting and that this communication will in- 
crease the interaction between veterinarians, 
physicians, health care professionals, and labo- 
ratory investigators who have a mutual interest 
in cardiovascular disease. 
Technical Considerations 
Physicians and technicians who are experi- 
enced in echocardiography should have little 
difficulty learning to perform or interpret ani- 
mal studies. While there are slight qualitative 
and considerable quantitative differences be- 
tween those studies obtained from humans'-5 
and those obtained from domesticated ani- 
mals,- established principles of imaging and 
interpretation are relevant. Despite similarities, 
the veterinarian or laboratory investigator must 
be familiar with normal anatomical and physio- 
logical differences between species. Cats and 
horses can be compared as an example. The 
normal left ventricular internal dimension in 
the cat is about 12 mm, the heart can be 
oriented almost horizontally in the thorax, and 
the heart rate often exceeds 200 beats/ 
min.11*18*33-36,39 The thoroughbred horse has a 
left ventricular internal dimension of up to 135 
mm, a relatively upright cardiac axis, and a 
resting heart rate of < 40 beats/min.9.24-26*32*42 
Knowledge of such interspecies variation is im- 
portant because it influences transducer selec- 
tion and placement, echocardiographic control 
settings, and obtained frame rate during cross- 
sectional and color flow imaging. To image the 
Vol. 6, No. 3, 1989 ECHOCARDIOGRAPHY. A Jml. of CV Ultrasound & Allied Tech. 229 
BONAGURA AND MILLER 
common domesticated species, transducer fre- 
quencies between 2.25 and 7.5 MHz are 
range of probes generally used for pediatric to 
adult imaging.’-5 The depth of field needed to 
image a cat can be as shallow as 4 cm, while a 
horse or mature cow can require 35 cm. Since 
most available echocardiography machines have 
a maximal depth of field of < 25 cm, the opera- 
tor must interrogate the equine and bovine 
hearts from each hemithorax to obtain reason- 
able anatomical and blood flow informa- 
This physiological variation also influences 
the frame rate obtained during color flow imag- 
ing, impacting on the observer’s overall subjec- 
tive impression of motion and blood flow, and 
possibly the accuracy of color-coded Doppler. 
For example, we used three different manufac- 
turers’ instruments and found that the imaging 
frame rate during adequate color-coded Doppler 
can vary from 8 to 60 frames/sec. This is cause 
for concern as some instruments map the car- 
diac cycle of a cat with only three frames. If the 
heart rate is 240 beats/min, then there are 4 
beats/sec. If the frame rate is 12 frames/sec, 
then there are 3 framesheat. One might ques- 
tion whether the temporal processing of flow 
data can accurately proceed at this rate? Color 
flow imaging in the horse often occurs at sample 
volume depths of up to 20 cm. Fortunately, the 
limitations placed on frame rate during flow- 
mapping at such depths is partially offset by the 
slow heart rate of the resting equine subject. 
A variety of mechanical sector scanning and 
phased array instruments have been used suc- 
cessfully for Doppler echocardiography in ani- 
mals. Initial instrument settings are similar to 
those utilized for human patients of equivalent 
size.’-5 Sector angle, gain settings, time gain 
compensation, reject, and other controls must 
be individualized for the animal, the type of 
study, and the region of interest. The depth of 
penetration must be varied for each species. 
Most normal horses are studied at a 20-24 cm 
depth of field, most cats require a field of only 
4-6 cm, and most dogs are imaged at depths 
ranging from 6-14 cm. 
Selection of transducer frequency, focusing, 
and scanhead footprint or diameter relate to the 
needed,7,15,22,23,32.33,37,41,42,44.46 this represents the 
tion.9,14,24,32 
species under study and whether the goal is ana- 
tomical detail or Doppler-derived velocity in- 
formation. The following are general guidelines 
for diagnostic imaging. Cats and small dogs 
(usually < 5.0 kg) can be imaged successfully 
with a 7.5-MHz or 5-MHz (short focused) trans- 
ducer. Most dogs are examined with either a 
5-MHz (medium or variable focused) or 3.5- 
MHz transducer. Generally, horses and cattle 
require transducers with frequencies ranging 
from 2.25 to 3.5 MHz, the selection varying with 
the weight and chest conformation of the 
animal. 
Commercial instruments that were manufac- 
tured for Doppler echocardiography in humans 
have been used successfully for Doppler studies 
in both open- and closed-chest animal^.^^-^' 
When performing Doppler echocardiography, 
transducers with lower frequencies than those 
used for imaging usually provide the best sig- 
nal-to-noise ratio and superior color flow-map- 
ping?*4 Stand alone, continuous-wave Doppler 
transducers (typically 1.9 MHz) also perform 
well in animals because the small size of the 
transducer allows access to narrow intercostal 
acoustic windows and to the suprasternal notch. 
Some transducers that were designed for simul- 
taneous imaging with Doppler are so large that 
the study can only be done with difficulty. Ac- 
cordingly, pediatric transducers or probes with 
smaller footprints should be selected when pos- 
sible. When performing Doppler echocardiogra-phy in a cat or small dog, a 5-MHz (medium 
focus) transducer can be used because the re- 
gions of interest are often within 4-6 cm of the 
transducer. In most dogs (especially foxhound- 
type laboratory animals), a 3.5-MHz to 2.25- 
MHz transducer provides reasonable imaging 
with satisfactory Doppler signals. A 2.25-2.5- 
MHz transducer is used for Doppler echocardi- 
ography in horses or cattle. In these large ani- 
mals, the maximum depth of field available for 
pulsed-Doppler studies can be a limiting factor. 
It should be mentioned that we have experi- 
enced apparent differences between manufac- 
turers’ instruments in the quality and ease of 
obtaining Doppler signals in animals. Such dif- 
ferences in Doppler sensitivity may partially 
determine the ultimate carrier frequency of the 
chosen transducer. 
230 ECHOCARDIOGRAPHY: A J r l . of CV Ultrasound & Allied Tech. Vol. 6, No. 3, 1989 
VETERINARY ECHOCARDIOGRAPHY 
Vol. 6, No. 3, 1989 ECHOCARDIOGRAPHY: A Jrnl. of CV Ultrasound & Allied Tech. 231 
The aforementioned guidelines can be fol- 
lowed for color flow imaging as well. General 
recommendations for using color-coded Doppler 
in patients are applicable to animal ~tudies.4,~ A 
variety of operator selected color maps, process- 
ing options, and image controls are available, 
depending on the instrument manufacturer. 
When applying color to the cross-sectional 
image, it is important to either reduce overall 
tissue imaging gain or to increase reject because 
color coding with some instruments cannot 
proceed if the pixel is occupied by tissue density 
or intraluminal noise. Low-velocity reject may 
be required to partially filter “flash” artifacts 
that seem to reflect from valves, chamber walls, 
and edges of lung (most commonly in tachycar- 
diac or tachypneic animals). Frame rate is opti- 
mized by narrowing sector and color imaging 
angles, suppressing imaging outside the color 
sector, decreasing depth of field, and altering 
the color processing. On some units, processing 
is adjusted and frame rate increased by reducing 
the level of color quality or increasing the limit 
of low-velocity reject. Other instruments pro- 
vide pre-processing controls of packet sizes.5 
Reducing color quality or packet size to increase 
frame rate is a compromise, as we have obtained 
the best color image with medium or large 
packet sizes. 
Techniques for Recording Doppler 
Echocardiograms 
Animal Positioning 
The position of the animal is critical for ob- 
taining studies of diagnostic quality. Large ani- 
mals are examined while they stand, manually 
restrained, and often in s t o ~ k s . ~ . ~ ~ * ~ ~ , ~ ~ , ~ ~ , ~ ~ Frac- 
tious animals are lightly tranquilized (usually 
with xylazine). It is advantageous to advance 
the near forelimb to access the cardiac windows. 
It is our opinion that small animals are best 
imaged while they are gently restrained in lat- 
eral recumbency, sternum facing the operator, 
with the probe directed from below through a 
pre-cut hole in the imaging table.22,33,37 The ani- 
mal can be positioned to accommodate more 
cranial (superior) or caudal (inferior) acoustic 
windows and turned to allow imaging from each 
hemithorax. Alternatively, dogs can be studied 
while they stand or are restrained in a sling that 
has cutouts over the area of transducer place- 
ment. This method also works well for 
calves, and other similar-sized animals. 
While most small animals lay quietly, mild 
sedation with intramuscular or subcutaneous 
acepromazine (3 mg/square meter body surface 
area) can be administered. In cats, 2 mg/kg ke- 
tamine HCl given intravenously approximately 
15 minutes after acepromazine provides about 
15-20 minutes of mild chemical restraint. 
Where available, buprenorphine (0.0075-0.01 
mg/kg, intravenously) can be used following 
acepromazine to provide excellent chemical re- 
straint for longer studies. When performing in- 
tercurrent Doppler and two-dimensional M- 
mode examinations during prolonged or inva- 
sive experiments, the anesthetized animal can 
be placed in left lateral recumbency, echoed 
from the left hemithorax for Doppler derived 
data, and from above with the transducer at the 
right sternal edge, for consistent two-dimen- 
sional and M-mode studies. In this case, a radio- 
graphic foam wedge, placed under the thoracic 
spine brings the heart closer to the thoracic wall 
and facilitates imaging from the right hemith- 
orax. 
The Imaging Table 
We use rectangular, custom-made, Plexiglas 
tables22 that can be mounted on a stainless steel 
surgical table (that can be varied in height) to 
image small animals. The table is made from 
%-% inch Plexiglas and is 48-49 inches long, 
16-20 inches wide, and has six support legs that 
are 8 inches long (this should be based on trans- 
ducer size and connecting cable flexibility). The 
four corner legs are constructed with flanges 
that overhang the surgical table and provide 
stability against sliding. The other two legs are 
glued in positions that provide central support 
and are located 16-18 inches from the ends of 
the table. An imaging port, a circle or oval at 
least 5 inches in diameter, with a center equi- 
distant (24 inches) from each end is cut immedi- 
ately adjacent to or through a long edge of the 
table. Depending on the size of the imaging 
probes and animals studied, the imaging port 
location and shape can be varied. If the imaging 
BONAGURA AND MILLER 
port is placed too far from the table edge, near 
the virtual center of the table, the operator may 
become uncomfortable. A table that allows 
imaging from below the recumbent small animal 
subject is one of the important factors in ob- 
taining replicable and diagnostic Doppler echo- 
cardiography studies in small animal^.^^*^^ 
Imaging Planes 
While there are an infinite number of poten- 
tial imaging planes or views of the heart, there 
are certain tomographic planes used consis- 
centrate on those that are most beneficial for 
routine diagnostic imaging, Doppler echocardi- 
ography, and research. A number of angled and 
short-axis views, especially from the left he- 
tently (Table 1).7.15.22.23,32,33,37,41,44,46 We will con- 
mithorax, are used to identify congenital lesions 
and cardiac masses, but these will not be dis- 
cussed. Suprasternal notch imaging is some- 
what limited by the size of most small animals 
or the tremendous distance between the notch 
and the heart in the horse and cow. Subcostal 
positions are used less often in animals because 
right parasternal views have some resemblance 
to subcostal planes in human patient^.^.^^.^^ The 
imaging planes (Table I) are classified by: (1) 
the general location and relative position of the 
transducer, i.e., those obtained from the cranial 
or caudal right or left hemithorax; (2) the gen- 
eral orientation of the sector to the heart, i.e., 
long-axis, short-axis, apical, and angled; and (3) 
by the anatomical image obtained (optimized 
structures) (Figs. 1-3). 
TABLE I 
Image Planes Used for Echocardiography in Animals 
Right hemithorax 
1. Long axis 4/5 chamber images 
a. Long axis 4 chamber view 
b. Optimized for the ventricular inlets and atrial septum (dorsocranial transducer location) 
c. Optimized for the left ventricular outlet and ascending aorta 
d. Modified 5 chamber view (ventrocaudal transducer location) 
2. Short axis images at the level of the: 
a. Left ventricular apex 
b. Left ventricular papillary muscles 
c. Left ventricular chordae tendineae 
d. Mitral valve 
e. Aorta and left atrium (& pulmonary valve) 
3. Angled image optimized for the right ventricular inlet and outlet, pulmonary valve, and long axis of the pulmonary 
artery (cranial transducer location) 
Left Hemithorax 
1. Caudal (Apical) 4/5 chamber images 
a.Apical 4 chamber view optimized for the left ventricular inlet 
b. Apical 5 chamber view optimized for the left ventricular outflow tract and proximal aorta 
c. Apical 4 chamber view optimized for the right ventricular inlet (cranial transducer location) 
a. Optimized for the left ventricular inlet 
b. Optimized for the left ventricular outlet and aorta 
a. Optimized for the left ventricular inlet 
b. Optimized for the left ventricular outlet and aorta 
2. Caudal (Apical) 2 chamber images 
3. Cranial long axis views 
4. Cranial angled view optimized for the long axis of the pulmonary artery 
5. Cranial angled views optimized for the right atrium, vena cavae and right ventricular inlet 
6. Cranial angled view of the left ventricular outlet (equine) 
7. Cranial short axis view at the level of the cardiac base 
1. Subcostal images 
2. Images from the suprasternal notch 
Other image planes 
232 ECHOCARDIOGRAPHY A Jrnl. of CV Ultrasound & Allied Tech. Vol. 6, No. 3, 1989 
VETERINARY ECHOCARDIOGRAPHY 
Figure 1. Two-dimensional echocardiogram frozen 
during diastole. Right intercostal (parasternal), four- 
chambered, long-axis image f rom a healthy Stan- 
dardbred horse. RA = right atrium; RV = right ventri- 
cle; LA = left atrium; LV = left ventricle. Overall scan 
depth is 24 cm. 
We have tried to be specific in describing the 
method to obtain these tomographic planes. 
First, we indicate the point of transducer place- 
ment, then the rotation of the sector, and fi- 
nally, the craniocaudal and dorsoventral angu- 
Figure 2. Two-dimensional echocardiogram frozen 
during diastole. Right intercostal (parasternal), short- 
axis image at the level of the papillary muscles from a 
healthy dog. R V = right ventricle; I V S = interventri- 
cular septum; LV = left ventricle; PPM = posterior 
(caudodorsal or mural) papillary muscle; APM = ante- 
rior (cranioventral or septal) papillary muscle. Overall 
scan depth is 12 cm. 
Figure 3. Two-dimensional echocardiogram frozen 
during diastole. Left caudal intercostal (apical) four- 
chamber image from a female greyhound. RA = right 
atrium; RV = right ventricle; LA = left atrium; LV 
= left ventricle. There is a sample volume located at the 
left ventricular inlet. 
lation of the central (axial) echo beam. When 
the transducer is placed at the right hemithorax, 
it is assumed that the central (axial) echo beam 
is oriented in a right-to-left direction. Most 
transducer placements at the left hemithorax 
are oriented from left-to-right, however, some 
left parasternal views (as for the pulmonary ar- 
tery or a cranial long-axis image of the left ven- 
tricular inlet) are obtained by maintaining ori- 
entation of the sector and axial beam mostly to 
the left of the midline. The clockwise or coun- 
terclockwise rotation of the reference dot or 
notch that marks the edge of the sector is de- 
fined relative to the subject's torso. Sector ori- 
entation perpendicular to the long axis of the 
torso represents 0" (or 180") rotation. Rotation 
is defined from the perspective of looking down 
the transducer towards the thorax. Most opera- 
tors, when imaging small animals through pre- 
cut imaging ports, hold the transducer with 
their right hand; consequently, supination of 
the wrist yields clockwise rotation. Guidelines 
for angulation follow veterinary anatomical no- 
menclature, i.e., cranial caudal (superior infe- 
rior) and ventral dorsal (anterior posterior) an- 
gulation of the central (axial) echo beam. Rela- 
tive angulation is arbitrarily coded as none [O] 
to steep [+++I. Zero angulation places the 
Vol. 6, No. 3, 1989 ECHOCARDIOGRAPHY: A Jml. of CV Ultrasound & Allied Tech. 233 
BONAGURA AND MILLER 
transducer perpendicular to the thoracic wall. 
Steep [+++I angulation indicates that the 
transducer footprint surface is barely being kept 
in contact with the skin. 
While Doppler echocardiography is often 
performed in the experimental laboratory using 
open-chest animal mode1s,47-57*59 the following 
comments pertain to more physiological closed- 
chest studies in the intact anima1.22*33,37*42*- 
46*58*60-62 These descriptions are, at best, general 
guidelines for performing echocardiographic 
studies in the dog and for obtaining most of the 
image planes listed in Table I. Following a de- 
scription of the canine examination we offer 
brief suggestions for imaging cats and horses. 
Examination Method and Normal 
Echocardiographic Findings 
Right Intercostal Views 
We begin most canine and feline studies using 
a right parasternal (intercostal) position to ob- 
tain long-axis views of the heart.22,23*32933*- 
37,41*42*44*46 The standard four-chamber, long-axis 
view used by most veterinary cardiologists rep- 
resents a tomogram that is almost an interme- 
diate image between a human subcostal view 
and parasternal long-axis In this plane, 
the cardiac septa are aligned nearly perpendicu- 
lar to the axial beam (Fig. 1). To obtain this 
image, the transducer is placed within 5 cm of 
the sternal edge at the right 4th-5th intercostal 
space, with the reference dot or notch held 
under the operator's thumb, perpendicular to 
the long axis of the animal's body (or slightly 
rotated 30" clockwise). The axial beam is then 
directed slightly caudally [ +] with minimal dor- 
sal [ +] beam angulation. Color flow imaging can 
be used to map flow through the ventricular 
inlets and left ventricular outlet, however, flow 
is generally perpendicular to the axial beam in 
this view. Owing to the large angle between the 
interrogating beam and normal blood flow, 
there is little if any signal aliasing of normal 
flow whereas high velocity flow and eccentric 
jets caused by valvular regurgitation or aortic 
stenosis are readily observed. 
The four-chamber view is optimized for the 
atrial septum (and atrial septal defects), the 
right pulmonary vein, and inlet valves by plac- 
ing the transducer in a slightly more dorsal po- 
sition (in the same intercostal space) with the 
beam angle either held constant or directed 
craniad [+I, (Figs. 4A and 4B, Color Plate 1). 
With the transducer either in this or the origi- 
nal location, the left ventricular outlet and 
proximal aorta are obtained by rotating the 
transducer 45-60' (clockwise) and then direct- 
ing the axial beam cranially [+ to ++] and pos- 
sibly dorsally [+I. Echo dropout of septal de- 
fects or abnormal flow associated with ventricu- 
lar septal defects or aortic valve disease may be 
detected from this plane (Fig. 5, Color Plate 2). 
Placing the transducer one or even two inter- 
costal spaces caudad (and slightly ventrad) to 
the four-chamber view initially described will 
produce 4/5-chamber long-axis images that are 
more similar to a human parasternal long-axis 
view and is better aligned with flow (Color Plate 
3). From this ventrocaudal position, the trans- 
ducer is rotated 30-60" clockwise, and the axial 
beam directed more steeply dorsad [++ to +++I 
and cranially [ +] for the left atrium/ventricular 
inlet with more cranial angulation [++I for the 
tricuspid inlet and left ventricular outlet/aorta. 
When using this view for color flow imaging, 
signal aliasing may be observed in normals as 
velocities often exceed the Nyquist limit. It is 
not uncommon to observe physiological tricus- 
pid backflow. In some dogs, these views provide 
alignment to flow that is acceptable for quanti- 
fying velocities by spectral pulsed-Doppler 
echocardiography . 
Short axis tomograms are now ob- 
turned to the initially described four-chambered 
long-axis view, the sector is rotated 90' clock- 
wise and directed slightly caudodorsad [0 to +]. 
From this position, the transducer is swept 
ventrally to image the left ventricular apex and 
the sector is gradually directed dorsally towards 
the cardiacbase. At the papillary muscle level, 
the cranioventral (septal or anterior) papillary 
muscle is identified by its more distant location 
from the transducer (Fig. 2). Directing the 
transducer towards the base now yields a con- 
sistent series of short-axis tomograms at chor- 
dal, mitral, and aortic levels.22,33,37 As for the 
long-axis views, when approaching the level of 
tained.22,23,32,33,37,41,42,44,46 The transducer is re- 
234 ECHOCARDIOGRAPHY: A J r l . of CV Ultrasound & Allied Tech. Vol. 6, No. 3,1989 
VETERINARY ECHOCARDIOGRAPHY 
Figure 4A. Two-dimensional echocardiogram fro- 
zen during diastole. Right parasternal four-chamber 
image obtained from a dog with tricuspid valve dyspla- 
sia, tricuspid regurgitation, patent foramen ovale, and 
right-to-left atrial shunting. There is marked dilation 
of the right atrium (RA) and right ventricle (RV). The 
Ventricular septum is displaced into the left ventricle 
(LV). The septal and lateral tricuspid ka@ts are exces- 
sively long and insert into a single, abnormal papillary 
muscle. 
the aortic root, the operator should rotate the 
transducer an additional 45"-60" clockwise 
and angulate cranially [+ to ++I to complete 
the image. At this or at a slightly more dorsal 
level, the right ventricular outflow tract, pulmo- 
nary valve, and main pulmonary artery also can 
be visualized. During these short-axis examina- 
tions, the areas beneath the septal tricuspid 
leaflet and the right ventricular outlet septum 
are examined (ideally with color flow imaging) 
for ventricular septal defects. The left atrium 
and aortic root are perused by color-coded 
Doppler for regurgitation. The aortic/left atrial 
image is used to assess the extent of some mitral 
regurgitant jets and to pinpoint lesions to spe- 
cific aortic valve cusps as the noncoronary cusp 
can be identified adjacent to the atrial septum. 
Physiological aortic or mitral regurgitation is 
not typically found in unsedated healthy dogs, 
however, a brief period of valve closure backflow 
is sometimes observed. Similar to the situation 
in human patient^,^-^ the limits of normal for 
such "backflow" require further study. It should 
be noted that valvular regurgitation across all 
valves is commonly observed by color-flow 
Figure 4B. Two-dimensional echocardiogram fro- 
zen during systole f rom the same dog. The transducer 
has been placed in a more dorsocranial position than 
Figure 4A. The foramen ovale has been forced open by 
increasing right atrial pressure (arrowheads). Color 
flow imaging and saline contrast echocardiography (not 
shown) indicated right-to-kft shunting and tricuspid 
regurgitation. LA = left atrium; LV = left ventricle; RA 
= right atrium; RV = right ventricle. 
Doppler in healthy dogs undergoing anesthesia. 
These short-axis tomograms also are used to 
guide the cursor for M-mode studies and are 
ideal for laboratory studies of regional wall mo- 
tion and for assessing myocardial perfusion by 
contrast echocardiography (Figs. 6 and 7). 
Figure 5. Two-dimensional echocardiogram frozen 
during diastole from a 5-year-old Standardbred gelding 
with a ventricular septal defect. Right parasternal 
long-axis image optimized for the left ventricular outlet. 
The aortic root and one cusp of the aortic valve (AV) 
have prolapsed into the defect. R V = right ventricle; Ao 
= aorta. 
Vol. 6, No. 3, 1989 ECROCARDIOGRAPHY: A Jrnl. of CV Ultrasound 8. Allied Tech. 236 
From a modified short-axis view adjacent to 
the level of the aortic valve, flow through the 
right ventricular inlet and outlet is inspected 
and the atrial septum is examined for interatrial 
shunting. This view is obtained by advancing 
the transducer 1-2 intercostal spaces cranially 
from the previously described short-axis aortic 
position, rotating clockwise 135"-160°, and di- 
recting the axial beam dorsally [++ to +++I 
and cranially [+ to ++I for the pulmonary ar- 
tery or caudally [ + to ++I for the right ventricu- 
lar inflow. Venous return from the caudal vena 
cava along the atrial septum predominates the 
right atrial flow pattern at this level and is 
coded red. As flow changes direction in the right 
ventricular cavity there is a loss of color, but 
diastolic and systolic flow towards the pulmo- 
nary valve are both coded blue (Color Plate 4). 
Signal aliasing in the right ventricular outlet is 
common during systole in normal animals. Pul- 
monary backflow is observed in some normal 
animals during diastole. When interrogated by 
pulsed-Doppler echocardiography, this signal is 
of low velocity. Steep dorsal angulation into the 
main pulmonary artery shows branching of the 
vessel and can be helpful in assessing retro- 
grade, turbulent flow from a PDA or a surgically 
created Blalock-Taussig or Waterson shunt. 
Right ventricular outlet and pulmonary artery 
velocities can be measured from this view; these 
are the only velocities routinely quantified from 
locations on the right hemithorax. While 
Doppler signals from flow across the tricuspid 
valve can also be quantified in this short-axis 
plane, we usually measure these velocities from 
left-sided apical views. 
Contrast echocardiography can be used to 
complement anatomical studies from the right 
hemithorax. Agitated or sonicated saline, blood, 
carbon dioxide, indocyanine green dye, Reno- 
grafin, Albunex, hydrogen peroxide, salts of 
diatrizoate, and other microcavitating fluids can 
be injected into the venous system, coronary ar- 
teries, aorta, or the heart to outline flow. Such 
studies are valuable in detecting cardiac shunt- 
ing and valvular regurgitati~n,~.~~.~'~~~,~~,~~~~~ di- 
lated coronary sinus (from persistent left cra- 
nial vena cava),64 and outlining coronary blood 
supply and myocardial perfusion de fe~ t s .~~-~O 
The latter application has received considerable 
attention in canine models of coronary disease. 
Since air is a potent echo target, echocardiogra- 
phy can be used to detect air emboli during an- 
e ~ t h e s i a . ~ ~ 
It is interesting that homes often have spon- 
taneous contrast in the heart.72-74 This is proba- 
bly a normal finding related to rouleaux of red 
blood cells. Marked echocontrast and swirling 
pattern of echocontrast, however, can be ob- 
served in pathological conditions, especially tri- 
cuspid endocarditis in the horse and left atrial 
dilation in cats with cardiomyopathy. 
The general principles of imaging described 
for dogs are applicable to cats as well.11*18933- 
36*3940 In this species, the heart is oriented more 
horizontally in the thorax, thus, slight modifica- 
tions of the previous guidelines may be needed. 
Additional comments are needed about 
equine studies.9,24,32,43.65,72-75 Th e horse is exam- 
ined while it stands and (for safety) the operator 
stands facing the same general direction as the 
subject and holds the transducer with his or her 
left hand while placing the echocardiograph to 
his or her right side. If the reference marker is 
held under the thumb, many operators find it 
easier to supinate the wrist, thereby rotating 
counterclockwise for short-axis views from the 
right hemithorax (as opposed to clockwise in the 
recumbent dog). The examiner is advised to 
begin with a standard four-chambered view 
(Fig. 1) and to proceed from this point. In the 
horse, the usual location for transducer place- 
ment for this image plane is immediately cau- 
dodorsal to the olecranon in the standing ani- 
mal. Once this point is located, the right foreleg 
is advanced slightly to improve access to acous- 
tic windows. Because of the more upright posi- 
tion of the equine heart, slight counterclockwise 
rotation (0-30") may be needed, as well as slight 
caudodorsal angulation [+/+I. From this point, 
other views are easily obtained. 
The horse is technically challengingsince the 
depth of penetration needed to image the distal 
left atrial wall usually is not available. Conse- 
quently, mitral regurgitation can be difficult to 
detect from the right hemithorax with color- 
coded Doppler echocardiography. Conversely, 
tricuspid regurgitation is easily visualized in the 
BONAGURA AND MILLER 
236 ECHOCARDIOGRAPHY: A Jml. of CV Ultrasound & Allied Tech. Vol. 6, No. 3, 1989 
VETERINARY ECHOCARDIOGRAPHY 
Figure 6. M-mode echocardwgrams obtained from different anesthetized dogs. Various levels are demonstrated: 
Apical (A); ventricular (B); mitral (C,D,E); and aortic (F,G). The electrocardiogram (ECG), aortic pressure (AP), 
phonocardwgram (PCG), and first (Sd and second (Sd heart sounds are indicated. TA = transducer artifact; S 
= ventricular septum; LVW = left ventricular wall; A M V = anterior mitral valve; P M V = posterior mitral valve; AV 
= aortic valve; A o = aorta; LA = left atrium. The excursions of the anterior mitral leaflet are defined (panel E) and the 
opening (arrowhead) and closing points of the aortic valve (arrow) are indicated in panel F. The left atrial dimension is 
actually the left auricular luminal dimension and represents a source of potential error in animal M-mode studies. 
(From Bonagura 50'' with permission). 
Vol. 6, No. 3, 1989 ECHOCARDIOGRAPHY: A Jrnl. of CV Ultrasound & Allied Tech. 231 
238 
BONAGURA AND MILLER 
ECHOCARDIOGRAPHY: A Jml. of CV Ultrasound & Allied Tech. Vol. 6, No. 3, 1989 
Figure 7 . Contrast M-mode echocardiogram ob- 
tained from a calf with a ventricular septa1 defect. An 
injection of saline and patient blood was made into the 
left ventricle. Following a period of ventricular tachy- 
cardia (ectopic QRS), the left and then the right ven- 
tricle is opacifkd. Later in the study (right panel) mi- 
crobubbles concentrate in the left ventricular outfEow 
tract and still shunt to the right ventricle. RV = right 
ventricle; Ao = aorta. (From Bongura JD, Pipers FS63 
with permission). 
near field (Color Plate 3). While general princi- 
ples of beam rotation and angulation hold 
across the species, the actual dorsoventral 
placement of the transducer must be varied 
much more for equine studies. 
It is difficult to align the echo beam parallel to 
the flow for Doppler studies in the horse,6l be- 
cause true apical windows are unavailable and 
the heart is a considerable distance from the 
suprasternal notch. To obtain spectral Doppler 
velocities from the right hemithorax and screen 
for tricuspid regurgitation, a ventrocaudal 
transducer location is used (Table I). The trans- 
ducer is placed ventrally from the usual four- 
chamber long-axis view, the transducer angled 
steeply dorsad [++ to +++I and cranially [+ to 
++I, then the reference marker is rotated grad- 
ually (from 0 to +60° clockwise) until the right 
ventricular inlet is aligned with the beam. For 
mapping of the right ventricular outlet, the 
transducer is placed about two intercostal 
spaces cranial (and 2-4 cm dorsal) from the 
original four-chambered position, rotated coun- 
terclockwise 30' to 60°, and directed craniad [+ 
to ++I and steeply dorsad [+++I to better align 
with right ventricular outflow. In this plane, the 
broad tricuspid to right ventricular inflow is 
coded red, and flow distal to the supraventricu- 
lar crest is blue. Spectral tracings of pulmonary 
artery velocity can be made but the valve is 
often 18-20 cm from the transducer and an ef- 
fort must be made to record parallel to flow. 
Pulmonary backflow is not uncommonly ob- 
served. 
Left Intercostal Views 
Imaging of small animals from the left he- 
mithorax permits the operator to more effec- 
tively align the transducer with blood flow for 
Doppler studies (Fig. 3, Color Plates 
5,6,7).22.28,33,37p58,62 The apical (caudal intercos- 
tal) views resemble those applied in human pa- 
tients and are used to record velocities across 
the atrioventricular valves out of the left ven- 
tricle. The apical four- and five-chambered 
views in the dog are obtained with the trans- 
ducer placed at the left fifth or sixth intercostal 
space and the reference marker (sector edge) 
placed perpendicular to the long axis of the pa- 
tient at which time the transducer is directed 
slightly cranially [+I and dorsally [+ to ++I 
(Fig. 3). Diastolic ventricular inflow is red and 
generally biphasic (E and A waves), but is coded 
blue as blood curls up from the apex into the left 
ventricular outflow tract (Color Plate 5). Signal 
aliasing of color flow images may be seen in 
normal animals. To obtain an optimal angle on 
right ventricular inflow, the transducer is placed 
in the cranial aspect of the intercostal space 
with cranial angulation of the beam [++I main- 
tained, or the transducer is simply positioned 
one space craniad. Aortic flow may be best ob- 
tained by sliding the transducer ventrally 1-3 
cm (or even one interspace caudal), rotating the 
sector slightly counterclockwise (-30') and di- 
recting the axial beam more steeply craniad [ ++ 
to +++I and slightly dorsad [+ to ++I. 
We have found the two-chambered view of 
the left heart to be complementary and often 
superior for recording mitral and aortic spectra. 
For this view, the transducer is maintained in 
the relatively caudoventral location just de- 
scribed, the sector rotated 90' to 120' clockwise, 
and dorsal angulation [+ to ++I is maintained. 
For the left ventricular inlet minimal or slight 
VETERINARY ECHOCARDIOGRAPHY 
Plate 6). In addition to providing image planes 
for recording ventricular inlet and outlet veloci- 
ties, the left apical views are useful for detection 
of mitral, aortic, and tricuspid regurgitation, as 
well as aortic stenosis and some cases of intra- 
cardiac shunting. 
A variety of additional long- and short-axis 
and angled views can be obtained cranially on 
the left hemithorax. The aorta is prominent in 
many of these views (Fig. 8):Some of these 
image planes have been described by Thomas22 
and O'Grady and colleagues3' for routine two- 
dimensional echocardiography in dogs. One ad- 
ditional plane that merits consideration for 
Doppler echocardiography is the left cranial 
image optimized for the right ventricular outlet 
and pulmonary artery (Color Plates 7 and 8). 
For this view, the transducer is placed at the 
second or third intercostal space near the ster- 
nal edge. The sector is rotated clockwise 90" to 
120" (roughly parallel to the long axis of the 
torso), and the pulmonary artery is imaged by 
directing the transducer steeply dorsad [+++I, 
usually adding minimal degrees of cranial angu- 
lation. From this perspective the operator can 
interrogate forward and regurgitant flow across 
the pulmonary valve, document aortic backflow 
into the pulmonary artery (Color Plate 8), and 
use continuous-wave Doppler to estimate pres- 
sure drop across a stenotic pulmonary valve. 
Similar left-sided views can be obtained in 
cats,33 however, for alignment with aortic flow 
the transducer may need to be placed as caudal 
as possible and directed steeply cranially as lung 
Figure 8. (A): Two-dimensional echocardiogram 
frozen during systole. Left cranial short-axis image op- 
timized for the aorta (Ao) and atria (LA, RA) obtained 
from a clinically healthy dog. The aortic valve is par- 
tially open. TV = area of the tricuspid valve. (B): Two- 
[+] cranial angulation is applied, while the ex- 
aminer uses steeper cranial angulation [++ to 
+++I to interrogate the outlet and aorta (Color 
dimensional echocardiogram frozen during systole from 
a dog with infective endocarditis of the aortic valve. 
Left parasternal image optimized for the left ventricu- 
lar outlet. The aortic valve is markedly thickened and 
abnormally echodense (arrows). There is some left ven- 
tricular dilatation. L V= left ventricle; LVW = left 
ventricular wall; I V S = interventricular septum. (C): 
Two-dimemionul echocardiogram frozen during dias- 
tole. Left cranial long-axis image of the left heart in a 
dog with aortic regurgitation. This black and white re- 
production of a color j2ow image demonstrates a regur- 
gitant jet (AR) striking the ventricular septum. LA 
= left atrium; LV = left ventricle; Ao = aorta. 
Vol. 6, No. 3, 1989 ECHOCARDIOGRAPHY A Jrnl. of CV Ultrasound & Allied Tech. 239 
interference is a problem here. The operator 
must experiment with more dorsal/ventral po- 
sitioning in the caudal intercostal spaces. Fre- 
quently, a two-chambered view is obtained with 
the aorta at the edge of the sector. This allows 
good alignment with flow. One must be careful 
not to erroneously sample the pulmonary artery 
because it is adjacent to the aorta in this view 
and overall image quality from this position 
tends to be poor. Color flow is very helpful in 
guiding spectral recording in cats. There seems 
to be lower peak velocities more spectral 
broadening of the signals in cats when com- 
pared to dogs. 
Studies from the left hemithorax can be used 
to interrogate the left cardiac valves and ven- 
tricular septum of the h ~ r s e . ~ ~ * ~ ’ A long-axis 
view of the left ventricular inlet is obtained with 
the transducer located at the fourth to fifth in- 
tercostal space, 3-6 cm dorsal to the olecranon. 
The transducer is rotated so that the sector is 
perpendicular to the long axis of the body (the 
reference marker is dorsal, i.e., 12 o’clock). A 
four-chambered view (mainly of the left side of 
the heart) that places mitral inflow more paral- 
lel to the interrogating beam is obtained by 
sliding the transducer ventrally (below the level 
of the elbow) and angling the transducer cran- 
ially [+ to ++I and dorsally [+ to ++I with more 
cranial angulation (and 30” counterclockwise 
rotation from vertical) needed to see the left 
ventricular outflow tract. If the transducer is 
then repositioned cranially, usually two inter- 
costal spaces, rotated 30” counterclockwise, and 
directed dorsally [+++I , the left ventricular 
outlet and aortic valve can be evaluated. From 
these different positions at the left hemithorax, 
mitral inflow (red), regurgitation (blue), aortic 
outflow (blue), and regurgitation (red) have 
been imaged using color coding and verified 
with spectral recordings. 
Initial Evaluation of Doppler 
Echocardiographic Studies 
Doppler echocardiography studies obtained 
from domesticated animals are first examined 
for obvious abnormalities of structure, function, 
and flow. These can be qualitatively evaluated 
as one would assess data from human pa- 
tients.’” In the subsequent section, spontane- 
ous lesions of comparative interest are discussed 
and some of the methods used for identification 
of these conditions are illustrated. 
Animal studies can also be quantified, 
thereby permitting objective assessment of car- 
diac enlargement, abnormal blood flow, and al- 
tered ventricular function. Most studies that 
have evaluated the relationship between M- 
mode or two-dimensional echocardiographic 
measurements of chamber and wall dimensions 
compared to body size have demonstrated sig- 
nificant (generally linear) correlations between 
any quantitative anatomical study should ac- 
count for the subject’s body weight or surface 
area, or should measure serial changes using the 
animal as its own control. In contrast, quanti- 
tative functional data, like shortening fraction 
or other estimates of global left ventricular 
function, are similar between ~ p e c i e s . 6 ~ ’ ” ~ ~ ~ ~ ~ ~ ~ ~ ’ ’ ~ - 
25*28,33,34*36*37,41,46 Left ventricular shortening frac- 
tion, typically between 30%-40% in unsedated 
animals tends to be slightly higher in cats when 
compared to dogs, horses, cows, sheep, and pigs. 
Echocardiography can be used to predict 
ventricular volumes and myocardial mass in 
dogs77-87 and horsesm and to measure ventricu- 
lar function. Since measured values from nor- 
mal animals are repeatable on a day-to-day 
basi~,6’~~*~’ echocardiography can be used to doc- 
ument progressive changes of cardiac anatomy 
and indices of ventricular function. This capac- 
ity has been employed in canine studies of hy- 
perten~ion~’-’~ and heart fail~re.’~-’~ Loading 
conditions, heart rate, anesthetic agents, seda- 
tives, and spontaneous or induced cardiac dis- 
eases significantly alter cardiac dimensions and 
echocardiographic indices of ventricular func- 
tion.18,34-36,43,45.96-111 For example, general anes- 
thesia, myocardial ischemia, dilated cardiomy- 
opathy, and taurine deficiency reduce left ven- 
tricular ejection phase indices in animals (Figs. 
10A and 11). Sympathomimetic drugs increase 
ventricular shortening fraction and can even 
produce ventricular outflow gradients and sys- 
tolic anterior motion of the mitral valve in nor- 
mal dog^."^,'^^ 
It is valuable to inspect the shape and motion 
of the ventricular septum in animals with heart 
disease. Abnormalities have been observed in 
these variables (Fig. 9) .19,25.28,33,34.36.37,41,46,76 Thus 
9 
BONAGURA AND MILLER 
240 ECHOCARDIOGRAPHY: A Jml. of CV Ultrasound 8i Allied Tech. Vol. 6, No. 3, 1989 
VETERINARY ECHOCARDIOGRAPHY 
A 
00- 
5 5 
50- 
4 5 
0 . 
0 40- 
I . - 
v . 
(I) . 
35- 
30- 
25- 
20 
o 2 4 B 0 10 12 14 ie ie 20 22 24 20 20 30 32 34 30 
BODY HEIGHT (KG) 
Figure 9. The relationship between the diastolic dimension of the left ventricle (DDLV) and body 
weight in healthy dogs examined in our laboratory. The predicted valve and 95% confidence intervals are 
indicated. This relationship is similar to data reported by others for dogs and cats. (From Bonagura JD, 
O%rady MR, Herring Ds28 with permission). 
experimental models of ventricular loading and 
in dogs with spontaneous heart di~ease."""~ 
Ventricular septal motion is a reflection of 
overall left ventricular shape and responds to 
the relative pressure and volume loads of the 
ventricles. Changes in septal motion and in the 
radius of ventricular septal curvature are obvi- 
ous when examining short-axis tomograms 
from dogs with spontaneous pressure or volume 
overload of the right ~entric1e.l'~ The M-mode 
correlates to abnormal septal position, as in 
human patients, include flattened or paradoxi- 
cal ventricular septal motion (Figs. 4A,12A 
and 12B). 
Analysis of velocity spectra obtained from 
pulsed- and continuous-wave Doppler has been 
useful in the diagnosis and assessment of ex- 
perimental, congenital, and spontaneous ac- 
quired heart disease in animals.*51954957959*60~97,- 
103-106~122-124 The challenge to the veterinary car- 
diologist is to consistently obtain data that 
approximates the accuracy demonstrated by a 
number of prominent laboratories using open- 
chest animal models. There is at this time a 
paucity of published, Doppler derived data from 
healthy, closed-chest, unanesthetized ani- 
mals.61*62 Normal values for peak velocities ob- 
tained by pulsed-Doppler for unsedated healthy 
dogs in our laboratory are: Aorta = less than 170 
cm/sec, mean = 120 cm/sec; Mitral E = less 
than 100 cm/sec, mean = 76 cm/sec; Mitral A- 
= less than 75 cm/sec, mean = 49 cm/sec; Tri- 
cuspid E = less than 80 cm/sec, mean = 60 cm/ 
sec; Tricuspid A = less than 60 cm/sec, mean 
= 48 cm/sec; Pulmonary artery from the right or 
left hemithorax = less than 130 cm/sec, mean 
= 106 cm/sec (right) and 107 cm/sec (left). 
These data are very close to those reported by 
Vol. 6, No. 3, 1989 ECHOCARDIOGRAPHY. A J m l . of CV Ultrasound & Allied Tech. 241 
BONAGURA AND MILLER 
Gaber6' using a different instrument. Tranqui- 
lization with acepromazine (3 mg/m2, BSA) had 
little effect on Doppler echocardiographyvalues 
in our studies of healthy dogs, generally reduc- 
ing velocities by e 10 cm/sec. Pulsed-Doppler 
velocity spectra are similar in appearance to 
those obtained from human patients (Figs. 
11,13-16), however, summation of mitral and 
tricuspid inlet E and A points is common, par- 
ticularly in cats (Fig. 15). Physiological tricus- 
pid and pulmonic backflow are not uncommonly 
found in normal animals (Fig. 13). 
Doppler echocardiography is used increas- 
ingly to assess systolic and diastolic function in 
human patients.'~~,~ Many of the assumptions 
made regarding noninvasive assessment of car- 
diac output4' and ventricular function are based 
on animal-especially d o g - s t u d i e ~ ; ~ ~ ~ * ~ ' ~ ~ ~ ~ 
although a potential limitation of some studies 
may be the open-chest models often used. It is 
beyond the scope of this article to detail the 
experimental literature of ventricular function. 
Some generalizations can be made as they are 
relevant to the interpretation of veterinary 
Doppler echocardiography studies. Reduction in 
left ventricular systolic function, as develops 
with myocardial ischemia, dilated cardiomyopa- 
thy, and following cardiodepressant drugs, 
alters a variety of left ventricular ejection phase 
ractional shortening, ve- in~ces~19-21,29,96,103-112 F 
Figure 10. (A): M-mode echocardiogram from a 
hound with dilated cardiomyopathy. The left ventricle 
(LV) is greatly dilated to approximately 85 mm. Con- 
traction of the ventricular septum and left ventricular 
wall (W) is diminished. The mitral valve E point (ar- 
rowhead) to septa1 distance is increased. The mitral 
closure is delayed with a 'B' shoulder. The right panel 
of the aortic rootlleft atrium shows a dilated left atrium 
(LA). The aortic valve is most evident in diastole (open 
arrows). RV = right ventricle (From Bonugura JD, 
Herring DS30 with permission). (B) M-mode echocar- 
diogram from a cat with hypertrophic cardiomyopathy. 
The ventricular septum (S) and left ventricular wall 
(L) are hypertrophied for a cat. The left ventricular 
lumen is slightly reduced in size and the mitral valve 
(M) is crowded within the lumen. Systolic contraction 
is normal (double arrow). There is systolic anterior 
motion of the mitral valve (arrowhead), suggesting ob- 
structive myopathy and a small pericardial effusion 
(lower arrow). (From Bonagura JD, Herring DS3' with 
permission). 
242 ECHOCARDIOGRAPHY: A Jml. of CV Ultrasound & Allied Tech. Vol. 6, No. 3, 1989 
VETERINARY ECHOCARDIOGRAPHY 
Figure 1 1. Doppler echocardiograms from a normal 
anesthetized dog (left panel) and a dog with congenital 
subaortic stenosis (center and right panels). The left 
panel shows a normal outlet velocity waveform ob- 
tained by pulsed-Doppler. Because of anesthesia, the 
peak velocity is reduced (calibration markers = 0.2 
mlsec). The tracing in the center panel was obtained 
from the left apex. Outlet velocity, measured by contin- 
uous-wave Doppler, is increased to at least 3 mlsec and 
aortic regurgitation (AR) is also noted. Aortic velocity 
obtained from the suprasternal notch (right panel) 
yielded a higher peak velocity approximating 4 mlsec. 
Estimated pressure gradient was 64 mmHg, which is a 
moderate obstruction for dogs with this lesion. 
locity of circumferential shortening, peak aortic 
velocity, and estimated ejection fraction and 
stroke volume all decrease (Figs. 10A and 11) 
and aortic acceleration time increases. It is ap- 
parent that diastolic function as assessed by 
Doppler echocardiography is complex involving 
interrelated Some of the 
changes observed in experimental studies of in- 
duced diastolic dysfunction have been observed 
in animals with spontaneous heart disease and 
presumed diastolic dysfunction (Fig. 16). Mitral 
and tricuspid E to A ratios, filling fractions, and 
acceleration and deceleration rates have been 
examined in canine models of ventricular dia- 
stolic dysfunction, but there is virtually no in- 
formation detailing these abnormalities in 
spontaneous heart diseases of animals. 
Assessment of Spontaneous Heart 
Disease in Animals Using 
Doppler Echocardiography 
Domesticated animals are afflicted with a va- 
riety of spontaneous congenital and acquired 
Figure 12A. M-mode echocardiogram from a Do- 
berman Pinscher with an ostium primum atrial septal 
defect (ASD), congestive heart failure, and pleural ef- 
fusion. There is significant right ventricular (RV) uol- 
ume overload, diastolic displacement of the ventricular 
septum into the left ventricle (LV), and paradoxical 
systolic septal motion. There is also some overall mo- 
tion artifact secondary to respiratory distress. The 
small arrows indicate parts of the tricuspid valve. (B): 
M-mode echocardiogram from a dog with congenital 
right ventricular outfiw obstruction. The right ven- 
tricular free wall and ventricular septum are hypertro- 
phied. Ventricular septal motion is abnormally flut be- 
cause of pressure overload of the right ventricle (RV). 
Systolic thickening is normal. Sd = diastolic septal 
thickness; S, = nadir of septal excursion; Pa = apogee 
(maximal excursion) of left ventricular wall; TV = tri- 
cuspid apparatus. (From DeMadron E, Bonagura JD, 
O'Grad~"~ with permission). 
heart diseases (Table 11). Many of these lesions 
have the potential to serve as models for analo- 
gous conditions of humans. One important dif- 
Vol. 6, No. 3, 1989 ECHOCARDIOGRAPHY: A Jml. of CV Ultrasound & Allied Tech. 243 
BONAGURA AND MILLER 
Figure 13. Pulsed-Doppler echocardiogram from a 
clinically normal dog under general anesthesia. The 
sample volume was placed at the left ventricular inlet 
using a left apical four-chamber image. Phasic diastolic 
transmitral flow (the E and A waves) are recorded as 
well as a phonocardiogram (top trace), ECG, and aortic 
pressure curve. 
ference between adults and animals is the rela- 
tive scarcity of extramural coronary disease and 
transmural myocardial infarctions in the com- 
mon domesticated species. While microvascular 
changes have been recognized in dogs with dia- 
betes mellitus, congenital subaortic stenosis, 
and myxomatous valvular heart disease, and in 
cats with feline hypertrophic cardiomyopa- 
the clinical significance of these le- 
sions is unresolved. The reader is referred to 
general textbooks of veterinary medicine for 
more detailed descriptions of the clinical and 
pathological features of spontaneous heart dis- 
eases in animal^."^-^^^ We will briefly define 
important clinical conditions and attempt to il- 
lustrate the value of Doppler echocardiography 
in assessing these disorders. 
Pericardial Disease and Cardiac Mass Lesions 
Pericardial effusion, cardiac tamponade, per- 
itoneopericardial diaphragmatic hernia, and in- 
trapericardial mass lesions are frequently re- 
ported in veterinary medicine (Table 11) .125-131 
Furthermore, there is a significant volume of 
published data regarding the dog as an experi- 
mental model of pericardial effision in human 
patients. Echocardiography has been used ex- 
perimentally132-139 and ~ l in i ca l ly~~”- ’~~ to iden- 
tify fluid and blood within the pericardial space, 
indicate the development of hemodynamic im- 
pairment and cardiac tamponade, and demon- 
strate intrapericardial and cardiac mass lesions 
(Figs. 17-22).1*154 Most cardiac masses in ani- 
mals cause clinical signs secondary to intraperi- 
cardial bleeding or pulmonary metastasis, al- 
though an occasional intracardiac tumor may 
obstruct venous return or cause systemic arte- 
rial embolization. 
Salient features of pericardial effusion in dogs 
are development of a sonolucent space between 
the epicardium and parietal pericardium, dis- 
placement of the right ventricular free wall from 
the thoracic cage, and abnormal cardiac motion. 
Asin humans, gravitational and anatomical 
features of the pericardial cardiac attachments 
influence the location of fluid accumulation. 
Echodense material may be identified within 
the effusate secondary to hemorrhage or fi- 
brinous exudation. Cardiac masses may be ob- 
served; these usually involve the right atrium or 
aortic Swinging of the heart is evident 
Figure 15. Pulsed-Doppler echocardiogram from a 
cat with idiopathic hypertrophic obstructive cardiomy- 
opathy. The sample volume was placed in the left 
atrium using a left apical image plane. Transmitral 
inflow velocity (MVIF) consists of one positive wave- 
form because of the rapid heart rate. High-velocity neg- 
ative systolic signals representing mitral regurgitation 
(MR) are indicated. The signal is aliased above the 
baseline (AL >). 
244 ECHOCARDIOGRAPHY: A Jml. of CV Ultrasound & Allied Tech. Vol. 6, No. 3,1989 
VETERINARY ECHOCARDIOGRAPHY 
Figure 16. Pulsed-Doppler echocardiogram from a 
13-year-old Poodle with severe chronic respiratory dis- 
ease. The sample volume was placed in the right ven- 
tricular inlet using a right parasternal, ventral position 
four-chamber image. This dog had clinical and electro- 
cardiographic evidence of cor pulmonale and pulmo- 
nary hypertension including high-velocity tricuspid 
and pulmonary insufficiency. The echocardiogram 
shows abnormal reversal of tricuspid E and A waves, 
presumably from right ventricular hypertrophy and 
abnormal ventricular compliance. 
within large effusions. Diastolic collapse of the 
right ventricle or right atrium herald cardiac 
tamponade. The onset of this collapse also de- 
pends on diastolic characteristics of the right 
ventricle and overall blood volume s t a t ~ s . l ~ ~ , l ~ ~ 
Associated pleural effusions frequently are ob- 
served. 
Constrictive pericarditis has been recognized 
echocardiographically in a small number of ani- 
mals. While it is difficult to accurately assess 
pericardial t h i c k n e ~ s , l ~ ~ * ' ~ ~ there may be reduc- 
tion in ventricular cavity size, atrial dilation, 
abnormal septa1 motion, abrupt flattening of 
ventricular diastolic expansion, and reduced 
atrioventricular valve E-F slope. Vena caval 
distension and enlargement of hepatic veins are 
associated ultrasonic findings of right-sided 
failure in pericardial diseases. 
Valvular Heart Disease 
Valvular lesions, the most commonly en- 
countered cardiac disorders in veterinary prac- 
tice,lZ5-l3l include infective e n d ~ c a r d i t i s ~ ~ ~ ~ ~ . ~ ~ ~ ' ~ ~ 
congenital m a ~ f o r m a ~ ~ o n s , ~ ~ ~ ~ ~ ~ ~ ~ . 5 8 . ' 3 1 . ~ ~ 6 , 1 7 3 , 1 7 6 , 1 8 1 
and acquired, typically degenerative disorders of 
(Table 11). Bacterial 
endocarditis is recognized in both small and 
large animals with the valve pre-dilection dif- 
fering considerably between species (Figs. 8 and 
23). Clinical features are similar to those in 
human patients. Of the congenital valvar le- 
sions, pulmonic stenosis, usually the result of 
valve dysplasia, and fibrous subaortic stenosis 
are most common (Figs. 11,12B,24, Color Plate 
4). Both conditions represent genetically trans- 
mitted malformations in some canine breeds. 
Dysplasia of the atrioventricular valves is diag- 
nosed in both small and large animals and refers 
to a spectrum of lesions which includes thick or 
shortened valve cusps, either very long or stout 
chordae tendineae, and anomalies of the papil- 
lary muscles (Fig. 4). Less frequently, there is 
atresia of the atrioventricular valve. The af- 
fected atrioventricular valve is incompetent, al- 
though stenosis also has been observed. Spo- 
radic cases of atrioventricular valve stenosis are 
recognized in dogs (Fig. 251, but there is no con- 
sistent counterpart to rheumatic valvular dis- 
ease in the domesticated species. The most im- 
portant cause of heart failure encountered in 
veterinary practice is myxomatous degeneration 
of the atrioventricular valves, a condition char- 
acterized grossly by shortening and thickening 
of the valve leaflets (Fig. 26, Color Plate 1). This 
lesion causes progressive mitral and tricuspid 
regurgitation almost exclusively in mature dogs, 
and resembles advanced cases of mitral valve 
prolapse syndrome in human patients. Rupture 
of a chorda tendinea can occur in conjunction 
with this, as well as other disorders, including 
endocarditis. Aortic regurgitation in animals is 
associated with congenital subaortic stenosis, 
bacterial endocarditis (Figs. 8B and 23) and, in 
the mature horse, incompetency secondary to 
degenerative lesions of the valves. Pulmonic in- 
sufficiency is most frequently observed with 
congenital heart disease (Fig. 4), after cardiac 
surgery or balloon valvuloplasty, and with cor 
pulmonale. 
These congenital and acquired valvular dis- 
orders have been identified using Doppler echo- 
cardiography. 16,29,40,44,93,155-184 It may be possible 
various types29,40,44,93,165-184 
Vol. 6, No. 3, 1989 ECHOCARDIOGRAPHY: A Jrnl. of CV Ultrasound & Allied Tech. 245 
BONAGURA AND MILLER 
TABLE I1 
Cardiovascular Lesions Evaluated by Doppler-Echocardiography 
Valvular Heart Disease 
Congenital 
1. Pulmonic stenosis 
2. Aortic stenosis, Subaortic stenosis 
3. Mitral valve dysplasia (incompetency/stenosis) 
4. Tricuspid valve dysplasia (incompetency/stenosis) 
5. Valve atresia (usually right-sided heart valves) 
1. Myxomatous degeneration of the atrioventricular valves (dog) causing valvular regurgitation 
2. Degenerative thickening of the aortic, mitral, and tricuspid valves causing valvar regurgitation (horse) 
3. Bacterial endocarditis 
4. Rupture of mitral valve chordae tendineae (dog, horse) 
Acquired 
Myocardial pisease 
1. Dilated cardiomyopathy (dog, cat, horse, cattle) 
-Idiopathic dilated cardiomyopathy 
-Taurine deficiency (cat) 
-Doxorubicin cardiotoxicity (dog) 
2. Myocarditis/myocardial necrosis 
-Vitamin E or selenium deficiency (horse, cattle) 
-Post-viral myocarditis (dog) 
3. Hypertrophic cardiomyopathy (cat, dog) 
4. Restrictive cardiomyopathy (cat) 
5. Hyperthyroid heart disease (cat) 
6. Hypertensive heart disease (dog, cat) 
Pericardial Disease/Cardiac Mass Lesions 
1. Congenital pericardial diseases (hernia, cyst) 
2. Idiopathic pericardial effision/hemorrhage (dog, cat, horse) 
3. Hemorrhagic pericardial effision secondary to neoplasia 
-Right atrial hemangiosarcoma (dog) 
-Heart base tumor/chemodectoma (dog) 
-Lymphosarcoma (cat, cattle) 
-Metastatic carcinoma 
-1ntrapericardial metallic foreign-body (cattle) 
-Secondary to bacterial or fungal infection 
5. Constrictive and constrictive-effusive pericarditis 
6. Left atrial thrombus associated with feline cardiomyopathy 
1. Secondary to congenital heart disease (dog, cat) 
2. Dirofilariasis-heartworm disease (dog, cat) 
3. Cor pulmonale secondary to chronic respiratory disease 
4. Idiopathic (?primary) pulmonary hypertension 
Congenital cardiac shunt 
1. Atrial septal defects 
2. Ventricular septal defects 
3. Patent ductus arteriosus (dog, cat) 
4. Tetralogy of Fallot/pseudotruncus arteriosus 
5. Complex congenital heart disease 
4. Suppurative or granulomatous pericarditis 
Pulmonary Hypertension/Cor Pulmonale 
Cardiac arrhvthmia 
This a partial list of lesions encountered in the species most commonly imaged in veterinary practice (canine, feline, equine, 
bovine); Parenthesis ( ) indicates that the lesion is particularly prominent in or generally limited to that species. 
246 ECHOCARDIOGRAPHY: A J m l . of CV Ultrasound & Allied Tech. Vol. 6, No. 3, 1989 
VETERINARY ECHOCARDIOGRAPHY 
Figure 17. Two-dimensional echocardiogram fro- 
zen during diastole. Right parasternal four-chamber 
image f rom a dog with pericardial effusion and cardiac 
tamponade. The heart is surrounded by a n echo-free 
fluidspace. The left parietal pericardium is most dis- 
tant from the transducer. I n the near field, the right 
atrium has collapsed. I n real time, this was a phasic 
diastolic collapse. 
Figure 19. Two-dimensional echocardiogram from 
a cat with restrictive cardwmyopathy, atrial fibrilla- 
tion, and congestive heart failure. Long-axis image 
f rom the right hemithorax. The left atrium and right 
pulmonary vein are tremendously dilated and there is a 
large, circular left atrial mass lesion, which is a 
thrombus, attached to the atrial wall. A small pericar- 
dial effusion is evident behind the left ventricle. 
to detect abnormal valve anatomy (Figs. features, however, cannot be specific. Cases of 
4,8,26,27), especially valve thickening, using severe myxomatous degeneration that echocar- 
two-dimensional and M-mode studies. The echo diographically resemble an infective vegetation 
Figure 18. Two-dimensional echocardiogram ob- 
tained from a cat with a congenital peritoneopericardial 
diaphragmatic hernia. T h e frozen image shows a 
short-axis view of the left ventricle (LV) obtained f rom 
the right hemithorax. Within the pericardial space, 
there is tissue density compatible with liver. The gall- 
bladder was found on other views. LVW = left ventric- 
ular wall; PERI = parietal pericardium. 
Figure 20. Two-dimensional echocardiogram fro- 
zen during diastole. Left apical four-chamber image 
f rom a 9-year-old German Shepherd with cardiac neo- 
plasia, tricuspid insufficiency, ascites, and left bundle 
branch block. The right atrium (RA) is markedly di- 
lated. At the inlet of the right ventricle (RV) there are 
multiple irregular tissue densities. These were attached 
to the ventricular septum and circumferentially about 
the tricuspid anulus (arrowheads) and appeared to ob- 
struct ventricular inflow. LV = left ventricle. 
Vol. 6, No. 3, 1989 ECHOCARDIOGRAPHY: A Jrnl. of CV Ultrasound & Allied Tech. 247 
BONAGURA AND MILLER 
Figure 2 1. Pulsed-Doppler echocardiogram f rom 
the dog shown i n Figure 20. The sample volume was 
placed between the cardiac mass lesions in the tricuspid 
orifice. A high-velocity diastolic signal that exceeds 1 
mlsec suggests that the mass is causing stenosis of the 
right ventricular inlet. The E and A waves are sum- 
mated because of sinus tachycardia. An aliased je t of 
tricuspid regurgitation also is recorded during some 
cardiac cycles. 
are noteworthy. Abnormal valve motion is often 
observed and includes reduced opening (steno- 
sis or low cardiac output) (Fig. 25), exuberant 
motion or prolapse (myxomatous disease, valve 
dysplasia), diastolic fluttering and premature 
mitral valve closure (semi-lunar valve regurgi- 
tation), (Fig. 23) and chaotic motion (ruptured 
or avulsed valve support apparatus)." While di- 
astolic mitral valve fluttering can develop with a 
lesion of any aortic cusp, clinical and experi- 
mental studies suggest that fluttering of the 
ventricular septum can indicate a lesion of the 
noncoronary cusp (Fig. 8C). Systolic mitral 
valve fluttering has been observed with myxo- 
matous disease in dogs with musical murmurs. 
Midsystolic closure of the aortic valve has been 
observed with a number of lesions including 
congenital subaortic stenosis in dogs. Finally, 
but no less important, is the understanding that 
pulsed- and continuous-wave Doppler can be 
used for identification of abnormal blood flow 
caused by valvular di~ease. '~~~" '~ Thus, Doppler 
studies often verify the cause of heart murmurs 
(Figs. 8,11,15,20,24, Color Plates 1,3,4). 
The clinician can estimate the hemodynamic 
severity of the lesion by combining data from 
M-mode, two-dimensional, and Doppler studies. 
The hemodynamic significance of valvar lesions 
can be estimated by quantifying the adaptive 
responses of the cardiac chambers and great 
vessels to valvular incompetency or obstruction. 
In this regard, dilatation, hypertrophy, and 
post-stenotic dilatation are recognized through 
serial studies or by comparing the animal's 
echocardiographic data to normals of similar 
body size (Figs. 4,9,10,12,23).19*27~28.30'93 In cases 
of mitral regurgitation, calculation of left ven- 
tricular shortening fraction is useful in distin- 
guishing animals with dilated cardiomyopathy 
from those with myxomatous valvular disease 
where the ventricle is hypercontractile.2'~'3~165~166 
Experimental data in dogs suggests that mitral 
regurgitant fraction might be estimated by 
Doppler ech~cardiography.~~' Analysis of ven- 
tricular septal position, radius of septal curva- 
Figure 22. M-mode echocardiogram f rom a dog 
with infiltrative myocardial disease who was examined 
for unexplained periods of ventricular tachycardia (see 
ECG). The left ventricular wall (LVW) is markedly 
thickened, hypokinetic, and inhomogeneous in echo- 
genicity, with layers of relative sonolucency. Two-di- 
mensional images (not shown) indicated multifocal tu- 
morous thickening of the right ventricular wall and 
diffuse infiltration within the left ventricular free wall 
and apex. These findings are typical of neoplosia, how- 
ever, additional studies were not permitted and a nec- 
ropsy was not obtained in this dog. E N D 0 = left ven- 
tricular endocardium; E P I = left ventricular epicar- 
diumlpericardial interface; IVS = interventricular 
septum; RV = right ventricle; LV = left ventricle. 
248 ECHOCARDIOGRAPHY: A Jrnl. of CV Ultrasound & Allied Tech. Vol. 6, No. 3,1989 
VETERINARY ECHOCARDIOGRAPHY 
Figure 23. M-mode echocardiogram from a cow with aortic valve endocarditis, aortic insufficiency, and 
congestive heart failure. The left ventricle (LV) is dilated, the left ventricular wall (L VW) hypercontractile, and 
there are diastolic thumbprint echoes (open arrow) i n the outflow tract which represent prolapsing of a flail aortic 
cusp. The right panel, obtained across the aortic root (A) and the affected aortic valve (AV), shows the vegetation 
(VEG) in diastole. There is diastolic fluttering of the mitral valve (arrow) secondary to aortic regurgitation and 
premature closure of the anterior (AMV) and posterior (PMV) mitral valve leaflets (arrowheads) suggesting 
elevated end-diastolic pressure. 
ture on the short-axis image of the left ventricle, 
and septa1 motion during the cardiac cycle pro- 
vides information regarding relative right ven- 
tricular volume and pressure (Figs. 2,4,12).l14-l17 
The modified Bernoulli equation, shown to be 
accurate in canine models of aortic and pulmo- 
nary obstruction and in spontaneous subaortic 
s t e n o ~ i s , 5 ~ - ~ ~ has been applied clinically to esti- 
mate severity of valve obstruction (Figs. 11,24). 
The continuity equation has been successfully 
applied to canine models of aortic valve stenosis 
to assess valve cross-sectional area.184 A sudden 
drop-off in the velocity profile can be observed 
during spectral recordings of valvular regurgi- 
tation when there is elevation of ventricular 
end-diastolic p r e ~ s u r e . ~ , ~ In well compensated 
states, the estimated pressure drop across the 
insufficient valve is maintained throughout the 
regurgitant period (Figs. 11 & 24). 
Myocardial Diseases 
Although dogs and pigs are extensively used 
in studies of myocardial ischemia and infarc- 
~~on,67,69,70,104,106,1~5,186 spontaneous myocardial 
disorders in animals are rarely caused by coro- 
Vol. 6, No. 3,1989 ECHOCARDIOGRAPHY: A Jml. of CV Ultrasound & Allied Tech. 249 
BONAGURA AND MILLER 
Figure 24. Continuous-wave Doppler echocardio- 
gram from a golden retriever puppy with congenital 
pulmonic stenosis. T h e right ventricular outlet velocity 
is increased to approximately 2.8 mlsec (PS); there is 
associated low-velocity pulmonary insufficiency (PI). 
nary stenosis. Of greater importance to veteri- 
narians are myocardial traurnala7that result 
from automobile accidents, and cardiomyopa- 
thies that have been recognized in many spe- 
cies.188-201 While dilated cardiomyopathy de- 
Figure 25. M-mode echocardiogram obtained from 
a n Irish Setter dog with catheterization-proven mitral 
stenosis of uncertain cause. T h e anterior (AMV) and 
posterior (PMV) leaflets do not separate normally dur- 
ing diastole and there is reduction of mitral E-F slope. 
T h e anterior leaflet is moderately thickened. (From 
Pipers FS, Bonagura JD, Hamlin RL, et allm with 
permission). 
Figure 26. Two-dimensional echocardiogram, re- 
played f rom videotape and frozen during diastole. Right 
parasternal four-chamber image optimized for the left 
ventricular inlet, A thickened, myxomatous mitral 
valve is evident, especially the anterior leaflet (AMV). 
Real-time imaging revealed the typical hypercontractile 
left ventricle observed in this primary valvular lesion. 
LA = left atrium; LV = left ventricle. 
velops sporadically in large animals and pet fer- 
rets, it is most common in large breed dogs and 
represents a major cause of cardiovascular 
death in this species (Fig. 10A).29~40~44J88J91Jg4Jg6 
Figure 27. Two-dimensional echocardiogram fro- 
zen during diastole in a dog with severe heartworm 
disease caused by Dirofilaria immitis. Right paraster- 
nal short-axis view at the, mitral valve level. The hy- 
perechoic areas within the tricuspid valve orifice repre- 
sent adult heartworms. T h e markedly dilated main 
pulmonary artery and flnttened interventricular sep- 
tum are due to pulmonary hypertension. 
250 ECHOCARDIOGRAPHY: A Jml. of CV Ultrasound & Allied Tech. Vol. 6, No. 3,1989 
VETERINARY ECHOCARDIOGRAPHY 
Figure 28. Two-dimensional echocardiogram fro- 
zen during diastole. Right parasternal long-axis four- 
chamber image from a cat with an endocardial cushion 
defect. Note the loss of atrial septum and the abnormal 
appearance of the edge of the ventricular septum. The 
right atrium and ventricle are dilated. RA = right 
atrium; RV = right ventricle; LA = left atrium; LV 
= left ventricle. 
Dilated cardiomyopathy is also observed in dogs 
undergoing treatment with doxorubicin and in 
puppies with parvovirus myocarditis.'30~'90~198 
Until recently, dilated cardiomyopathy was 
common in at^.^^^^^^^^^^^^^,^^^ Identification of 
low plasma taurine concentrations in most af- 
fected cats2" and correction of this dietary 
problem has virtually eliminated the condition 
in the United States and Canada. Currently, 
most feline myocardial diseases are related to 
either idiopathic hypertrophic cardiomyopathy 
(Fig. lOB), hyperthyroid heart disease (a fre- 
quent disorder of aged ~ a t s ) , ~ ~ , ~ ~ ~ , ~ ~ ~ , ~ ~ ~ and hy- 
pertensive heart disease (associated with 
chronic renal failure).'28 
Echocardiographic features of dilated cardio- 
myopathy in animals include generalized car- 
diac dilatation, global hypokinesis of the left 
ventricle (regional dysfunction develops in 
some dogs), reduced fractional shortening 
(usually < 20%) and aortic root excursion, in- 
creased E point to septal separation (typically 
> 8 mm in the dog), and decreased left ventricu- 
lar wall and interventricular septal thickening 
fractions. The mitral valve may exhibit a de- 
layed systolic closure characterized by a B 
shoulder between the A and C points of mitral 
excursion on the M-mode echocardiogram. 
Doppler echocardiography indicates mitral re- 
gurgitation, tricuspid regurgitation, and in- 
creased aortic acceleration time, a finding that 
would be anticipated from animal studies of in- 
duced myocardial fai1~re.l'~ Atrial fibrillation 
and ventricular tachycardia are frequent com- 
plications of dilated cardiomyopathy in dogs. 
The potential hemodynamic consequences of 
these rhythm disturbances can be appreciated 
through the altered valve motions, ventricular 
contractions, and Doppler velocity signals that 
are observed.lss 
Hypertrophic cardiomyopathy in cats is rec- 
ognized by Doppler echocardiography through 
the identification of symmetric or asymmetric 
left ventricular hypertrophy, reduction of ven- 
tricular luminal volume, normal to increased 
shortening fraction, left atrial enlargement 
(with left atrial thrombus in some cases, Fig. 
19), and possibly systolic anterior motion of the 
mitral va1ve.29,44,189,193 D oppler studies may dem- 
onstrate left ventricular outflow obstruction, 
mitral regurgitation (Fig. 15), and increased late 
diastolic ventricular inlet velocities, however, 
no detailed study of diastolic function in these 
cats has been reported. Systemic hypertension 
and hyperthyroidism (from functional thyroid 
adenomas) can induce similar changes in the 
echocardiogram. With hyperthyroidism, how- 
ever, left ventricular shortening fraction is 
usually supranormal, often > 50% and most ab- 
normalities revert towards normal following 
successful treatment of the thyrotoxico- 
The echocardiographic findings of experi- 
mental myocardial contusion in dogs are similar 
to those observed in a limited number of clinical 
cases and include increased end-diastolic thick- 
ness, decreased regional systolic function, in- 
crease in echocardiographic brightness, and as- 
sociated pericardial effusion. Sonolucent zones 
within the myocardium correlated to areas of 
hematoma.la7 We have observed similar find- 
ings in cases of intramyocardial neoplasia 
caused by lymphosarcoma or metastatic carci- 
noma (Fig. 22), however, associated clinical 
findings and the tendency towards areas of neo- 
plasia associated nodularity permit these condi- 
tions to be distinguished. 
sis~44,193,195,197,201 
Vol. 6, No. 3, 1989 ECHOCARDIOGRAPHY: A Jrnl. of CV Ultrasound & Allied Tech. 251 
252 
BONAGURA AND MILLER 
Figure 14 
Color Plate 2 
Color Plate I 
Color Plate 3 
Color Plate 4 Color Plate 5 
ECHOCARDIOGRAPHY: A Jml. of CV Ultrasound & Allied Tech. Vol. 6, No. 3, 1989 
VETERINARY ECHOCARDIOGRAPHY 
Color Plate 6 Color Plate 7 
Color Plate 8 
Figure 14. Pulsed-Doppler echocardiogram from a clinically normal dog under general anesthesia. The sample 
volume was placed in the pulmonary outflow using a left apical angled image optimized for the long axis of the 
pulmonary artery. Pulmonary ejection velocity (depressed owing to anesthesia) and low-velocity pulmonary insufi- 
ciency (PI) are noted. Thepressure trace at the top is from the aorta. 
Color Plate 1. Two-dimensional echocardiogram frozen during systole (videotape playback) from a dog with 
myxomatous atrioventricular valvular degeneration. The right parasternal long-axis view is optimized for the inlet 
valves. Color flow imaging demonstrates jets of both tricuspid (TR) and mitral (MR) regurgitation. A variance map 
was used, R A = right atrium; R V = right ventricle; LA = left atrium; LV = left ventricle. 
Color Plate 2. Two-dimensional echocardiogram frozen during systole from a horse with a ventricular septa1 
defect. Right parasternal long-axis image optimized for the left ventricular outflow tract (LVOT). Color flow imaging 
demonstrates left-to-right shunting (arrowheads) into the inlet of the right ventricle (RV). A variance map was used. 
LA = left atrium; Ao = aorta. 
Vol. 6, No. 3, 1989 ECHOCARDIOGRAPHY: A Jrnl. of CV Ultrasound & Allied Tech. 253 
BONAGURA AND MILLER 
Color Plate 3. Two-dimensional echocardiogram frozen during systole from a horse with tricuspid regurgitation. 
Right parasternal long-axis image, ventral position. Color flow imaging demonstrates a regurgitant je t (arrow) with 
some signal aliasing at the valve. An enhancedlvariance map was used. RV = right ventricle; LV = left ventricle; Ao 
= aorta; I V S = interventricular septum. 
Color Plate 4. Two-dimensional echocardiogram frozen during systole from a dog with