Page 166 - Clinical Small Animal Internal Medicine

134 Section 3 Cardiovascular Disease

(a)
VetBooks.ir Carina LA

(b)

(c)

LB
Trachea

Figure 16.7 Thoracic radiographs of three different dogs with compensated (a,b) and decompensated (c) degenerative mitral valve
disease. (a) A marked left atrial enlargement (LA) is seen on this lateral radiograph. Note the tracheal and carina dorsal elevation as well as
the straightening of the caudal part of the cardiac silhouette, suggesting left ventricular dilation as well. (b) On this dorsoventral view,
enlargement of the left auricular appendage produces a bulge (large arrow) at the 2–3 o’clock position. Additionally, the dilated LA body
(thin arrows) creates a “mass effect” in the dorsocaudal region of the cardiac silhouette. (c) This lateral radiograph shows diffuse
cardiogenic pulmonary edema that is more severe in the caudodorsal perihilar area (arrow). Left heart enlargement is responsible for
dorsal elevation of the intrathoracic trachea, carina, and left main bronchus (LB). Note also the abnormal increased sternal contact of the
heart, suggesting right ventricular enlargement (which was further confirmed to result from pulmonary arterial hypertension). Source:
Medical Imaging Unit, ENVA.

time. M‐mode echocardiograms display motion over
Conventional Echocardiography time of the various tissue interfaces crossed by the lin-
ear M‐mode ultrasound beam. Currently, the 2D mode
Over the last 30 years, standard transthoracic echocardi- is always used to guide accurate placement of the
ography has become a major imaging tool for the diag- M‐mode cursor, which appears as a vertical line on
nosis, management, and follow‐up of canine and feline 2D echocardiograms. M‐mode echocardiography has a
heart diseases, allowing noninvasive assessment of heart much higher spatial and temporal resolution than 2D
morphology (ventricles, atria, cardiac valves, auricular echocardiography, and therefore allows recording of
appendages) and function, as well as examination of the the motion of subtle cardiac structures.
anatomy of the proximal great vessels. Transthoracic 2D and M‐mode echocardiography
can be performed on animals in lateral recumbency or
in standing position, as the measurements obtained in
General Principles and Technique
both positions show similar variability. Some animals
Conventional echocardiography combines 2D and M‐ may not tolerate a recumbent position because of dis-
mode imaging. M‐mode echocardiography provides comfort or dyspnea, making the standing position eas-
one‐dimensional views of the heart, while 2D echocar- ier and more suitable. Placing the patient in lateral
diography displays cross‐sectional or 2D cardiac images recumbency decreases lung interference but, on the
(in transverse and longitudinal planes) moving in real other hand, may increase stress in nervous animals.