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10

Normal Cardiovascular Imaging
Merrilee Holland

Department of Clinical Sciences, College of Veterinary Medicine, Auburn, AL, USA

10.1 Normal Thoracic Radiographs Evaluation of the border of the left ventricle (LV) on the
lateral projection is crucial for early detection of cardiac
Evaluation of the cardiac silhouette, pulmonary vascula- disease. Rounding of the left ventricular border on the lat-
ture, great vessels, and pulmonary parenchyma on tangen- eral projection is one of the earliest changes associated
tial projections is the key to successful interpretation of with cardiac disease. On the ventrodorsal image, the left
cardiovascular disease. On the lateral projection in a nor- ventricular border if enlarged or elongated will be rounded
mal sized cat, the cardiac silhouette should be no more and may be located in the left or right hemithorax.
than two intercostal spaces in width (Figure 10.1). In Widening of the heart base coincides with left and later
larger cat breeds over 12 pounds, the cardiac silhouette right atrial enlargement. Evaluation of all four sets of pul-
can normally be up to 2.5 intercostal spaces wide monary vessels for assessment of arterial and venous size
(Figure 10.2). In a normal older cat, the cardiac silhouette changes assists in determination of cardiovascular disease.
slumps down or sits along the sternum. A line placed to The size and shape of the aorta can be altered in patients
measure heart size from this projection does not begin at with systemic hypertension. The caudal vena cava is
the aorta and extend to the apex. Instead, a line should be enlarged in patients with biventricular heart failure,
placed through the middle of the heart and measurement arrhythmogenic right ventricular cardiomyopathy, or
should be made along this line from the sternum dorsally decompensated congenital defect.
to the highest point.
Once the width of the cardiac silhouette has been estab-
lished, this measurement can be compared to the number 10.2 Scanning Tips
of intercostal spaces on the lateral projection. On the ven-
trodorsal image, the apex of the heart should be in the left Most cats do not appreciate being restrained so it is helpful
hemithorax slightly to the left of the spinal column. to learn to perform part or all of the examination with the
Normally in cats the diaphragm does not contact the apex cat positioned sternally on a cardiac table. This skill will be
of the heart even during the expiratory phase of respira- beneficial especially if the cat is presenting in respiratory
tion. There is greater anatomic variability of the left atrial distress from heart failure. Patient compliance is improved
position at the 1–2’o clock position on the ventrodorsal if the room is quiet, foot traffic is minimized, and lights are
view in cats compared to canine patients. The pulmonary dimmed. People with loud voices should whisper.
artery and vein should be the same size and less than the Typically, the right side of the exam can be performed
width of the ninth rib on the ventrodorsal image. The cau- with the patient sternal. It is more difficult to obtain proper
dal lobar arteries need to be traced to their origins overly- alignment for Doppler studies on the left side in sternal
ing the cardiac silhouette to look for subtle enlargement of recumbency, especially in a normal patient. If the cat’s
the caudal lobar arteries associated with pulmonary patience has been exhausted, evaluation on the left side
hypertension. can be done with the cat in left lateral recumbency. The less
Thoracic radiographs in cats with cardiovascular disease restraint the better; however, use of a muzzle or Elizabethan
are not specific for the underlying cause (Figure 10.3). collar may be needed to facilitate the examination. Location

Feline Diagnostic Imaging, First Edition. Edited by Merrilee Holland and Judith Hudson.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.