Case Studies In Small Animal

Cardiovascular Medicine

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Case 3

Comparison Case 2

The following echocardiograms are from a cat with a large VSD. The defect in the interventricular septum seen in the two-dimensional echocardiogram on top is easily visualized immediately beneath the aorta (AO). Defects that can be seen this easily are usually large. The flow through the defect is left-to-right as seen in the color flow Doppler. The continuous wave Doppler on the bottom shows that the peak velocity of the jet is only 2.36 meters/second. This translates into a pressure gradient across the interventricular septum of only 22 mm Hg. This means the systolic pressure in the left ventricle is only 22 mm Hg higher than the systolic pressure in the right ventricle. The systolic systemic arterial pressure in this cat was measured with a Parks Doppler blood pressure measuring device to be 145 mm Hg. Since there is no aortic stenosis, the systolic pressure in the left ventricle must be 145 mm Hg also. This means the systolic pressure in the right ventricle must be 22 mm Hg less than this or 123 mmHg which means the cat has severe pulmonary hypertension. This high pressure could be due to high flow, high resistance, or both. To only be due to high flow, the size of the defect would have to be similar in size to the aortic orifice so that no to little resistance to blood flow occurred. It does not appear to be that large. Consequently, this cat most likely has significant pulmonary vascular disease because of high flows and/or pressures in the pulmonary vessels because of the long-standing large VSD. Pulmonary vascular disease in this situation is not reversible and there is nothing that can be done definitely for the cat. It is likely that the pulmonary vascular disease will progress to the point that pulmonary vascular resistance exceeds systemic vascular resistance. At this time, the shunt will reverse to become a right-to-left shunt (Eisenmenger's syndrome) causing cyanosis and polycythemia.

 

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Mark D. Kittleson, D.V.M., Ph.D. All rights reserved.