Case Studies In Small Animal

Cardiovascular Medicine

CASE 12

Two-Dimensional Echocardiograms

This right parasternal long-axis view of the four cardiac chambers shows remarkable right ventricular (RV) and right atrial (RA) chamber enlargement. The left ventricular (LV) and left atrial (LA) chambers are smaller than normal. The right ventricular free wall at the top of the picture is thicker than normal.

In this cross-sectional view of the ventricles, it again can be appreciated that the right ventricular chamber is very large and the left ventricular chamber is small. In addition, the interventricular septum is flattened in this diastolic frame. This suggests that the diastolic pressure in the right ventricle is higher than it is in the left ventricle. This could be because of a higher than normal right ventricular diastolic pressure or because of a higher than normal right ventricular diastolic pressure combined with a lower than normal left ventricular diastolic pressure. It is most likely the latter. I have never seen an instance in which a lower than normal left ventricular diastolic pressure in isolation caused septal flattening. PE; pleural effusion.

The same view as the previous figure shows that the left ventricle becomes round again as septal flattening disappears in systole. The left ventricular chamber is still smaller than normal being about 18 mm wide in this early systolic frame (normal for this dog would be around 35 mm). At face value this looks like the left ventricular chamber is approximately one-half its normal size. However, the volume of the ventricle is the true variable that we are interested in. To make a rough approximation of chamber volume one can cube the diameter and divide it by 1.5. This makes the volume of the left ventricular chamber in this dog about 4 ml whereas it should be about 28 ml so chamber volume is 1/7 of normal.

This longitudinal section again shows the four cardiac chambers and their relative sizes. In addition, there is a large mass in the right caudal lobar pulmonary artery branch (arrow). This artery is also markedly enlarged.

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