You are presented with a cat which has pulmonary edema, a gallop heart rhythm, a heart murmur and weak femoral arterial pulses. The radiographs reveal generalized cardiomegaly with pulmonary edema. The electrocardiogram reveals a normal sinus rhythm and left ventricular enlargement.
Does this cat have cardiomyopathy and if so what type is it?
Routine two-dimensional echocardiography reveals a heart typical of left ventricular concentric hypertrophy; i.e., the cavity of the left ventricle is reduced relative to the increased thickness of the interventricular septum and the left ventricular free wall. The left atrium is increased in size. The right side of the heart appears normal.
The M-mode Echocardiogram is used to determine the thickness of the interventricular septum, the left ventricular internal dimension, and the left ventricular free wall in both diastole and systole.
- IVS-DIASTOLE 5mm
- IVS-SYSTOLE 8mm
- LVID-DIASTOLE 10mm
- LVID-SYSTOLE 5mm
- LVFW-DIASTOLE 5mm
- LVFW-SYSTOLW 8mm
There is no real value in performing a Doppler Echocardiographic study in this individual. A Doppler examination however may show evidence of reduced left ventricular compliance (diastolic disease) and / or increased velocity of blood flow across the left ventricular outflow tract.
Diagnosis: This is a typical case of Hypertrophic Cardiomyopathy in the cat. This may be due to thyrotoxicosis or it may be idiopathic.
Note that Dilated Cardiomyopathy would have presented with the following Two-dimensional and M-mode Echocardiographic findings. The left ventricular lumen would be increased in size and the left atrium would also be increased in internal dimension. The M-mode examination would have revealed a normal thickness to the interventricular septum and left ventricular free wall, and an increase in the left ventricular internal dimension in diastole (>18mm) and a relative reduction in the left ventricular internal dimension in systole. Thus the index of left ventricular contractility, fractional shortening
[(LVID-D – LVID-S)/LVID-D], would be reduced (normal = 25-45%).