A 12 year old dog presents to you for a 6 month history of a chronic cough. The cough is exacerbated by excitement, exercise and stress. The cough has progressed markedly over the last month. On physical examination a thrill is palpated over the left chest and a marked systolic heart murmur is noted with a point of maximal intensity over the left cardiac apex. On thoracic radiography the heart is enlarged, the left atrium is enlarged, there is a prominent interstitial pattern in the lungs which is mainly a peribronchial pattern. The EKG reveals left ventricular enlargement and left atrial enlargement. There is no evidence of a dysrhythmia.
Is the cough due to pulmonary edema a result of heart failure?
The Two-dimensional Echocardiogram reveals an enlarged left ventricular and left atrial cavity. Subjectively, the left ventricle appears to be strong (adequate contractility). The M-mode Echocardiogram reveals increased left ventricular internal dimensions in diastole and in systole, and normal contractility (fractional shortening = 47%).
- LVID-DIASTOLE 40mm
- LVID-SYSTOLE 21mm
- F. Shortening 47%
- Left Atrial-S 22mm
Given that the index of contractility is normal, can we suggest that the heart is strong enough and thus not responsible for the cough? In the face of mitral valve insufficiency, we anticipate that it is easier for the left ventricle to contract. Thus the adequate contractility calculated may merely reflect that the ventricle may be ejecting blood in the wrong direction. It has been suggested that if the LVID-S is normal then the heart is probably normal in strength in spite of the mitral valve insufficiency.
Thus as the LVID-S is normal, we believe that the left ventricle and thus the heart is not responsible for the cough. Thus therapy for pulmonary edema of cardiogenic causes is not necessary at this time.
Doppler Echocardiography can be used to demonstrate the existence of mitral valve insufficiency. Although this confirms the existence of MI, it adds little new knowledge to this case. The Doppler examination may provide evidence of the amount of forward flow into the aorta and the amount of backward flow into the left atrium.