Case Studies In Small Animal

Cardiovascular Medicine

Case 10

Continuous Wave Doppler Echocardiography

This is a continuous wave Doppler tracing measuring the peak velocity of the jet that starts at the mitral valve and projects back into the left atrium (LA). The transducer has been placed at the apex of the left ventricle (apex beat on the left side of the chest) and the ultrasound beam then is aligned to be parallel with the color flow jet emanating into the left atrium. The peak velocity is 4.9 meters/second. This translates into a peak pressure gradient between the left ventricle (LV) and the left atrium of 96 mm Hg. This means the left ventricular pressure is 96 mm Hg higher than the left atrial pressure in systole. This dog's systolic systemic arterial blood pressure was measured to be 145 mm Hg. What is his left atrial pressure during systole?

This tracing also shows the effect of a premature beat on hemodynamics. The third beat comes in too early (i.e., it is premature). This gives the left ventricle less time to fill because of the shorter diastolic interval. Consequently, the stroke volume of the premature beat is reduced which results in a reduced systolic systemic arterial blood pressure and a lesser peak velocity of blood flow on this continuous wave Doppler trace.

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