On the value of apex cardiography for timing intracardiac events

Abstract

The left apex cardiogram was recorded in the dog by means of a pulse transducer with an infinite time constant. The time relation between the left apex cardiogram and left ventricular and aortic pressure tracings (recorded by means of high fidelity micromanometers) and their first time derivatives (dp/dt) was studied. Both the onset of the upstroke and the protodiastolic nadir of the left apex cardiogram and of the left ventricular pressure curve were found to occur nearly simultaneously. This close relation was preserved during various acutely induced hemodynamic changes and during right and left ventricular pacing. The E point of the left apex cardiogram occurred simultaneously with the peak dp/dt of the left ventricular pressure, or followed it with a time lag of 2 to 35 msec. Diastolic waves also occurred simultaneously. It is concluded that the left apex cardiogram provides a reliable noninvasive technique for the timing of intracardiac events.