Influence of acute hemodynamic changes on the apex cardiogram in dogs

Abstract

The effect of various alterations in preload, afterload and inotropic state of the left ventricle on the apex cardiogram was studied in 42 anesthetized dogs, in an attempt to clarify some of the determinants of the apical impulse. Conventional and calibrated apex cardiograms were recorded simultaneously with high-fidelity left ventricular and arterial pressure tracings, electrocardiogram and first time derivatives (dp/dt) of the apex cardiogram and left ventricular pressure. A definite relation between left ventricular pressure and the apex cardiogram could be demonstrated with regard to the diastolic as well as systolic components of both curves. Higher systolic deflections in the apex cardiogram were found for the same left ventricular systolic pressure whenever left ventricular end-diastolic volume or stroke volume was increased. A high correlation existed between diastolic waves of left ventricular pressure and calibrated precordial pulsation tracings.It was concluded that the amplitude of the systolic complex of the apex cardiogram depends on many factors, whereas the genesis of the diastolic components is probably much simpler. The results presented indicate that noninvasive recording of the apex cardiogram, using a method that measures precordial impulse pressure variations, may provide useful information related to left ventricular function and is particularly valuable in the assessment of left ventricular diastolic pressure events.