THE NORMAL APEX CARDIOGRAM: ITS TEMPORAL RELATIONSHIP TO ELECTRICAL, ACOUSTIC, AND MECHANICAL CARDIAC EVENTS

The configuration of the apex cardiogram and its temporal relationship to the electrocardiogram, phonocardiogram, carotid pulse, and jugular venous pulse were analyzed in 25 normal subjects. In two patients with rheumatic valvular disease simultaneous electrocardiograms, phonocardiograms, left intraventricular pressure and apex cardiograms were obtained. In all cases the apex cardiogram showed a characteristic and reproducible contour in both its systolic and diastolic components. The curves of the apex cardiogram display all consecutive phases of the cardiac cyle; contraction-and-emptying and relaxation-and-filling. It bears a constant relationship to the phonocardiogram and is more useful as a reference tracing for acoustic events than the electrocardiogram, carotid pulse, or jugular venous pulse. The onset of the systolic wave of the apex cardiogram precedes the rise of left intraventricular pressure and mitral valve closure. The maximal systolic peak of the apex cardiogram occurs simultaneously with the onset of left ventricular ejection and the rise of the carotid pulse pressure. Small deflections are frequently inscribed on the apex cardiogram at the time of mitral, tricuspid, and aortic valve closure. The wave form of the apex cardiogram is caused primarily by movements of the left ventricle against the chest wall. It is thus a translation of the sequence of hemodynamic events occurring in the underlying left ventricle. The inaccuracy of the jugular venous pulse for timing right- and left-sided cardiac events is emphasized.