Studies on Apexcardiogram : (I) Cardiac Dynamics in normal Subjects

Abstract

Modern developments in medical electronics have made it possible to record easily and precisely the apexcardiogram (ACG). Moreover, it has been shown that the ACG is of great value in the diagnosis of cardiovascular diseases. Recently, investigations on the ACG have been reported by many workers. Many of them, however, are concerned only with the analyses of patterns of the ACG in normal and abnormal subjects, and there are few reports on the relation of the ACG to cardiac dynamics. The E point of the ACG is described to represent the opening of the aortic valve and the O point, the opening of the mitral valve. The time relation of these points to the 1st heart sound and the 2nd heart sound of the PCG and the Q wave of the ECG is available to determine several dynamic phases of cardiac cycle. On the other hand, the ratio of diastolic filling wave (DFW ratio) to total amplitude of the ACG has been reported to be closely related to the left ventricular end-diastolic pressure. The purpose of this report is to investigate cardiac dynamics, DFW ratio, RFW ratio, and their relations to the cardiac rate in normal subjects. Subiects and Methods Fifty subjects without cardiovascular disease were studied in the basal state. Thirty-nine were men and eleven were women. Their ages ranged from 19 to 45 years, with an average of 31 years. ACG was recorded in the manner described by Benchimol and Dimond, with subjects lying on his left side, raising the left arm, and in mid expiration, using the piezoelectric microphone as a transducer (Fukuda electronics KK, TY 302) and multiplex research recorder (Fukuda electronics KK. MRR-150), at a paper speed of 100 mm/sec. Phonocardiogram (PCG) (the 4th left intercostalspace parasternally) and electrocardiogram (ECG) (lead II) were simultaneously recorded. Measurements of each phase of cardiac cycle, DFR ratio and RFW ratio were made as follows: R-R interval (R-R): R-R interval of the ECG. Systole (Q-11, SYS): Interval from the beginning of the Q wave to the beginning of the aortic component of the 2nd heart sound. Q-E interval or tension time (Q-E, TT): Interval from the beginning of the Q wave to the E point of the ACG.