Noninvasive Evaluation of Left Ventricular Relaxation by Apexcardiogram in Man

To evaiuate left ventricular (LV) relaxation, apexcardiogram (ACG), phonocardiogram (PCG) and electrocardiogram (ECG) were recorded simultaneously in 55 patients [17 normal (NOR), 17 hypertrophic cardiomyopathy (HCM) 13 dilated cardiomyopathy (DCM) and 8 hypertention (HT)]. LV pressure was measured by Millar's micromanometer during cardiac catheterization which was performed within a week after ACG study. Iia-O was taken as the time interval between Iia (aortic component of the second heart sound) and the O-point of ACG. △T was defined as the time interval from the point of ACG coincided with Iia to the point of the downstroke of ACG where the curve had fallen to 50% of the height of the deflection. △T correlated with time constant, an index of LV relaxation, and with LV peak negative dp/dt obtained by catheterization (r=0.63, -0.65 respectively). There was significant prolongation of Iia-O in HCM, DCM and HT when compared to NOR (p<0.001, respectively). There was also significant prolongation of △T in HCM, DCM and HT (p<0.001, p<0.001, p<0.01, respectively). This suggests that in these groups, LV relaxation is prolonged and ACG downstroke falls more slowly during early relaxation than NOR. There was no significant difference in Iia-O but was significant difference in △T between ICM (HCM and DCM) and HT (p<0.05). These result suggests that ACG downstroke pattern from Iia of PCG to the O-point of ACG reflect LV relaxation in HCM DCM and HT.