[Mode of production of the splitting of the second heart sound in post-extrasystolic beats].

The changes in left and right ventricular systolic time intervals (LV- and RVSTIs) and split interval of the second heart sound (IIA-IIP interval) associated with post-extrasystolic potentiation were studied in 48 patients including 37 without a significant intracardiac shunt or valvular regurgitation or pulmonary hypertension, 7 with aortic stenosis (AS) and 4 with hypertrophic obstructive cardiomyopathy (HOCM). In 19 out of 37 patients mentioned above, LV- and RVSTIs were measured from carotid pulse and pulmonary arterial pulse waves, and IIA-IIP interval of post-extrasystolic beat with a compensatory pause was compared to that of the preceding sinus beat. In the other 29 patients including AS and HOCM, LVSTI, total electromechanical systole of the right ventricle (Q-IIP) and IIA-IIP interval were compared. There was no significant difference in the coupling index [(compensatory pause-coupling interval)/preceding RR interval X 100(%)] among three groups. The following results were obtained: In all patients without HOCM, post-extrasystolic beats showed wider IIA-IIP interval than the control beats independent upon the diseased entity and severity of cardiac function. In pts with HOCM, a IIA-IIP interval was shortened in post-extrasystolic beats. A IIA-IIP interval at post-extrasystolic beats was prolonged in proportion to the augmentation of coupling index. However, this finding was no longer observed in cases with the coupling index of more than 80%. LVSTI: In patients without HOCM, almost no change or prolongation of left ventricular ejection time (LVET) and shortening of left ventricular preejection period (LPEP) were observed in post-extrasystolic beats. The degree of changes in LVET and LPEP was greater in patients with the abnormal left-sided PEP/ET than in patients with the normal PEP/ET. The degree of changes in LPEP was always greater than that in LVET, therefore, total electromechanical systole of the left ventricle (Q-IIA) was shortened in all patients. In HOCM, a marked prolongation of LVET and a shortening of LPEP were observed. The degree of changes in LVET was greater than that in LPEP, therefore, Q-IIA was prolonged in all patients. RVSTI: Prolongation of right ventricular ejection time (RVET) and shortening of right ventricular preejection period (RPEP) were observed in all patients in post-extrasystolic beats. The degree of changes in RVET and RPEP was increased in patients with the increased right-sided PEP/ET. The degree of changes in RVET was greater than or equal to that in LPEP, therefore, Q-IIP showed slight prolongation or no change.(ABSTRACT TRUNCATED AT 400 WORDS)