[Mechanism and clinical usefulness of S4-S1 interval in heart failure associated with left ventricular inflow pattern].

The interval between S4 and S1 detected by auscultation or phonocardiography is prolonged by exacerbation and shortened by improvement of heart failure. The timing of S4, S1, and the terminal point of the A wave of transmitral inflow velocities on pulsed Doppler echocardiography (At) was studied to elucidate the mechanism of the prolongation of the S4-S1 interval on exacerbation of heart failure. The study population consisted of 30 patients, nine with old myocardial infarction, six with dilated cardiomyopathy, six with hypertensive heart disease, nine with chronic hemodialysis, and 17 normal subjects. The interval from the peak of the A wave by apexcardiography and At to the onset of main vibration of S1 were measured as the S4-S1 interval and At-S1 interval, respectively. The P-Q interval and Q-S1 interval were also measured. Both intervals were compared during exacerbation and improvement of heart failure. Patients with P-Q prolongation were excluded. The S4-S1 interval was 102 +/- 24 msec during exacerbation of heart failure or before hemodialysis, and shortened to 76 +/- 18 msec after improvement of heart failure or after hemodialysis. The At-S1 interval was concordantly shortened from 59 +/- 31 msec to 30 +/- 23 msec (p < 0.001). However, both the P-Q interval and Q-S1 interval were not significantly changed before and after improvement of heart failure. The timing of S4 becomes parallel to that of At earlier during the exacerbation of heart failure. Thus, S4-S1 interval is a convenient and useful index to investigate patients with heart failure.