Amplitude of the first heart sound at rest and during exercise in normal subjects and in patients with coronary heart disease.

The response of S1 amplitude to exercise stress was investigated in patients with coronary heart disease. Phonocardiograms were recorded at rest and during a multistage bicycle ergometer exercise test in a group of 22 patients with angina pectoris and documented coronary disease, and in a normal control group comprised of 32 men. A symmetrical bandpass filter with 100-Hz center frequency and a 12 db per octave slope was used. Mean S1 amplitude increased approximately linearly with heart rate from rest to maximal exercise through several levels of submaximal effort in both control groups. An increase in heart rate of 40 beats above resting levels resulted in a mean increase in S1 amplitude of 281 per cent in the control group. There was a significantly smaller (p less than 0.01) mean increase in the patient group, 195 per cent. In 5 patients the S1 amplitude during exercise at the load precipitating angina was lower than at the highest load that could be tolerated without pain. S1 amplitude is easily measured and may provide a clinically useful method for evaluation of left ventricular function and documentation of an abnormal left ventricular response to exercise stress.