Evaluation of contractile state of the left ventricle from the peak of the first derivative of the apexcardiogram.

Simultaneous records of the electrocardiogram, phonocardiogram, apexcardiogram (ACG), and the first derivative of the apexcardiogram (dA/dt) were obtained in 50 normal subjects and in 38 patients with ischemic heart disease. This allowed us to measure the ratio of peak dA/dt to total amplitude of the first derivative in percent and the interval from electrical stimulation to peak dA/dt (R to peak dA/dt). In 16 additional normal subjects the effects of pharmacological agents with positive and negative inotropic action were studied with the above parameters. During isoprenaline infusion the ratio of peak to total amplitude dA/dt was increased and the interval R to peak dA/dt was shortened, while after propranolol the ratio of peak dA/dt diminished and the interval R to peak dA/dt showed elongation. In normal subjects the ratio of peak dA/dt averaged 48 +/- 14% and it is significantly lower in patients with ischemic heart disease (32 +/- 13%, p < 0.001). In controls the interval R to peak dA/dt was 73 +/- 15 msec., whereas in ischemic heart disease it showed elongation (121 +/- 15 msec., p < 0.01). It is concluded that the ratio peak dA/dt and the interval R to peak dA/dt, expressing noninvasively the rate of pressure changes and the duration of the development of maximum tension during isovolumic contraction, provide useful information on left ventricular function.