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.