Using a calibrated displacement transducer, the total amplitude of the systolic wave of the left apexcardiogram (S), its first derivative (dS) and the normalized first derivative (nS), were evaluated as noninvasive indices of left ventricular function in human subjects. A strong correlation was present between peak dS and S in normal subjects (r=0.95, P less than 0.001). At an identical S, abnormal hearts had a lower peak dS, and this allowed a separation between groups with normal and abnormal ventricular dynamics. The index peak nS was significantly lower in patients with congestive cardiomyopathy (P less than 0.005) and ischemica heart disease in the presence of a low ejection fraction (P less than 0.001). It correlated significantly with LVEDP (r=-0.69, P less than 0.001), with ejection fraction (r=0.66, P less than 0.001) and with left ventricular contractility indices derived from isovolumic left ventricular pressure and its first derivative, recorded simultaneously by means of high fidelity micromanometers (peak VCE: r=0.76; Vmax total pressure: r=0.70; peak dP/dt: r = 0.69; P less than 0.001). The index peak nS was superior to S and peak dS, being less variable, independent of thorax circumference and better correlated with hemodynamic parameters. A close relationship was also present between the total amplitude of the atrial wave (A) and its peak first derivative (peak dA) in normal subjects (r = 0.98, P less than 0.001). For an identical A wave amplitude, patients with an increased left ventricular anddiastolic volume had lower values for peak dA (P less than 0.001).