Influence of acute hemodynamic changes on the peak velocity of contractile element shortening and maximum velocity obtained by the calibrated apex cardiography in dogs.

The effect of various alterations in preload, afterload and inotropic state of the left ventricle on the noninvasive peak velocity of contractile element shortening (Vpm) and maximum velocity of contractile element shortening (Vmax) was studied in the anesthetized dogs in an attempt to test the methods and clarify some of the determinants of these parameters. Calibrated displacement left apex cardiogram obtained with time constant 3 sec and calibrated first derivative of apex cardiogram were recorded simultaneously with left ventricular pressure and its first derivative, electrocardiogram and phonocardiogram. The values of Vpm obtained from catheterization and calibrated apex cardiography were similar in magnitude and standard deviations under various hemodynamic interventions. A highly significant relation was found between these invasive and noninvasive parameters of myocardial contractility. Both Vpm and Vmax were elevated during the administrations of isoprenaline and strophanthin, where only Vpm showed a decrease after extreme volume or pressure load. In conclusion, the results from this study suggest that Vpm and Vmax of the calibrated apex cardiography are a reliable noninvasive tool for assessing left ventricular function; furthermore, Vpm is relatively load independent, whereas Vmax is virtually unchanged over a broad range of loading conditions.