Evaluation of pressure-derived indices of right ventricular contractility

Myocardial function was studied in 23 subjects using indices of contractility based on the right ventricular pressure pulse. Pressure-velocity curves were plotted during early systole and contractile element velocity was derived. The pressure-velocity curves varied in shape and curves with single, linear descending slopes occurred in only 7 subjects. The other pressure-velocity curves were either biphasic or hyperbolic in form. The derivation of Vmax and Vpm and beat-to-beat analysis of these indices was therefore difficult. The effects of a number of physiological variables, e.g. right ventricular enddiastolic pressure, respiration and the infusion of isoprenaline were examined. It was demonstrated that Vmax and Vpm were not independent of the loading conditions of the ventricle. The infusion of isoprenaline changed the shape of the pressure-velocity curves and increased the problems of analysis. The theoretical and practical difficulties involved in this type of analysis are discussed.