Concurrent Measurement of Left Ventricular dP/dt _max, Isometric Contractile Force and Cardiac Loading in the Intact Monkey

Abstract

Eight rhesus monkeys were implanted with catheters to measure left ventricular and arterial pressure; an isometric strain gauge was sutured onto the myocardium in four of them. The maximum rate of rise of ventricular pressure (dP/dt_maχ) and left ventricular force of contraction (LVF) were determined during positive inotropic responses elicited by administration of isoproterenol and by several controlled behavioral situations. Both dP/dt and LVF increased concomitantly during the testing situations; linear correlation coefficients relating the variables typically exceeded 0.8 (p < 0.01). The possible influence of altered loading conditions on dP/dt was investigated in four animals after surgical denervation of their hearts to eliminate direct neural reflex effects. Arterial pressure and left ventricular filling pressure were increased by infusion of phenylephrine and decreased by nitroglycerine. Alterations in loading did not exert any significant influence on dP/dt_maχ in the intact monkey with a denervated heart.