The effect of changes in cardiac frequency on left and right ventricular dP/dt max at different contractile states of the myocardium

Abstract

In 17 canine heart-lung preparations the dependence of frequency potentiation of the right and left ventricular myocardium on the basic inotropic state of the heart was investigated. The effect of unipolar stimulation of the right atrium on dP/dt max in both ventricles was measured. The aortic pressure was maintained constant. Shortly after isolation of the heart, a stepwise increase of rate from 140 to 200 beats/min only had a very weak influence on left ventricular dP/dt max. With deterioration of the myocardium the frequency potentiation of dP/dt max increased considerably. End-diastolic pressure regularly decreased with rising cardiac frequency. Since the real positive inotropic effect is masked by the concomitant fall in diastolic loading, the end-diastolic pressure was maintained constant in a second group of 8 hearts during rate variation. The most pronounced inotropic effect was now found shortly after isolation of the heart. A rate increase of 30 beats/min resulted in a 20% rise of dP/dt max. The frequency potentiation decreased with deterioration of the heart resulting in a 12% dP/dt max increase at an estimated inotropic state of 50% of control. When the contractile state of the heart was improved above the control state by calcium application the frequency potentiation of the myocardium decreased. In the right ventricle similar results were obtained except for the fact that no significant correlation between the steepness of the frequency characteristics and the contractile state of the heart could be found when the end-diastolic pressure was kept constant.

High-energy phosphates, myocardial contractile function and material properties after short periods of oxygen deficiency

“…The different results regarding the ATP-function relationship might arise in part from different ways to judge myocardial function. Especially measurements in the intact circulation are known to be sensitive to changes of the loading conditions and heart rate (25,37,42,43). Regional postischemic measurement of function is also known to be dependent on circulatory changes (1,40) and bears the additional risk of overestimation of an existing injury, since interaction might amplify reduced function (e.g., disturbed excitation leading to a slightly delayed contraction could amplify reduced systolic contraction).…”

Quantitative data on the afterload dependence of left ventricular dP/dtmax in isolated canine hearts

“…76, No. 1 (1981 1978 a, Reeck et al 1978 b) and the interval between the heart beats (Covell et al 1967, Limbourg et al 1971, Schmidt et al 1979.…”

Hemodynamic effects of the D- and L-isomers of sotalol on normal myocardium

“…This type of experiment combined the advantage of measuring myocardial contractility during stable standard loading conditions with the disadvantage of using much higher drug concentrations than measured in humans [6] and a limited relevance to the complex in vivo situation. Most in vivo studies, on the other hand, determine indices of contractility, which are not independent of changes of the loading conditions or of the heart rate caused by the drug in question [8,9].It was thus the aim of our study to undertake an in vivo comparison of effects of D-sotalol on myocardial function and on the peripheral circulation with that of the L-isomer and the racemic DL-sotalol. By using an isovolumic in situ technique, we were able to determine the systolic function independent of changes in the loading conditions in vivo, as shown in several other studies on drug effects [10][11][12].…”

“…This type of experiment combined the advantage of measuring myocardial contractility during stable standard loading conditions with the disadvantage of using much higher drug concentrations than measured in humans [6] and a limited relevance to the complex in vivo situation. Most in vivo studies, on the other hand, determine indices of contractility, which are not independent of changes of the loading conditions or of the heart rate caused by the drug in question [8,9].…”