Inotropic changes in the left ventricle: the effect of changes in heart rate, aortic pressure and end‐diastolic pressure

Abstract

SUMMARY1. Under conditions where heart rate, mean aortic pressure and enddiastolic pressure in the left ventricle are held constant, the intravenous infusion of isoprenaline is accompanied by large changes in dP/dt max in the left ventricle.2. Under similar conditions, during stepwise increments in the rate of infusion of isoprenaline the changes in dP/dt max (measured at a constant paced heart rate) were proportional to changes in the free (intrinsic) heart rate. It is concluded that dP/dt max is a quantitative index of inotropic changes in the left ventricle.3. In comparison to dP/dt max, three other variables which have been used to indicate inotropic changes in the heart (peak pressure in the left ventricle, duration of systole and stroke work at constant end-diastolic pressure), were shown to be unreliable indices of inotropic changes.4. Using dP/dt max to indicate inotropic changes, alteration in the heart rate while mean aortic pressure and end-diastolic pressure in the left ventricle were held constant, and in mean aortic pressure while heart rate and end-diastolic pressure in the left ventricle were held constant, were each shown to be accompanied by small inotropic changes in the heart.5. Under similar conditions, changes in end-diastolic pressure in the left ventricle alone were not accompanied by inotropic changes as indicated by dP/dt max.

THE CARDIOVASCULAR EFFECTS OF ICI 118,587: A β1‐ADRENOCEPTOR PARTIAL AGONIST

“…Before discussing the results it is important to consider problems associated with the measurement of direct effects of compounds on the intact heart. Firstly, quantitative measurements of the inotropic effects of compounds on the heart are technically difficult and of doubtful reliability when obtained in the presence of the large changes in heart rate and blood pressure which may be caused by doses of isoprenaline and noradrenaline (Furnival et al, 1970;Mason, Braunwald, Covell, Sonnenblick & Ross, 1971). However, previous experiments in carefully controlled preparations have shown that the same relative changes in force and rate are brought about by many compounds which act on the heart through the P-adrenoceptor (Furnival, Linden & Snow, 1971: Harry, Kappagoda, Linden & Snow, 1973Robie, Nutter, Moody& McNay, 1974;Bolter & Ledsome, 1976).…”

The inotropic and chronotropic effects of catecholamines on the dog heart

“…The maximum rate of rise of pressure in the left ventricle of the heart, (dP/dt max) measured at a constant heart rate and mean systemic arterial pressure during each series of infusions, was used as an index of inotropic changes (Furnival, Linden & Snow, 1970).…”

Electrical Resynchronization

“…Benefit was demonstrated by an increase in RV dP/dt max , a well-validated index of ventricular systolic performance. 11,12 We selected this as our primary RV outcome because it can be measured independently of ventricular geometry and is insensitive to changes in afterload. Although dP/dt max is affected by alterations in preload, there is no reason to believe that the pacing intervention altered preload acutely, particularly because heart rate was held constant.…”