RELAXATION-SYSTOLIC PRESSURE RELATION - A LOAD-INDEPENDENT ASSESSMENTOF LEFT-VENTRICULAR CONTRACTILITY

This contribution reviews the regulation of left ventricular pressure (LVP) fall by load and relates this regulation to left ventricular con tractility. Load regulation of LVP fall has to be distinguished from n eurohumoral regulation, from effects induced by arterial reflected wav es and from long-term load effects on contractility. The response of L VP fall to a moderate elevation of systolic LVP is highly variable. It depends on the ratio between the actual systolic pressure and peak is ovolumetric pressure, defined as ''relative load''. Up to a relative l oad of 81% to 84%, LVP fall accelerates. Above this relative load, LVP fall decelerates. Depending on the level of relative load there is a wide variety of effects ranging from moderate acceleration of LVP fall to marked deceleration of LVP fall. Acceleration of LVP fall in respo nse to a load elevation is associated with normal cardiac function, wh ile slowing of LVP fall is associated with impaired cardiac function. Similar but opposite effects are observed with reductions of systolic LVP. Effects of changes in systolic LVP on time constant tau reveal a fair correlation with systolic elastance (Ees), peak dP/dt(max) and re gional fractional shortening (or ejection fraction). There is an excel lent correlation with measured isovolumetric LVP, indicating that cont raction-relaxation coupling is close when contractility is expressed i n terms of peak isovolumetric pressure. Assessment of contractility wi th systolic LVP-relaxation relation is precise and load independent an d can be performed with the sole use of a high-fidelity pressure gauge positioned in the left ventricular cavity.