Cardiac Mechanics and Energetics

Abstract

This review summarizes the first author’s almost 30-year research carried out with his co-workers for a better understanding of the mechanics and energetics of the canine heart beating under various normal and abnormal conditions of preload, afterload, heart rate, and contractility. This research began with Suga’s proposal of Emax (end-systolic maximum elastance) as an index of ventricular contractility on the basis of the left ventricular (LV) pressure-volume (P-V) relationship and its time-varying elastance model. This model demonstrates a temporal and spatial integration of crossbridge activities within the ventricular wall. On the basis of this model, Suga further established PVA (systolic P-V area) as a measure of the total mechanical energy generated by ventricular contraction. We then experimentally found that PVA closely correlates with myocardial oxygen consumption (Vo2) at a given Emax. and that the Vo2-PVA relation shifts up and down with increases and decreases, respectively, in Emax. The Vo2-PVA relation indicates the oxygen cost of PVA and separates Vo2 into PVA-independent and PVA-dependent components. The PVA-independent Vo2-Emax relation indicates the oxygen cost of Emax. Our two-decade research has indicated that this Vo2-PVA-Emax framework is a new paradigm to characterize the mechanoenergetics of normal and pathological hearts.