Global cardiac function: mechano-energetico-informatics

This review on the global cardiac function covers cardiac mechanics, energetics, and informatics that I have developed with my collaborators over the last 30 years in Japan and USA. We first established Emax (end-systolic maximum elastance or pressure/volume ratio) as a new index of ventricular contractility using canine hearts. We then expanded the Emax concept to PVA (systolic pressure–volume area consisting of external mechanical work and mechanical potential energy) as an innovative measure of total mechanical energy of ventricular contraction and discovered it to be a reliable determinant of ventricular energetics or O2 consumption (VO2). We have discovered that Emax shifts the VO2–PVA relation and the Emax dependency (O2 cost of Emax) varies among different pathophysiological hearts. We also searched for the basis of Emax in crossbridge behavior information contained in an X-ray diffraction of papillary muscle. Recently, we established a new integrative analysis to estimate total Ca2+ recruited for excitation–contraction coupling in a beating heart using the Emax–PVA–VO2 information. These global, mechano-energetico-informatic approaches seem to facilitate better understanding of cardiac function, as required in the present post-genomic era when more physiomic knowledge is required not only in cardiac function but also in all other physiologic functions.