Cardiac Energetics: From Emax to Pressure–volume Area

Summary 1. To celebrate this Festschrift for Professor Colin Gibbs, as an invited speaker, I would like to review briefly my 35 year research career in cardiac physiology. 2. My career started in the late 1960s in Tokyo with my serendipitous discovery of E max (ventricular end‐systolic maximum elastance) as a load‐independent contractility index based on the time‐varying elastance (E(t)) model of the ventricle. Professor K Sagawa at the Johns Hopkins University, USA, whom I joined in 1971, encouraged me to go further. 3. The next serendipitous event in my career was the discovery of ventricular pressure–volume area (PVA) as a measure of total mechanical energy of ventricular contraction in the late 1970s. The PVA concept was theoretically deducible from the E(t) and E max concept and correlated surprisingly well with ventricular O 2 consumption (V o 2 ). 4. Professor Gibbs' intuitive recognition of the significance of PVA in myocardial energetics in the 1980–1990s greatly encouraged me thereafter. The third serendipitous event in my career occurred in the mid 1990s and was my discovery of a novel integrative analysis method to assess the total amount of Ca 2+ recruited in each excitation–contraction coupling from the decay rate of postextrasystolic potentiation, taking advantage of the E max –PVA–V o 2 framework. 5. I am now hoping to experience one more serendipitous experience by developing an integrative analysis method of cross‐bridge cycling in a beating heart using the E max and PVA concepts.