Effect of coronary hyperemia on Emax and oxygen consumption in blood-perfused rabbit hearts. Energetic consequences of Gregg's phenomenon.

To assess the relation between increases in contractile function and oxygen consumption (VO2) during increased coronary flow (Gregg's phenomenon), we measured the end-systolic pressure-volume relation and the relation between VO2 and left ventricular systolic pressure-volume area (PVA, a measure of total mechanical energy output) in blood-perfused, isovolumically contracting rabbit hearts during control and intracoronary adenosine infusion. During adenosine infusion at a constant perfusion pressure (93 +/- 11 mm Hg), coronary flow increased by 99 +/- 76% (p less than 0.01), and the slope of the end-systolic pressure-volume relation, Emax (ventricular contractility index), increased by 18 +/- 15% (p less than 0.01). When compared at the same left ventricular volume, PVA increased by 20 +/- 14% (p less than 0.01) and VO2 by 19 +/- 15% (p less than 0.01) with adenosine. The VO2-PVA relation was linear under each condition (both median r = 0.98). With increased coronary flow, the VO2-intercept of the VO2-PVA ...