title: [Physiology of cardiac performance].
abstract: We previously proposed i) Emax (end-systolic maximum elastance of the ventricle) as an index of contractility independent of preload and afterload and ii) PVA (systolic pressure-volume area of the ventricle) as a measure of the total mechanical energy generated by the ventricular contraction. Emax is defined as the slope of the end-systolic pressure-volume relation, which is relatively linear within the normal working range of the left ventricle. A working pressure-volume point starts from the end-diastolic pressure-volume curve, comes close to or slightly exceeds the end-systolic pressure-volume line, and returns to the end-diastolic curve. Thus, the end-diastolic and end-systolic pressure-volume curves envelop a family of pressure-volume trajectories of variously loaded contractions in a stable contractility. Emax increases with enhanced contractility and decreases with depressed contractility. PVA is an area between the end-diastolic and end-systolic pressure-volume curves on the origin side of the systolic pressure-volume trajectory. PVA linearly correlates with myocardial oxygen consumption regardless of ventricular loading conditions in a given Emax and this load-independent oxygen consumption-PVA relation is elevated with an enhanced Emax. Consequently, Emax and PVA have proved to be key measures and concepts in the physiology of cardiac performance.
authors.affiliation: 2nd Department of Physiology, Okayama University Medical School.
authors.forename: T
authors.initials: T
authors.lastname: Namba
authors.forename: M
authors.initials: M
authors.lastname: Takaki
authors.forename: J
authors.initials: J
authors.lastname: Araki
authors.forename: K
authors.initials: K
authors.lastname: Ishioka
authors.forename: T
authors.initials: T
authors.lastname: Akashi
authors.forename: T
authors.initials: T
authors.lastname: Matsushita
authors.forename: W
authors.initials: W
authors.lastname: Fujii
authors.forename: H
authors.initials: H
authors.lastname: Suga
mesh_terms: D004452:Echocardiography; D004734:Energy Metabolism; D006321:Heart / Q000502:physiology*; D006801:Humans; D009200:Myocardial Contraction / Q000502:physiology*; D009206:Myocardium / Q000378:metabolism; D010101:Oxygen Consumption