[Physiology of cardiac performance].
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.
Namba
T
T
2nd Department of Physiology, Okayama University Medical School.
Takaki
M
M
Araki
J
J
Ishioka
K
K
Akashi
T
T
Matsushita
T
T
Fujii
W
W
Suga
H
H
D004452:Echocardiography; D004734:Energy Metabolism; D006321:Heart / Q000502:physiology*; D006801:Humans; D009200:Myocardial Contraction / Q000502:physiology*; D009206:Myocardium / Q000378:metabolism; D010101:Oxygen Consumption