Left ventricular pressure versus volume relationship

The normally contracting left ventricle ejects blood under pressure and the relationship between left ventricular pressure generation and ejection can be expressed in a plot of developed pressure versus volume. In the idealized pressure-volume loop, the left ventricular end-diastolic pressure is represented by point A. Isovolumic contraction at the beginning of systole is represented by line AB. As the developed left ventricular pressure exceeds that of the aorta, the aortic valve opens at point B. This leads to left ventricular ejection of blood (line BC). The volume of blood ejected (point B minus point C) represents the forward effective stroke volume of this contraction. At end-ejection, the aortic valve closes at point C followed by isovolumic relaxation (line CD). The mitral valve then opens at point D with left ventricular diastolic filling represented by line DA. The shaded area enclosed by the PV loop (ABCD) represents the external left ventricular stroke work, which can be represented mathematically as ∫PdV.