Figure 1.

Basic elements of the left ventricular pressure-volume (PV) diagram. (A) The normal PV loop has 4 discrete phases. Beginning at end-diastole, when the mitral valve closes, in the bottom right hand corner of the loop is isovolumic contraction. During this phase, ventricular pressure increases without any changes in ventricular volume because both the mitral and aortic valves are closed. Then comes the ejection phase when the aortic valve opens as ventricular pressure exceeds diastolic pressure. At the end of ejection, the point of end-systole is reached (top left corner of the loop), and isovolumic relaxation begins. This gives way to the filling phase when ventricular pressure falls below left atrial pressure and the mitral valve opens. (B) The PV loop is bound by 2 fundamental relationships such that the top left corner of the loop (end-systole) is determined by the end-systolic pressure-volume relationship (ESPVR), while the bottom portion of the loop is bound by the nonlinear end-diastolic pressure-volume relationship (EDPVR). (C) The ESPVR’s slope—called end-systolic elastance (E_es), provides a load-independent estimate of contractility. A larger E_es, indicating a steeper ESPVR, implies greater contractility and vice versa. (D) The PV loop is also a helpful tool for visualizing myocardial energetics. The area within the loop, or stroke work (SW), represents the energy exerted during each cardiac cycle to eject blood into the systemic circulation. The potential energy is the energy stored in myofilaments after systolic contraction and is represented by the area bound by the ESPVR and EDPVR, but outside the PV loop. PV area is the sum of potential energy and SW and is linearly related to myocardial oxygen consumption. Figure produced with BioRender.