Pressure-volume loops in the cath lab. A conductance catheter is used to measure pressure-volume loops in humans. The time landmarks during the cardiac cycle include the following: B, aortic valve opening and the beginning of ejection; C, aortic valve closure; D, mitral valve opening; and A, end-diastole. During diastole (D-A tract) LV filling occurs, with a low end-diastolic LV pressure increase in the normal heart. During isovolumic contraction, or pre-ejection systole, (A-B tract) LV volume is unchanged but LV pressure rises to point B when it equals aortic pressure, and the aortic valve opens: isotonic systole, or systolic ejection phase (B-C tract), starts. When LV systolic emptying ends (C point), the aortic valve closes, and isovolumic diastolic relaxation starts. (C-D tract). Smaller end-systolic volume and higher end-systolic pressure are typical markers of higher contractility. Counter-directional changes identify compromised contractility. Focusing on end-systolic volume and on end-systolic pressure it immediately appears that the upper left corner of the pressure volume loop (C point) quantifies both measures.