Left ventricular function in systole and diastole in aortic incompetence.

Left ventricular pressure-volume relationships were studied in 30 patients with aortic incompetence: six with an acute lesion, 21 with chronic disease and three patients in whom a cusp perforation was superimposed on chronic disease. In acute aortic incompetence, systolic function was depressed and in diastole an unprepared ventricle with a normal modulus of elasticity and a normal rate of change of instantaneous stiffness of the pressure-volume relationship was unable to tolerate the volume load, so that the early diastolic and end-diastolic pressures were elevated. Compliance was greatly reduced at these volumes because the ventricle was operating on the steep portion of its pressure-volume curve. In chronic aortic imcompetence, systolic function was, however, normal but adaptive processes allowed the ventricle to operate with a smaller rate of change of instantaneous stiffness and a flatter pressure-volume curve, so that the volume load could be accommodated at a lower end-diastolic pressure. In patients with an acute phase superimposed on chronic disease, the sudden additional volume overload shifted the position of the diastolic pressure of the patient from the adaptive pressure-volume curve of chronic aortic incompetence, so that although the rate of change of instantaneous stiffness was low, the lowest diastolic pressure recorded and the left ventricular end-diastolic pressures were elevated.