Alteration of the left ventricular pressure-volume relationship in man and its effect on the mitral echocardiographic early diastolic closure slope.

Abstract

The previously demonstrated relationship between the mitral valve E-F slope and the rate and timing of early left ventricular (LV) filling has suggested that LV compliance is a major determinant of the E-F slope. Accordingly high fidelity simultaneous pressure-volume (P-V) curves were constructed at rest and following the steady state infusion of low dose (33 .+-. 4 .mu.g/min) nitroglycerin (TNG) for 10 patients undergoing cardiac catheterization. The mitral echogram recorded no more than 5 min prior to the resting and TNG left ventriculograms were compared to the P-V curves so obtained. The increases in the mitral E-Fo slopes observed in all patients with TNG (74 .+-. 13 mm/s-102 .+-. 16 mm/s, P < 0.01) were associated with variable downward shifts of the P-V curves. The greater increases in E-Fo slope were associated with greater downward shifts of the early diastolic P-V curves; smaller increases were associated with less obvious shifts. These early diastolic P-V shifts were associated with increases in the volume of blood entering the LV during the first third of diastole (53 .+-. 6 ml-69 .+-. 8 ml, P < 0.001). The pressure-volume relationship in early diastole is a more important determinant of the mitral E-Fo slope than the late diastolic P-V relationship and probably explains the poor correlation to mean diastolic compliance previously reported.