Left ventricular function from end-systolic stress-shortening relations in mitral valve prolapse

Left ventricular (LV) function was studied from end-systolic stress-shortening relations in 13 patients with mitral valve prolapse (MVP). Studies were made noninvasively using M-mode echocardiography with blood pressure measurements on the right arm from a Baumanometer cuff. Fifteen age and sex-matched normal subjects formed the control group. LV end-diastolic dimension was normal in MVP, while shortening fraction (p less than 0.05) and velocity of circumferential fiber shortening (mean Vcf) in the short axis of the ventricle were increased (p less than 0.05). Ventricular afterload, as measured by meridional end-systolic stress was reduced in MVP (p less than 0.01) but the slope of the stress-shortening curve was not different form normal. The decrease in end-systolic stress was related to the severity of prolapse (r = 0.63, p less than 0.05). The study implied that mid- or basal LV contractility was normal in MVP. The increased shortening fraction of the LV minor axis was in keeping with geometrical changes and a reduced ventricular afterload.