Does normal pump function belie muscle dysfunction in patients with chronic severe mitral regurgitation?

Left ventricular cineangiography and micromanometry were performed simultaneously in 27 patients with chronic severe mitral regurgitation (MR group) and in 23 normal subjects (NL group). Stress (sigma) and volume (V) were computed frame by frame. Measurements were repeated after pharmacologic load manipulation in subsets of MR (n = 10) and NL (n = 11) groups. An inverse relationship (r = -.90) between EFc (ejection fraction determined from a common preload) and sigma es (afterload) was observed for the NL group. For the MR group, 10 of 14 with EFs less than 0.60 and four of 13 with EFs greater than 0.60 had muscle dysfunction, falling below the 95% prediction band of the normal EFc-sigma es relationship. Maximum myocardial stiffness (maxEN) determined from the end-systolic stress-strain relationship of Mirsky, sigma es = maxEN.gamma.loge(Ves/Vo), was 1398 +/- 716 in the MR (n = 10) vs 1165 +/- 394 in the NL group (n = 11, NS). EF was 0.62 +/- 0.13 in the MR and 0.65 +/- 0.08 in the NL group. Mitral valve surgery was performed on 19 of the patients with MR. All survived and all but one were symptomatically improved; that patient required reoperation in the early postoperative period because of transverse midventricular disruption. Thus, contractile function as assessed by stress-strain and EFc-afterload relationships is frequently normal in individuals with MR when EF is normal. When EF is depressed, contractile function as assessed by EFc-afterload relationships is frequently depressed, but this does not preclude a satisfactory surgical result.