The Assessment of Left Ventricular Intrinsic Contractility in Pure Rheumatic Mitral Stenosis

Kim, Dong Soo; Lee, Kyung Soon

Abstract

The status of left ventricular (LV) intrinsic contractile function in pure rheumatic mitral stenosis is an unsettled issue. Although the overall LV ejection performance is reduced in a number of patients with MS, it is the product of the interaction of four variables; intrinsic myocardial contractile state, end-diastolic myocardial length(preload), afterload and LV myocardial mass. Although LV intrinsic contractility in MS has been found to be normal in previous studies, we found it to be decreased on the basis of newer techniques for assessing cardiac mechanics. Reliable load-independent indexes of intrinsic contractility using M-mode echocardiography are end-systolic pressure or end-systolic meridian wall stress to end-systolic volume or dimension ratio and fractional fiber shortening to end-systolic stress relations. We assessed LV intrinsic myocardial contractile state as measured by the aforementioned methods in patients with pure rheumatic MS. The results were as follows; 1) The clinical characteristics are no statistical significance of differences between the 2 groups. 2) Preload (LV end-diastolic volume index) was increased in patients with MS(77+/-23 VS 67+/-21 ml/m2, p<0.05). Fractional fiber shortening and LV ejection fraction were significantly lower in patients with MS(31+/-7 VS 40+/-7%, 66+/-9 VS 77+/-8%, p<0.001). 3) End-systolic stress was significantly elevated in the patient population compared with the control subjects (70.1+/-18 VS 50.5+/-10 dynes-cm2x103, p<0.001) The increased in end-systolic stress in the presence of reduced systolic blood pressure(106+/-8 VS 116+/-7mmHg, p<0.001) was due to a higher end-systolic volume index(26+/-12 VS 15+/-6ml/m2 p<0.005) and reduced systolic wall thickening (1.13+/-0.2 VS 1.54+/-0.2cm, p<0.001). 4) The end-systolic stress to volume index ratio and systolic pressure to end-systoli volume ratio were significantly lower in patients with MS(p<0.001). Relation between LV end-systolic wall stress and fractional shortening in patients with MS superimposed on 95% confidence limits of values in 105 normal control subjects derived from a previous study(r=-0.58, p<0.005). Thirty-six(75%) patients were below the 95% confidence limits of normal values.