Relationship between left ventricular morphology and postoperative cardiac function following valve replacement for mitral stenosis.

The left ventricular myocardium excised from 14 patients who had mitral stenosis and who underwent mitral valve replacement was examined, and myocardial fibrosis was quantitated in relation to cardiac function. Conventional mitral valve replacement was performed with cold potassium-induced cardioplegia associated with systemic hypothermia (28 degrees C rectal temperature) and topical cooling. All 14 patients had perivascular fibrosis; the amounts ranged from 16% to 54% of the whole tissue excised. The mean left ventricular end-diastolic volume index (LVEDVI) determined by M-mode echocardiography increased significantly (p less than 0.001) from 66.9 +/- 4.6 ml/m2 preoperatively to 79.0 +/- 2.9 ml/m2 postoperatively. The difference between preoperative and postoperative LVEDVIs was significantly correlated (p less than 0.01) to the percentage of myocardial fibrosis (r = 0.72), in that the index increased postoperatively when myocardial fibrosis was more than 35% and decreased when fibrosis was less than 35%. After mitral valve replacement, the mean ejection fraction increased when fibrosis was less than 35% of whole tissue (+0.12 +/- 0.04) and decreased when fibrosis was greater than 35% (-0.02 +/- 0.02, p less than 0.01). No measured preoperative hemodynamic parameters were predictive of prognosis. These data suggest that the degree of myocardial fibrosis is related to left ventricular performance after mitral valve replacement.