Function and structure of the failing left ventricular myocardium in aortic valve disease before and after valve replacement

Abstract

Left ventricular (LV) cineangiography and endomyocardial biopsies were performed preoperatively in 49 patients (pts) with aortic stenosis (AS) and 35 pts with aortic insufficiency (AI). LV failure (group 1) was present in 15 pts with AS and 17 pts with AI. In these pts ejection fraction (EF) was less than 57% and either cardiac index was less than 2.5 L/min/m2 and/or LV end-diastolic pressure was greater than 20 mm Hg. Macroscopic LV hypertrophy was assessed by angiographic muscle mass (LMMI, g/m2). Morphometric evaluation of LV biopsies included the determination of muscle fiber diameter (MFD, mu), percent interstitial fibrosis (IF, %), volume fraction of myofibrils (VFM, %) and the calculation of LV fibrous content (FC, g/m2). Pts of group 1 and 2 were restudied 22.5 and 24.0 months, respectively, after successful aortic valve replacement. Preoperatively, group 1 pts had a significantly higher LMMI, MFD, and FC than did the patients in group 2 (non-failing group consisting of 34 pts with AS and 18 with AI). IF and VFM did not differ. After surgery EF increased significantly from 44% to 59% in group 1, whereas it remained unchanged in group 2 (66%). Although in both groups LMMI and MFD decreased significantly these quantities were increased after surgery in group 1 as compared to group 2. IF, VFM, and FC did not change significantly in group 1 after valve replacement. There was no difference in these latter three quantities between groups 1 and 2 after surgery. It is concluded that 1) macroscopic and microscopic hypertrophy is more marked in the failing than in the non-failing left ventricle, 2) left ventricular pump function is not related to percent interstitial fibrosis, and 3) at an intermediate time after aortic valve replacement pts with previously failing left ventricle show considerable improvement of ejection performance, but residual hypertrophy persists.