COMPARISON OF LEFT VENTRICULAR MYOCARDIAL STRUCTURE AND FUNCTION IN PATIENTS WITH AORTIC STENOSIS -VERSUS- PURE AORTIC REGURGITATION

Objective-To support the structural and functional distinction between Aortic stenosis (AS) and aortic regurgitation (AR). Methods-Specimens taken from 70 selected patients (35 with AS and 35 with AR) undergoing aortic valve replacement (AVR) were analyzed for cardiomyocytes dimensions and structure, interstitial fibrosis and contractile function. For normal values of contractile function 10 donor hearts were analyzed. Results-Cardiomyocytes diameter was higher in AS than in AR (22.7±2.2µm versus 13.2±0.7µm,p<0.001). Length was higher in AR (121.2±9.4µm versus 95.6±3.7µm,p<0.001). Collagen volume fraction was increased in AS and AR but lower in AS specimens (7.7±2.3 versus 8.9±2.3,p=0.01). Myofibril density was reduced in AR (38±4% versus 48±5%, p<0.001). Cardiomyocytes diameter and length were in close relationship with relative LV wall thickness (R2=0.85; p<0.001 and R2=0.68;p=0.003). Cardiomyocytes of AS patients had higher Fpassive (6.6±0.3 kN/m2 versus 4.6±0.2 kN/m2,p<0.001) but their total force was comparable. Fpassive was also significantly higher in AS patients with restrictive than pseudo normal LV filling (7.3±0.5 vs 6.7±0.6,p=0.004). In AS but not in AR patients, Fpassive showed significant relationships with the cardiomyocytes diameter (R2=0.88;p<0.001 versus R2=0.31;p=0.6). Conclusions-LV myocardial structure and function differ in AS and AR allowing for compensative adjustment of the diastolic/systolic properties of the myocardium.