Reduced left ventricular myocardial blood flow per unit mass in aortic stenosis

Abstract

Myocardial blood flow (MBF) per unit mass was measured in 10 patients (pts) with severe aortic stenosis (AS) and no significant aortic insufficiency, normal ejection fractions, and normal coronary arteriograms, using xenon-133 and a multiple crystal scintillation camera. MBF per unit mass was reduced in AS (53 ± 13 ml/100 g.min) in comparison to a group of 7 normal control pts (69 ± 12 ml/100 g.min) (P<0.05). When normalized for heart rate, MBF remained depressed in aortic stenosis (0.65 ± 0.11 ml/100 g.beat). MBF/beat was strongly related to peak left ventricular wall stress in both groups (r = 0.97). Individual values of MBF/beat were normalized for peak stress using an analysis of covariance; the adjusted mean values were 0.62 ± 0.03 ml/100 g.beat for the AS pts and 0.84 ± 0.03 ml/100 g.beat for the control pts. There was no overlap between groups in adjusted MBF per beat. Values of MBF per beat and peak stress for a group of 10 cardiomyopathy pts with depressed contractility were observed to fall close to the regression line for AS patients. The results suggest that variability in resting MBF in these AS patients is due primarily to differences in LV stress and that reduction in MBF per beat in this group may be due to reduced contractility.