Is myocardial blood flow per unit mass reduced in patients with severe aortic stenosis compared to normal controls?
Myocardial blood flow per unit mass is reduced in severe aortic stenosis, which appears primarily related to differences in left ventricular stress and reduced contractility.
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 mg/100g.min) in comparison to a group of seven normal control patients (69 +/- 12 ml/100g.min) (P less than 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 covarience; the adjusted mean values were 0.62 +/- 0.03 ml/100g.beat for the AS patients and 0.84 +/- 0.03 ml/100 g.beat for the control patients. There was no overlap between groups in adjusted MBF per beat. Values of MBF per beat and peak stress for a group of ten cardiomyopathy patients 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.
Johnson et al. (Wed,) studied this question.
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