Adaptation of the left ventricular function parameters to dynamic exercise in aortic stenosis

The left ventricular volumes, the left ventricular ejection fraction, the stroke volume index and the cardiac index were non-invasively determined in 47 patients suffering from moderate to severe pure aortic stenosis using radionuclide angiography at rest and at peak supine exercise. Each patient was previously submitted to right and left heart catheterization and to selective coronary angiography. The left ventricular ejection fraction decreased significantly during exercise (0.62 +/- 0.09 to 0.59 +/- 0.09, P less than 0.01). End-systolic volume, end-diastolic volume, stroke volume index and cardiac index increased significantly. The stroke volume variations were linked to the end-diastolic volume variations by a strong relationship (r = 0.84, P less than 0.001) and to left ventricular mass by a weak, but significant, inverse relationship (r = -0.42, P less than 0.05). No relation existed between stroke volume index variations and any other variables, particularly systolic gradient, aortic valve area and resting left ventricular ejection fraction. The results suggest that, in aortic stenosis, the adaptation of the left ventricular pump function during exercise is mostly dependent upon the diastolic properties of the left ventricular wall and is limited by the progression of left ventricular hypertrophy, i.e. diastolic stiffness. By contrast, the role of the basal systolic pump function and of the severity of the valvular obstruction seems of limited importance.