Hemodynamic effects of exercise in patients with aortic stenosis

Abstract

Hemodynamic data obtained by right and left heart catheterization at rest and during exercise in thirty-two patients with aortic stenosis were reviewed. Eighteen patients had either minimal or no aortic regurgitation (group I) and fourteen patients had moderate to moderately severe aortic regurgitation (group II). The mean systolic pressure gradient (ΔP) across the aortic valve decreased or remained unchanged during exercise in eleven of eighteen patients in group I and in nine of fourteen patients in group II. Net forward aortic valve systolic flow (AVSF) increased during exercise in fourteen of eighteen patients in group I and in thirteen of fourteen patients in group II. Thus, in some patients the change in ΔP during exercise appears to be at variance with the predictability implied by the Gorlin equation which states that ΔP should be directly related to (AVSF) 2. It is unlikely that this discrepancy can be explained on the basis of a systematic measuring error involving one or more of the various factors in the equation. This suggests that the aortic valve may not behave as a fixed orifice under all hemodynamic conditions, and that orifice hydraulics might be different depending on the mechanics of contraction. Average cardiac index (CI) was 2.5 L. per minute per M 2. at rest and 3.8 L. per minute per M 2. during exercise for patients in group 1, and 2.2 L. per minute per M 2. at rest and 3.9 L. per minute per M 2. during exercise for patients in group 2. Arterial and left ventricular systolic and diastolic pressures increased, and systemic resistance decreased during exercise. Thus, resting cardiac output is maintained and it increases during exercise at the expense of marked elevation in both systolic and diastolic pressures in the left ventricle. An analysis of the relationship between stroke work index (SWI) and left ventricular end diastolic pressure (LV edp) in patients from group I revealed, in general, two types of responses to exercise. Six patients had an increase in SWI averaging 39 per cent associated with a 67 per cent increase in LV edp. In sharp contrast, ten other patients demonstrated an increase in SWI averaging only 1.3 per cent whereas LV edp increased by an average of 129 per cent. It is apparent therefore that the response to exercise makes it possible to separate patients with remaining myocardial reserve from those without. Thus, exercise data in patients with aortic stenosis provide objective, quantitative information useful in making a decision when and if to perform corrective surgery.