Response of sympathetic nervous system activity to dynamic exercise in patients with chronic mitral regurgitation and after valve replacement.

ABSTRACT

To evaluate sympathetic activity during dynamic exercise, 8 patients with mitral regurgitation (MR), 17 patients after mitral valve replacement (MVR) and 5 control subjects were studied by echocardiography, right heart catheterization and by estimation of plasma catecholamines from the right atrium during supine bicycle exercise. No differences in left ventricular (LV) systolic function were noted at rest and during exercise between the patients with MR and control subjects, but it was significantly lower in patients with MVR (p < 0.05) than in control subjects. Plasma norepinephrine (NE) levels during exercise were significantly higher in patients with MR and MVR than in control subjects (p < 0.01 and p < 0.05, respectively). Significant rise in plasma epinephrine levels were noted only in patients with MVR (p < 0.05) during exercise. The relationship of systolic blood pressure/end-systolic dimension and plasma NE levels during exercise, showed lower LV inotropic reserve in patients than in control subjects. Cardiac index (CI) and plasma NE relationship further showed that rise in CI at peak exercise was achieved in patients by a compensatory greater increase in plasma NE. Thus in MR, myocardial dysfunction may be manifested during exercise by a compensatory sympathetic activation and that it continues after MVR.