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

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.

Hemodynamic changes during dynamic exercise in patients after mitral valve replacement for chronic mitral regurgitation.

To evaluate hemodynamic changes during dynamic exercise, we investigated 13 patients after mitral valve replacement (MVR) for chronic mitral regurgitation (MR) and 5 control subjects by right heart catheterisation during supine bicycle exercise. According to the sizes of the St. Jude Medical (SJM) prosthesis during MVR, patients were divided into group A (n = 8) with SJM 31mm and group B (n = 5) with SJM 29mm. Significant rise in cardiac index (CI) was noted during exercise in both groups A and B (from 3.3 +/- 0.8 to 5.5 +/- 0.9 l/min/m2, p < 0.01 and from 3.0 +/- 0.6 to 5.6 +/- 0.6 l/min/m2, p < 0.01 respectively) and also in control subjects (from 3.4 +/- 0.7 to 6.2 +/- 0.6 l/min/m2, p < 0.01). Mean pulmonary artery and pulmonary capillary wedge pressure were significantly higher during exercise in patients of both groups A and B than control subjects (p < 0.05 and p < 0.01 respectively). Total pulmonary vascular resistance was significantly higher during exercise in both groups A and B than control subjects (p < 0.05 and p < 0.01 respectively). No difference in hemodynamics were noted between the patients of group A and B during exercise. It is concluded that response of CI to exercise in patients after MVR for chronic MR was adequate in comparison to control subjects irrespective of two different valve sizes.