Normal sympathetic neural activity in patients with mitral valve prolapse.

The hemodynamic and neurohumoral responses to head-up tilt and isometric exercise were studied in 14 mitral valve prolapse (MVP) patients with and 10 MVP patients without complaints and in 16 healthy control subjects. Plasma catecholamines at rest were not different between the three groups and neither were their changes during either test. The hemodynamic changes during head-up tilt were not different between the three groups. The symptomatic MVP patients showed a lower rise in diastolic blood pressure (14.3 +/- 6.4%) than the controls (22.9 +/- 9.6%) (p less than 0.05) during isometric exercise. In view of the fact that the neurohumoral responses to both tests were the same for all groups, we cannot support the suggestions from other studies that MVP patients have an impaired or enhanced sympathetic tone. Moreover, since there were no differences between symptomatic and asymptomatic MVP patients it is doubtful whether the complaints of symptomatic MVP patients are related to a high sympathetic neural activity.