Dysautonomia in mitral valve prolapse.

Many of the clinical features of patients with mitral valve prolapse can logically be attributed to abnormal autonomic neural function. Accordingly, we have studied heart rate and blood pressure response to a standardized Valsalva maneuver and postural test in 44 untreated patients with demonstrated mitral valve prolapse. Fifteen healthy subjects of similar age served as controls. The directional changes of blood pressure and heart rate were similar in control subjects and patients in both tests, but patients differed from control subjects by their widely oscillating heart rate during the upright posture, and their exaggerated and prolonged bradycardia during the recovery phase of the Valsalva maneuver and following their return to recumbency in the postural test. This bradycardia persisted for 30 to 90 seconds after blood pressure returned to control values. Patients also showed a greater respiratory variation of R-R interval, which became especially marked during the adjustment to changes of posture. We postulate an abnormal central modulation of baroreflexes as the best explanation for the dysautonomic responses of symptomatic patients with prolapsed mitral valves.