Increased plasma catecholamine levels in patients with symptomatic mitral valve prolapse.

Total plasma catecholamine levels, plasma norepinephrine levels, heart rate, and systolic and diastolic pressures were measured in 15 symptomatic patients with mitral valve prolapse and in 19 normal subjects in supine baseline conditions and in a standing position. In the 15 symptomatic patients, total plasma catecholamine levels and plasma norepinephrine levels were significantly elevated in both positions, and heart rate was lower than in normal subjects in the supine position but returned to normal in the upright position. Thus, symptomatic patients with mitral valve prolapse demonstrate increased resting sympathetic tone. In addition, the associated supine bradycardia suggested that increased vagal tone might also be present at rest. These observations support the hypothesis of a dual autonomic dysfunction in these patients and could account for some of the clinical manifestations of the mitral valve prolapse syndrome.