[Diurnal variation of the QT intervals in idiopathic mitral valve prolapse].

Diurnal variation of QT intervals was analyzed using Holter monitoring for 44 patients with mitral valve prolapse (MVP), and the relationship between ECG changes and autonomic nervous dysfunction was assessed by measuring blood catecholamine during bicycle ergometer exercise and various autonomic functional tests. The following results were obtained. 1. The QT intervals in MVP patients had greater diurnal variations and the averaged QTc was in a high level all the time. 2. Positivity of the autonomic functional tests and the catecholamine level after exercise were significantly high in patients of MVP. 3. After catecholamine depletion by beta-blocking agent (carteolol: 15 mg a day, 5 to 12 months' duration), the variation of QTc became less marked. These data indicate the presence of autonomic dysfunction in patients of MVP.