[Prolonged QTc intervals in Parkinson's disease--relation to sudden death and autonomic dysfunction]

Sudden death has been reported in Parkinson's disease (PD), but the cause of death has not been fully clarified. A prolonged QT interval on the electrocardiogram (ECG) of patients without cardiac dysfunction is an independent risk factor for sudden death regardless of etiology. QT prolongation is believed to be related to cardiac autonomic dysfunction. We suspected that QTc intervals, as well as QT intervals, might be related to the clinical characteristics of PD and to the function of the autonomic nervous system in PD and also postulated a relationship between QTc prolongation and sudden death in PD. We investigated the QTc intervals on the ECGs of 48 PD patients (20 males 28 females) aged 64.5 +/- 9.4 years and 44 controls aged 60.0 +/- 8.2 years, and excluded patients with heart disease. QTc intervals were determined by using ECG-8210, ECAPS12 (Nihon-Kohden). The autonomic nervous system was evaluated by measuring CVR-R and performing orthostatic tests. Since the autonomic nervous system is considered to play an important role in the mechanism of diurnal blood pressure variation (DBPV), we assessed DBPV in 19 PD patients by determining blood pressure automatically every 30 minutes for 24 hours with an ambulatory blood pressure monitor (90202, Space Lab). QTc intervals were significantly longer in the PD patients (412 +/- 26 msec) than in the controls (401 +/- 14 msec) (p < 0.02, t-test). QTc prolongation was significantly correlated with severity according to Hoehn and Yahr stage (r = 0.509, p < 0.001), orthostatic hypotension, and decreased CVR-R ratio but not with duration of PD or treatment. The incidence of QTc prolongation was higher in the PD patients with non-dipper type DBPV than in those with the dipper type. Two of the PD patients died suddenly. Their QTc intervals a year before their death were 451 msec and 470 msec, respectively, suggesting that cardiac dysautonomia may have been involved in the cause of their death. These findings suggest that cardiac autonomic dysfunction is related to the severity of PD, and that it may predispose such patients to cardiac disorders including sudden cardiac death.