Cardiac parasympathetic dysfunction concurrent with cardiac sympathetic denervation in Parkinson's disease

We aimed to characterize the relationship between cardiac sympathetic and parasympathetic dysfunction employing cardiac (123)I-meta-iodobenzylguanidine (MIBG) uptake and other autonomic function parameters in Parkinson's disease (PD). 79 PD patients were studied. We performed (123)I-MIBG myocardial scintigraphy to assess the extent of cardiac sympathetic denervation. Electrocardiogram readings at rest and postural change in blood pressure were also examined. Coefficient variation of RR intervals (CVR-R) was used as an index for cardiac parasympathetic activity. Cardiac (123)I-MIBG uptake did not vary significantly among the Hoehn-Yahr (H-Y) stages. There was a significant correlation between cardiac (123)I-MIBG uptake and CVR-R (early, r=0.457, p<0.001; late, r=0.442, p<0.001). While the correlation was present among the patients who had had the disease less than two years (early, r=0.558, p<0.001; late, r=0.530, p<0.001), the patients with the disease duration longer than two years did not have such a significant correlation. Age, disease duration, corrected QT interval, or postural blood pressure change did not correlate with cardiac (123)I-MIBG uptake. Orthostatic hypotension was observed in 13 out of 72 subjects, and reduced CVR-R was a major determinant for the development of orthostatic hypotension. We conclude that cardiac parasympathetic dysfunction occurs concurrent with sympathetic denervation as revealed by (123)I-MIBG myocardial scintigraphy in PD and contributes to the development of orthostatic hypotension.