We aimed to characterize the relationship between cardiac sympathetic and parasympathetic dysfunction employing cardiac 123I-meta-iodobenzylguanidine (MIBG) uptake and other autonomic function parameters in Parkinson's disease (PD). 79 PD patients were studied. We performed 123I-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 123I-MIBG uptake did not vary significantly among the Hoehn-Yahr (H-Y) stages. There was a significant correlation between cardiac 123I-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 123I-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 123I-MIBG myocardial scintigraphy in PD and contributes to the development of orthostatic hypotension.
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