Abstract
BACKGROUND: Parkinson's disease (PD) is a progressive neurodegenerative disorder that causes motor symptoms and autonomic dysfunction. However, autonomic function tests commonly performed in PD can only evaluate either the sympathetic or parasympathetic nervous system. Therefore, the purpose of this pilot study is to investigate whether power spectral analysis of heart rate variability could detect both sympathetic and parasympathetic nervous dysfunctions in patients with PD. METHODS: Seventeen patients with PD and 11 healthy control subjects underwent electrocardiogram recording for the spectral analysis of heart rate variability to obtain values of low-frequency (LF) (0.04-0.15 Hz) and high-frequency (HF) (0.15-0.4 Hz) powers. Moreover, we examined the coefficient of variation of R-R intervals (CVRR) as a parameter of parasympathetic function in all participants and performed (123)I-metaiodobenzylguanidine scintigraphy to measure the heart-to-mediastinum ratio as a parameter of cardiac sympathetic innervation in patients with PD. RESULTS: The median age of control subjects and PD patients was 63 and 66 years old, respectively. The median Hoehn and Yahr scale of PD patients was stage 2. The values of resting LF and HF powers widely varied. The median values of resting LF powers of control subjects and PD patients and those of HF powers were 169 and 70 ms(2), 279 and 65 ms(2), respectively, the difference was statistically insignificant. Approximately 41% of patients with PD had values below the first quartile of resting LF powers (< 58 ms(2)) or HF powers (< 50 ms(2)); however, no control subject had such low values. Positive correlations were found between resting LF powers and heart-to-mediastinum ratios of (123)I-metaiodobenzylguanidine uptake (r = 0.6) and between resting HF powers and CVRRs (r = 0.7). The resting LF power was also associated with CVRRs and constipation. Furthermore, a positive correlation was observed between resting LF powers and resting HF powers in patients with PD (r = 0.8). CONCLUSIONS: The power spectral analysis of heart rate variability may be useful as a screening tool for detecting autonomic dysfunctions by detecting low resting LF and HF powers in patients with PD. Sympathetic and parasympathetic nerves may be concurrently damaged in patients with PD.