Cardiovascular autonomic dysfunction in Parkinsonian syndromes

Abstract

Abstract Autonomic nervous system (ANS) disturbances are common in Parkinson's disease (PD), but also in other Parkinsonian syndromes, especially in multiple system atrophy (MSA). The differentiation between various Parkinsonian syndromes may be difficult, but it is important for prognostic and therapeutic purposes. The aim of this study was to determine the ability of different analysis methods to reveal cardiovascular regulation disturbances in PD and to evaluate the diagnostic capacity of autonomic tests to differentiate between various Parkinsonian syndromes. Furthermore, this study aimed to evaluate the relationships between ANS disturbances and the clinical characteristics of PD. In addition, the cardiac autonomic function was evaluated during various sleep stages for the first time in untreated PD patients by using spectral heart rate variability (HRV) measures to determine possible sleep stage specific cardiovascular regulation disturbances. Cardiovascular autonomic reflexes were evaluated in 62 untreated and newly diagnosed PD patients, 34 PD patients under antiparkinsonian medication, 47 MSA patients and 15 patients with progressive supranuclear palsy (PSP). The usefulness of different analysis methods was evaluated in a subgroup of 32 untreated PD patients. A further 21 untreated PD patients underwent one-night polysomnography for nocturnal heart rate variability analysis. PD patients with hypokinesia/rigidity as their initial onset sign had a significantly lower max-min ratio in the deep breathing test than those patients with tremor as the initial sign. MSA patients showed significant reductions in both HRV and blood pressure responses during orthostatic provocation, whereas PSP patients had normal results. Absolute spectral measures yielded the clearest indicators separating the PD patients from the controls, while the cardiovascular reflexes proved more useful than the normalised spectral HRV measures in revealing the differences between the two groups. HRV was abnormally decreased during non-REM sleep in PD patients but not during REM sleep or the S1 sleep stage. The normalized high frequency power was significantly decreased in PD patients during sleep stages S2-4, while the standard deviation of the R-R intervals was increased during the same sleep stages, possibly corresponding to the increased motility of PD patients during these sleep stages. The clinical characteristics of PD deserve particular attention in connection with ANS disturbances, since autonomic failure seems to be more pronounced in PD patients with hypokinesia/rigidity as their initial sign. The evaluation of the autonomic function may also be helpful in the differential diagnosis of Parkinsonian syndromes. Spectral analysis methods should be implemented in the evaluation of ANS dysfunction to achieve the best possible efficacy in the differentiation of pathological responses from normal ones. Nocturnal analysis of cardiovascular regulation revealed new and interesting features of pathologic HRV in PD patients, thus when HRV is evaluated, the different sleep stages should be analysed separately