Objective: Assessment of cardiac vagal modulation through the analysis of heart rate deceleration capacity (DC) in idiopathic Parkinson’s disease (PD).

Background: Cardiac autonomic dysfunction manifests as a reduced heart rate variability (HRV) in idiopathic PD. Previous HRV studies have reported an impaired sympathetic control of cardiac chronotropism, but inconsistent results exist as to whether parasympathetic modulation of the heart is actually altered in PD [1, 2]. Most existing studies have applied standard approaches to HRV analysis, which do not capture many specific properties of cardiac control dynamics. The novel HRV measure DC quantifies the vagally mediated oscillations of heart rate, with low DC indicating increased risk of adverse events [3].

Method: Conventional HRV measures from the time and frequency domains, as well as features derived from the Phase Rectified Signal Averaging algorithm, were obtained from short-term electrocardiogram recordings in 20 idiopathic PD patients and 27 healthy controls. Linear regression modelling was applied to compare HRV measures after controlling for age, sex, and mean heart rate. The standardized distribution of HRV features was assessed.

Results: Significant changes in HRV were found only in PD patients over 60 years old. Global and intermediate-term HRV measures were significantly reduced in PD patients compared to controls (SDNN: p = 0.023; LF power: p = 0.011). However, differences in conventional beat-to-beat HRV measures, such as rMSSD and HF power, were not statistically significant between PD patients and controls. In contrast, DC values were significantly lower in PD patients than controls (p = 0.038). Additionally, the standardized distribution analysis showed that 15% of PD patients (n = 3) have DC Z-values below the normal range (3-7, mean ± two standard deviations) (Figure 1).

Conclusion: HRV analysis is a sensitive method for the assessment of cardiac autonomic function, yet conventional HRV measures of vagal modulation may not detect cardiac vagal dysfunction in idiopathic PD patients. The novel HRV feature DC may be more appropriate for the short-term non-invasive assessment of subclinical cardiac parasympathetic dysfunction in PD. Further study to examine the association between DC and cardiac adverse events in PD is needed to clarify the clinical relevance of DC in this population.

References: 1. Kallio M et al. (2000). Heart rate variability in patients with untreated Parkinson’s disease. Eur J Neurol 7(6): 667-672 2. Oka H et al. (2011). Cardiovascular dysautonomia in de novo Parkinson’s disease without orthostatic hypotension. Eur J Neurol 18(2): 286-292 3. Bauer A et al. (2006). Deceleration capacity of heart rate as a predictor of mortality after myocardial infarction: cohort study. Lancet 367(9523): 1674-81

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MDS Abstracts - https://www.mdsabstracts.org/abstract/deceleration-capacity-of-heart-rate-is-cardiac-vagal-modulation-impaired-in-idiopathic-parkinsons-disease/