Heart rate circadian profile in the differential diagnosis between Parkinson disease and multiple system atrophy.

Clinical diagnostic criteria indicate presence of autonomic features as the primary hallmark of Multiple System Atrophy (MSA). However involvement of the autonomic system is also a recognized feature of Parkinson's Disease (PD), yielding a broad clinical overlap between the two diseases. Laboratory assessments may help in the differential diagnosis between PD and MSA. Ambulatory Monitoring of Blood Pressure (AMBP) is a suitable tool to study the circadian rhythm of blood pressure (BP) and heart rate (HR). Different studies reported a reduction of physiological BP nocturnal dipping in PD and MSA patients, but failed to identify a distinctive pattern discriminating the two diseases. On the other hand, HR nocturnal behavior has not been exhaustively analyzed. In the present study we compared the profiles of HR circadian rhythm in 61 PD and 19 MSA patients who underwent 24 h AMBP. We found higher nocturnal HR (nHR) (71.5 beats/min ± 7.4) in MSA compared with PD (63.8 beats/min ± 9.6) as well as significantly lower nocturnal decline of HR (ndHR) in MSA (7.3% ± 8.2) vs. PD (14% ± 7.5). At a Receiver Operating Curve analysis nHR and ndHR significantly discriminated MSA from PD. nHR showed a sensitivity of 84.2% and a specificity of 62.3% (AUC 0.76; 95% IC 0.65-0.85); ndHR showed a sensitivity of 68% of and a specificity of 77% (AUC 0.72; 95% IC 0.61-0.82). According to our findings, nHR is increased and ndHR is reduced in MSA compared to PD. Moreover, these two indices discriminate between the two diseases with acceptable accuracy.