R-R interval variation in Parkinson's disease and multiple system atrophy.

OBJECTIVE To investigate whether the cardiac R-R interval variation (RRIV) is of value in differentiating patients with Parkinson's disease (PD) from multiple system atrophy (MSA). BACKGROUND RRIV assessment is a simple procedure, reflecting mainly vagal efferent activity. Reduced RRIV was reported in MSA. METHODS RRIV at rest and after 120 s of deep breathing was assessed blindly to clinical diagnosis in 22 PD and 20 MSA patients. The results were compared with data from 23 age-matched healthy subjects. RESULTS RRIV at rest was 7.1 +/- 2.7% in PD and 9.7 +/- 7.2% in MSA, increasing after deep breathing to 11.2 +/- 6.3 and 12.3 +/- 6.6% correspondingly. The frequency of the RRIV abnormalities in the PD group (4/22, 18.2%) and MSA (6/20, 30%) were higher than among controls (P < 0.004). CONCLUSIONS RRIV, either at rest or after deep breathing, may be abnormal both in PD and MSA, but does not distinguish between these disorders.