A pilot study on short term heart rate variability & its correlation with disease activity in Indian patients with rheumatoid arthritis

BACKGROUND & OBJECTIVES: Cardiovascular complications may lead to mortality in patients with rheumatoid arthritis (RA). We assessed heart rate variability (HRV), an important autonomic function, to quantify the risk for cardiovascular complications in Indian patients with RA. METHODS: The study was carried out in RA patients (n=45) diagnosed as per American College of Rheumatology criteria and healthy controls. HRV recording and analysis was done using Nevrokard software using time and frequency domain analyses. The overall autonomic tone, parasympathetic drive, sympathetic drive and sympatho-vagal ratio were quantified by using various parameters. It included standard deviation of all R-R intervals (SDNN), standard deviation of successive differences between adjoining normal cycles (SDSD), root-mean square of successive differences (RMSSD), and number of R-R intervals differing by >50 ms from adjacent intervals (NN50) in the time domain analysis. In frequency domain analysis, low frequency (LF) and high frequency (HF), LF/HF and total power were assessed. RESULTS: Demographic profile was comparable between groups; however, systolic BP was higher in patients with RA. SDNN, SDSD, RMSSD, NN50, LF and HF power and total power (ms × ms) were significantly lower in patients with RA versus healthy controls (P<0.001). Disease activity score at 28 joints indicating severity of the disease was significantly and positively correlated with SDSD (r=0.375, R(2)=14.06; P=0.045) while LF and HF power (ms × ms) were significantly and inversely correlated with rheumatoid factor (r=-0.438 and -0.445; R(2)=19.1 and 19.8; P=0.017 and 0.016, respectively). INTERPRETATION & CONCLUSIONS: HRV was significantly altered in patients with RA and independently associated with disease activity. Hence autonomic function testing, using HRV, may be useful as part of cardiovascular risk assessment in these patients.