To determine if there is a difference between autonomic cardiac control as measured by heart rate variability (HRV) in women with rheumatoid arthritis (RA) compared to a healthy control group.
The RA group (45) and control group (39) were matched for age and body mass index (BMI). Three techniques were used: time domain, frequency domain and Poincarè plot analysis. All possible confounding factors were excluded and the test environment strictly regulated.
Basal heart rate was significantly higher in the RA patients. In the supine position significant differences existed between RA patients and controls (P ≤ 0.01). Indicators of parasympathetic activity showed significantly lower variation in the RA group (root mean square of the standard deviation [RMSSD] = 14.70, percentage of successive normal-to-normal interval differences larger than 50 ms [pNN50] = 0.50, standard deviation [SD]1 = 10.50, high frequency [HF] (ms(2)) = 31) compared to controls (RMSSD = 29.40, pNN50 = 7.8, SD1 = 20.9, HF (ms(2)) = 141.00). Indicators of sympathetic variation were also significantly lower in RA patients (SD2 = 36.70, low frequency [LF] (ms(2)) = 65) compared to controls (SD2 = 49.50, LF (ms(2)) = 175). In the standing position eight variables indicated autonomic impairment by significant differences (P ≤ 0.01) between the groups. The response of the RA group to an orthostatic stressor showed less vagal withdrawal, (P-values for RMSSD = 0.038, pNN50 = 0.022, SD1 = 0.043 and HF [ms(2) ] = 0.008 respectively); and lower sympathetic response (P-values for SD2 = 0.001 and LF [ms(2) ] < 0.001) when compared to controls.
An inability of the autonomic nervous system to efficiently compensate for internal and external environmental changes may predispose RA patients to arrhythmias, thereby increasing cardiovascular mortality. All three methods used showed the same outcome, implying decreased HRV and thus an increased risk for arrhythmias in RA patients. Evaluating the autonomic nervous system might be critical in planning management of RA patients.