Background The prevalence of cardiovascular autonomic dysfunction (CAN) has previously been described with large variation (10–90%) in patients with systemic lupus erythematosus (SLE). CAN is assessed by heart rate variability (HRV) or cardiovascular autonomic reflex tests (CARTs), but these two methods have not previously been compared in SLE patients. Further, little is known about the autonomic nervous system (ANS) impairments at different stages of CAN. Consequently, the purpose of this study is, in a large cohort of SLE patients, to determine the prevalence of CAN and to characterize the ANS function at different CAN-stages by HRV and CARTs.

Methods CAN was tested in 111 SLE patients with a 5-minute HRV-test and three CARTs. HRV-items reflecting parasympathetic (PNS) function (high frequency power, HFP) and mixed PNS-sympathetic (SNS) function (low frequency power, LFP; total power, TP; LFP/HFP-ratio and peak LF) were calculated. CAN was staged by the number of abnormal CARTs; early CAN: one abnormal CART, definite CAN: two or more abnormal CARTs. Fifty-five SLE patients were age and gender matched to 55 CAN-tested healthy controls (HC).

Results The prevalence of definite CAN in SLE is higher than in HCs (24.1% vs. 1.9%, p=0.001). CAN-stage was significantly associated all HRV-measures, except LF/HF-ratio. SLE patients without definite CAN had lower PNS activity than HCs without definite CAN (HFP: 42.7 vs. 87.5 ms², p=0.006; LFP/HFP-ratio: 1.79 vs. 1.00, p=0.010, resp.). Furthermore, SLE patients with definite CAN had signs of lower mixed PNS-SNS-function as determined by LFP, TP and peak LF (all p<0.05), see table 1.

Conclusions The prevalence of CAN in SLE patients was 12 times higher than in HCs. In SLE patients, early CAN was associated with impaired PNS function, whereas definite CAN was characterized by impaired function of the PNS and SNS.