Cardiac autonomic modulation at rest and during orthostatic stress among different systemic sclerosis subsets

Objective: To compare autonomic heart rate variability (HRV) parameters at rest and during active stand in a population of SSc patients, taking into account SSc subsets age-matched to healthy control subjects. Methods: Sixty-nine consecutive SSc patients were enrolled in study; these included 12 subjects with early SSc, 39 with limited cutaneous (lcSSc) and 18 with diffuse cutaneous SSc (dcSSc) along with 36 age-and sex-matched healthy controls (HC). ECG and respiration were recorded in supine position and in orthostatism (ORT). HRV analysis was performed on samples of 300 beats. Spectral analysis identified two oscillatory components, low frequency (LFnu, sympathetic) and high frequency (HFnu, vagal). Symbolic analysis identified three patterns, 0 V%, (sympathetic) and 2UV% and 2LV%, (vagal). The %Delta ORT was calculated from the differences between HRV in ORT and SUP, normalized (%) by the HRV values at rest. Results: SSc as a whole had higher markers of sympathetic (LF, 0 V%) and lower markers of vagal modulation (HR, 2UV%, 2LV%) compared to HCs. In addition, %Delta LFnu, %Delta HFnu, %Delta 0V,%Delta 2UV and %Delta 2LV were lower in SSc than HC. dcSSc and lcSSc were dissimilar to HC as far as rest indexes were concerned (up arrow LF/HF, up arrow LFnu, down arrow HFnu, up arrow 0 V% and down arrow 2UV%) while no differences could be detected between HC and EaSSc. Conclusion: SSc showed a reduced vagal and increased sympathetic modulation at rest and a blunted autonomic response to ORT in comparison to HC. These alterations were mostly detectable in the advanced and fibrotic forms of SSc (dcSSc and lcSSc), while EaSSc were similar to HC.