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Introduction Reduced heart rate variability (HRV), a non-invasive marker of autonomic nervous system (ANS) function, has been linked to cardiovascular (CV) morbidity and mortality. Patients with systemic sclerosis (SSc) carry increased CV risk that is often underestimated by routine risk prediction. We investigated the relationship between HRV and CV risk parameters.Material and Methods We retrospectively analyzed SSc patients (fulfilling the 2013 ACR/EULAR classification criteria, with no manifested CV disease) previously assessed for cardiovascular (CV) risk, who had a 10-second ECG available within 14 days of risk assessment, as the relevant CV risk measures are usually slow progressing.For CV risk assessment, we collected the SCORE, SCORE2, modified SCORE (=SCOREx1.5), pulse wave velocity, ankle-brachial index, and ultrasound [CV risk category, carotid intima-media thickness (cIMT), carotid plaque presence and morphology]. HRV was quantified using the root mean square of successive differences (RMSSD), an index valid for use with ultra-short recordings. RMSSD values were compared with age- (5-year bracket) and sex-matched controls from the published LIFELINES cohort. We also collected clinical and laboratory data and explored their associations with HRV.Results 38 SSc patients [35 female, 3 male; 26 limited cutaneous (lc)SSc, 12 diffuse cutaneous (dc)SSc] were included. Mean±SD age was 52.8 ± 13.2 years, disease duration 7.5 ± 7.5 years, mRSS 7.0 ± 8.7, and ESSG activity index 1.6 ± 1.4.RMSSD was significantly reduced in SSc patients compared with matched healthy controls (median 18.1 vs. 26.6; p=0.002)(figure 1-left). This reduction was evident in both lcSSc (median 19.9 vs. 24.6; p=0.015) and dcSSc (median 14.3 vs. 29.2; p=0.039). RMSSD tended to be lower in patients with longer disease duration (>10 years) compared with those with <=10 years (p=0.066).In dcSSc, RMSSD was independently associated with increased cIMT (beta=-0.33per ms; p=0.002), even after adjustment for major CV risk factors (age, sex, systolic blood pressure, LDL cholesterol, smoking, diabetes)(figure 1-right).RMSSD was significantly reduced in patients classified as having a high/very high CV risk by carotid ultrasound compared with those at low risk (median 13.7 vs. 20.8, p=0.03). RMSSD was also lower in patients with carotid plaques compared with those without, although this did not reach statistical significance (p=0.074).Conclusions Autonomic dysfunction may represent both a marker of and a possible contributor to CV risk in SSc, a possibility that warrants prospective investigation.Acknowledgment Supported by MHCR023728.Abstract P.138 Figure 1Heart rate variability reflects subclinical atherosclerosis in patients with systemic sclerosis