Objective. Multisite photoplethysmography (PPG) cardiovascular assessments can evaluate endothelial, peripheral autonomic and arterial dysfunction. The aim of this pilot study was to investigate the potential clinical utility of the technology in assessing patients with SSc and primary RP (PRP). Methods. Multisite PPG pulse measurements, a reference ankle brachial pressure index (ABPI) and a full clinical assessment were undertaken for three subject groups: SSc, PRP and controls. Endothelial and autonomic function and arterial disease measures were obtained using pulse wave analysis. Results. Nineteen SSc, 19 PRP and 23 control subjects were assessed and compared. Endothelial function was significantly impaired in SSc ( P < 0.02), but with no difference between controls and PRP. Receiver operating characteristic–based classification accuracy was 81% (sensitivity 90%, specificity 74%) for separating SSc from controls and 82% (sensitivity 84%, specificity 79%) for separating SSc from PRP. SSc patients with digital ulcers had significantly lower endothelial function compared with those without ulcers ( P < 0.05). Autonomic dysfunction was suggested in both SSc and PRP and was most exaggerated in patients with diffuse SSc. All groups had overall normal ABPI and arterial stiffness timing measures. Bilateral timing differences at the toes, which represents peripheral occlusive arterial disease, did show increased asymmetry in SSc ( P < 0.02). Conclusion. Multisite PPG pulse technology showed potential diagnostic ability. By using measures of endothelial function, it differentiated SSc from control and PRP subjects with an accuracy of at least 81%. Objective pulse-derived measures of autonomic function and arterial disease in SSc have also been reported in this pilot study.
McKay, N. D., Griffiths, B., Di Maria, C., Hedley, S., Murray, A., & Allen, J. (2014). Novel photoplethysmography cardiovascular assessments in patients with Raynaud's phenomenon and systemic sclerosis: A pilot study. Rheumatology, 53(10), 1855-1863. https://doi.org/10.1093/rheumatology/keu196