Publication:

POS0929 Micro Vascular Imaging as a Novel Tool to Quantify Blood Flow in the Fingertips in Patients With Systemic Sclerosis vs. Healthy Controls: a Single-Center Feasibility Study

Background Systemic sclerosis (SSc) is characterized by tissue fibrosis and vasculopathy. Raynaud’s phenomenon is present in almost all patients (1). Nailfold video capillaroscopy is an established imaging tool for a morphologic assessment but is not able to quantify blood flow (2). Micro Vascular Imaging (MVI) is a novel ultrasound technique for blood flow quantification, especially of small vessels with low flow (3). The technique has not been used in SSc to quantify blood flow.

          Objectives
          To evaluate Micro Vascular Imaging (MVI) as a novel ultrasound tool for flow quantification of small fingertip vessels in healthy controls (HC) compared to SSc patients.
        
        
          Methods
          In this single-center prospective cohort study MVI scans of the second to fifth fingertip were performed in 20 healthy controls vs. SSc patients. Demographic data were analyzed using descriptive statistics. For flow velocity analysis, MVI peak systolic (PS) and end-diastolic (ED) flow values were used. Receiver operator characteristics (ROC) curves were generated to detect an optimal cut-off value for each parameter to discriminate between HCs vs. SSc patients. Sensitivity and specificity were reported with 95% CI based on Youden’s J.
        
        
          Results
          
            The median age of the 20 HCs was 26 years (19-56), and 13 (65%) were female. 19 (95%) participants were right-handed. Twenty female SSc patients were included. The median age was 60 years (24-79). All SSc patients were right-handed (100%). SSc patients were older than HCs (p<0.0001) and included more female participants (p=0.0083). Some of the recruited SSc patients were past (n=4, 20%) or current (n=2, 10%) smokers, while all HCs were non-smokers (p=0.0293). No differences were found regarding dexterity (p>0.9999). 13 SSc patients had limited cutaneous SSc, five had diffuse cutaneous SSc, one patient was diagnosed with Very Early Diagnosis of Systemic Sclerosis, and one patient had no skin involvement (
            sine
            scleroderma). Eighteen patients (90%) reported the presence of RP.
          
          It was shown that PS flow velocity and ED flow velocity were significantly higher in HCs (Figure 1). For all fingers measured, the difference of the medians (D) for PS velocity was 4.675 cm/s (95% CI 3.3-5.25, p<0.0001), for ED velocity 1.375 cm/s (95% CI 0.85-1.65, p<0.0001). No correlation with age was found, neither in HCs (r2=0.03 for PS flow, r2=0.18 for ED flow), nor in SSc patients (r2=0.08 for PS flow, r2=0.01 for ED flow).
          
            Figure 1.
            
              Comparison of peak systolic (PS) and end-diastolic (ED) blood flow of Digitus II-V in healthy controls (blue) vs. systemic sclerosis patients (red).
            
            
          
          The highest PS velocity was measured on Digitus II with 5.225 cm/s (95% CI 2.95-7.5, p<0.0001), and 2.325 (95% CI 1.1-3.1, p<0.0001) for ED flow velocitiy, while lowest values were observed at Digitus V with PS = 3.325 cm/s (95% CI 2.2-5, p<0.001), and ED = 0.875 cm/s (95% CI 0.6-1.6, p<0.001). For PS flow velocity, an optimal cut-off point of <6.13 cm/s showed excellent sensitivity (0.90, 95% CI 0.70-0.98) and specificity (0.85, 95% CI 0.64-0.95), corresponding to a LR+ of 6.0. For ED flow velocity, the optimal cut-off point was calculated at <2.13 cm/s, sensitivity was 0.85 (95% CI 0.64-0.95), specificity was 0.80 (95% CI 0.58-0.92), corresponding to a LR+ of 4.25.
        
        
          Conclusion
          We present the first study of MVI as a novel imaging technique to measure blood flow velocity in patients with SSc. We report the method’s feasibility and discriminative cut-off points between HCs and SSc. In an extenstion of this study, we aim to longitudinally assess the results with organ manifestations or vascular complications of SSc in a larger cohort.
        
        
          References
          [1]Allanore, Y.; Simms, R.; Distler, O.; Trojanowska, M.; Pope, J.; Denton, C.P.; Varga, J. Systemic Sclerosis. Nat Rev Dis Primers 2015, 1, 15002, doi:10.1038/nrdp.2015.2.
          [2]Cutolo, M. Detection of Microvascular Changes in Systemic Sclerosis and Other Rheumatic Diseases. 13.
          [3]Deegan, A.J.; Wang, R.K. Microvascular Imaging of the Skin. Phys. Med. Biol. 2019, 64, 07TR01, doi:10.1088/1361-6560/ab03f1
        
        
          Disclosure of Interests
          None declared