Introduction: Cardiovascular (CV) disease including coronary microvascular dysfunction is the leading cause of morbidity and mortality in patients with autoimmune conditions and may be linked with Raynaud phenomenon (RP). Positron emission tomography/computed tomography (PET/CT) has emerged as the noninvasive gold standard for the evaluation of coronary microvascular function. As such, we sought to determine the prevalence of coronary microvascular dysfunction as assessed by PET/CT-derived coronary flow reserve (MFR) in patients with primary and secondary RP evaluated for dyspnea or chest pain. Materials and methods: Patients with a diagnosis of RP in the electronic health record who underwent dynamic rest-stress 82-Rubidium PET/CT from 09/2012-09/2019 for evaluation of chest pain or dyspnea were studied. Heart rate-blood pressure product corrected MFR was calculated (Corridor 4DM, INVIA). Patients were grouped based on their comorbid autoimmune condition, and differences in MFR and clinical predictors of reduced MFR (< 2.0) were compared between patients and healthy controls (n=17, 35% female, age: 35 ± 5 years, BMI 27 ± 4kg/m 2 ). Results: 49 patients with RP (84% female, age: 65 ± 11 years, BMI: 33 ± 11 kg/m 2 ) were studied. Of these, 11 had primary RP, 18 had systemic sclerosis (SSc) and 20 had other autoimmune diagnosis (n=6 systemic lupus erythematosus, n=6 rheumatoid arthritis, n=4 overlap syndrome, n=2 Sjogren’s syndrome, n=2 inflammatory arthritis). Patients with primary RP had MFR comparable to healthy participants. In patients with secondary RP, only those with underlying SSc had significantly reduced MFR compared to healthy participants (p=0.002, 1.62 ± 0.32 vs 2.22 ± 0.44). In multivariable logistic regression, SSc was an independent predictor of reduced MFR. In addition, there was a modest significant correlation between time since autoimmune disease diagnosis and MFR (r= -0.37; 95% CI: -0.61 to -0.09; p=0.01). Inflammatory markers (sedimentation rate: r= -0.19, C-reactive protein: r= -0.31) were not significantly associated with MFR (p>0.05). Conclusions: Our findings suggest that there is reduced PET/CT MFR compared to healthy participants in patients with SSC and secondary RP, and that SSc may be an independent predictor of reduced MFR. Patients with primary RP had MFR values that were comparable to healthy participants. Larger prospective studies are warranted to fully elucidate the prognostic value of MFR in patients with secondary RP.
