Abstract Background Spontaneous coronary artery dissection (SCAD) is an increasingly recognised cause of non-atherosclerotic myocardial infarction (MI). Systemic inflammatory diseases are commonly associated with SCAD patients, but the link between inflammatory diseases and SCAD remains unclear. Purpose To determine the prevalence of systemic inflammatory disease (SID) and elevated inflammatory markers (EIM) at SCAD presentation. To compare long-term outcomes between SCAD patients with and without SID, and with and without EIM at presentation. Methods We reviewed patients enrolled in the Canadian SCAD Study who had laboratory measurements of inflammatory markers at presentation with SCAD. We compared the baseline demographics, presence of SID, presentation characteristics, and long-term outcomes between patients with and without SID, and between patients presenting with and without EIM at time of SCAD. SID was determined using past medical history and patient self-identification. C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) were used as inflammatory biomarkers. Major adverse cardiovascular events (MACE) were defined as the composite of all-cause mortality, stroke or transient ischemic attack, MI, hospitalization for heart failure and unplanned revascularization. Results Of 1307 patients with SCAD, 360 had inflammatory markers measured at presentation. Of these 360 patients, 150 (43.1%) had EIM at presentation, and 13 (3.6%) reported a history of SID. Mean age was 52.9±9.8 years for patients with EIM, vs. 50.8±10.9years for patients without EIM (p=0.06). Patients with EIM had significantly higher body mass index compared to those without EIM (35.5% vs 17.6%, p=0.001). Of the patients with reported SID, there was higher prevalence of diabetes and hypertension. There was no significant difference in mean inflammatory marker levels, ESR (13.4±15.6mm/h vs 13.7±13.2mm/h, p=0.965) and CRP (15.6± 23.1mg/L vs 11.9± 26.8mg/L, p=0.644) among SID vs. no SID patients at SCAD presentation. Overall mean follow-up was 3.7±1.9 years. There was no difference in in-hospital MACE and overall MACE between patients with EIM vs. no EIM, and between SID and no SID cohorts. There were also no significant difference in angiographic findings, fibromuscular dysplasia prevalence, proportion treated conservatively vs. with revascularization in these cohorts. Conclusion There was no significant difference between presentation, laboratory values, treatment, or outcomes between SCAD patients with or without SID, and between patients who present with and without EIM. This suggests that both active inflammation and history of inflammatory diseases do not contribute to SCAD or outcomes.Table 1.SCAD cohort demographics & data