Abstract Body (Do not enter title and authors here): Introduction:
Spontaneous coronary artery dissection (SCAD) is an important cause of acute coronary syndrome, especially in young and middle-aged women. Little is known about characteristics of SCAD across age groups. While SCAD can occur across a broad age spectrum, age-specific differences in SCAD manifestations are underexplored.

Methods:
Sub-analysis of the iSCAD Registry with stratification of patients into 3 age groups at time of index SCAD: < 40 years (y), 40-65 y and 65+ y. Data are reported for patients with complete investigator case report form and patient baseline questionnaire. Differences of characteristics between groups were calculated across strata using Kruskal-Wallis test or chi-square test, with statistical significance defined as p < 0.05.

Results:
Among 960 eligible participants, mean age was 49.8 y and 93.4% were female (no difference by group). Overall, 88.7% of participants were White. While racial distribution was similar across age groups (p=0.20), the <40 y group had a numerically higher proportion of Black patients (11.2% < 40 y vs. 6.3% 40-65 y vs. 2.4% 65+y). Patients ≥40 years were more likely to have hypertension and hyperlipidemia while patients <40y were more likely to have an inherited connective tissue disorder and pregnancy-related SCAD. Extra-coronary vascular abnormalities were prevalent in all 3 but fibromuscular dysplasia (FMD) was less common in <40 y group. Emotional and physical stressors were not different across groups. Primary clinical presentation of SCAD was most commonly non-ST elevation MI across all groups (p=NS). Younger patients (<40 y) had predominant LAD involvement (69.3% vs. 59.6% 40-65 y vs. 38.2% 65+ y, p< 0.01). Compared to older groups, patients <40 y were less frequently managed with medical therapy only and more frequently received revascularization and mechanical circulatory support.

Conclusions:
In this large multicenter SCAD cohort, age-stratified analyses revealed distinct clinical and angiographic profiles. Patients <40 y had more pregnancy-related SCAD and connective tissue disorders, while older patients had more traditional risk factors and FMD. LAD involvement and revascularization were more common in younger patients. These findings underscore the importance of age-specific approaches to SCAD care.