Early Natural History of Spontaneous Coronary Artery Dissection

Background: Risks and mechanisms of extension of conservatively managed spontaneous coronary artery dissection (SCAD) remain incompletely understood. Study objectives were to (1) evaluate mechanisms of early SCAD evolution through serial angiographic analysis, and (2) determine predictors of early SCAD progression. Methods and Results: Retrospective registry study of patients with SCAD managed with an initial conservative strategy (n=240). Patients who experienced significant SCAD progression within 14 days, defined as clinical worsening plus new critical coronary obstruction on repeat angiography, were compared with remaining controls. A total of 42 of 240 (17.5%) experienced significant SCAD progression after index conservative approach; 91% by day 6. Isolated intramural hematoma (IMH) at baseline (no intimal dissection) was observed more frequently in those experiencing progression compared with controls (69.1% versus 44.4%;P =0.004). Multivariable predictors of SCAD progression included lesion severity, multivessel involvement, and isolated IMH. To investigate mechanisms of SCAD evolution, all repeat angiograms ≤14 days were compared with corresponding baselines (n=82 patient angiogram pairs). Of those with isolated IMH at baseline, 20% developed intimal dissection at repeat study. IMH was associated with greater longitudinal lesion extension (11.5 versus 2.8 mm;P =0.01), worsening Thrombolysis in Myocardial Infarction flow (−0.8 versus 0.1;P =0.003), and a nonsignificant lower rate of angiographic improvement (20.0% versus 31.3%;P =0.16) compared with the group with baseline intimal dissection. Optical coherence tomography subgroup analysis (n=17) indicated intimo-medial thickness to be lowest at the midpoint of IMH.Conclusions: Conservatively managed SCAD carries a 1:6 hazard for serious deterioration within 6 days. The risk was higher in those with isolated IMH at baseline. IMH often precedes development of intimal dissection, which has implications for mechanisms of SCAD.