Spontaneous coronary artery dissection (SCAD) found typically in young females without classical coronary risk factors is thought to be a very rare cause of acute coronary syndrome (ACS). The prevalence of SCAD in ACS subjects has been unclear, probably due to the nature of coronary angiography. The aim of this study was to use optical coherence tomography (OCT) to investigate the prevalence of SCAD in ACS. This study consisted of 326 patients with ACS (with or without ST-segment elevation) who underwent OCT to explore the entire culprit artery. According to OCT findings, patients were divided into a SCAD, a plaque rupture (PR), and a non-SCAD/non-PR group. OCT revealed 13 (4.0%) SCADs and 160 (49.1%) plaque ruptures in ACS subjects. The percentage of females versus males was greater in the SCAD group (SCAD: 53.8% vs. PR: 20.0% vs. non-SCAD/non-PR: 23.5%, p=0.02) while no difference was observed in age (SCAD: 67.3±13.3 vs. PR: 66.5±11.1 vs. non-SCAD/non-PR: 67.0±10.5, p=0.90). The prevalence of dyslipidemia (SCAD: 30.8% vs. PR: 63.8% vs. non-SCAD/non-PR: 67.5%, p=0.03) and current smoking (SCAD: 7.7% vs. PR: 57.9% vs. non-SCAD/non-PR: 59.7%, p<0.01) were significantly lower in the SCAD group. SCAD is not a rare cause for ACS, especially in females without classical coronary risk factors.

Background— Plaque rupture and secondary thrombus formation play key roles in the onset of acute coronary syndrome (ACS). One pathological study suggested that the morphologies of plaque rupture differed between rest-onset and exertion-triggered rupture in men who experienced sudden death. The aim of the present study was to use optical coherence tomography to investigate the relationship in patients with ACS between the morphology of a ruptured plaque and the patient’s activity at the onset of ACS. Methods and Results— The study population was drawn from 43 consecutive ACS patients (with or without ST-segment elevation) who underwent optical coherence tomography and presented with a ruptured plaque at the culprit site. Patients were divided into a rest group and an exertion group on the basis of their activities at the onset of ACS. The thickness of the broken fibrous cap correlated positively with activity at the onset of ACS. The culprit plaque ruptured at the shoulder more frequently in the exertion group than in the rest group (rest 57% versus exertion 93%, P =0.014). The thickness of the broken fibrous cap in the exertion group was significantly higher than in the rest-onset group (rest onset: 50 μm [interquartile median 15 μm]; exertion: 90 μm [interquartile median 65 μm], P <0.01). Conclusions— The morphologies of exertion-triggered and rest-onset ruptured plaques differ in ACS patients. Our data suggest that a thin-cap fibroatheroma is a lesion predisposed to rupture both at rest and during the patient’s day-to day activity, and some plaque rupture may occur in thick fibrous caps depending on exertion levels.

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