Plaque instability frequently occurs days or weeks before occlusive coronary thrombosis - A pathological thrombectomy study in primary percutaneous coronary intervention

Background - Acute ST-elevation myocardial infarction (STEMI) is caused by sudden occlusive coronary thrombosis, after plaque disruption; however, a considerable time interval between plaque disturbance and the onset of symptoms has been suggested. We therefore studied the age of intracoronary thrombi, aspirated during angioplasty in patients with acute STEMI. Methods and Results - Percutaneous intracoronary thrombectomy during angioplasty was performed in 211 consecutive STEMI patients within 6 hours after onset of anginal symptoms. The aspirated material was histologically screened on thrombus and plaque components, and thrombus age was classified as fresh ( < 1 day), lytic thrombus ( 1 to 5 days), and organized thrombus ( > 5 days). In all patients, intracoronary-derived material was retrieved in the filter of the collection bottle. Thrombus was identified in 199 (95 %) of 211 patients. In 12 patients (5 %), only plaque components were identified, and in 85 patients (41 %), both thrombus and plaque material were aspirated. In 18 (9 %) of 199 patients, the thrombus was organized, and in 70 patients (35 %), the thrombus showed lytic changes, whereas in 98 (49 %), a completely fresh thrombus was found. In 14 (7 %) of 199 patients, the thrombus showed combined features of both fresh thrombus and organized thrombus. Conclusions - In at least 50 % of patients with acute STEMI, coronary thrombi were days or weeks old. This indicates that sudden coronary occlusion is often preceded by a variable period of plaque instability and thrombus formation, initiated days or weeks before onset of symptoms.