Pathological analysis of aspirated materials from the culprit lesion in patients with acute myocardial infarction

OBJECTIVE: To analyze the components of retrieved materials from the culprit lesion in ST-segment elevation myocardial infarction (STEMI) patients by manual aspiration during primary percutaneous coronary intervention (PCI). METHODS: Visible retrieved materials were collected, fixed in formalin and processed for paraffin embedding, sectioned and stained with hematoxylin and eosin (HE). The retrieved materials were microscopically divided into erythrocyte-rich thrombi, platelet/fibrin-rich thrombi, combined thrombi (similar proportions of erythrocytes and platelet/fibrin components), atherosclerotic plaque materials and edematous components. Based on pathological findings, thrombus materials were classified into fresh ( 5 d) after formation. All patients were further classified into plaque positive and plaque negative groups. Clinical and angiographic data were also obtained for analyzing possible association between pathological findings and surrogates of myocardial reperfusion, including myocardial blush grade (MBG), enzymatic estimated infarction size (peak CK and CK-MB levels), left ventricular end diastolic diameter (LVEDD) and left ventricular ejection fraction (LVEF) which were assessed 16 h after procedure. RESULTS: Visible samples were collected from 49 patients by manual catheter aspiration (thrombus components in 46 patients, atherosclerotic plaque only in 3 patients). Frequency of erythrocyte-rich thrombi, platelet/fibrin-rich thrombi and combined thrombi were 41.3% (19/46), 30.4% (14/46) and 28.2% (13/46), respectively. The incidence of fresh, lytic, fresh/lytic and organized thrombi were 47.8% (22/46), 32.6% (15/46), 10.9% (5/46) and 8.7% (4/46), respectively. Plaque materials were found in 57.1% (28/49) patients, including ruptured plaque accompanied by thrombus formation [8.2% (4/49)], fibrous plaque [6.1% (3/49)] and thickened intima [2.0% (1/49)]. Baseline characteristics did not differ between plaque positive (n = 28) and plaque negative (n = 21) groups. Ratios of MBG 3 were higher in plaque positive group than in plaque negative group [82.1% (23/28) vs. 52.4% (11/21), P = 0.025]. Peak CK and CK-MB levels were lower in the former than in the later [(1705 +/- 1647) U/L vs. (2629 +/- 2013) U/L, P = 0.042; (146 +/- 136) microg/L vs. (258 +/- 215) microg/L, P = 0.016; respectively]. Furthermore, LVEF were higher in plaque positive group than in plaque negative group (0.59 +/- 0.10 vs. 0.52 +/- 0.08, P = 0.012). CONCLUSION: Manual catheter aspiration during primary PCI in STEMI patients is an effective way for removing thrombus and plaque materials, and plaque debulking before stenting or pre-dilation and this procedure might probably improve myocardial reperfusion, limit infarction size and improve cardiac function.