Clinical significance of intracoronary thrombus aspirated during primary percutaneous intervention: An immunohistopathological study

Background: Manual thrombus aspiration during primary percutaneous intervention provides us with aspirated thrombus sample, that may contain material from the disrupted plaque. Immunohistopathological analysis of thrombus can yield valuable information about the clinical and cardiovascular outcomes and possible mechanisms of myocardial infarction. Material and Methods: We studied and analysed the immunohistopathological features of coronary thrombus aspirated from patients undergoing primary percutaneous coronary angioplasty. Immunohistological staining included markers namely CD68, SMA and CD34 for macrophages, smooth muscle actin and endothelium, respectively. Major adverse cardiac events, angiographic outcome and infarct size were also noted. Results: Fifty-three patients (Mean age - 51.3 ± 13 years; males-47) who underwent primary percutaneous coronary intervention with aspiration thrombectomy were enrolled. Thrombus was successfully aspirated in 40 of 53 patients (75.4%). Patients with successful thrombus aspiration had higher ST-segment resolution (≥ 50%) as compared to patients with failed thrombus aspiration. Presence of RBC-rich thrombus on microscopy was more commonly associated with post-procedure TIMI flow of < 2 as compared to patients with fibrin-rich thrombus and a trend towards lower myocardial blush grade < 2 (P = 0.10), and a significantly higher final infarct size (37.5 ± 5% vs 25 ± 15%; P = 0.04 of myocardium) on nuclear scan. Immunohistology revealed presence of plaque material in 72% (26/36) of the samples. Conclusions: Immunohistopathological evaluation of intracoronary thrombus may be of prognostic importance. High prevalence of plaque material in the aspirated intracoronary thrombus suggests plaque rupture as a possible etiology for vessel occlusion in these patients