Novel high-burden thrombus criterion: Thrombectomy plus thrombolysis improves microvascular resistance in myocardial infarction

BACKGROUND: The thrombolysis in myocardial infarction (TIMI) thrombus grade has long been used to assess thrombus burden and guide treatment strategies. However, this grading system may not fully capture the complexities of thrombus management during PCI, which has caused potential biases in the selection and application of thrombectomy and coronary thrombolysis in large-scale randomized trials. To address this limitation, a novel high-burden thrombus criterion is proposed, defined as TIMI thrombus grade 4-5 after balloon angioplasty with a 2.0 mm balloon. A retrospective observational study was conducted to evaluate the clinical outcomes of combined thrombectomy/thrombolysis in high-burden thrombus patients, focusing on microcirculatory improvement and reperfusion. METHODS: This retrospective observational study included 175 STEMI patients who underwent emergency PCI and met the novel high-burden thrombus criterion. Patients were classified into three groups according to intraoperative thrombus management strategies: thrombectomy alone, coronary thrombolysis alone, and combined thrombectomy/thrombolysis. Myocardial microcirculatory function was assessed using the index of microvascular resistance (IMR) and TIMI frame count (TFC), and their correlations with left ventricular ejection fraction (EF) were analyzed. IMR reflects microvascular resistance, with higher values indicating poorer myocardial perfusion. RESULTS: No significant differences were observed in baseline clinical characteristics, infarct-related artery, stent implantation, or other factors among the three groups. The IMR in the combined thrombectomy/thrombolysis group was significantly lower than in the thrombectomy group and the thrombolysis group (26.07 ± 12.45 vs. 34.67 ± 11.79 vs. 32.97 ± 13.70, P < 0.01). TFC was also lower in the combined group compared with the other two groups (22.04 ± 9.94 vs. 28.70 ± 12.82 vs. 31.00 ± 12.69, P < 0.01). Compared with the thrombectomy and thrombolysis groups, the combined group demonstrated a higher EF and a lower LVEDd (56.91 ± 7.96 vs. 52.02 ± 10.85 vs. 53.22 ± 7.39, P < 0.01; 49.89 ± 3.78 vs. 50.51 ± 4.33 vs. 54.11 ± 5.39, P < 0.01). Correlation analysis revealed a significant negative association between IMR and EF (ρ = -0.256, P < 0.01). Additionally, symptom onset-to-balloon time (SOBT) correlated significantly with both IMR and TFC (ρ > 0.2, P < 0.01). CONCLUSION: The novel high-burden thrombus criterion provides a precise framework for guiding thrombus management strategies in clinical practice. In STEMI patients with high-burden thrombi after balloon angioplasty, combined thrombectomy/thrombolysis significantly reduces postoperative IMR, improves myocardial perfusion, facilitates left ventricular recovery, and enhances overall prognosis.