Intravascular Ultrasound Observation of the Mechanism of No-Reflow Phenomenon in Acute Myocardial Infarction

OBJECTIVE To study the mechanism of the no-reflow phenomenon using coronary angiography (CAG) and intravascular ultrasound (IVUS). METHODS A total of 120 patients with acute myocardial infarction (AMI) who successfully underwent indwelling intracoronary stent placement by percutaneous coronary intervention (PCI). All patients underwent pre- and post-PCI CAG and pre-IVUS. No-reflow was defined as post-PCI thrombolysis in myocardial infarction (TIMI) grade 0, 1, or 2 flow in the absence of mechanical obstruction. Normal reflow was defined as TIMI grade 3 flow. The pre-operation reference vascular area, minimal luminal cross-sectional area, plaque cross-sectional area, lesion length, plaque volume and plaque traits were measured by IVUS. RESULTS The no-reflow group was observed in 14 cases (11.6%) and normal blood-flow group in 106 cases (89.4%) based on CAG results. There was no statistically significant difference in the patients' medical history, reference vascular area (no-flow vs. normal-flow; 15.5 ± 3.2 vs. 16.2 ± 3.3, p > 0.05) and lesion length (21.9 ± 5.1 vs. 19.5 ± 4.8, p > 0.05) between the two groups. No-reflow patients had a longer symptom onset to reperfusion time compared to normal blood-flow group [(6.6 ± 3.1) h vs (4.3 ± 2.7) h; p < 0.05] and higher incidence of TIMI flow grade < 3 (71.4% vs 49.0%, p < 0.05). By IVUS examination, the no-reflow group had a significantly increased coronary plaque area and plaque volume compared to normal blood-flow group [(13.7 ± 3.0) mm2 vs (10.2 ± 2.9) mm2; (285.4 ± 99.8) mm3 vs (189.7 ± 86.4) mm3; p < 0.01]. The presence of IVUS-detected soft plaque (57.1% vs. 24.0%, p < 0.01), eccentric plaque (64.2% vs. 33.7%, p < 0.05), plaque rupture (50.0% vs. 21.2%, p < 0.01), and thrombosis (42.8% vs. 15.3%) were significantly more common in no-reflow group. CONCLUSION There was no obvious relationship between the coronary risk factors and no-reflow phenomenon. The symptom onset to reperfusion time, TIMI flow grade before stent deployment, plaque area, soft plaques, eccentric plaques, plaque rupture and thrombosis may be risk factors for the no-reflow phenomenon after PCI.