Association of culprit lesion plaque characteristics with flow restoration post-fibrinolysis in ST-segment elevation myocardial infarction: an intravascular ultrasound-virtual histology study

Background: Not every patient achieves normal coronary flow following fibrinolysis in STEMI (ST-segment elevation myocardial infarction). The culprit lesion plaque characteristics play a prominent role in the coronary flow before and during percutaneous coronary intervention. The main purpose was to determine the culprit lesion plaque features by virtual histology-intravascular ultrasound (VH-IVUS) in patients with STEMI following fibrinolysis in relation to baseline coronary angiogram TIMI (thrombolysis in myocardial infarction) flow. Pre-intervention IVUS was undertaken in 61 patients with STEMI after successful fibrinolysis. After the coronary angiogram, they were separated into the TIMI1-2 flow group (n = 31) and TIMI 3 flow group (n = 30). Culprit lesion plaque composition was evaluated by VH-IVUS. Results: On gray-scale IVUS, the lesion external elastic membrane cross-sectional area (EEM CSA) was significantly higher in the TIMI 1-2 groups as compared to the TIMI 3 group (15.71 +/- 3.73 mm(2) vs 13.91 +/- 2.94 mm(2), p = 0.041) with no significant difference in plaque burden (82.42% vs. 81.65%, p = 0.306) and plaque volume (108.3 mm(3) vs. 94.3 mm(3), p = 0.194). On VH-IVUS, at the minimal luminal area site (MLS), the fibrous area (5.83 mm(2) vs. 4.37 mm(2), p = 0.024), necrotic core (NC) area (0.95 mm(2) vs. 0.59 mm(2), p < 0.001), and NC percentage (11% vs. 7.1%, p = 0.024) were higher in the TIMI 1-2 groups in contrast to the TIMI 3 group. The absolute necrotic core (NC) volume (8.3 mm(3) vs. 3.65 mm(3), p < 0.001) and NC percentage (9.3% vs. 6.0%, p = 0.007) were significantly higher in the TIMI 1-2 groups as compared to the TIMI 3 group. Absolute dense calcium (DC) volume was higher in TIMI 1-2 groups with a trend towards significance (1.0 mm(3) vs.0.75 mm(3), p = 0.051). In multivariate analysis, absolute NC volume was the only independent predictor of TIMI 1-2 flow (odds ratio = 1.561; 95% CI 1.202-2.026, p = 0.001). Receiver operating characteristic curves showed absolute NC volume has best diagnostic accuracy (AUC = 0.816, p < 0.001) to predict TIMI 1-2 flow with an optimal cutoff value of 4.5 mm(3) with sensitivity and specificity of 79% and 61%, respectively. Conclusions: This study exemplifies that the necrotic core component of the culprit lesion plaque in STEMI is associated with the coronary flow after fibrinolysis. The absolute necrotic core volume is a key determinant of flow restoration post-fibrinolysis and aids in prognostication of less than TIMI 3 flow.