Time-Dependent Myocardial Necrosis in Patients With ST-Segment-Elevation Myocardial Infarction Without Angiographic Collateral Flow Visualized by Cardiac Magnetic Resonance Imaging: Results From the Multicenter STEMI-SCAR Project

Abstract

Background Acute complete occlusion of a coronary artery results in progressive ischemia, moving from the endocardium to the epicardium (ie, wavefront). Dependent on time to reperfusion and collateral flow, myocardial infarction ( MI ) will manifest, with transmural MI portending poor prognosis. Late gadolinium enhancement cardiac magnetic resonance imaging can detect MI with high diagnostic accuracy. Primary percutaneous coronary intervention is the preferred reperfusion strategy in patients with ST -segment-elevation MI with <12 hours of symptom onset. We sought to visualize time-dependent necrosis in a population with ST -segment-elevation MI by using late gadolinium enhancement cardiac magnetic resonance imaging (STEMI-SCAR project). Methods and Results ST -segment-elevation MI patients with single-vessel disease, complete occlusion with TIMI (Thrombolysis in Myocardial Infarction) score 0, absence of collateral flow (Rentrop score 0), and symptom onset <12 hours were consecutively enrolled. Using late gadolinium enhancement cardiac magnetic resonance imaging, the area at risk and infarct size, myocardial salvage index, transmurality index, and transmurality grade (0-50%, 51-75%, 76-100%) were determined. In total, 164 patients (aged 54±11 years, 80% male) were included. A receiver operating characteristic curve (area under the curve: 0.81) indicating transmural necrosis revealed the best diagnostic cutoff for a symptom-to-balloon time of 121 minutes: patients with >121 minutes demonstrated increased infarct size, transmurality index, and transmurality grade (all P<0.01) and decreased myocardial salvage index ( P<0.001) versus patients with symptom-to-balloon times ≤121 minutes. Conclusions In MI with no residual antegrade and no collateral flow, immediate reperfusion is vital. A symptom-to-balloon time of >121 minutes causes a high grade of transmural necrosis. In this pure ST -segment-elevation MI population, time to reperfusion to salvage myocardium was less than suggested by current guidelines.

Keywords: ST‐segment–elevation myocardial infarction; cardiac magnetic resonance imaging; coronary artery disease; necrosis.

Figure 1

Flowchart demonstrating the study population. CAD indicates coronary arterial disease; CMR, cardiac magnetic resonance; MI, myocardial infarction; STEMI, ST‐segment–elevation myocardial infarction; TIMI, Thrombolysis in Myocardial Infarction.

Figure 2

Transmurality index and myocardial salvage index: time‐dependent parameters. A, Transmurality index increased, with longer symptom‐to‐balloon time (minutes) mirroring the ischemic wavefront. B, In contrast, the myocardial salvage index decreased, with longer symptom‐to‐balloon time (minutes) indicating progressive loss of myocardial salvage.

Figure 3

ROC curve: cutoff of 121 minutes. ROC curve (AUC: 0.81; 95% CI, 0.73–0.90; P<0.0001) indicating transmural myocardial necrosis revealed the best diagnostic cutoff for a symptom‐to‐balloon time of 121 minutes. AUC indicates area under the curve; ROC, Receiver operating characteristic.

Figure 4

Symptom‐to‐balloon time of 106 minutes: subendocardial necrosis. A 46‐year‐old man presenting with chest pain and ST‐segment elevation in the anterior leads. Coronary angiography revealed TIMI 0 occlusion of the LAD (A, arrow); primary PCI with stent implant was performed, resulting in TIMI 3 flow after PCI (D). Symptom‐to‐balloon time was 106 minutes. CMR revealed a preserved global left ventricular ejection fraction (56%) with mild hypokinesia in the anteroseptal and apical wall. Late gadolinium enhancement CMR images revealed subendocardial necrosis (arrows) in the anteroseptal wall (B, C, E) and the apex (E, F), consistent with the region supplied by the infarct‐related artery (LAD). CMR indicates cardiac magnetic resonance; LAD, left anterior descending; PCI, percutaneous coronary intervention; TIMI, Thrombolysis in Myocardial Infarction.

Figure 5

Grade of transmurality at different symptom‐to‐balloon times. The left bar (cutoff: 90‐minute symptom‐to‐balloon time) demonstrates a significant percentage of subendocardial MI at ≤90 minutes of symptom‐to‐balloon time. The middle bar (cutoff: 121 minutes) demonstrates a smaller but still substantial percentage of subendocardial MI ≤121 minutes. The right bar (cutoff: 180 minutes) shows further reduction in the percentage of subendocardial MI ≤180 minutes. MI indicates myocardial infarction.

Figure 6

Symptom‐to‐balloon time of 141 minutes: transmural necrosis and extensive MVO. A 48‐year‐old man presenting with chest pain and ST‐segment elevation in the anterior leads. Coronary angiography revealed TIMI 0 occlusion of the LAD (A); primary PCI with stent implantation was performed, resulting in TIMI 3 flow after PCI (D). Symptom‐to‐balloon time was 141 minutes. CMR revealed impaired left ventricular ejection fraction (38%) with akinesia in the anteroseptal, septal, and apical wall. Late gadolinium enhancement CMR images revealed extensive transmural necrosis with concomitant MVO (arrows) in the anteroseptal and septal wall (B, C, E) and the apex (E, F), consistent with the region supplied by the infarct‐related artery (large LAD). CMR indicates cardiac magnetic resonance; LAD, left anterior descending; MVO, microvascular obstruction; PCI, percutaneous coronary intervention; TIMI, Thrombolysis in Myocardial Infarction.