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Impact of Multiple Myocardial Scars Detected by CMR After STEMI
Study Questions:
What is the prognostic importance of multiple myocardial scars on cardiac magnetic resonance (CMR) in patients following ST-segment elevation myocardial infarction (STEMI)?
Methods:
This was a single-center CMR substudy of DANAMI-3 (Third DANish Study of Optimal Acute Treatment of Patients With ST-Segment Elevation Myocardial Infarction). Included subjects, all of whom underwent successful primary percutaneous coronary intervention (PCI) for STEMI, had CMR during the index admission and follow-up CMR 90 days later. Notable exclusion criteria were atrial fibrillation and advanced chronic kidney disease (estimated glomerular filtration rate <30 ml/min/1.73 m2). T2-weighted imaging, which highlights myocardial edema, was used during index scans to demonstrate myocardial area at risk and thereby identify culprit territories. Late gadolinium enhancement (LGE) imaging was performed during index and follow-up scans to demonstrate acute infarct size and final infarct size, respectively. Multiple scars were said to be present if LGE was found in >1 coronary territory at follow-up. Images were analyzed by two blinded observers, and a third blinded observer reviewed all scans to verify the presence of multiple LGE areas. The primary endpoint comprised all-cause mortality and hospitalization for heart failure.
Results:
At follow-up CMR, 59/704 (8.4%) subjects had LGE in multiple coronary territories. Of these, 51/59 had baseline and follow-up CMR data available. Most of these patients (34, 66%) had nonculprit territory LGE on baseline scans. A small number of patients (7, 14%) had multiple culprit territories. New nonculprit LGE areas developing between index and follow-up CMR were observed in 10 patients (20%); nine of these patients had known multivessel disease on admission, and six underwent nonculprit PCI during the index admission. Compared to patients with LGE in a single coronary territory, patients with multiple infarct areas more frequently had hyperlipidemia (51% vs. 34%, p = 0.009) and pre-existing ischemic heart disease (22% vs. 4%, p < 0.001). Angiographically, patients with multiple infarct areas were more likely to have multivessel disease (78% vs. 38%, p < 0.001), chronic total occlusion of a nonculprit artery (36% vs. 8%, p < 0.001), and left anterior descending culprit lesions (48% vs. 40%, p = 0.005).
During a mean 39-month follow-up period, 20 patients (2.8%) died and 15 (2.1%) were hospitalized for heart failure. LGE in multiple coronary territories was associated with a higher risk of the composite endpoint (hazard ratio, 3.6; 95% confidence interval, 1.6-8.0; p = 0.002). This association remained statistically significant when adjusting for age, multivessel disease, diabetes mellitus, pre-existing ischemic heart disease, and final infarct size, though left ventricular ejection fraction was not considered in the multivariable model because of interaction with multiple-territory LGE.
Conclusions:
Infarction in multiple coronary territories, as evidenced by LGE on CMR, is a negative prognostic indicator among post-STEMI patients.
Perspective:
The strengths of this CMR study include its relatively large size and availability of angiographic data for all patients. Myocardial LGE burden has been shown to be a negative prognostic indicator in virtually every context, from ischemic heart disease to hypertrophic cardiomyopathy and myocarditis, so the findings in this cohort are not surprising. Given the fact that LGE distribution correlated with multivessel disease and previously known ischemic heart disease, it is not clear that a clinician’s assessment of future risk or choice of secondary prevention strategies would be influenced by a CMR finding of multiple-territory LGE.
Keywords: Acute Coronary Syndrome, Cicatrix, Angiography, Coronary Artery Disease, Coronary Occlusion, Diagnostic Imaging, Edema, Gadolinium, Heart Failure, Hyperlipidemias, Magnetic Resonance Imaging, Magnetic Resonance Spectroscopy, Myocardial Infarction, Myocardial Ischemia, Percutaneous Coronary Intervention, Secondary Prevention
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