Cardiac magnetic resonance with edema imaging identifies myocardium at risk and predicts worse outcome in patients with non-ST-segment elevation acute coronary syndrome

Abstract

Objectives: The aim of this study was to define the prevalence and significance of myocardial edema in patients with non-ST-segment elevation acute coronary syndrome (NSTE-ACS).

Background: Most patients with NSTE-ACS undergo angiography, yet not all have obstructive coronary artery disease (CAD) requiring revascularization. Identifying patients with myocardium at risk could enhance the effectiveness of an early invasive strategy. Cardiac magnetic resonance (CMR) can demonstrate edematous myocardium subjected to ischemia but has not been used to evaluate NSTE-ACS patients.

Methods: One hundred consecutive patients with NSTE-ACS were prospectively enrolled to undergo 30-min CMR, including T2-weighted edema imaging and late gadolinium enhancement before coronary angiography. Clinical management including revascularization decision-making was performed without CMR results.

Results: Of 88 adequate CMR studies, 57 (64.8%) showed myocardial edema. Obstructive CAD requiring revascularization was present in 87.7% of edema-positive patients versus 25.8% of edema-negative patients (p < 0.001). By multiple logistic regression analysis after adjusting for late gadolinium enhancement, perfusion, and wall motion scores, TIMI risk score was not predictive of obstructive CAD. Conversely, an increase in T2 score by 1 U increased the odds of subsequent coronary revascularization by 5.70 times (95% confidence interval: 2.38 to 13.62, p < 0.001). Adjusting for peak troponin-I, patients with edema showed a higher hazard of a cardiovascular event or death within 6 months after NSTE-ACS compared with those without edema (hazard ratio: 4.47, 95% confidence interval: 1.00 to 20.03; p = 0.050).

Conclusions: In NSTE-ACS patients, rapid CMR identifies reversibly injured myocardium due to obstructive CAD and predicts worse outcomes. Identifying myocardium at risk may help direct appropriate patients toward early invasive management.

Figure 1. Myocardial Edema at Initial Presentation With NSTE-ACS

Magnetic resonance images obtained in a 63-year-old female nonsmoker with chest pain, nonspecific electrocardiographic abnormalities, and troponin-I that increased from 0.04 to 2.36 mg/dl over the initial hours of hospital stay. T2-weighted imaging (A; vertical long-axis plane) shows infero-apical edema (arrow), and late postgadolinium enhancement (B) indicates irreversible injury. There is corresponding wall motion abnormality indicated by abnormal myocardial thickening at end-systole (C) compared with end-diastole (D) of a vertical long-axis cine. NSTE-ACS = non–ST-segment elevation acute coronary syndrome.

Figure 2. Myocardial Edema Without Necrosis in Unstable Angina

Magnetic resonance images were obtained in a 41-year-old male smoker with non–ST-segment elevation acute coronary syndrome and serially negative biomarkers including troponin-I and creatine kinase-myocardial band. T2-weighted imaging (A; horizontal long-axis and serial short axis planes) showed edema (arrows) involving the inferoseptum from base to apex. Edema was present without infarction, on the basis of lack of late gadolinium enhancement at the same slice locations (B). Contrast-to-noise in the edematous versus remote myocardial regions averaged 18.8 ± 5.1, consistent with prior reports using this technique. Resting perfusion showed a mild subendocardial abnormality (C, arrow). End-diastolic (D) and end-systolic (E) frames from a horizontal long-axis cine showed abnormal thickening of the septum (E, arrow) compared with the lateral wall. Overall left ventricular (LV) ejection fraction was 40%. Invasive angiography (F) confirmed high-grade right coronary artery (RCA) stenosis (F, arrow) supplying an occluded left anterior descending coronary artery, prompting surgical revascularization.

Figure 3. Edema at NSTE-ACS Presentation Portends Need for Coronary Revascularization

Presence of ≥70% coronary stenosis requiring revascularization was considerably higher in non–ST-segment elevation acute coronary syndrome (NSTE-ACS) patients with myocardial edema by magnetic resonance imaging compared with those without edema.

Figure 4. Distribution of Patients by Edema and Revascularization Status

Shaded circles indicate adverse events at 60-day follow-up; all but 2 occurred in the non–ST-segment elevation acute coronary syndrome patients who were edema-positive at baseline.

Figure 5. Kaplan-Meier Survival Function Estimates in Patients by Edema Status

Estimated survival functions for the time to major adverse cardiac event or death in non–ST-segment elevation acute coronary syndrome patients indicates a greater cumulative hazard of subsequent events in patients with edema at presentation compared with those without edema.