Contrast-Enhanced Cardiac Magnetic Resonance Imaging Accurately Differentiates Ischemic from Non-Ischemic Etiologies in Newly Diagnosed Cardiomyopathy

Objective: Patients with newly diagnosed cardiomyopathy frequently undergo coronary angiography to exclude significant coronary artery disease (CAD). Contrast-enhanced cardiac magnetic resonance imaging (CE-CMR) can detect myocardial scar in-vivo, and has the potential to identify patients with cardiomyopathy secondary to prior myocardial infarction. Aim: To investigate the accuracy of contrast-enhanced cardiac magnetic resonance imaging (CE-CMR) in differentiating ischemic from non-ischemic cardiomyopathy in patients with new onset heart failure and previously undiagnosed left ventricular systolic dysfunction.Methods: Forty eight patients (mean age 54 ± 8) were prospectively identified from symptoms and echocardiography, and underwent both CE-CMR and angiography. Patients with >70% diameter stenosis in ≥1 major epicardial vessel on angiography were considered to have an ischemic cardiomyopathy. Myocardial scar was assessed using delayed enhancement inversion-recovery imaging after gadolinium administration. Patients with subendocardial enhancement typical of a myocardial infarction were classified as having an ischemic etiology by CE-CMR.Results: Sixteen patients were classified as ischemic by angiography, and of these 15 had subendocardial enhancement on CE-CMR. The sensitivity and negative predictive value for CE-MRI were 94% and 97% respectively for detecting an ischemic cause. However 5 patients with subendocardial enhancement by CE-CMR had no obstructive coronary disease, suggesting misclassification by angiography, and reducing the specificity (82%) of CE-CMR.Conclusion: The lack of subendocardial scar on CE-CMR identifies patients with new-onset heart failure and cardiomyopathy who may not require angiography.