Utility of Delayed Enhanced Cardiac Magnetic Resonance in the Assessment of Cardiomyopathies

Heart failure is a major public health problem in the United States, with more than five million individuals afflicted and well over 600,000 new cases diagnosed each year.1 The estimated direct and indirect cost of heart failure is nearly $35 billion for 2008 alone. While coronary artery disease (CAD) is the leading cause of left ventricular (LV) dysfunction, anywhere from a third to one-half of all patients have LV dysfunction in the absence of significant epicardial CAD.2 Most of these patients are labeled with the general diagnosis of idiopathic nonischemic cardiomyopathy (NICMP), as no direct discernible etiology of their myocardial dysfunction is evident. Identifying the specific etiology of HF in these patients can have important prognostic implications.3 However, traditional imaging modalities such as echocardiography, nuclear scintigraphy, or coronary angiography are limited in their ability to specifically evaluate the myocardium and characterize tissue. In fact, even the utility of endomyocardial biopsy is uncertain because of frequent nonspecific findings and the inherent invasiveness and small but finite risk of the procedure.⁴

In recent years, delayed contrast enhancement cardiac magnetic resonance (DE-CMR) has emerged as a powerful noninvasive technique for directly assessing myocardial structure and tissue characterization. Studies have demonstrated its ability to detect both irreversible acute ischemic injury and chronic myocardial infarction with a high level of accuracy.s-11 Using this same technique in patients with NICMP, we have been able to detect unique patterns of myocardial scarring that aid in identifying a specific etiology of NICMP, thereby providing additional prognostic information and occasionally drastically altering patient management. This article will describe the potential role of DE-CMR in assessing patients with cardiomyopathy.