Featured Article: MRI viability imaging for cardiomyopathies

(APPLIED RADIOLOGY) -- Prabhakar Rajiah, MD and Scott Flamm, MD

Dr. Rajiah is a Clinical Fellow, Cardiovascular Imaging Laboratory, Imaging Institute, and Dr. Flamm is Section Head, Cardiovascular ImagingLaboratory, Imaging Institute, and on the Cardiovascular Medicine staff, Heart and Vascular Institute, Cleveland Clinic, Cleveland, OH.

Abstract: MRI plays an important role in managing patients with cardiomyopathy by determining the presence or extent of ischemic scar or interstitial fibrosis using viability imaging. Delayed Enhancement MRI is an excellent technique for accurate, reproducible detection and quantification of myocardial scar.

Cardiomyopathies are “a heterogeneous group of diseases of the myocardium associated with mechanical and/or electrical dysfunction, which usually but not invariably exhibit inappropriate ventricular hypertrophy or dilatation, due to a variety of etiologies that frequently are genetic. Cardiomyopathies are either confined to the heart or are part of generalized systemic disorders and often lead to cardiovascular death or progressive heart-failure–related disability.” There are multiple classification systems for cardiomyopathies. The most commonly used are those by the World Health Organization (WHO) and American Heart Association (AHA). The WHO classified cardiomyopathies broadly into dilated, hypertrophic, restrictive subtypes, and arrhythmogenic right-ventricular cardiomyopathy. As a result of further insights into the morphological and functional expression of the heart-muscle diseases, based frequently on advances in molecular biology and genetics, the AHA proposed a comprehensive classification of primary cardiomyopathies, which is not restricted by strict morphological definitions.

Cardiac MRI in the evaluation of cardiomyopathy

Cardiac magnetic resonance imaging (MRI) has become a “one-stop shop” imaging modality in the evaluation of various congenital and acquired cardiac disorders, including cardiomyopathies. Although MRI is helpful in evaluation of morphology and function, its most important role in cardiomyopathy is to determine the presence and extent of ischemic scar or interstitial fibrosis using viability imaging. Determination of the underlying cause of cardiomyopathy is essential in deciding further diagnostic and therapeutic options, and ultimately in determining prognosis. Echocardiography, cardiac catheterization and nuclear scintigraphy have limited roles in evaluation, as the appearances are nonspecific. Endomyocardial biopsy is not sensitive and is hindered by sampling error. Cardiac MRI employing viability imaging is an efficient, noninvasive method of characterization of the various cardiomyopathies based on the varied patterns of myocardial enhancement and distribution of scar. Identification of myocardial enhancement is useful in risk stratification, as it is a substrate for arrhythmias, indicates a higher incidence of cardiovascular events, and hence, is a negative prognostic factor.

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