Characterization of Irreversible Myocardial Injury in Cardiomyopathies by Contrast-enhanced CMR

Overview

Different studies have shown that fibrosis of the heart increases the risk for a sudden death from e.g. arrhythmias. Magnetic Resonance Imaging (CMR) can easily identify even small areas of fibrosis in the heart muscle after contrast agent application (Gadolinium). With the development of faster scanners and new contrast agents, the detection of small fibrotic areas may even be improved. In this study, we will apply dedicated T1- and T2-weighted CMR sequences before and after administration of Gadolinium-based contrast (Gadobutrol, Gadovist(r)), the study parameters will be full cardiac function, areas of edema, areas of inflammation and areas of fibrosis. We hypothesize, that we can detect fibrotic areas in the myocardium using Gadobutrol (Gadovist (r)) better than with the commonly used Gadolinium-DTPA contrast agents. We also hypothesize, that fibrosis of the myocardium is correlated to prognosis of the patients.

Dilated forms of cardiomyopathies present with left ventricular enlargement and reduced ejection fraction. Myocardial fibrosis as assessed by gradient echo sequences after contrast application ("late enhancement") has been proven to be of outstanding value for the detection of small irreversibly injured lesions and has been used to accurately characterize scarred tissue in infarcts (Kim et al, Circulation 1999), myocarditis (Mahrholdt et al., Circulation 2004), and hypertrophic cardiomyopathy (Moon et al., J Am Coll Cardiol 2004). Whereas fibrosis pattern have been described for non-ischemic cardiomyopathies (Mahrholdt et al., Eur Heart J 2005), little is known about the specific regional distribution of fibrous tissue within the group of dilated forms. McCrohon et al. have described a mid-mural and a patchy pattern in patients with global LV dysfunction and no evidence of relevant coronary artery disease (McCrohon et al., Circulation 2003). This study however, did not include right ventricular cardiomyopathy patients and patients with isolated non-compaction as two important dilated forms of cardiomyopathy. Justification/relevance/purpose The presence of fibrosis in dilated forms of cardiomyopathy may be predictive of progression of left ventricular dysfunction over time, as it may represent irreversible damage. Gadobutrol will be used as the only contrast agent in this study; the significantly higher relaxivity as compared to other contrast agents will potentially allow the visualization of small, focal areas of irreversible injury in the myocardium, thus increasing sensitivity of the method to identify even localized fibrotic areas. Objective, hypothesis We attempt to define disease-specific patterns of extent and spatial distribution of irreversible tissue injury within the group of dilated forms of cardiomyopathies. We hypothesize that in patients with dilated cardiomyopathies certain patterns of late enhancement can be identified, which are useful for a more specific phenotyping. We also hypothesize that the use of Gadobutrol (Gadovist®) as the only contrast agent identifies small areas of irreversible tissue injury better than standard contrast agents and may be beneficial for diagnosing small fibrotic changes.