Study Supports Use of CMR Imaging in Some Heart Patients

A study published on March 5 in The Journal of the American Medical Association (JAMA) supports the use of cardiac magnetic resonance (CMR) imaging to assess fibrosis by late gadolinium enhancement (LGE) and predict the risk of cardiovascular events.

These events include all-cause mortality and sudden cardiac death, in patients with dilated cardiomyopathy.

The prospective, longitudinal study of 472 patients with dilated cardiomyopathy found that LGE-CMR assessment of midwall replacement fibrosis provided independent prognostic information and improved risk stratification, beyond the use of left-ventricular ejection fraction, for all-cause mortality and sudden cardiac death.

Among 142 patients who were found to have midwall fibrosis detected by LGE-CMR, there were 38 deaths (26.8 percent) compared with 35 deaths (10.6 percent) among 330 patients without fibrosis. Both the presence and extent of fibrosis were independently and incrementally associated with all-cause mortality (p <0.001).

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Further, the secondary endpoint of sudden cardiac death (SCD) or aborted SCD due to an appropriate implantable cardioverter-defibrillators shock, nonfatal ventricular fibrillation or sustained ventricular tachycardia occurred in 65 patients (14 percent) with midwall fibrosis. Patients with fibrosis were more than five times more likely to experience SCD or aborted SCD than patients without fibrosis (p <0.001).

The authors conclude that “the potential clinical utility of midwall fibrosis evaluated by LGE-CMR in the risk stratification of patients with dilated cardiomyopathy requires further investigation.”

In a separate JAMA study, LGE-CMR was used to evaluate 1,055 ischemic heart disease patients and found that among 201 patients shown to have regional myocardial wall thinning (end-diastolic wall thickness ≤5.5 mm), 198 had scarring within the thinned area. However, 18 percent of these patients had limited scarring involving less than 50 percent of the thinned region of the wall.

The patients with limited scar burden had improvements in regional wall contractility and their wall thinning was resolved after revascularization, compared with patients with scarring involving more than 50 percent of the thinned area. The findings are inconsistent with common assumptions that viability testing is unnecessary for regions with wall thinning because thinning is synonymous with scarring, according to the authors.

In a related editorial comment, Deepak K. Gupta, MD, Raymond Y. Kwong, MD, MPH, and Marc A. Pfeffer, MD, PhD, FACC, Division of Cardiovascular Medicine, Brigham and Women’s Hospital, Boston, Mass., note that the two studies “provide a consistent message that detailed assessment of tissue composition, in particular fibrosis by LGE, may provide superior information than morphologic parameters, in both ischemic and non-ischemic cardiomyopathies.”

However, more studies are needed before the incremental information gained from LGE-CMR is sufficient to change clinical practice guidelines, they add.

Keywords: Myocardial Ischemia, Boston, Ventricular Fibrillation, Gadolinium, Magnetic Resonance Imaging, Tachycardia, Ventricular, Cicatrix, Stroke Volume, Fibrosis, Magnetic Resonance Spectroscopy, United States, Cardiomyopathy, Dilated, Defibrillators, Implantable, Death, Sudden, Cardiac

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