Myocardial fibrosis indicates sudden cardiac death risk

Reed Miller

February 10, 2011

Melbourne, Australia - Magnetic resonance imaging may be able to help identify heart-failure patients who would not benefit from an implantable cardioverter defibrillator (ICD), results of a study published in the February 15, 2011 issue of the Journal of the American College of Cardiology show [1].

Dr Leah Il es (Alfred Hospital, Melbourne, Australia) and colleagues prospectively enrolled 103 heart-failure patients indicated for an ICD for primary prevention of sudden cardiac death based on the current professional guidelines. They used cardiac MRI with late gadolinium enhancement (LGE) to identify regional fibrosis within the myocardium. The MR images were assessed by at least two independent blinded readers.

The median follow-up in the study was 573 days. The MRI with LGE identified regional fibrosis in 31 of 61 (51%) patients with nonischemic cardiomyopathy and in all 42 patients with ischemic cardiomyopathy. In the nonischemic group, nine of 31 ICDs (29%) discharged, and in the ischemic group, six of the 42 ICDs (14%) discharged, a nonsignificant difference. Left ventricular ejection fraction was similar in patients with and without device therapy and those with or without LGE.

However, in nonischemic cardiomyopathy patients without identified regional fibrosis, none of the ICDs discharged. This was a significantly lower discharge rate than the rates observed for both the ischemic cardiomyopathy patients and the nonischemic cardiomyopathy patients with regional fibrosis identified by MRI with LGE (p<0.04 and p<0.01, respectively). Kaplan-Meier analysis showed that patients with nonischemic cardiomyopathy and no regional fibrosis shown by MRI with LGE had significantly better freedom from device therapy and event-free survival than ischemic and nonischemic cardiomyopathy patients with regional fibrosis identified by MRI with LGE.

Although sudden cardiac death is a major cause of death in advanced heart failure patients, most heart-failure patients who receive an ICD for primary prevention of sudden cardiac death never receive device therapy, and the average rate of appropriate ICD shocks per year is about 5%, Iles and colleagues explain. In this study, patients in whom MRI with LGE did not find regional fibrosis had no events, suggesting that this group may be at particularly low risk for sudden cardiac death and may not need an ICD. However, some past studies have found a small number of ICD events even in patients with no regional fibrosis identified by MRI with LGE. Larger studies are needed to clarify the role of this test in risk-stratifying these patients. "Although our results are promising, rather than advocating a single test, we would favor a combination of clinical factors, including scar imaging, to provide the best assessment of risk for [sudden cardiac death] in this vulnerable population," the authors conclude.

In an accompanying editorial [2], Dr James Willerson (Texas Heart Institute, Houston) agrees with Iles et al's conclusion that this method for stratifying patient's risk should be tested in a larger study. "In future studies, it would be important to quantify the volume of fibrosis in patients with and without appropriate ICD discharges. Clearly, there were patients with fibrosis in both groups who did not suffer an ICD discharge," Willerson writes. "It would also be helpful to compare the degree of hypertrophy and frequency of nonsustained ventricular tachycardia with the predictive ability of fibrosis detection by LGE and to determine whether there is additive predictive power in combining the three methods."

The authors report they have no conflicts of interest to disclose .

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