SNOWMASS, COLO. – Detection of myocardial midwall fibrosis via cardiovascular magnetic resonance in patients with nonischemic dilated cardiomyopathy provides prognostic information independent of left ventricular ejection fraction.
"Low LVEF and fibrosis uniquely identify the need for an ICD [implantable cardioverter-defibrillator]. This is new information that helps refine our understanding of whom it is that’s uniquely at risk. We’ve always had these troublesome questions in patients with nonischemic heart failure," Dr. Clyde W. Yancy observed at the Annual Cardiovascular Conference at Snowmass.
He highlighted what he called "very provocative data" in a recent study led by Dr. Sanjay K. Prasad of Royal Brompton Hospital in London. The investigators evaluated 472 consecutive patients with nonischemic dilated cardiomyopathy using late gadolinium cardiovascular magnetic resonance (CMR). Thirty percent of them were found to have midwall fibrosis. Their all-cause mortality rate during a median 5.3 years of prospective follow-up was 26.8%, compared with 10.6% in the 330 patients without fibrosis. An arrhythmic composite event comprising sudden cardiac death (SCD), aborted SCD, or sustained ventricular tachycardia occurred in 29.6% of the group with fibrosis vs. 7% of patients without fibrosis.
Dr. Clyde W. Yancy
In a multivariate analysis adjusted for LVEF and other prognostic factors, the presence of midwall fibrosis was independently associated with a 2.43-fold increased risk of all-cause mortality, a 3.2-fold greater risk of cardiovascular mortality or heart transplantation, a 4.6-fold increase in SCD or aborted SCD, and a 1.6-fold increased likelihood of a composite of heart failure hospitalization, mortality from heart failure, or cardiac transplantation (JAMA 2013;309:896-908).
Dr. Yancy, who chaired the writing committee for the 2013 ACC/AHA Guideline for the Management of Heart Failure, noted that the guidelines grant a strong Class I/Level of Evidence B recommendation for implantation of an ICD for primary prevention in nonischemic dilated cardiomyopathy patients who are in New York Heart Association functional class II or III and have an LVEF of 35% or less. But there is a pressing need for refined implantation criteria. Basing the ICD decision on only these criteria results in a low rate of appropriate shocks, a high frequency of inappropriate shocks, and exclusion from device therapy of a group of patients with a high relative risk of SCD.
The British study provides reason for optimism in this regard. Using a greater than 15% estimated SCD risk based upon LVEF plus midwall fibrosis as a proposed indication for ICD implantation, the investigators found that an additional 12 patients in their cohort would receive an ICD and 43 others would now avoid ICD implantation, noted Dr. Yancy, professor of medicine and of medical social sciences and chief of cardiology at Northwestern University, Chicago.
He reported having no financial conflicts.