Abstract & Commentary
Does Late Gadolinium Enhancement on MRI in Atrial Fibrillation Patients Portend a Poor Prognosis?
Edward P. Gerstenfeld, MD
Professor of Medicine, Chief, Cardiac Electrophysiology, University of California, San Francisco
Dr. Gerstenfeld does research for Biosense Webster, Medtronic, and Rhythmia Medical.
Source: Neilan TG, et al. The incidence, pattern, and prognostic value of left ventricular myocardial scar by late gadolinium enhancement in patients with atrial fibrillation. J Am Coll Cardiol 2013;62:2205-2214.
Late gadolinium enhancement (LGE) of the left ventricle on magnetic resonance imaging (MRI) has been shown to correlate with fibrosis and adverse outcomes in a broad group of patients with cardiomyopathy. However, the prognostic significance in patients with atrial fibrillation (AF) has not been studied.
The authors performed high-resolution MRIs on 720 patients referred for ablation of AF at a single center, including 56 with a prior history of myocardial infarction (MI). LGE was detected in 108 patients (15%) overall, and in 13% of patients when those with prior MI were excluded. Mortality was assessed through use of the social security death index and medical record. Patients with LGE were older and more likely to have heart failure and sleep apnea. There were a total of 68 deaths over a median 42 months of follow-up. Mortality was 8.1%/patient-year in patients with LGE compared with 2.3%/patient-year in those without LGE. Excluding patients with prior MI by ECG or clinic history, the multivariate predictors of mortality included age and the extent of LGE, which provided the strongest associations with mortality.
Commentary
AF remains the most common supraventricular arrhythmia, with a mortality in AF patients twice that of age-matched controls. However, multiple studies have shown no mortality benefit to a rhythm control strategy of trying to maintain sinus rhythm compared to a strategy of controlling the ventricular rate. Therefore, it is unclear whether the increased mortality in AF patients is related to the presence of AF or if AF is merely a marker of poor prognosis. Predictors of increased mortality in AF patients have been scarce. LGE has been shown to predict mortality in patients with hypertrophic, ischemic, and non-ischemic cardiomyopathies. Although this study includes a unique subgroup of patients referred for AF ablation, the study raises some interesting questions. Many patients undergoing AF ablation undergo computed tomography (CT) or MRI prior to ablation as part of pulmonary vein mapping. Should MRI be the preferred modality? Although the resolution is lower, MRI does not expose the patient to radiation and may give additional prognostic information. Should those with left ventricular LGE be given special attention and more aggressive risk factor modification? Would earlier treatment of AF prevent the progression of LV fibrosis and LGE, or is it merely a marker of adverse prognosis associated with AF? Is there a role for angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, which may have a role in decreasing fibrosis, in these patients? Do the findings in the patients in this study referred for AF ablation extend to the greater population of patients with AF? As with many studies, the results have posed more questions than answers. At a minimum, I think it is reasonable to assess standard cardiac risk factors in those patients with AF who have LGE identified by MRI and perform aggressive risk-factor modification. In a recent study, patients referred for AF ablation who were randomized to aggressive risk factor management, including weight loss, also had a reduction in recurrent AF after ablation.1 Overall, when approaching the patient with recurrent AF, one should remember that the presence of AF may represent the "tip of the iceberg." While AF may be the presenting complaint, accompanying risk factors such as obesity, hyperlipidemia, diabetes, and coronary artery disease often accompany AF. One should not lose the opportunity to treat all these risk factors. Patients with AF and LGE on MRI may be a group who require heightened attention.
REFERENCE
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Abed HS, et al. Effect of weight reduction and cardiometabolic risk factor management on symptom burden and severity in patients with atrial fibrillation: A randomized clinical trial. JAMA 2013;310:2050-2060.
