PracticeUpdate: Cardiology - Winter 2018

EDITOR’S PICKS 10

Regression of Diffuse Ventricular Fibrosis Following Catheter Ablation in Patients With Atrial Fibrillation and Systolic Dysfunction JACC: Clinical Electrophysiology Take-home message • This study compared outcomes in 36 patients with persistent atrial fibrillation and an idiopathic cardiomyopathy who were randomly assigned to treatment using catheter ablation (CA) or medical rate control (MRC) to compare the effects of these treatments on ventricular remodeling. An additional 16 individuals served as normal controls. At baseline, myocardial T1 time was higher in both groups of patients compared with controls. At 6 months, myocardial T1 remained higher in both groups of patients than in normal controls. However, myocardial T1 was significantly decreased in the CA group compared with the MRC group. Additionally, the left ventricular ejection fraction was significantly improved in the CA group compared with the MRC group at 6 months. • These findings suggest that diffuse ventricular fibrosis regresses when CA is used to treat atrial fibrillation-mediated cardiomyopathy. The authors suggest that this indicates that it may be important to treat these arrhythmias quickly to help prevent ventricular remodeling. COMMENT By John M. Miller MD Lower T1 Times After AF Ablation in Heart Failure Patients –What’s the Big Deal? P rabhu et al, in a sub-study of the CAMERA-MRI trial (Cathe- ter Ablation versus Medical Rate Control in Atrial Fibrillation [AF] and Systolic Dysfunction – a Magnetic Resonance Imaging [MRI]-Guided Multi-centre Randomised Controlled Trial), provide results of MRI and left ventricular (LV) systolic function changes in patients with heart failure and persistent AF who either underwent catheter ablation (CA) to restore and maintain sinus rhythm, or standard rate control during ongoing AF. Only 18 patients were in each group, with another 16 patients without AF serving as controls. The authors report mildly (but statistically significantly) decreased T1 times in CA patients compared with rate control patients, and, although T1 times were better, they were still worse than control patients’ values – in small groups of patients, over a short follow-up.

Abstract OBJECTIVES This study sought to determine if diffuse ventricular fibrosis improves in patients with atrial fibrillation (AF)-mediated cardiomyo- pathy following the restoration of sinus rhythm. BACKGROUND AF coexists in 30% of heart failure (HF) patients and may be an underrecognized reversible cause of left ventricular systolic dys- function. Myocardial fibrosis is the hallmark of adverse cardiac remodeling in HF, yet its revers- ibility is unclear. METHODS Patients with persistent AF and an idiopathic cardiomyopathy (left ventricular ejec- tion fraction [LVEF] ≤45%) were randomized to catheter ablation (CA) or ongoing medical rate control as a pre-specified substudy of the CAM- ERA-MRI (Catheter Ablation versus Medical Rate Control in Atrial Fibrillation and Systolic Dysfunc- tion—an MRI-Guided Multi-centre Randomised

follow-up, finding such marked decreases in fibrosis over a rela- tively short time span is dramatic. Patients with the most fibrosis showed the biggest improvements with CA. The mechanism(s) by which fibrosis regresses is unclear; we used to think that “scar is forever”; however, a growing body of evidence suggests that reverse remodeling – actual regression of fibrosis, with associated improved function – is achievable. This study provides hope that even individuals with advanced LV fibrosis in the setting of AF may be able to reverse this process and enjoy improved function with successful CA, and the results may extend to other forms of arrhythmia-related LV dysfunction such as that associated with frequent premature ventricular com- plexes. Regression of fibrosis and recovery of function – now, THAT is a big deal!

So, what’s the big deal? T1 times strongly correlate with diffuse fibrosis, and shorter times with less fibrosis. Actual decrease in fibrosis on late gadolinium enhancement was seen in the CA group, more than the rate control group, accompanied by sig- nificant (14 percentage point) improvement in ejection fraction (EF) – with one-third of CA patients improving to a normal EF. Although there were relatively few patients and only 6 months of

Dr. Miller is Professor of Medicine at Indiana University School of Medicine as well as Director of Clinical Cardiac Electrophysiology and the Cardiac Electrophysiology Training Program at Indiana University in Indianapolis, Indiana.

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