Patients with heart failure (HF) commonly have persistent atrial fibrillation (AF), and vice versa. Many of these patients are unaware of their AF aside from the heart failure symptoms, but there is mounting evidence that the irregularity of AF and loss of atrial contraction can cause a cardiomyopathy in spite of good ventricular rate control. However, given the challenges of restoring sinus rhythm in these patients, it is unclear how many of these patients should pursue a rhythm control strategy. Several studies have actually suggested no long-term benefit, but this may be related to the limitations of current rhythm control strategies, or to irreversible factors such as ventricular fibrosis that do not allow for recovery of ventricular function even when sinus rhythm is restored.
An important trial, Catheter Ablation Versus Medical Rate Control in Atrial Fibrillation and Systolic Dysfunction (CAMERA-MRI), was published recently in the Journal of the American College of Cardiology.1 The investigators randomized 68 patients with persistent AF and systolic HF to catheter ablation versus continued rate control using medications. Only patients with a non-ischemic cardiomyopathy were studied, theorizing that they would be more likely to benefit compared to patients with coronary disease or valvular heart disease. Importantly, these were not just patients with recurrent persistent AF — they were patients with continuous persistent AF for an average of nearly two years, with 3/4 of patients having long-standing persistent AF over one year. In addition, almost all patients had previously failed amiodarone therapy and multiple cardioversions. The patients assigned to a rate control approach appeared to have controlled ventricular rates based on Holter monitoring.
The results were remarkable. In an intention-to-treat analysis, the improvement in ejection fraction was 18% in the catheter ablation group compared to 4% in the rate control group. Even more striking was that 58% of patients in the ablation group had normalization of the ejection fraction compared to only 9% of patients in the rate control group. Using implantable loop recorder data, the average burden of AF was only 1.6% at six months using a shorter than typical blanking period of only four weeks. There were very few complications. Interestingly, they also found that ventricular scar, detected as delayed enhancement on the pre-ablation MRI, was strongly predictive of an improvement in the ejection fraction. Patients with no scar had a 73% chance of normalizing their ejection fraction at six months.
The CAMERA-MRI study is unusual in that the entire group of patients assigned to ablation improved on average, rather than just the patients who had successful restoration of sinus rhythm as in prior studies. However, there are important considerations when interpreting the results. One problem is the limited follow-up of only six months, and the limited information provided about the rhythm outcome after ablation. To have only a 1.6% AF burden six months following an AF ablation procedure for patients with such advanced AF and HF is much better than success rates published in similar populations in other trials. Can this be reproduced? Was it related to the ablation technique? It is important to note that patients in the ablation group underwent more than just pulmonary vein isolation using point-by-point RF ablation. They also underwent additional ablation to isolate the entire posterior LA wall using a left atrial box lesion guided by Biosense Webster’s CARTO electroanatomic mapping system. Unfortunately, there is little information related to how the ablation was done and what the endpoints were in the EP lab.
Recent preliminary data from the multicenter Catheter Ablation versus Standard conventional Treatment in patients with LEft ventricular dysfunction and Atrial Fibrillation (CASTLE-AF) trial, which was presented at the ESC Congress in August 2017, showed that ablation for AF in patients with systolic HF and an implantable defibrillator was associated with a reduction in AF as well as mortality and heart failure hospitalizations.2 Given the increasing prevalence of both AF and HF, further studies like these are critical, and greater efforts to tackle persistent AF are needed.
- Prabhu S, Taylor AJ, Costello BT, et al. Catheter Ablation Versus Medical Rate Control in Atrial Fibrillation and Systolic Dysfunction: The CAMERA-MRI Study. J Am Coll Cardiol. 2017;70(16):1949-1961. doi: 10.1016/j.jacc.2017.08.041.
- Catheter ablation improves outcomes in patients with heart failure and atrial fibrillation (CASTLE-AF). ESC. Published August 27, 2017. Available online at http://bit.ly/2wG9kS1. Accessed October 20, 2017.