SNOWMASS, COLO. – Don’t be in a rush to refer a patient with drug-refractory, symptomatic atrial fibrillation (AF) for catheter ablation of the arrhythmia, a prominent electrophysiologist advised at the Annual Cardiovascular Conference at Snowmass.
“AF ablation is not salvation – and that’s coming from somebody who does these procedures. One really needs to be very selective in referring patients for this,” said Dr. N.A. Mark Estes III, professor of medicine and director of cardiac arrhythmia services at Tufts University, Boston.
Dr. N.A. Mark Estes III
Misconceptions about AF catheter ablation outcomes abound among nonelectrophysiologists. Results have often been overstated, Dr. Estes continued. And there’s a far more attractive alternative treatment option for those AF patients who are overweight or obese: weight loss.
In the Australian LEGACY study, which he considers practice changing, patients with AF who had a body mass index of at least 27 kg/m2 who participated in a simple structured weight management program and achieved a sustained loss of at least 10% of their body weight had a 65% reduction in their AF burden as objectively documented by repeated 7-day ambulatory monitoring over 5 years of follow-up. Moreover, 46% of patients who maintained that degree of weight reduction were totally free of AF without use of drugs or ablation procedures (J Am Coll Cardiol. 2015 May 26;65[20]:2159-69).
In a related study, the Australian investigators, led by Dr. Rajeev K. Pathak of the University of Adelaide, showed in the same study population that participation in a tailored exercise program paid added dividends on top of the weight loss. Patients who achieved at least a 2-MET increase in cardiorespiratory fitness had a significantly greater rate of freedom from AF than those who didn’t reach that fitness threshold (J Am Coll Cardiol. Sep 1;66[9]:985-96).
“The data are compelling for improved outcomes, including reduced AF burden, with lifestyle modification in obese patients with AF. This is first-line therapy. You can bet it will be in the guidelines soon. It should be in your practice now,” Dr. Estes declared.
“The starting point is weight reduction, even before sending patients to an electrophysiologist for ablation,” he continued. “And if you’ve got patients on drugs who’ve had ablation in whom there continues to be AF, weight reduction – particularly reaching that 10% threshold – results in a dramatic decline in the burden of AF,” he said.
One of the common misconceptions about catheter ablation for AF is that if the pulmonary vein isolation procedure is successful in eliminating the arrhythmia, then the patient can discontinue oral anticoagulant therapy.
“That rationale, while logical, doesn’t really hold up. In many of the ablation trials, including the AFFIRM trial, if you discontinue anticoagulation in patients in sinus rhythm the stroke rate goes back to the same as in patients with AF,” according to the cardiologist.
In a meta-analysis of prospective studies published through 2007, the single-procedure success rate for radiofrequency ablation in achieving sinus rhythm without the use of antiarrhythmic drugs was 57%, climbing to 71% with multiple ablation procedures. In contrast, antiarrhythmic drugs were substantially less successful, with about a 50% success rate as compared with a 25% placebo response (Circ Arrhythm Electrophysiol. 2009 Aug;2[4]:349-61).
“It’s notable that antiarrhythmic drug development has almost been stopped because the drugs don’t work, with the possible exception of amiodarone, which requires an individualized risk/benefit assessment,” according to Dr. Estes.
There is a major caveat regarding the ablation studies: They’ve mainly enrolled patients who are in their 50s, when AF is far less common than in later decades.
“Whether these results are going to hold up long-term in elderly patients who are hypertensive, diabetic, and may have sleep apnea really remains an unanswered question,” Dr. Estes observed.
Also, significant periprocedural complications occur in roughly 1 in 20 patients undergoing radiofrequency catheter ablation, although the safety data for cryoablation look somewhat better, he continued.
Dr. Estes predicted that the future of catheter ablation of AF hangs on three major ongoing rigorous randomized clinical trials comparing it to drug therapy with hard endpoints including all-cause mortality and cardiovascular hospitalizations. These are CASTLE-AF, with 420 patients; CABANA, with 2,200; and the German EAST study, with roughly 3,000 patients. Results are expected in 2018-2019.
Dr. Estes reported serving as a consultant to Boston Scientific, Medtronic, and St. Jude Medical.