Douglas Packer, Mayo Clinic, Rochester, USA, presented the results from the CABANA (Catheter ablation vs. anti-arrhythmic drug therapy for atrial fibrillation) trial pilot study at the American College of Cardiology Scientific Sessions, Atlanta, USA. “Ablative intervention was more effective than drug therapy for preventing recurrent symptomatic atrial fibrillation,” he said. However, Packer added, “treatment success rates in this population, which include a significant percentage with persistent and long-standing persistent AF, were lower than observed in other randomised clinical trials.”
The CABANA pivotal trial tested the hypothesis that primary catheter ablation for the elimination of AF is superior to state-of-the-art drug therapy for reducing recurrent AF in high-risk patients. The NaviStar ThermoCool device was used in the study.
Catheter ablation was performed percutaneously, with isolation of all four pulmonary veins. Additional adjunctive linear or circumferential ablation was conducted as necessary. In the medical management arm, patients could be treated with rhythm (16%), rate control (13%), or both (71%).
A total of 60 patients were randomised, in which 29 patients were randomised to catheter ablation, and 31 patients to medical management. Baseline characteristics were fairly similar between the two groups. About 80% had hypertension, 18% had diabetes, and 17% had underlying cardiomyopathies. About 35% had coronary artery disease, and 36% had class II or III heart failure. Paroxysmal AF was noted in 32%, and 68% had persistent or long-standing persistent AF. Prior anti-arrhythmic drugs had been tried in 30%, with 25% having failed one anti-arrhythmic drug. About 23% of patients had a history of atrial flutter. About 39% of the patients had a CHADS score of ≥2.
The incidence of freedom from symptomatic AF after the blanking period was significantly higher in the catheter ablation arm, as compared with the drug arm (65% vs. 41%, hazard ratio [HR] 0.46, 95% confidence interval [CI] 0.21–0.99, p=0.03). However, the incidence of any AF, atrial flutter, or atrial tachycardia was similar between the two arms (66% vs. 72%, HR 0.69, 95% CI 0.37–1.32, p=0.26). About 13% of patients crossed over from the drug arm to the catheter ablation arm over the duration of follow-up, and 21% of patients in the catheter ablation arm needed at least one other ablation procedure.
Adverse events after catheter ablation included moderate pulmonary vein stenosis in one patient. There were no cases of severe pulmonary vein stenosis. In addition, two patients developed an arteriovenous fistula or a pseudoaneurysm, with no atrial oesophageal fistulas.
Packer said that late recurrence of AF may reduce long-term effectiveness of ablation and that the relative effectiveness of the two therapies could be similar over time. “This pilot study establishes the feasibility and importance of conducting a pivotal trial for establishing long-term outcome, mortality, quality of life, and cost of therapy for AF.”
“There is another critical point, and I think this is the real message of a trial like CABANA: It is not about the recurrence of atrial fibrillation,” he said. “It has to be about mortality. It has to be about other aggravating issues like stroke. It has to be about cost, and it has to be about complications. In a way you could say that the recurrence of atrial fibrillation is a surrogate. If these patients have a very good quality of life at low cost to the healthcare system, then we are talking benefit,” Packer said.
The CABANA pilot study was funded by St Jude Medical. The CABANA trial will enrol up to 3,000 patients to be followed for five years. The primary endpoint is total mortality, and secondary endpoints include a host of cardiovascular endpoints, including hospitalisations, bleeding, and stroke.
