May 11, 2012 (Boston, Massachusetts) — Radiofrequency (RF) catheter ablation with pulmonary vein isolation is not only safe as a first-line treatment for paroxysmal or persistent atrial fibrillation (AF), it's more likely to suppress AF recurrences than is standard antiarrhythmic drug (AAD) therapy, suggests a randomized trial with a two-year follow-up — one of the longest for an AF-ablation trial . A single ablation procedure reduced the risk of AF recurrence by a significant 44% compared with AAD.
Importantly, in the second Radiofrequency Ablation vs Antiarrhythmic Drugs as First-Line Therapy of Atrial Fibrillation (RAAFT 2) trial, which followed all patients with transtelephonic monitoring (TTM), RF ablation's significant advantage over AAD was in reducing bouts of AF that were either symptomatic or asymptomatic.
"So to be able to claim victory with ablation, you really need to monitor these patients very judiciously," said RAAFT 2 co–principal investigator Dr Carlos Morillo (Hamilton Health Sciences-McMaster University, ON) when presenting the study here at the Heart Rhythm Society 2012 Scientific Sessions. Ablation also significantly cut the frequency of solely symptomatic AF, he said.
"These findings support the indication of radiofrequency pulmonary vein isolation as first-line therapy in patients with paroxysmal atrial fibrillation," he said, pointing out that the catheter therapy is currently relegated to second-tier status for paroxysmal AF not responsive to AAD in the most recent Canadian Cardiovascular Society guidelines.
US guidelines are even more restrictive. On the other hand, heartwire reported in 2010 that a European Society of Cardiology guidance supports catheter ablation for paroxysmal AF without an AAD attempt.
RAAFT 2 shows that catheter ablation as performed in the trial is a good therapy for paroxysmal AF, Morillo told heartwire , but also "that there's still 50% of patients who, after one single ablation, have a recurrence. Still, that's much better than the 72% at two years with antiarrhythmic drugs. So it's much better but still has limitations."
RAAFT 2 randomized 127 patients not previously treated with AAD — 87.5% with a history of paroxysmal AF and the rest with persistent AF — either to undergo RF ablation within four to six weeks or to initiate AAD, with 90 days allowed for titrating doses. The patients, most from Canada or Germany but also some from Italy, the Czech Republic, and the US, had normal systolic function, and none had hypertension or heart failure. All were followed with TTM.
"These were highly symptomatic patients," Morillo said, noting that patients averaged about 47 AF episodes within the previous six months; yet they were low risk for stroke, with CHADS2 scores averaging 0.5 in the ablation group and 0.7 among those getting AAD.
In the ablation group, 15.2% required an additional ablation, including one during the initial treatment period and nine during follow-up. Seven patients (10.6%) went on AAD therapy.
In the AAD group, 59% had to discontinue at least one antiarrhythmic drug and 29 patients (47.5%) underwent catheter ablation during the follow-up; AAD consisted usually of either flecainide or propafenone (Rythmol, GlaxoSmithKline).
Morillo said patients in the trial were "highly committed," with 19% in both groups having been "fully compliant" with TTM (which meant transmissions biweekly and in the event of symptoms). In the ablation group, 86.4% were compliant at least 75% of the time, as were 78.7% of the AAD group.
RAAFT-2 primary outcomes: Recurrence rates at two years for symptomatic or asymptomatic AF, atrial flutter, or atrial tachycardia lasting > 30 seconds.
|End point||Ablation, n=66 (%)||AAD, n=61 (%)||HR (95% CI) p|
|Recurrence of AF, atrial flutter, or atrial tachycardia||55||72||0.56 (0.35-0.90) 0.02|
|Symptomatic recurrence of AF, atrial flutter, or atrial tachycardia||47||59||0.56 (0.33-0.95) 0.03|
|Symptomatic AF only||41||58||0.52 (0.30-0.89) 0.01|
|Recurrence by clinical criteria only||24||31||0.86 (0.42-1.72) 0.66|
"Of note," Morillo said in his presentation, "when we excluded the transtelephonic monitor, we couldn't show any difference in recurrence of the primary outcome, 31% in the antiarrhythmic drug [group] and 24% in the catheter ablation [group], highlighting the need for very strict monitoring in these patients to be able to define a successful outcome."
RF ablation also performed better than AAD for the trial's primary safety outcome, a cluster of adverse events specific to each therapy.
In the ablation group, 7.7% of patients had an event in the safety cluster, which included death, tamponade, severe pulmonary vein stenosis, thromboembolism, vascular complications, phrenic nerve injury, or compete AV block within 30 days; tamponade accounted for nearly all of it.
Of AAD patients, 19.7% experienced an event in the safety cluster, which contained death, torsades de pointes, bradycardia requiring a pacemaker, syncope, QRS-interval prolongation > 50% of baseline, atrial flutter, or any other significant event leading to drug withdrawal — which accounted for most of the events.
The literature suggests that most patients with paroxysmal AF require more than one ablation to control symptoms, Morillo said, and based on RAAFT 2, it's far more likely to happen within a year of the first ablation. "Actually, we haven't seen many recurring in the second year."
Sponsored by the Population Health Research Institute of McMaster University with support from Biosense Webster. Morillo discloses receiving consulting fees or honoraria from Boehringer Ingelheim, Sanofi, Medtronic, and Merck; being on a speaker's bureau for Boehringer Ingelheim and Merck; and receiving research grants from St Jude Medical, Boston Scientific, Biosense Webster, and Medtronic.
Heartwire from Medscape © 2012 Medscape, LLC
Cite this: RAAFT 2: Catheter Ablation Can Be First Line of Defense Against Paroxysmal AF - Medscape - May 11, 2012.