VA: Novel Ablation Catheter Tackles Persistent Afib
By Chris Kaiser, Cardiology Editor,
October 13, 2011
Action Points
Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.
In this clinical trial subjects with persistent atrial fibrillation who were randomized to RF ablation were more likely to achieve a 90% reduction in episodes of atrial fibrillation than those on medical therapy.
Complications occured in 12.3% of subjects, including four periprocedural strokes. The trial was not designed to assess efficacy with respect to long-term stroke prevention.
Review
A radiofrequency ablation catheter system with a multi-electrode design was better at reducing atrial fibrillation (Afib) in patients with persistent or long-standing Afib compared with those on medical management, a randomized trial found.
Of the 138 patients randomized to ablation, 55.8% had an atrial fibrillation and atrial flutter burden reduction of greater than 90% and were free of antiarrhythmic drug therapy at six months, compared with 26.4% of the 72 patients in the medical management arm, according to a study presented at the Venice Arrhythmias 2011 conference this week in Venice, Italy.
The rate of seven-day acute procedural events in the ablation arm was 12.3%, "a rate comparable to other persistent Afib studies," reported Lucas Boersma, MD, PhD, from St. Antonius Ziekenhuis in the Netherlands, and colleagues.
The acute event rate had an upper 95% confidence interval of 19%, which did not meet the prespecified performance goal of 16%. However, the prespecified acute safety endpoint was established in 2006 and was based on patients with paroxysmal atrial fibrillation, John Hummel, MD, director of clinical electrophysiology research at the Ohio State Medical Center in Columbus and an investigator in the trial, told MedPage Today in an interview.
"The patients in this trial were much sicker and had more complex disease than those on whom we modeled our prespecified acute safety endpoint," Hummel said. He also noted that some of the acute events, such as urinary tract infection and pneumonia, had little to do with the catheter system.
"Patients with persistent or long-standing atrial fibrillation, especially those refractory to drug therapy, are particularly challenging, and this new technology holds promise as an option for them," Hummel said.
For the TTOP-AF trial (Tailored Treatment of Persistent Atrial Fibrillation), researchers enrolled 210 patients who were symptomatic and drug refractory. Patients came from 23 sites in the U.S. and one in the Netherlands.
Patients were randomized 2:1 to ablation or medical management. Follow-up was at one, three, and six months in both arms. At three months, those in the ablation arm could be sent for retreatment with ablation if needed. After four months, those in the medical arm could cross over to ablation if needed.
Researchers defined persistent atrial fibrillation as continuous Afib for more than seven days but less than one year, or Afib recurrence within seven days of direct current cardioversion.
They defined long-standing persistent atrial fibrillation as continuous Afib for more than a year but less than four years.
The protocol included the use of three investigational ablation catheters, each designed for specific anatomic targets: pulmonary vein, left atrial septum, and left atrial body. The catheters apply "linear lesions through multiple neighboring electrodes at the same time," Hummel said, as opposed to the conventional point-by-point ablative technique.
The acute safety endpoint involved the use of all three catheters, which included isolating the pulmonary vein, ablating the complex atrial fractionated electrograms, and having the patient in sinus rhythm.
There were no significant differences at baseline between the two arms of the study, including with CHADS2 score, ejection fraction, and number of failed antiarrhythmic drugs.
A total of 93% of patients in the ablation arm had acute success and 35% required retreatment at three months. In the medical arm, 83% received a therapeutic intervention, 78% underwent cardioversion, and 86% had a change in drug dose or type.
The primary effectiveness endpoint included acute safety, chronic safety, and chronic effectiveness. In the intention-to-treat analysis, 55.8% of the ablation patients met the primary effectiveness endpoint at six months versus 26.4% of those being medically managed. The difference was significant at P<0.0001.
"That's a huge difference and a welcome finding because these patients are among the more difficult patients to ablate," Hummel said.
Acute safety events in the ablation arm included four strokes, two cases ofcardiac tamponade, two pseudoaneurysms, and two cases of heart failure with one resulting in death. Hummel noted that the acute stroke rate of 2.7% in TTOP-AF is comparable to other studies.
Chronic safety events in the ablation arm included four asymptomatic pulmonary vein stenoses, one symptomatic pulmonary vein stenosis, one stroke, one persistent atrial septal defect secondary to septal puncture, and one pericardial effusion. The medically managed arm had two cases of gastrointestinal bleeding and one case of atrial fibrillation with rapid ventricular response.
There was "very little difference" in the number of chronic safety adverse events between the two arms when analyzed by cumulative follow-up per patient per month, Hummel said. The ablative arm had 1,243 cumulative follow-up months, whereas the medical arm had 420 months. The number of adverse events per patient per month was 0.008 versus 0.007.
"Prolonged duration atrial fibrillation is a more difficult condition to provide meaningful therapy [for] than patients with shorter episodes of atrial fibrillation," Bruce Wilkoff, MD, president of the Heart Rhythm Society, told MedPage Today. "Medications have not been very effective in this situation, and this new procedure shows significant promise as an alternative."
Medtronic, who sponsored the study, has sent these data to the FDA for review. The catheter system is not available in the U.S, although it has been available in Europe and Canada for several years.