New ablation catheter looks promising
NIEUWEGEIN, THE NETHERLANDS. The Holy Grail of pulmonary vein isolation (PVI) procedures is to consistently achieve complete elimination of afib in one hour or less. Many approaches have been developed and tried to achieve this goal. Electroanatomical (CARTO) mapping, catheters with irrigated tips, mesh catheters, robot-assisted systems (Stereotaxis and Hansen Sensei), cryoablation, HIFU (high intensity focused ultrasound) powered ablation, and CARTO mapping with CT scan or MRI overlay are some examples of these novel approaches. Unfortunately, none of them have "found" the Holy Grail. Most procedures still take about 3 hours, expose the patient to significant amounts of radiation through the use of fluoroscopy, are sometimes accompanied by complications (1.5 – 6% of cases), and have a long-term success rate of about 50% unless performed by highly skilled and experienced EPs.

A new ablation catheter has now been developed which may well revolutionize the world of PVIs. The catheter, developed by Ablation Frontiers Inc., has several unique features. It is a combined circular mapping and ablation catheter with 10 independent platinum electrodes of 3 mm length and 3 mm spacing. The nominal diameter of the catheter is 25 mm, but can be varied by simply turning a handle on the catheter control mechanism. The catheter receives radiofrequency power from a unique generator that can deliver either unipolar or bipolar energy to individual electrodes, or to the whole array of electrodes simultaneously. NOTE: Unipolar energy consists of current flowing from the electrodes at the catheter tip to the dispersive electrodes on the patient's back. Bipolar energy consists of current flowing between adjacent selected pairs of electrodes on the catheter tip. Bipolar current can be applied simultaneously with unipolar current or it can be field sequential.

A team of American and Dutch electrophysiologists recently carried out a trial of the new ablation system in a group of 98 lone, paroxysmal afibbers (75% male) with a left atrial diameter of less than 45 mm. The ablation was performed using a 4:1 ratio of duty-cycled bipolar/unipolar radiofrequency energy simultaneously at all selected electrode pairs until complete electrical isolation was achieved between the pulmonary veins and the left atrium. NOTE: The lesion line was placed just outside (on the atrium side) the antrum (edge) of the pulmonary veins and encircled each vein with a continuous band of ablated tissue. Average total procedure time was 84 minutes (range of 45 – 180 minutes) and average fluoroscopy exposure was 18 minutes (range of 9 – 45 minutes).

There were no procedural or post-procedural complications and no stenosis was observed at the 3-month follow-up. All patients were followed up with 7-day Holter monitoring after six months. Among the 53 patients who had gone 6 months or longer following their procedure at the writing of the report, 44 were free of afib without the use of antiarrhythmic drugs. In other words, this is an excellent single procedure success rate of 83%. It is also worth noting that none of the afib episodes observed in the Holter monitoring were asymptomatic. NOTE: Four of the 5 authors of this report have financial ties to Ablation Frontiers, Inc.

Boersma, LVA, et al. Pulmonary vein isolation by duty-cycled bipolar and unipolar radiofrequency energy with multielectrode ablation catheter. Heart Rhythm, Vol. 5, December 2008, pp. 1635-42
Kistler, PM. Multielectrode ablation for paroxysmal atrial fibrillation: pulmonary vein isolation made easy? Heart Rhythm, Vol. 5, December 2008, pp. 1643-44

Editor's comment: The results obtained with this new catheter do indeed look promising. It makes sense that the application of bipolar energy would produce better results than the use of unipolar energy, and it also seems reasonable that the capability to apply energy to 10 "catheter tips" simultaneously would shorten procedure time when compared to point-by-point ablation with a single catheter tip. One concern might be that the Ablation Frontiers catheter is non-irrigated; however, the authors of the report specifically point out that no char formation was observed on the electrodes after withdrawal of the catheter.