MAASTRICHT, THE NETHERLANDS. Pulmonary vein isolation (PVI) using cryoablation is a procedure very similar to the standard PVI using radiofrequency energy for lesion creation except that it uses a nitrogen-cooled (–90o C) catheter rather than an electrically-heated catheter. Cryoablation is potentially safer than RF ablation in that the risk of pulmonary vein stenosis and esophageal injury is pretty well non-existent. The procedure also has the advantage that, since no pain is felt during lesion creation, it does not require conscious sedation or anaesthesia.
EPs at the Academic Hospital in Maastricht recently reported on the long-term success of the procedure. Their study included 70 patients (54 men and 16 women), 77% of whom had lone AF with the remaining having arterial hypertension (14%) or minimal heart disease (9%). The age of the patients ranged between 21 and 65 years (average of 40 years), their average left atrial diameter was 38 mm, and the left ventricular ejection fraction averaged 59% – in other words, a pretty healthy group. The patients had all failed one or two antiarrhythmic drugs (none had been on amiodarone), and had suffered from symptomatic afib episodes for an average of 4 years.
All patients underwent a segmental PVI using cryoablation. The Maastricht EPs were able to locate the specific offending vein(s) in 14% of cases and isolated only that vein or veins. In other cases, all veins were targeted. The patients were followed for an average of 33 months; the first 180 days via a transtelephonic event recorder and the following months via periodic Holter monitoring. At the end of the follow-up period, 49% were still in sinus rhythm without the use of antiarrhythmics, 22% were afib-free with the use of antiarrhythmics, 11% were improved more than 50% with the use of antiarrhythmics, and the remaining 18% had not benefited from the procedure. The researchers point out that the 10 patients in which the offending vein could be identified were all free of afib at the end of the follow-up period. They make the following interesting statement:
"Atrial fibrillation is a disease with different stages. In early stages, paroxysmal and nonsustained episodes are the rule. In this stage, the triggers, mostly located in the pulmonary veins, are the main culprit of AF. Over time, atrial remodeling starts to occur, and more substrate becomes available to sustain longer episodes. Therefore, self-perpetuation of AF (AF begets AF) leads to the idea that a treatment strategy employed early in the disease would be more likely to succeed".
The average procedure time was almost 6 hours with a fluoroscopy time of 88 minutes. One patient suffered a stroke during or after the procedure, another experienced a pulmonary embolism, and a third experienced transient phrenic nerve paralysis. No cases of stenosis or esophageal injury were detected.
Moreira, W, et al. Long-term follow-up after cryothermic ostial pulmonary vein isolation in paroxysmal atrial fibrillation. Journal of the American College of Cardiology, Vol. 51, No. 8, February 26, 2008, pp. 850-55
Editor's comment: A total success rate of 49% in a group of prime PVI candidates is not impressive; thus, there would seem to be no advantage of choosing cryoablation over a RF ablation carried out by a top-rated EP.