Nice, France - Long-term data in almost 500 patients show that cryoablation of atrial fibrillation (AF) appears safer than conventional radiofrequency ablation but may have a slightly lower success rate. Dr Yves Van Belle (Erasmus Medical Center, Rotterdam, the Netherlands) and Dr Burghard Schumacher (Kerckhoff Klinik, Bad Neuheim, Germany) reported their data on two series of patients at Cardiostim 2008.

Cryoablation works on the same premise as radiofrequency (RF) ablation, with the aim of blocking electrical conduction in myocardial tissue, Dr Philippe Ritter (president, Cardiostim) explained to heartwire. "But instead of heat, cryoablation uses cold, and the lesions that you create are progressive. This is an emerging technology that appears to have a lower complication rate than RF ablation. It's quite exciting and the safety is there, but we need some more years to look at it and compare it with RF ablation." Ritter added that cryoablation is also easier to perform than RF ablation, but the literature so far lists a higher recurrence rate of AF with this newer technique, although some experts at the meeting said they believed this was due to a learning curve with cryoablation.

Both Van Belle and Schumacher found that the main complication with cryoablation in their patients was a temporary palsy of the phrenic nerve. In all cases, this was transient and had disappeared by the time of the last follow-up. This compares with more severe adverse events seen with RF ablation, such as atrioesophageal fistula, stroke, tamponade and pulmonary vein stenosis, giving a major complication rate of around 4%.

Van Belle reported data on 139 patients who underwent cryoballoon ablation of the pulmonary veins for paroxysmal AF. All patients had symptomatic AF despite having tried antiarrhythmic drugs.

Of the patients, 77 initially had no AF on antiarrhythmic drugs following cryoablation, while 62 had an early recurrence. Of the 77 patients whose first procedure was a success, almost 70% were eventually free of AF without the use of antiarrhythmics. Of the 62 in whom the procedure failed the first time, some opted for repeat procedures while others opted for medical treatment. Overall, the success of cryoablation was 59% after a mean of 1.2 procedures, with a follow-up time of a year, on average.

We stopped trying to make the procedures shorter and started doing two freezes per vein or three or four . . . and we started to see better results.

There were 4% of patients who suffered temporary paralysis of the phrenic nerve pulse, and 3% who had pericardial effusion—something Van Belle said "was probably because his team was very aggressive with anticoagulation during the procedure, stemming from when we used RF ablation"—and 0.7% who suffered air embolism.

Van Belle concluded that cryoablation "is a very effective treatment for paroxysmal AF, with temporary phrenic nerve palsy being the main complication."

He acknowledged that there was a problem with recurrence, however, "so we stopped trying to make the procedures shorter and started doing two freezes per vein or three or four, compared with the one freeze we had begun with, and we started to see better results."

Schumacher presented the results of 346 patients with paroxysmal or persistent AF who underwent ablation at one of three centers in Germany with the Arctic Front cryoballoon (CryoCath, Montreal, QC). Of these, 293 had drug-refractory paroxysmal AF while 53 had persistent AF.

We had a 74% success rate in paroxysmal AF with cryoablation, which is comparable to that achieved with alternative forms of ablation.

Following one procedure of cryoablation, 74% of those with paroxysmal AF were free of AF and in permanent sinus rhythm; this figure was much lower for those with persistent AF—just 38%. Predictors of AF recurrence were persistent AF and a left atrial long axis of 60 mm or more, Schumacher said.

Pericardial effusion occurred in two of 346 patients (0.5%), while transient phrenic nerve palsy was found in 26 patients (7.5%). But like Van Belle's patients, all patients with phrenic nerve palsy recovered fully during follow-up, Schumacher noted. "There were no thromboembolic events, no pulmonary vein stenosis, no esophageal injury, and no coronary artery injury," he added.

"We had a 74% success rate in paroxysmal AF with cryoablation, which is comparable to that achieved with alternative forms of ablation and adds to the impressive data from Dr Van Belle and his colleagues in Rotterdam," he concluded.