Comparing Adverse Effects

“I found it very reassuring that the complication rates with both approaches were extremely low,” Dr Calkins observed. “There were no deaths, esophageal fistulas, or pulmonary vein stenosis.” He noted that with cryoballoon ablation, practitioners have been concerned about phrenic nerve injury, since the incidence in previously reported studies was 2% or 3%. “In this study, only 1 in 300 patients—in other words, 0.3%—had permanent phrenic nerve injury at 1 year.”

Table 1: A Comparison of Key Safety End Points


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End Point

RF Group (n=376)

CA Group (n=374)

P Value

Primary Safety End Point

51 (12.8%)

40 (10.2%)

Death from any cause*

0

2 (0.5%)**

.50

Stroke or transient ischemic attack from any cause*

2 (0.5%)

2 (0.5%)

1.00

Atrial arrhythmia***

13 (3.5%)

8 (2.1%)

.38

Atrial flutter/atrial tachycardia

10 (2.7%)

3 (0.8%)

.09

Non-arrhythmia-related serious adverse events*

Groin site complications

Unresolved phrenic nerve injury at discharge

At 3 months

At >12 months

 36 (9.6%)

 16 (4.3%)

 0

 0

 0

 28 (7.5%)

 7 (1.9%)

 10 (2.7%)

 2 (0.5%)

 1 (0.3%)

 .36

 .09

 .001

 .25

 .50

*This end point was a component of the primary safety end point, which was a composite of death from any cause, stroke, or transient ischemic attack from any cause, and serious adverse events.

**These deaths were not related to the treatment or device

***Included palpitations, presyncope, sick sinus syndrome, supraventricular extrasystoles, and syncope

Reference: Kuck KH, Brugada J, Fürnkranz A, et al; on behalf of the FIRE AND ICE Investigators. Cryoballoon or radiofrequency ablation for paroxysmal atrial fibrillation. N Engl J Med. 2016;374(23):2235-2245. doi: 10.1056/NEJMoa1602014.

Length of Procedure

Total procedure duration and left atrial dwell time were shorter in the cryoablation than in the RF group, although fluoroscopy time was slightly longer (Table 2). The study authors stated that circumferential single-step ablations utilized by cryoablation require less time. However, cryoablation requires pulmonary vein venography. This necessitates more fluoroscopy time, since RF requires occlusive angiography, according to the authors.

Nevertheless, the shorter overall procedure time of cryoablation over RF demonstrated in the study was “a major advantage demonstrated in the study,” according to Grant Simons, MD, assistant clinical professor of medicine at Mt. Sinai School of Medicine in New York and Director of Cardiac Electrophysiology, Englewood Hospital and Medical Center in Englewood, New Jersey. “The patient is on the table for a shorter time, which is beneficial to the patient,” he told The Cardiology Advisor.

Previous studies have also demonstrated shorter procedure time with cryoablation over RF. For example, DeVille et al found a 13% reduction in procedure time  (174 vs 200 minutes), as well as a 21% reduction in fluoroscopy time (33 vs 42 min).11

“We look for a quick and easy tool for isolating pulmonary veins,” explained Dr Simons. “We have been waiting for years for a 1-shot catheter and the cryoballoon is the first FDA-approved device that enables a 1-shot approach, rather than the point-by-point one required for RF ablation, to isolate pulmonary veins.”

Table 2: A Comparison of Procedure Duration

End Point

RF Group (n=376)

CA Group (n=374)

P Value

Total procedure duration (min)

140.9 ± 54.9

124.4 ± 39.0

<.001

Left atrial dwell time (min)

108.6 ± 44.9

92.3 ± 31.4

<.001

Total fluoroscopy time (min)

16.6 ± 17.8

21.7 ± 13.9

<.001


Reference: Kuck KH, Brugada J, Fürnkranz A, et al; on behalf of the FIRE and ICE Investigators. Cryoballoon or radiofrequency ablation for paroxysmal atrial fibrillation. N Engl J Med. 2016;374(23):2235-2245. doi: 10.1056/NEJMoa1602014.

RF Ablation Still Useful

Despite the positive results of the study demonstrating the advantages of cryoablation, it is important not to dismiss RF and to recognize that RF was the first technology approved for AF ablation and therefore has the longest track record, Dr Simons noted. “Furthermore, the availability of contract force sensing has also allowed more consistent and durable lesion formation,” he said.

Additionally, “it is a matter of operator preference,” Dr Calkins said. “Skilled RF operators should not abandon an approach with which they have been getting good results.”

Although isolating the pulmonary veins, which is the cornerstone for treating AF can be accomplished with either method, cryoablation with the cryoballoon is designed only for ablation of the pulmonary veins, Dr Calkins pointed out. This is especially relevant for patients who have both atrial fibrillation and atrial flutter and also those who are suspected to have non pulmonary vein triggers, for which RF is more appropriate.