Acute and long-term efficacy and safety of catheter cryoablation of the cavotricuspid isthmus for treatment of type 1 atrial flutter

Background

Atrial flutter (AFL) is commonly treated by radiofrequency catheter ablation. Catheter-based cryoablation may be an effective alternative with potential advantages.

Objective

The purpose of this study was to study the acute and long-term safety and efficacy of catheter-based cryoablation for treatment of cavotricuspid isthmus–dependent (typical and reverse typical) AFL.

Methods

Catheter-based cryoablation was performed with a 10Fr catheter in 160 patients with cavotricuspid isthmus–dependent AFL (122 men and 38 women; mean age 63.1 ± 9.3 years, mean left ventricular ejection fraction 54.6% ± 10.4%); 94 (58.8%) of these patients also had atrial fibrillation (AF). All patients underwent right atrial (RA) activation mapping and pacing at the cavotricuspid isthmus to demonstrate concealed entrainment and confirm cavotricuspid isthmus dependence of AFL. Catheter-based cryoablation of the cavotricuspid isthmus was performed with multiple freezes (average freeze time 2.3 ± 0.5 minutes) until bidirectional block was demonstrated during pacing from the low lateral RA and coronary sinus, respectively. Patients were evaluated at 1, 3, and 6 months and underwent weekly and symptomatic event monitoring. Acute procedural success was defined as cavotricuspid isthmus block persisting 30 minutes after ablation. Long-term success was defined as absence of AFL during follow-up.

Results

Acute success was achieved in 140 (87.5%) of 160 patients. Total procedure time was 200 ± 71 minutes, ablation time (including a 30-minute waiting period after ablation) was 139 ± 62 minutes, and fluoroscopy time was 35 ± 26 minutes. An average of 20.5 ± 11.3 freezes, for a total ablation time of 47.4 ± 24.3 minutes, were required to achieve cavotricuspid isthmus block, with average and nadir temperatures of −81.5°C ± 3.7°C and −85.6° ± 3.6°C, respectively. Four patients (2.5%) had procedure-related adverse events. Of 132 patients with acute efficacy who completed 6-month follow-up, 8 (6%) were lost to follow-up or were noncompliant with event recordings. Using survival analysis, 106 (80.3%) remained free of AFL on strict analysis of event recordings only, and 119 (90.2%) remained clinically free of AFL.

Conclusion

This large pivotal study demonstrated the acute and long-term efficacy and safety of catheter-based cryoablation for cavotricuspid isthmus–dependent AFL, similar to rates previously reported for radiofrequency catheter ablation.

Introduction

The incidence of cavotricuspid isthmus–dependent atrial flutter (AFL) has been estimated at more than 200,000 in the United States, with a prevalence of 800,000.1, 2 Radiofrequency (RF) catheter ablation is safe and effective treatment of AFL, with cure rates greater than 95%.3, 4 In studies using large-tip RF ablation catheters, acute efficacy ranged from 88% to 93%, long-term 6-month efficacy from 87% to 97%, and complications from 2.7% to 3.6%.3, 4 RF catheter ablation of AFL has been shown to improve quality of life and to reduce recurrence of atrial fibrillation (AF) and frequency of hospitalization compared with medical therapy.⁵

Catheter cryoablation has been used to treat supraventricular arrhythmias, with comparable efficacy and potentially fewer complications compared with RF catheter ablation.6, 7, 8, 9, 10, 11 Unlike RF catheter ablation, catheter-based cryoablation does not cause coagulum formation or endocardial charring.6, 7, 8, 9, 10, 11 It does not cause pain, potentially reducing the amount of sedation required during ablation.7, 8, 9, 10 However, the efficacy of catheter-based cryoablation for treatment of AFL has not been systematically evaluated in a large clinical trial. In this report, the acute and 6-month follow-up results in a total of 160 patients treated with catheter-based cryoablation are presented.