118/An early experience of atrial fibrillation cryoablation in a newly established EP centre

Background: One in four middle-aged adults in Europe and US will develop atrial fibrillation (AF). The 2017 HRS/EHRA/ECAS/APHRS/SOLAECE Expert Consensus Statement on Catheter and Surgical Ablation of Atrial Fibrillation outlined symptomatic relief of AF as a primary indication for ablation.
Aims and objectives: To gauge AF cryoablation success rates, complications, age, gender distribution and the number of patients who were on NOACs versus warfarin. To determine how AF subtype, left atrial (LA) size, ejection fraction and previous DC cardioversion (DCCV) impacted on AF recurrence post ablation. To determine the number of patients who were able to stop antiarrhythmics post ablation.
Methods: We employed a retrospective analysis of our cryoablation service from February 2018 to February 2019 at Worcester Royal Hospital. Our sample size was 50 patients. We audited against the BHRS standards for Interventional Electrophysiology study and catheter ablation in adults. We used clinical databases to collate cryoablation reports, clinical data and investigations. We systematically input data into an excel spreadsheet and used this program to create tables and graphs.
Results: The gender distribution was 60% male and 40% female. The average age of patients was 62 years. Twenty-two percent had persistent and 78% paroxysmal atrial fibrillation (PAF), 8% were on warfarin and 92% on a NOAC (73.9% on apixaban, 19.6% rivaroxaban and 6.5% dabigatran). The average CHADSVASC score was 2. 72.7% of patients with PAF had previous DCCV prior to cryoablation versus 25.6% in persistent AF. Patients with PAF: 61.5% had a normal LA size, 23.1% mildly dilated, 10.3% moderately dilated and 5.1% severely dilated LA. Patients with persistent AF: 36.4% had a normal LA size, 45.6% mildly dilated, 9% moderately dilated and 9% severely dilated LA. Immediate complications: MAJOR- one periprocedural CVA, one periprocedural TIA; MINOR- one phrenic nerve paresis with full recovery at end of case and two patients had prolonged bleeding from puncture site. At the 3 months clinic review: two patients had ECG proven PAF-listed for redo cryoablation, three with probable PAF-(24-hour ECGs were requested); three had persistent AF (one failed DCCV- amiodarone commenced, flecainide started in another and the third was offered redo cryoablation but opted for amiodarone). One patient was found to be in atrial flutter (offered DCCV). Success rate at 3 months: 89.7%
PAF and 72.7% for persistent AF. Success rate at 6 months: 84.6% PAF and 63.6% for persistent AF. Forty percent of patients who had recurrence of AF within 6 months of cryoablation had previous DCCV whereas 60% of them did not. All patients who had a recurrence of AF had preserved EF. Counterintuitively no patients with moderate to severe LA dilatation had a recurrence of AF. 32.1% of patients with a normal LA size had recurrence at 6 months and 28.6% with mild LA enlargement had recurrence at 6 months. Forty-eight percent of patients who underwent cryoablation were on antiarrhythmics. Of these, 70.8% were on flecainide, 25% on amiodarone and 4.2% on sotalol. Antiarrhythmic discontinuation: 33.3% immediately post-procedure, 41.7% at 3 months check and 4.2% at 6 months.
Conclusion: Our success rates at 6 months of 84.6% for PAF and 63.6% for persistent AF mirrored international trends. We had no deaths, aortic injuries or atrio-oesophageal fistulas. We had low complication rates and an inverse relationship between left atrial size and ejection fraction with AF recurrence.