High Incidence of Atrial Fibrillation After Atrial Flutter Ablation

The incidence of atrial fibrillation (AF) after atrial flutter (AFL) ablation is high, particularly in patients with prior AF compared to those without, according to a meta-analysis published in JACC: Clinical Electrophysiology.

Researchers conducted a systematic review and meta-analysis of studies published between 1996 and 2015.

“Because of the well-defined anatomic substrate of AFL and the disappointing efficacy of antiarrhythmic drug therapy in treating AFL, catheter ablation of the CTI [cavotricuspid isthmus] is a common procedure,” they wrote. This procedure is usually successful long-term if bidirectional CTI block is achieved.

In total, 8257 patients (average weighted age: 62.7 ± 12.4 years) from 48 studies were included in the analysis (ablation success rate: 96%; 79% male).

Researchers also included AF rates from studies with less than 2 years of follow-up based on follow-up type. They categorized the types of follow-up into 3 groups: group 1 included electrocardiogram, clinical follow-up and symptom-drive evaluation; group 2 included scheduled 24-hour outpatient Holter monitoring for at least 7 days per year regardless of symptoms; and group 3 included more than 7 days of scheduled outpatient Holter monitoring per year or patients with implanted cardiac devices. Possible risk factors for AF development after AFL ablation in patients without prior AF were also evaluated.

New-onset AF incidence correlated with follow-up duration (28.8% for a weighted mean follow-up of 30.4 months), and new-onset AF incidence with less than 2 years of follow-up was 12.4% among group 1, 19% among group 2, and 45% among group 3. The mean duration of follow-up was 15.3 months, 18.5 months, and 16.3 months, respectively.

AF incidence after AFL ablation was 35.3% in patients with and without prior AF during a mean follow-up of 29.7 months, whereas AF incidence in studies with less than 2 years of follow-up was 54% in patients with prior AF vs 13.9% in those without prior AF (odds ratio [OR]: 2.93; 95% confidence interval [CI]: 2.42-3.56; P<.00001).

Of the 48 studies, radiofrequency ablation was used in 46 and cryoablation was used in 2. Bidirectional CTI block was achieved in the majority of followed patients (96%), and in the majority of studies, patients with recurrent AFL had repeat AFL ablation.

In 35 studies, AF incidence after AFL ablation in patients with prior AF was 42% vs 58% in patients without prior AF, and none of these studies utilized “intense monitoring” (ie, more than 7 days routine scheduled outpatient Holter monitoring regardless of symptoms).

During a mean weighted follow-up of 29.7 months, researchers found the overall incidence of AF after ablation was 35.3%. In patients without prior AF, the incidence was 23.2% and 52.1% in patients with prior AF (OR: 4.05; 95% CI: 3.24-5.07; P<.00001). Furthermore, a subgroup analysis based on follow-up duration demonstrated a significant variation of this probability between the group of patients followed up for less than 2 years and the group followed up for more than 2 years (P<.0001).

“To our knowledge, this is the first meta-analysis to clearly demonstrate the impact of the follow-up duration and the type of monitoring during follow-up on the incidence of AF after AFL ablation with confirmed bidirectional block,” researchers wrote.

However, it should be noted that the studies analyzed were a combination of prospective, retrospective, and randomized control studies and clinicians should take into account reporting biases that are possible when presenting meta-analyses. In addition, the majority of patients included were male.

“Current guidelines recommend anticoagulation to decrease the risk of stroke with no difference between AFL and AF patients,” they continued. “However, it does not clearly address the anticoagulation plan or type of arrhythmia monitoring after successful AFL ablation in patients with no documented prior AF.”

Patients who have structural or valvular heart disease or large left atriums may have increased AF incidences after AFL ablation. This insight could be helpful in choosing anticoagulation medication for patients with high HAS-BLED scores (a score that helps stratify AF patients by bleeding risk).

Future studies should compare rates of procedure complications, future AF hospital admissions, and future use of antiarrhythmic medications and/or AF ablation. Stroke risk in patients without prior AF after AFL ablation should also be examined.

Reference

Maskoun W, Pina MI, Ayoub K, et al. Incidence of atrial fibrillation after atrial fluter ablation. JACC Clin Electrophysiol. 2016. doi:10.1016/j.jacep.2016.03.014.