Cavotricuspid isthmus ablation is a curative therapy for atrial flutter (A.flutter). Atrial Fibrillation (AF) often occurs in patients following atrial flutter ablation in 15-82% of patients. To study the predictive factors for AF post A.flutter ablation, 148 patients who underwent CTI between Jan 2004 and Dec 2005 were observed. This study published by Valerie Laurent et al (JICE,2009,24:119-125.) examined the clinical, biological, electrocardiographic and electrophysiologic predictive factors of AF post A.flutter ablation.

After catheter ablation was performed, the patients referring cardiologist was contacted to complete a questionnaire that evaluated if patient was in sinus rhythm post ablation or if atrial flutter or AF was present at follow-up. Univariate and multivariate analysis was done to study the predictive factors. The factors tested in the model include age, gender, body mass index, clinical factors like diabetes, hypertension, thyroid disease, COPD, dyslipidemia, structural heart disease, heart failure, history of AF and type of flutter and electrophysiologic characteristics like direction of reentrant circuit, inducible AF, duration of block and anti-arrhythmic treatment after discharge. 53 patients were discharged on anti-arrhythmic drugs (36%) and AF could be induced at the end of ablation procedure in 20 patients (13%).

Patients were followed for 21 months. During follow-up 20 patients (13.5%) developed recurrence of A.flutter and some of them had a re- ablation procedure. 40 patients (27%) developed new onset AF (paroxysmal 55%, permanent 45%). On analysis, there were no baseline differences between the 40 patients who developed AF and those who did not. 18 of these patients had a pre-ablation history of AF and 22 had no prior history of AF. Univariate analysis showed that 4 of the 21 factors tested – younger age, paroxysmal A.flutter, inducible AF at the end of ablation and preablation history of AF predicted occurrence of AF following CTI ablation. Multivariate analysis showed that inducible AF and paroxysmal atrial flutter as the factors predicting occurrence of AF post A.flutter ablation.

The incidence of AF in this study was calculated to be 152 per 1000 patient years. The incidence of AF in the Framingham cohort of age < 70 years is 6.2 per 1000 person years. Clearly, incidence of AF post ablation is 25 times higher than the incidence of AF in the general population as suggested by the Framingham cohort. Also, presence of anti-arrhythmic therapy in some patients also underestimates the true incidence of AF.

Interestingly, 25% of patients who neither had a prior history of AF nor any structural heart disease also had new onset of AF post A.flutter ablation. This leads us to believe that these two atrial arrhythmias may share a similar substrate and correspond to the evolution of a more generalized electrophysiologic disease.

The study has a few clinical implications. Since inducible AF post ablation was a predictive factor for AF, this parameter should be taken into account while making treatment recommendations with anti-arrhythmic and anti-thrombotic agents. The study also emphasizes the need for a close follow-up of patients after CTI ablation.