BACKGROUND: There is strong evidence to suggest an association between typical cavotricuspid isthmus (CTI) dependent atrial flutter (AFL) and atrial fibrillation (AF). The long-term morbidity and mortality of typical AFL ablation has been well defined; however, the effect of AF on morbidity and mortality post typical AFL ablation has not been described. We predict AF will be associated with a less favorable long-term morbidity and mortality after CTI ablation for typical AFL.OBJECTIVE: Retrospective observational cohort study to compare the outcomes of typical AFL ablation in patients with and without a history of AF.METHODS:Five hundred and forty-seven patients who underwent (CTI) ablation without pulmonary vein isolation between November 2011 and December 2015 were included in the study and followed for a mean of 30.1 months. Twelve-lead ECG, Holter monitor, event monitor, and device interrogations were reviewed to accurately confirm rhythms. Comparison testing was conducted to determine outcome differences between patients with and without pre-existing AF.RESULTS: Among the 547 patients there were 256 patients with a history of AF prior to CTI ablation (group hxAF) and 291 patients without a history of AF prior to CTI ablation (group NohxAF). The mean age was 65.3±10.3 years old in hxAF and 64.5±12.2 years old in NohxAF (p=0.389). All other demographics of both groups were the same except the hxAF group had fewer males (65.2% vs. 77.7%, p=0.001) and more Caucasians (88.7% vs. 82.1, p=0.04). Both groups had similar echocardiogram findings (LVEF, left atrial volume index, mitral valve, aortic valve, and pulmonary artery systolic pressure). As expected, recurrence of AF at 12 months was significantly increased in the hxAF group (69.9% vs. 21.6%, pCONCLUSIONS:AF increases the all-cause mortality and hospital readmission at 12 months post typical AFL ablation.