BACKGROUND New-onset atrial fibrillation (AF) is not uncommon after ablation of typical atrial flutter (AFL); however, limited data are available for a risk prediction model for the future occurrence of AF in patients with typical AFL undergoing successful catheter ablation. OBJECTIVE This study aimed to determine whether the HATCH score (which is based on hypertension, age >= 75 years, transient ischemic attack or stroke, chronic obstructive pulmonary disease, and heart failure) is useful for risk prediction of subsequent AF after ablation of typical AFL. METHODS A total of 216 consecutive patients presenting with typical AFL and no history of AF who underwent successful catheter ablation were enrolled in the study. The clinical endpoint was occurrence of new-onset AF during follow-up after ablation. RESULTS During a follow-up period of 29.1 +/- 18.3 months, 85 patients (39%) experienced at least 1 episode of AF. Multivariate Cox regression analysis demonstrated that the HATCH score (hazard ratio 1.784; 95% confidence interval 1.352-2.324; P < .001) and left atrial diameter (hazard ratio 1.270; 95% confidence interval 1.115-1.426; P < .001) were independently associated with new-onset AF after typical AFL ablation. The area under the receiver operator characteristic curve based on the HATCH score for prediction of new-onset AF was 0.743. The HATCH score could be used to stratify the patients into 2 groups with different incidences of new-onset AF (69% vs 27%, P < .001) at a cutoff value of 2. CONCLUSIONS The HATCH score is a useful predictor of new-onset AF after typical AFL ablation.