The APPLE score: a novel and simple score for the prediction of rhythm outcomes after catheter ablation of atrial fibrillation

Background: Recurrent atrial fibrillation (AF) occurs in up to 50 % of patients within 1 year after catheter ablation, and a clinical risk score to predict recurrence remains a critical unmet need. The aim of this study was to (1) develop a simple score for the prediction of rhythm outcome following catheter ablation; (2) compare it with the CHADS₂ and CHA₂DS₂-VASc scores, and (3) validate it in an external cohort. Methods: Rhythm outcome between 3 and 12 months after AF catheter ablation were documented. The APPLE score [one point for age >65 years, persistent AF, impaired eGFR (<60 ml/min/1.73 m²), LA diameter ≥43 mm, EF < 50 %] was associated with AF recurrence and was validated in an external cohort in 261 patients with comparable ablation and follow-up. Results: In 1145 patients (60 ± 10 years, 65 % male, 62 % paroxysmal AF) the APPLE score showed better prediction of AF recurrences (AUC 0.634, 95 % CI 0.600–0.668, p < 0.001) than CHADS₂ (AUC 0.538) and CHA₂DS₂-VASc (AUC 0.542). Compared to patients with an APPLE score of 0, the odds ratio for AF recurrences was 1.73, 2.79 and 4.70 for APPLE scores 1, 2, or ≥3, respectively (all p < 0.05). In the external validation cohort, the APPLE score showed similar results (AUC 0.624, 95 % CI 0.562–0.687, p < 0.001). Conclusions: The novel APPLE score is superior to the CHADS₂ and CHA₂DS₂-VASc scores for prediction of rhythm outcome after catheter ablation. It holds promise as a useful tool to identify patients with low, intermediate, and high risk for AF recurrence.