Optimizing atrial fibrillation detection through ECG feature selection using Extra-Trees and statistical association measures

INTRODUCTION: Atrial fibrillation (AFib) is the most prevalent abnormal heart rhythm, significantly increasing the risk of stroke and heart failure. Accurate and timely detection remains challenging, particularly due to the complexity of 12‑lead electrocardiogram (ECG) interpretation. While machine learning (ML) and deep learning (DL) models have demonstrated high accuracy in AFib detection, selecting the optimal input features is often non-trivial. This study aims to develop a hybrid feature selection methodology that objectively identifies the most discriminative ECG-based features for distinguishing AFib from normal sinus rhythm (NSR). MATERIAL & METHODS: We propose a hybrid framework that combines Extremely Randomized Trees (Extra-Trees) with statistical association measures to identify physiologically meaningful ECG features. Our analysis evaluates morphological, entropy-based and spectral hand-crafted features extracted from 12‑lead ECG recordings of patients who underwent catheter ablation for AFib. Two novel metrics, the feature importance score (FIS) and overall feature importance score (OFIS), are introduced to quantify feature relevance. RESULTS: The proposed approach ranked 97 extracted features and identified the 10 most important per ECG lead and 20 most relevant overall, with high consistency across leads. The interquartile range of RR-intervals achieved the highest normalized OFIS value (0.064), followed by other rhythm-related and entropy-based measures, confirming their strong discriminative power. The dimensionality of the feature space was thus reduced by nearly 80% while preserving interpretability and physiological meaning. CONCLUSIONS: This methodology provides a reproducible, interpretable and statistically grounded framework for ECG-based feature discovery, offering a preprocessing step for ML/DL models and aiding clinicians in real-time AFib detection.