A novel electrocardiographic risk score for sudden cardiac arrest in patients with atrial fibrillation: The SCAAF-ERS

Background Atrial fibrillation (AF) increases the risk of sudden cardiac arrest (SCA). Patients with AF are excluded from electrocardiogram (ECG) risk predictor analyses for SCA owing to their complex ECG. Objective This study aimed to develop an ECG risk score (ERS) to predict SCA in individuals with AF. Methods We performed a case-control study using SCA cases from a community-based study in Oregon, USA (population ∼1 million; 2002-2020). Subjects aged ≥18 years with medical records and pre-arrest ECGs showing AF were included. Controls had AF ECGs without SCA history. For validation, cases and controls were selected from a California study (population ∼850,000; 2015-2023). Significant ECG variables were used to develop an sudden cardiac arrest in atrial fibrillation electrical risk score (SCAAF-ERS). Results In the discovery group (447 cases, 138 controls; mean age 74.9 years; 73.5% male), the SCAAF-ERS (0-5) was developed by assigning 1 point for each significant factor: prolonged QTc, QRS-T angle >100°, Tpeak-Tend >94 ms, left ventricular hypertrophy, and delayed QRS transition. Adjusting for demographics and comorbidities, SCA risk increased 1.5 times (95% confidence interval [CI]: 1.2-1.9) per point increase. An SCAAF-ERS ≥4 (16%) resulted in an odds ratio (OR) of 12.9 (95% CI: 3.4-48.1). In the validation group (315 cases, 138 controls; mean age 77.7 years; 64.5% male), SCA risk doubled per point increase (OR: 2.4,95% CI: 1.9-3.1). An SCAAF-ERS ≥3 (27%) resulted an OR 22.9 (95% CI: 9.0-58.3). Conclusion SCA risk was predicted successfully from AF ECGs, with a novel risk score displaying 13- to 23-fold increased odds. Further validation of the SCAAF-ERS in larger, diverse populations is warranted.