Electrocardiographic Predictors of Ventricular Arrhythmic Events in ICD Recipients: Signal Beyond the Left Ventricular Ejection Fraction Threshold

Background and Objectives: Selection for implantable cardioverter-defibrillator (ICD) therapy anchored in left ventricular ejection fraction (LVEF) may miss at-risk patients with LVEF > 35%. We tested whether a simple electrocardiogram (ECG) burden adds discrimination for appropriate ICD therapy beyond clinical factors and LVEF. Methods Single-center retrospective cohort of 237 ICD recipients. Six routinely reported ECG abnormalities were prespecified and summed as an ECG burden (0–6), then categorized as 0–1, 2–3, or ≥ 4 abnormalities. Logistic regression estimated odds ratios (OR) with 95% CIs for appropriate ICD therapy. Multivariable models included LVEF category (≤ 35% vs > 35%), ischemic vs non-ischemic cardiomyopathy, ICD indication (secondary vs primary prevention), and ECG burden category. Discrimination of the clinical + LVEF model with and without ECG burden was assessed by the C-statistic and DeLong test. Results Mean age was 62.1 ± 16.2 years; 71% male; 61% ischemic; 72% primary prevention; follow-up 7.6 ± 2.9 years. High ECG burden (≥ 4) independently predicted appropriate therapy (OR 3.6, 95% CI 1.8–7.2; p < 0.001). Adding ECG burden to a clinical + LVEF model improved discrimination, increasing the C-statistic from 0.67 to 0.75 (DeLong p = 0.01). Kaplan–Meier curves showed graded separation across burden categories (log-rank p < 0.001). Among patients with LVEF > 35%, observed therapy was higher with high burden (~ 26.3%) than with low burden (~ 6.2%). Conclusions An ECG burden based on six routine abnormalities provides independent and incremental prognostic value beyond LVEF, including in patients with preserved LVEF. This approach uses routinely available measures and may help refine risk-aligned ICD decisions. Prospective multicenter validation is warranted.