Predictors of electrocardiographic screening failure for the subcutaneous implantable cardioverter-defibrillator in children: A prospective multicenter study

Background: Subcutaneous implantable cardioverter-defibrillator (SICD) shows promise for select patients at risk of sudden cardiac death. However, patients need to pass an electrocardiographic (ECG) screening (ECG-S) test before they can receive an SICD. Predictors of ECG-S failure in children are unclear. Objective: The purpose of this study was to identify the incidence and predictive factors for failure of ECG-S in children. Methods: Patients 18 years and younger with a preexisting ICD underwent ECG-S for SICD. ECG and demographic data were analyzed for factors predictive of failure. Results: Seventy-three patients (mean age 14.2 ± 3.3 years; range 5–18 years) with hypertrophic cardiomyopathy (n = 24, 33%), long QT syndrome (n =18, 25%), other inherited arrhythmia syndromes (n = 20, 27%), congenital heart disease (n = 9, 12%), and miscellaneous conditions (n = 2) with an existing transvenous ICD underwent prospective ECG-S. Nineteen (26%) failed ECG-S. Failed patients had a longer corrected QT (QTc) interval (457 ms vs 425 ms; P =.03), a longer QRS duration (120 ms vs 98 ms; P =.04), and a lower ratio of R-wave to T-wave amplitudes (R:T ratio) in lead aVF (4 vs 5; P =.001). Multivariable logistic regression identified QTc interval (odds ratio [OR] 4.31; P =.04), QRS duration (OR 4.93; P =.03), R:T ratio in lead aVF (OR 3.13; P =.08) as predictors of failure. A risk score with 1 point each for QTc interval >440 ms, QRS duration >120 ms, and R:T ratio <6.5 in lead aVF was associated with probability of failure of 15.4% (1 point), 47.4% (2 points), and 88.6% (3 points), respectively. Conclusion: ECG-S failure for SICD occurred in 26% of children, which is higher than the reported incidence in adults. Factors predicting ECG-S failure included longer QTc interval, longer QRS duration, and lower R:T ratio in lead aVF.