Usefulness of a standard 12-lead electrocardiogram to predict the eligibility for a subcutaneous defibrillator.

Background: Currently, the eligibility for a subcutaneous implantable defibrillator (S-ICD) system relies on a pre-implant vector screening based on the automated screening tool (AST). We investigated which 12-lead ECG characteristics are associated with eligibility for an S-ICD in a heterogeneous population at risk for sudden cardiac death (SCD). The goal is to determine patient eligibility for S-ICD using the standard 12-lead ECG, thereby avoiding additional AST screening.

Methods: We evaluated the eligibility for an S-ICD in 254 consecutive patients at risk for SCD. We identified 12-lead ECG parameters which were independently associated with AST passing (≥1 vector) using multivariable logistical regression analysis in our derivation cohort. The final model was tested in a separate validation cohort.

Results: The overall passing rate was 92% in our derivation cohort. Independent 12-lead ECG characteristics associated with AST passing were QRS ≤ 130 ms, absence of QRS/T discordance in lead II and R/T-ratio ≥3.5 in lead II. Eighty-three of 254 patients (33%) fulfilled these three criteria and had a passing rate of 100%. Of the validation cohort, 37 of 60 patients (62%) fulfilled all three criteria and also had a passing rate of 100%. The interobserver agreement for applying the ECG model was 90% (Cohen's Kappa = 0.80).

Conclusion: Using the standard 12-lead ECG, we developed a simple screening model with a high specificity for S-ICD eligibility. Our results suggest that patients who fulfill the three ECG criteria do not need additional AST-screening.