A new electrocardiogram marker to identify patients at low risk for ventricular tachyarrhythmias: Sum magnitude of the absolute QRST integral

Objective: We proposed and tested a novel electrocardiogram marker of risk of ventricular arrhythmias (VAs). Methods: Digital orthogonal electrocardiograms were recorded at rest before implantable cardioverter-defibrillator (ICD) implantation in 508 participants of a primary prevention ICDs prospective cohort study (mean ± SD age, 60 ± 12 years; 377 male [74%]). The sum magnitude of the absolute QRST integral in 3 orthogonal leads (SAI QRST) was calculated. A derivation cohort of 128 patients was used to define a cutoff; a validation cohort (n = 380) was used to test a predictive value. Results: During a mean follow-up of 18 months, 58 patients received appropriate ICD therapies. The SAI QRST was lower in patients with VA (105.2 ± 60.1 vs 138.4 ± 85.7 mV - ms, P = .002). In the Cox proportional hazards analysis, patients with SAI QRST not exceeding 145 mV - ms had about 4-fold higher risk of VA (hazard ratio, 3.6; 95% confidence interval, 1.96-6.71; P < .0001) and a 6-fold higher risk of monomorphic ventricular tachycardia (hazard ratio, 6.58; 95% confidence interval, 1.46-29.69; P = .014), whereas prediction of polymorphic ventricular tachycardia or ventricular fibrillation did not reach statistical significance. Conclusion: High SAI QRST is associated with low risk of sustained VA in patients with structural heart disease.