Abstract 2659: Increased Variability of the QRST Integral Ratio in an Orthogonal ECG Stratifies the Risk of Sustained Ventricular Tachyarrhythmias in Primary Prevention ICD Patients
Introduction. Risk stratification for primary prevention implantable cardioverter-defibrillators (ICDs) is currently suboptimal and novel approaches are needed. It is known that the scalar ECG QRST integral represents the summed heterogeneity of action potential morphology throughout the ventricles. We hypothesized that increased variability of the QRST integral ratio predicts ventricular tachycardia (VT) / ventricular fibrillation (VF) in patients at risk for sudden cardiac death (SCD).
Methods. Digital orthogonal ECGs were recorded during sinus rhythm for 5–10 min at rest before ICD implantation in 101 participants of PROSE-ICD, a multicenter prospective cohort study of primary prevention ICD patients (mean age 59 ±11, 52 patients with ischemic and 48 with non-ischemic cardiomyopathy). The QRST integral, integral of the absolute QRST value, and QRST integral ratio was measured in each beat in the epoch by the customize software (implemented in Matlab). The QRST integral ratio was derived by dividing the sum of positive areas under the QRST curve by the sum of negative areas under the QRST curve. The beat-to-beat QRST integral ratio variance was calculated. Patients were followed prospectively for at least 3 months, sustained VT/VF with appropriate ICD therapies served as endpoints for analysis.
Results. During a mean follow-up of 5 ±7 months, 16 patients had sustained VT/VF and received appropriate ICD therapies. In all orthogonal leads integral of the absolute QRST value in patients with VT/VF at follow-up was significantly smaller than in patients without VT/VF (in lead Z 43.5 ±25.0 vs. 74.0 ±58.5, P=0.034). The unadjusted QRST integral ratio variance was significantly higher (0.025 ±0.031 vs. 0.006 ±0.007, P=0.016) in patients with appropriate ICD therapies in the lead Z. A similar trend was observed in the leads X and Y. In a multivariate Cox regression model adjusted for heart rate and etiology of cardiomyopathy, the QRST integral ratio was a significant predictor of VT/VF (HR 2.79; 95% CI 1.002–7.795, P=0.05).
Conclusion. QRST integral ratio variability is a novel, easily quantified ECG marker for SCD risk stratification in primary prevention populations that deserves further study.