Abstract 9375: Sum Absolute QRST Integral Predicts Low Risk of Ventricular Tachyarrhythmias and Sudden Cardiac Death In MADIT II Study

Abstract

Introduction. The need to extend risk stratification beyond use of ejection fraction is well recognized. New ECG risk marker, sum absolute QRST integral (SAI QRST) was recently proposed and was shown to be associated with low risk of sustained ventricular tachycardia (VT)/ventricular fibrillation (VF) in patients with structural heart disease and primary prevention implantable cardioverter-defibrillators (ICDs). The objective of this study was to validate predictive value of SAI QRST in analysis of landmark ICD trial MADIT II. Methods. Baseline orthogonal ECGs were recorded at rest during sinus rhythm in 750 MADIT II study participants and analyzed by customized Matlab software. Absolute QRST integral was measured as the arithmetic sum of areas under the QRST curve, averaged during a 5-minute epoch. Then the sum magnitude of three orthogonal leads absolute QRST integral (SAI QRST) was calculated. Primary end-point for analysis was sustained VT/VF with appropriate ICD therapies (shock or antitachycardia pacing), or sudden cardiac death. Results. During 3.5 years of follow-up, 143 patients experienced sustained VT/VF with appropriate ICD therapies, or died suddenly. In univariate analysis lowest quartile of SAI QRST (< 116 mV*ms) was associated with decreased risk of sustained VT/VF with appropriate ICD therapies or sudden cardiac death (Figure 1). In multivariate analysis after adjustment for blood urea nitrogen and New York Heart Association functional class, low quartile SAI QRST was associated with decreased risk of VT/VF or sudden cardiac death as compared to three higher SAI QRST quartiles (Hazard Ratio 0.64 ; 95% CI 0.42 - 0.99 ; p=0.045). Conclusion . In post-myocardial infarction patients with depressed ejection fraction the lowest quartile of SAI QRST is associated with lower risk of sustained ventricular tachyarrhythmias and sudden cardiac death than it is observed in patients with higher SAI QRST values. Further study of SAI QRST is warranted.