T-wave Morphology Restitution Dependency with Heart Rate Range and Its Association with Sudden Cardiac Death in Chronic Heart Failure

Abstract

The index of T-wave morphology restitution (TMR) has recently been presented as a sudden cardiac death (SCD) predictor in a population of chronic heart failure (CHF) patients. This index quantifies the level of variation in the T-wave morphology per RR interval (RRI) increment. The impact of using different definitions of ranges of RRI (∆RRI) and the study of the interaction between TMR and ∆RRI are relevant for both the optimization and the mechanistic interpretation of the index. This study aims to investigate the interaction between ∆RRI and TMR and to assess whether different definitions of ∆RRI (patientsindependent or patient-specific) may affect the predictive value of TMR. Holter ECG recordings from 651 patients with CHF, including SCD, victims of other causes and survivors, were analyzed. Mann-Whitney test was used to evaluate significant differences between SCD victims and the rest of patients. In the patient-independent analysis, TMR values only showed significant differences when 0.25s≤ ∆RR≤0.3s, while in the patient-specific analysis TMR values were significantly different when ∆RR≥0.6 of the maximum RR range, ∆RR max . In conclusion, the index TMR is a predictor of SCD robust to variations in ∆RR values evaluated in segments comprising at least 0.6 of ∆RR max . IntroductionThe action potential duration (APD) restitution (APDR) curve represents the interaction between local APD and local cycle length [1]. The morphology of the T-wave reflects the distribution of the repolarization sequence along the ventricle [2][3][4]. Therefore, the spatio-temporal inhomogeneity of the ventricular repolarization process as a response to changes in heart rate may be captured by an index measuring T-wave morphological changes.In a recent study, the index of T-wave morphology restitution (TMR) was proposed and proved to predict sudden cardiac death (SCD) in a population of 651 chronic heart failure (CHF) patients [5]. The TMR is calculated as the difference in the morphology of two T-waves measured at two RR intervals (RRI) defining the maximum intrasubject RRI range, ∆RRI, and normalized by ∆RRI. The impact of using different definitions of ∆RRI and the study of the interaction between TMR and ∆RRI are relevant for both the optimization and the mechanistic interpretation of the index. This study aims to investigate the interaction between ∆RRI and TMR and to assess whether different definitions of ∆RRI may affect the predictive value of TMR.In this study we calculated the evolution of the index TMR with an patient-independent and patient-specific change in ∆RR. Then, we calculated the SCD predictive value of TMR at each value of ∆RR and we compared the patient-independent and patient-specific results. 2.Materials and Methods MaterialsThe study population included 651 consecutive patients with symptomatic CHF corresponding to NYHA classes II and III enrolled in the MUSIC study, a prospective, multicenter study designed to assess risk predictors for cardiovascular mortality in ambulatory patients with CHF [6]. ...