Repolarization heterogeneity in patients with cardiac resynchronization therapy and its relation to ventricular tachyarrhythmias.

BACKGROUND: Cardiac resynchronization therapy (CRT) has been shown to induce left ventricular reverse remodeling, but little is known about its influence on ventricular repolarization.

OBJECTIVE: The purpose of this study was to evaluate changes in ventricular repolarization of native conduction after CRT and its relation to ventricular tachycardia (VT) and ventricular fibrillation (VF) during long-term follow-up.

METHODS: We prospectively included 64 patients with heart failure treated with CRT. QT interval, TpTe, and TpTe/QT ratio were analyzed from 20-minute high-resolution ECGs that were recorded at baseline and 1, 3, 6, 9, and 12 months after CRT implantation. CRT was temporary inhibited during follow-up to record intrinsic ECG. Patients with a decrease of left ventricular end-systolic volume ≥15% at 12-month follow-up (mid-term follow-up) were considered as responders. Occurrences of VT/VF during follow-up were noted.

RESULTS: Significant increase of repolarization heterogeneity in the first months after implantation was observed (P <.05) but then declined during 12 months of follow-up. Patients with VT/VF during long-term follow-up had higher repolarization heterogeneity at mid-term follow-up than patients without VT/VF (TpTe/QT ratio: 0.263 [0.204-0.278] vs 0.225 [0.204-0.239]; P = .045). Echocardiographic response at mid-term follow-up did not significantly influence the rate of VT/VF (log-rank P = .252). In multivariate Cox regression analysis, only high repolarization heterogeneity at mid-term follow-up (TpTe/QT ratio >0.260) was independently associated with high risk of VT/VF (hazard ratio 4.29; 95% confidence interval 1.40-13.15; P = .011).

CONCLUSION: CRT induces time-dependent changes in repolarization parameters in the first year after implantation. High repolarization heterogeneity at mid-term follow-up was associated with higher rate of VT/VF during long-term follow-up.