Effect of biventricular pacing on ventricular repolarization and functional indices in patients with heart failure: lack of association with arrhythmic events

We prospectively assessed the effects of biventricular (BiV) pacing on electrocardiographic (ECG) and vectorcardiographic (VCG) descriptors of ventricular depolarization and repolarization and their association with appropriate implantable cardioverter defibrillator (ICD) activation. We studied 70 consecutive heart failure (HF) (37 ischaemic) patients (64 males, age 66.3 years) with a history of syncope or sustained ventricular tachycardia (VT) who underwent implantation of a BiV-ICD. An invasive electrophysiological study (EPS) was performed before the implantation and 12-lead digital ECGs before and 30 days after implantation. Serial echocardiographic studies were performed. Follow-up duration was 1 year. Maximum (P < 0.001) and minimum (P = 0.004) QT intervals were significantly decreased, whereas QT dispersion was not altered (P = 0.086). QRS duration was shortened (P < 0.001), whereas QRS dispersion was significantly decreased (P = 0.034). Spatial T and QRS vector amplitudes decreased (P < 0.001, for both), whereas the spatial QRS-T angle was not affected (P = 0.671). Twenty-seven (38.6%) patients, experienced appropriate ICD therapies during follow-up. None of the ECG or VCG parameters (pre- or post-implant) were able to identify patients with appropriate ICD therapies during follow-up. Only the presence of a previous episode of sustained VT (spontaneous or inducible on EPS) was strongly associated with appropriate ICD therapies (multivariate P = 0.00 014; odds ratio 24.5). Improvement or no alteration of ECG and VCG descriptors of ventricular depolarization and repolarization was demonstrated after implantation of a BiV-ICD in HF patients. None of these parameters were associated with appropriate ICD therapies, whereas a previous episode of VT or induction of sustained VT on EPS predicted appropriate ICD treatments.