CRT35: SUDDEN CARDIAC DEATH FOLLOWING CARDIAC RESYNCHRONIZATION THERAPY IS RELATED TO INCREASED QT DISPERSION

Recent studies suggest that biventricular pacing with defibrillator back-up (BiVP-D) improves mortality in patients with heart failure. In animal studies and in acute human studies, epicardial left ventricular pacing and BiVP has been shown to prolong the QT interval and the transmural dispersion of repolarisation, both of which predispose to ventricular tachyarrhythmias. We investigated whether BiVP leads to changes in QT interval and QT dispersion (QTd) and whether such changes relate to sudden cardiac death in patients undergoing BiVP.

76 patients with heart failure in NYHA class II (n=1), III (n=45) or IV (n=30) on optimum drug treatment and with a wide QRS complex (160.7 (3.3) [mean (SEM)] underwent novo BiVP (n= 62) or upgrading from right ventricular to BiVP (n=14). QTd, evaluated from the 6 standard chest leads and corrected for rate (QTcd), was measured before and 1 month following implantation.

Over a follow-up period of 829 (range: 342 to 1492) days, 7 patients died suddenly and 1 was resuscitated from ventricular fibrillation (VF). Whereas QTcd increased by 58.7 (23.7) ms from baseline in non responders, it decreased by 3.5 (5.2) ms in responders (p=0.0005, ANOVA). Baseline QRS and QT interval duration and changes from baseline in these variables did not emerge as predictors of outcome

Sudden cardiac death in patients treated with BiVP is related to increased QTcd following implantation. Further studies are needed to determine whether evaluation of QTcd at the time of BiVP implantation can be used to risk-stratify patients for the use of BiVP-D.