Introduction
Cardiac resynchronization therapy (CRT) was shown to improve symptoms and decrease mortality in patients with heart failure (HF) with a wide QRS 1-3. However, data on the benefit of the device by QRS morphology are conflicting. Current ESC Guidelines provide a Class II recommendation for CRT-D implantation in patients without left bundle branch block (LBBB) 4, yet several randomized studies have reported on the relative absence of clinical benefit of CRT in non-LBBB patients compared to those with LBBB. 5Therefore, studies on improved risk stratification for CRT-D in patients without LBBB are needed.
Recent studies have attempted to identify subgroups of non-LBBB patients who may respond clinically to CRT, such as those with prolonged PR intervals (≥230 ms) 6 or those with (RBBB) with concomitant left-sided delay and those with significant burden of right ventricular pacing, with conflicting results 7. Our data from MADIT-CRT suggest a possible harm, with increased risk for ventricular tachyarrhythmias (VTA) among non-LBBB patients implanted with a CRT-D device compared with implantable cardioverter-defibrillator (ICD)-only therapy. 8,9 The exact pathophysiology behind this observation remains unclear, however these findings indicate a possible pro-arrhythmic effect of CRT in this population that may lead to subsequent adverse outcomes. 10-13
Accordingly, the primary aim of the present study was to identify risk factors (RF) for VTA in patients without LBBB who were enrolled in MADIT-CRT. We hypothesized that combined RF assessment can be used to identify those in whom CRT implantation would beneficial vs. proarrhythmic.