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.