• Andrew Brenyo, Mohan Rao, Alon Barsheshet, David Cannom, Aurelio Quesada, Scott McNitt, David T Huang, Arthur J Moss, and Wojciech Zareba.
• Cardiology Division of the Department of Medicine, University of Rochester Medical Center, Rochester, New York 14642, USA. Andrew_Brenyo@urmc.rochester.edu
• J. Cardiovasc. Electrophysiol. 2013 Apr 1; 24 (4): 442-8.

BackgroundMildly symptomatic heart failure (HF) patients derive substantial clinical benefit from cardiac resynchronization therapy with defibrillator (CRT-D) as shown in MADIT-CRT. The presence of QRS axis deviation may influence response to CRT-D. The objective of this study was to determine whether QRS axis deviation will be associated with differential benefit from CRT-D.MethodsBaseline electrocardiograms of 1,820 patients from MADIT-CRT were evaluated for left axis deviation (LAD: quantitative QRS axis -30 to -90) or right axis deviation (RAD: QRS axis 90-180) in left bundle branch block (LBBB), right bundle branch block (RBBB), and nonspecific interventricular conduction delay QRS morphologies. The primary endpoints were the first occurrence of a HF event or death and the separate occurrence of all-cause mortality as in MADIT-CRT.ResultsAmong LBBB patients, those with LAD had a higher risk of primary events at 2 years than non-LAD patients (20% vs 16%; P = 0.024). The same was observed among RBBB patients (20% vs 10%; P = 0.05) but not in IVCD patients (22% vs 23%; P = NS). RAD did not convey any increased risk of the primary combined endpoint in any QRS morphology subgroup. When analyzing the benefit of CRT-D in the non-LBBB subgroups, there was no significant difference in hazard ratios for CRT-D versus ICD for either LAD or RAD. However, LBBB patients without LAD showed a trend toward greater benefit from CRT therapy than LBBB patients with LAD (HR for no LAD: 0.37, 95% CI: 0.26-0.53 and with LAD: 0.54, 95% CI: 0.36-0.79; P value for interaction = 0.18).ConclusionsLAD in non-LBBB patients (RBBB or IVCD) is not associated with an increased benefit from CRT. In LBBB patients, those without LAD seem to benefit more from CRT-D than those with LAD.© 2012 Wiley Periodicals, Inc.

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