QRS Axis and the Benefit of Cardiac Resynchronization Therapy in Patients with Mildly Symptomatic Heart Failure Enrolled in MADIT-CRT


  • Registration Identification Number: NCT00180271.

  • The MADIT-CRT study was supported by a research grant from Boston Scientific, St. Paul, Minnesota, to the University of Rochester School of Medicine and Dentistry.

  • Alon Barsheshet is a Mirowski-Moss Career Development Award Recipient in Cardiology.

  • Dr. Moss reports receiving honoraria and Dr. Cannom reports receiving travel support from Boston Scientific. Other authors: No disclosures.

Andrew Brenyo, M.D., University of Rochester Medical Center, Division of Cardiology, Box 679C Rochester, NY 14642, USA. Fax: 585-273-5283; E-mail:Andrew_Brenyo@urmc.rochester.edu


Cardiac Resynchronization Therapy and QRS Axis. Background: Mildly 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.

Methods : Baseline 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.

Results: Among 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).

Conclusions: LAD 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. (J Cardiovasc Electrophysiol, Vol. 24, pp. 442-448, April 2013)