The Association Between Biventricular Pacing and Cardiac Resynchronization Therapy-Defibrillator Efficacy When Compared With Implantable Cardioverter Defibrillator on Outcomes and Reverse Remodeling

Study Questions:

What is the relationship between biventricular (BIV) pacing percentage thresholds and the efficacy of cardiac resynchronization therapy (CRT)?


Using Kaplan–Meier plots, the authors estimated the threshold of BIV pacing percentage needed for CRT-D to be superior to implantable cardioverter-defibrillators (ICDs) on the endpoint of heart failure (HF) or death in 1,219 left bundle branch block (LBBB) patients in the MADIT-CRT trial.


In multivariable Cox analyses, no difference was seen in the risk of HF/death between ICD and CRT-D patients with BIV pacing ≤90% [hazard ratio (HR) = 0.78 (0.47–1.30), p = 0.3], and with increasing BIV pacing the risk of HF/death was decreased [CRT-D BIV 91–96% vs. ICD: HR = 0.63 (0.42–0.94), p = 0.024 and CRT-D BIV ≥97% vs. ICD: HR = 0.32 (0.23–0.44), p < 0.001]. The risk of death alone was reduced by 52% in CRT-D patients with BIV ≥97% (HR = 0.48, p < 0.016), when compared with ICD patients. Within the CRT-D group, for every 1 percentage point increase in BIV pacing, the risk of HF/death and death alone significantly decreased by 6% and 10%, respectively. Increasing BIV pacing percentage was associated with significant reductions in left ventricular volume.


In patients with LBBB, who were in sinus rhythm at enrollment, BIV pacing exceeding 90% was associated with a benefit of CRT-D in HF/death when compared with ICD patients. Furthermore, BIV pacing ≥97% was associated with an even further reduction in HF/death, a significant 52% reduction in death alone, and increased reverse remodeling.


Based on the results of this and prior analyses, clinicians should make every effort to maximize BIV pacing, preferably to near 100%.

Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Implantable Devices, EP Basic Science, SCD/Ventricular Arrhythmias, Acute Heart Failure

Keywords: Cardiac Pacing, Artificial, Heart Failure, Bundle-Branch Block, Defibrillators, Implantable, Cardiac Resynchronization Therapy

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