QRS Morphology, Left Ventricular Lead Location, and Clinical Outcome in Patients Receiving Cardiac Resynchronization Therapy

Study Questions:

What is the impact of electrical and anatomical location of the left ventricular (LV) lead in relation to baseline QRS morphology on the cardiac resynchronization therapy (CRT) outcome?


An LV lead electrical delay (LVLED) was measured intra-procedurally as an interval between QRS onset on the surface electrocardiogram (ECG) to the peak of sensed electrogram on LV lead and corrected for QRS width. The impact of the LVLED on time to first heart failure hospitalization (HFH), and composite outcome of all-cause mortality, HFH, LV assist device (LVAD) implantation, and cardiac transplantation at 3 years was assessed.


Among 144 patients (ages 67 ± 12 years, QRS duration 156 ± 28 ms, non–left bundle branch block [LBBB] 43%), HFH was higher in non-LBBB compared with LBBB patients (43.5 vs. 24%, p = 0.015). Within LBBB, patients with the long LVLED (≥50%) had 17% HFH versus 53% in the short LVLED (<50%), p = 0.002. Likewise in non-LBBB, patients with the long LVLED compared with the short LVLED had a lower HFH (36 vs. 61%, p = 0.026). In the adjusted Cox proportional hazards model, the long LVLED in LBBB and non-LBBB was associated with an improved outcome. Specifically, in non-LBBB, LVLED ≥50% was associated with improved event-free survival with respect to time to first HFH (hazard ratio, 0.34; p = 0.011) and composite outcome (hazard ratio, 0.41; p = 0.019).


The authors concluded that CRT delivered from an LV pacing site characterized by the long LVLED was associated with the most favorable outcome in LBBB and non-LBBB patients.


This study reports that in patients receiving CRT for advanced systolic HF and associated intraventricular conduction abnormality, LV lead placement in a region of a significant electrical delay (i.e., long LVLED) was associated with an improved event-free survival with respect to time to the first HFH and the composite outcome of all-cause mortality, HFH, LVAD implantation, and cardiac transplantation. Overall, it appears that the electrical location of the LV lead is associated with improved clinical outcomes in patients with both non-LBBB and LBBB QRS morphologies. These results need to be validated prospectively in a large multicenter trial.

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

Keywords: Heart Failure, Bundle-Branch Block, Hospitalization, Cardiac Resynchronization Therapy

< Back to Listings