Lead one ratio in left bundle branch block predicts poor cardiac resynchronization therapy response
Zak Loring1,2, Daniel J Friedman1,2, Kasper Emerek1,3
1Division of Cardiology, Department of Medicine, Duke University Medical Center, Durham, North Carolina.
Insights
A low electrocardiogram (ECG) lead one ratio (LOR) predicts worse outcomes after cardiac resynchronization therapy (CRT) in patients with left bundle branch block (LBBB). This ratio may identify high-risk individuals needing CRT.
Area of Science:
- Cardiology
- Electrophysiology
- Medical Diagnostics
Background:
- A low electrocardiogram (ECG) lead one ratio (LOR) is linked to reduced left ventricular ejection fraction (LVEF) and poorer outcomes in left bundle branch block (LBBB).
- The effect of LOR on cardiac resynchronization therapy (CRT) outcomes in LBBB patients remains unclear.
Purpose of the Study:
- To investigate the association between baseline ECG LOR and clinical outcomes following CRT implantation in LBBB patients.
- To evaluate the impact of LOR on echocardiographic changes, specifically LVEF and LV volumes, after CRT.
Main Methods:
- A cohort of 496 consecutive CRT-defibrillator recipients with LBBB was analyzed.
- Time to heart transplant, left ventricular assist device (LVAD) implantation, or death was compared between LOR groups (<12 vs. ≥12) using Cox-proportional hazard models.
- Changes in LVEF and LV volumes post-CRT were assessed based on LOR.
Main Results:
- A baseline LOR <12 was associated with a 1.69-fold increased risk of heart transplant, LVAD, or death (adjusted HR: 1.69; P=.01).
- Patients with LOR <12 showed less reduction in LV end-diastolic volume (-4% vs. -13%; P=.04) and LV end-systolic volume (-9% vs. -22%; P=.03) after CRT.
- In patients with QRS duration ≥150 ms, LOR <12 significantly increased the risk of adverse events (adjusted HR: 2.01; P=.008).
Conclusions:
- A low baseline ECG LOR (<12) is a predictor of worse outcomes after CRT in LBBB patients.
- The LOR may be particularly useful in identifying high-risk patients with a QRS duration ≥150 ms who may not benefit optimally from CRT.
- This ECG marker could aid in risk stratification for patients undergoing CRT implantation.
Background:
A low electrocardiogram (ECG) lead one ratio (LOR) of the maximum positive/negative QRS amplitudes is associated with lower left ventricular ejection fraction (LVEF) and worse outcomes in left bundle branch block (LBBB); however, the impact of LOR on cardiac resynchronization therapy (CRT) outcomes is unknown. We compared clinical outcomes and echocardiographic changes after CRT implantation by LOR.
Methods:
Consecutive CRT-defibrillator recipients with LBBB implanted between 2006 and 2015 at Duke University Medical Center were included (N = 496). Time to heart transplant, left ventricular assist device (LVAD) implantation, or death was compared among patients with LOR <12 vs ≥12 using Cox-proportional hazard models. Changes in LVEF and LV volumes after CRT were compared by LOR.
Results:
Baseline ECG LOR <12 was associated with an adjusted hazard ratio (HR) of 1.69 (95% CI: 1.12-2.40, P = .01) for heart transplant, LVAD, or death. Patients with LOR <12 had less reduction of LV end diastolic volume (ΔLVEDV -4 ± 21 vs -13 ± 23%, P = .04) and LV end systolic volume (ΔLVESV -9 ± 27 vs -22 ± 26%, P = .03) after CRT. In patients with QRS duration (QRSd) ≥150 ms, LOR <12 was associated with an adjusted HR of 2.01 (95% CI 1.21-3.35, P = .008) for heart transplant, LVAD, or death, compared with LOR ≥12.
Conclusions:
Baseline ECG LOR <12 portends worse outcomes after CRT implantation in patients with LBBB, specifically among those with QRSd ≥150 ms. This ECG ratio may identify patients with a class I indication for CRT implantation at high risk for poor postimplantation outcomes.
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