Horizontal QRS axis predicts response to cardiac resynchronization therapy in heart failure patients with left bundle
Zhisheng Chen1, Jianmin Chu2, Jing Wang2
1Department of Cardiovascular Medicine, First Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong, China; Clinical Research Centre, First Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong, China; Centre for Precision Health, School of Medical and Health Sciences, Edith Cowan University, Perth, Western Australia, Australia; School of Medical and Health Sciences, Edith Cowan University, Perth, Western Australia, Australia.
Insights
The horizontal QRS axis accurately predicts cardiac resynchronization therapy (CRT) response in heart failure (HF) patients with left bundle branch block (LBBB). This finding improves patient selection for CRT and predicts prognosis, including reduced hospitalization and mortality.
Area of Science:
- Cardiology
- Electrophysiology
- Heart Failure Management
Background:
- Standard electrocardiogram (ECG) criteria for left bundle branch block (LBBB) have limited accuracy in predicting left ventricular electrical dyssynchrony.
- This limitation complicates the selection of optimal candidates for cardiac resynchronization therapy (CRT).
Purpose of the Study:
- To evaluate the predictive capability of the horizontal QRS axis for CRT response in heart failure (HF) patients diagnosed with LBBB.
- To assess the prognostic value of the horizontal QRS axis in this patient cohort.
Main Methods:
- Calculated horizontal QRS axis direction and magnitude using V2 and V6 lead amplitudes.
- Defined CRT response by a ≥10% increase in left ventricular ejection fraction and ≥1 NYHA class reduction at 1 year post-implantation.
- Assessed composite endpoint of HF hospitalization or all-cause mortality.
Main Results:
- CRT responders exhibited significantly more backward deviation and larger magnitude of the horizontal QRS axis compared to non-responders (P < .001 for both).
- The horizontal QRS axis direction and magnitude independently predicted CRT response (AUC 0.778 and 0.749, respectively).
- Combining both parameters improved prediction (AUC 0.814) and predicted the composite endpoint, showing reduced hazard ratios for hospitalization or mortality.
Conclusions:
- The horizontal QRS axis is a precise predictor of CRT response in HF patients with LBBB.
- Its direction and magnitude offer valuable prognostic information, aiding in the selection of CRT candidates and predicting clinical outcomes.
Background:
Electrocardiogram criteria for left bundle branch block (LBBB) inadequately predict left ventricular electrical dyssynchrony, complicating cardiac resynchronization therapy (CRT) candidate selection.
Objective:
This study aimed to investigate the predictive value of the horizontal QRS axis for CRT response in heart failure (HF) patients with LBBB patterns.
Methods:
The direction and magnitude of the horizontal QRS axis were calculated using the net amplitudes in leads V2 and V6. CRT response was defined as a ≥10% increase in left ventricular ejection fraction and at least 1 New York Heart Association class reduction 1 year after CRT implantation. The composite end point included HF hospitalization or all-cause mortality.
Results:
Of 244 consecutive CRT recipients, 156 (63.9%) responded favorably; 88 (36.1%) were nonresponders. The horizontal QRS axis demonstrated significant backward deviation (-75.5° [-79.7° to -69.0°] vs -65.0° [-73.0° to -46.5°]; P < .001) and larger magnitude (35.5 ± 10.9 mm vs 25.5 ± 10.5 mm; P < .001) in CRT responders compared with nonresponders. The direction and magnitude independently predicted CRT response with an area under the curve of 0.778 (95% confidence interval [CI], 0.717-0.839) and 0.749 (95% CI, 0.685-0.814), respectively. Combining both parameters increased the area under the curve to 0.814 (95% CI, 0.760-0.868). Moreover, the direction and magnitude of the horizontal QRS axis, or their combination, predicted the composite end point of HF hospitalization or all-cause mortality, with hazard ratios of 0.36 (95% CI, 0.22-0.60), 0.41 (95% CI, 0.25-0.67), and 0.25 (95% CI, 0.15-0.41), respectively.
Conclusion:
Horizontal QRS axis accurately predicts CRT response and prognosis in HF patients with LBBB.
More Related Videos
10:17Real-Time Cardiac Mapping with a Noninvasive Imageless Electrocardiographic Imaging System
Published on: April 11, 2025
06:57Ablation of Ischemic Ventricular Tachycardia Using a Multipolar Catheter and 3-dimensional Mapping System for High-density Electro-anatomical Reconstruction
Published on: January 31, 2019
Related Concept Videos
01:22Heart Failure Drugs: β-Blockers
01:29Electrocardiogram
Three major waveforms are present in a typical ECG recording: the P wave, the QRS complex, and...
01:28Electrocardiogram Fundamentals
An electrocardiogram (ECG) is a diagnostic tool for identifying cardiac conditions such as arrhythmias, conduction abnormalities, and myocardial ischemia.
Definition
An electrocardiogram (ECG) visualizes the heart's electrical activity by tracing the electrical movement associated with each heartbeat on a graph or monitor. As the heart beats, an electrical wave passes through it, correlating with the cardiac cycle events.
Parts of an ECG
An ECG utilizes electrodes on the skin...