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Updated: Jun 12, 2026
Benefits of Cardiac Resynchronization Therapy in an Asynchronous Heart Failure Model Induced by Left Bundle Branch Ablation and Rapid Pacing
Published on: December 11, 2017
Myocardial infarction does not preclude electrical and hemodynamic benefits of cardiac resynchronization therapy in
Leonard M Rademakers1, Roeland van Kerckhoven, Caroline J M van Deursen
1Departments of Physiology and Cardiothoracic Surgery, Cardiovascular Research Institute Maastricht, Maastricht, The Netherlands.
Insights
Cardiac resynchronization therapy effectively improves heart function in ischemic cardiomyopathy, even with infarction. Optimal lead placement and timing are crucial for best results in these patients.
Area of Science:
- Cardiology
- Biomedical Engineering
- Heart Failure Research
Background:
- Ischemic cardiomyopathy patients often show reduced benefit from cardiac resynchronization therapy (CRT).
- Investigating CRT efficacy in a novel animal model of dyssynchronous ischemic cardiomyopathy is essential.
- Understanding the impact of myocardial infarction on CRT short-term efficacy is key.
Purpose of the Study:
- To evaluate the influence of infarction presence on short-term CRT efficacy in a canine model.
- To compare CRT response in hearts with left bundle branch block (LBBB) versus LBBB with myocardial infarction.
- To identify optimal pacing strategies for infarcted hearts.
Main Methods:
- Canine hearts with induced LBBB and chronic myocardial infarction (anterior or circumflex artery embolization) were studied.
- Right ventricular and multi-site left ventricular (LV) pacing were performed.
- LV pump function was assessed using conductance catheterization; electrical synchrony was mapped using epicardial ECG.
Main Results:
- Similar average and maximal improvements in electrical resynchronization and LV pump function were observed across groups (LBBB, LBBB+LADi, LBBB+LCXi).
- Optimal pacing sites varied based on infarction location (apical, midlateral, basal-lateral).
- Pacing at the site of maximal QRS shortening, not latest electrical activation, yielded the best results. The effective range of atrioventricular delays was smaller in infarcted hearts.
Conclusions:
- Cardiac resynchronization therapy demonstrates comparable efficacy in improving resynchronization and LV function in both infarcted and noninfarcted hearts.
- Optimal lead positioning and precise timing of LV stimulation are more critical in infarcted hearts for maximizing CRT benefits.
Background:
Several studies suggest that patients with ischemic cardiomyopathy benefit less from cardiac resynchronization therapy. In a novel animal model of dyssynchronous ischemic cardiomyopathy, we investigated the extent to which the presence of infarction influences the short-term efficacy of cardiac resynchronization therapy.
Methods And Results:
Experiments were performed in canine hearts with left bundle branch block (LBBB, n=19) and chronic myocardial infarction, created by embolization of the left anterior descending or left circumflex arteries followed by LBBB (LBBB+left anterior descending infarction [LADi; n=11] and LBBB+left circumflex infarction [LCXi; n=7], respectively). Pacing leads were positioned in the right atrium and right ventricle and at 8 sites on the left ventricular (LV) free wall. LV pump function was measured using the conductance catheter technique, and synchrony of electrical activation was measured using epicardial mapping and ECG. Average and maximal improvement in electric resynchronization and LV pump function by right ventricular+LV pacing was similar in the 3 groups; however, the site of optimal electrical and mechanical benefit was LV apical in LBBB hearts, LV midlateral in LBBB+LCXi hearts and LV basal-lateral in LBBB+LADi hearts. The best site of pacing was not the site of latest electrical activation but that providing the largest shortening of the QRS complex. During single-site LV pacing the range of atrioventricular delays yielding > or =70% of maximal hemodynamic effect was approximately 50% smaller in infarcted than noninfarcted LBBB hearts (P<0.05).
Conclusions:
Cardiac resynchronization therapy can improve resynchronization and LV pump function to a similar degree in infarcted and noninfarcted hearts. Optimal lead positioning and timing of LV stimulation, however, require more attention in the infarcted hearts.
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