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Left ventricular resynchronization therapy in a canine model of left bundle branch block
Lili Liu1, Bruce Tockman, Steven Girouard
1Heart Failure Research Department, Guidant Corporation, St. Paul, Minnesota 55112, USA.
Summary
Left ventricular (LV) and biventricular (BV) stimulation resynchronized cardiac function in a canine model with left bundle branch block (LBBB). This cardiac resynchronization therapy improved hemodynamic performance and corrected abnormal wall motion.
Area of Science:
- Cardiology
- Biomedical Engineering
- Physiology
Background:
- Heart failure patients with left bundle branch block (LBBB) exhibit positive responses to cardiac resynchronization therapy (CRT).
- The underlying mechanism may involve left ventricular (LV) resynchronization.
- A reliable animal model is crucial for studying CRT mechanisms.
Purpose of the Study:
- To investigate the efficacy of LV and biventricular (BV) stimulation in a canine model of LBBB.
- To elucidate the hemodynamic and mechanical effects of CRT in LBBB.
- To assess the resynchronization potential of different pacing strategies.
Main Methods:
- Anesthetized canine model of LBBB induced by radiofrequency ablation.
- Hemodynamic assessment (LV dP/dt, aortic pulse pressure) during various pacing modes (RV, LV, BV) and atrioventricular delays.
- Echocardiographic evaluation of septal and LV posterior wall motion.
Main Results:
- LBBB induction caused QRS widening and hemodynamic deterioration.
- LV and BV stimulation significantly improved LV dP/dt (16%) and pulse pressure (7%) post-ablation (P < 0.001).
- LV stimulation corrected paradoxical septal wall motion observed in LBBB.
Conclusions:
- LV and BV stimulation effectively improve cardiac function in a canine LBBB model.
- Resynchronization of LV electrical activation and mechanical contraction is the primary mechanism.
- These findings support the role of CRT in managing LBBB-associated heart failure.