Abstract 12227: Early Stimulation of Fast-Conducting Endocardial Tissue Underlies Improvements in Endocardial Pacing
Introduction: Cardiac resynchronization therapy (CRT) delivered via left ventricular (LV) endocardial pacing (ENDO-CRT) is associated with improved acute haemodynamic response compared to LV epicardial pacing (EPI-CRT). The mechanisms underlying this improved response remain controversial.
Hypothesis: We used computational electrophysiological models to test the hypotheses that the following ordered cardiac properties are advantageous to ENDO-CRT: fast endocardial conduction (FEC), inherent geometry, asymmetric transmural conduction, and tissue anisotropy.
Methods: Cardiac activation was simulated using the mono-domain tissue excitation model in 2D canine and human, and 3D canine biventricular models. The latest activation times (LATs) for LV endocardial and biventricular epicardial tissue were calculated (LVLAT and TLAT), as well the percentage decrease in LATs for endocardial (en) vs epicardial (ep) LV pacing (defined as %dLV=100*(LVLATep- LVLATen)/LVLATep and %dT=100*( TLATep- TLATen)/TLATep respectively).
Results: Normal canine cardiac anatomy is responsible for %dLV and %dT values of 7.4% and 5.5%, respectively. Concentric and eccentric remodelled anatomies resulted in %dT values of 15.6% and 1.3%, respectively. The 3D biventricular paced canine model resulted in %dLV and %dT values of -7.1% and 1.5%, in contrast to the experimental observations of 16% and 11%, respectively. Adding FEC to this model altered %dLV and %dT to 13.1% and 10.1%, respectively.
Conclusions: Our results provide a physiological explanation for improved response to ENDO-CRT. We predict that patients with viable fast-conducting endocardial tissue and/or distal Purkinje network, as well as concentric remodelling, are more likely to benefit from reduced ATs and increased synchrony arising from endocardial pacing.
Author Disclosures: E.R. Hyde: Other Research Support; Significant; Boston Scientific Corp.. G. Plank: None. C.A. Rinaldi: Research Grant; Significant; St Jude Medical, Medtronic, and Boston Scientific. S.A. Niederer: Research Grant; Significant; British Heart Foundation.
- © 2015 by American Heart Association, Inc.