Introduction: Left atrial (LA) dyssynchrony, defined as LA septal-lateral delay, is felt to improve with bifocal pacing.
Methods: Eight canines underwent sternotomy during general anesthesia. Bipolar plunge electrodes delivered transmyocardially over the septal, anterior, posterior, and lateral LA recorded local activation during pacing just faster than sinus from sinus node, right atrial appendage (RAA)+Bachmann’s Bundle (BBR), RAA+Coronary Sinus Ostium (CSO) and RAA+Low Lateral Left Atrium (LLL).
Results: All canines presented in sinus rhythm. Pacing from sinus node synchronously activated the septum at BBR and CSO, and activated the LA from septal to lateral by simultaneously propagating anterior and posterior wavefronts. RAA+ CSO pacing and RAA+ LLL pacing resulted in multiple wave-fronts anteriorly and posteriorly in the LA with associated activation dispersion. RAA+ BBR pacing produced simultaneously propagating LA anterior and posterior wavefronts, similar to sinus node pacing.
Conclusions: In this canine model, pacing induced left atrial conduction delay and activation dispersion, seen with bifocal RAA+CSO and RAA+LLL pacing may be avoided by bifocal pacing from RAA+BBR. Establishing clinical utility requires human studies for validation.