Biatrial activation patterns and hemodynamics during Bachmann bundle pacing: learnings from a porcine model
A Gil Ramirez, J Norup Hertel, T Mohaissen, S M Sattler, J G L M Luermans, K Vernooy, B J M Hermans, S M Chaldoupi, J Hansen, T Jespersen, S Dalgas Nissen, D LinzAbstract
Background
Coordinated atrial activation is essential for effective atrioventricular coupling and cardiac performance. Compared to traditional right atrial appendage (RAA) pacing, the Bachmann bundle (BB), the major interatrial conduction pathway, is emerging as a more physiological pacing area and may correct atrial dyssynchronization. Yet, the immediate hemodynamical impact of BB pacing remains unclear.
Purpose
To compare intracardiac pressure responses and atrial activation patterns during RAA and BB pacing in a porcine model. We hypothesized that BB pacing would produce a more synchronized total atrial activation with favorable hemodynamic effects compared with RAA pacing.
Methods
Three Landrace pigs (~50kg) underwent biatrial electroanatomical mapping (CARTO 3 system v7) and invasive hemodynamics assessment under general anesthesia. After baseline sinus rhythm activation mapping with a high-density mapping catheter (Octaray), atrial pacing was performed with a contact force enabled catheter (ThermoCool SmartTouch) from the left atrial earliest activation site to identify the BB area by mapping the right atrial breakthrough of retrograde BB conduction (Figure 1A). Then, pacing from the RAA and BB area was conducted at decremental cycle lengths, lasting ≥1 minute to achieve hemodynamic stability. Lastly, high-density activation maps were obtained during pacing at 600ms. Pressures from the left and right atrium, right and left ventricle, pulmonary artery and femoral artery were simultaneously recorded.
Results
BB pacing produced a P-wave similar to sinus rhythm in duration and morphology (64ms (62-79) vs 67ms (66-78) respectively, p=0.36) (Figure 1B). Additionally, BB pacing was related to a shorter total atrial activation time compared to RAA pacing, although not statistically significant (80ms (79-117) vs 125ms (120-155), p=0.25). Left atrial activation did not differ between conditions. Hemodynamically, BB pacing resulted in higher intracardiac and systemic pressures across all measured sites and pacing cycle lengths compared with RAA pacing: Left ventricular mean pressure was +14.61% (56.23±4.77 mmHg vs 49.06±7.48 mmHg; p=0.003); left atria mean pressure +7.55% (14.10±2.23 mmHg vs 13.11±1.55 mmHg; p=0.01), and femoral pressure +16.45% (77.20±11.40 mmHg vs 66.29±14.90 mmHg; p<0.001). No significant differences were observed in right atrial or ventricular pressures (Figure 1C).
Conclusions
This study establishes a reproducible large-animal model for simultaneous evaluation of atrial activation patterns and hemodynamics for the assessment of different atrial pacing approaches. BB pacing shortens left atrial activation times and acutely increases systemic and ventricular pressures compared with conventional RAA pacing. Ongoing analyses may support future development of physiological atrial pacing strategies.