Background: Biatrial tachycardias (biAT) are complex arrhythmias involving electrical propagation between the right (RA) and the left atrium (LA) through the interatrial connections (IACs). Critical pathways along the IACs may contribute to arrhythmia maintenance during atrial fibrillation (AF), but remain clinically underdetected due to challenges in identifying IACs from the endocardium.
Methods: An in silico model to study biAT was developed. A patient-specific biatrial bilayer model derived from MRI was augmented to include the Bachmann's bundle (BB), fossa ovalis (FO), upper posterior (UP), and coronary sinus (CS) connections. Paroxysmal AF-induced remodeling was simulated using the Courtemanche ionic model. Monodomain simulations were run in openCARP. Reentry was induced using a decremental pacing protocol, and biAT was sustained for 5 s. Critical pathways across 6 possible interatrial loops were identified on the epicardial surface using the openDGM framework. Extracellular potentials were computed on the endocardial surface using a five-spline multipolar radial catheter positioned in the vecinity of the BB in both atria. In total, 10 bipolar electrograms (EGMs) were computed between consecutive pairs of electrodes for each catheter location. A total of 26 catheter placement configurations in LA and RA were evaluated, defined by a central position and inner and outer concentric rings.
Results: Endocardial bipolar EGMs had different activation patterns across the BB during biAT. Bipolar EGMs on the RA showed slightly higher number of BB activations than the ones in the LA (36.7±1.5 vs 31.8 ± 6.4). Epicardial unipolar EGMs alone did not aid identifying critical pathways. Increased bipolar fractionation impeded critical loop identification from the endocardium.
Conclusion: This study represents a first step toward identifying critical interatrial pathways and personalizing biatrial electrical coupling in computational models. Identification of critical pathways remains highly dependent on catheter configuration.