Importance of right and left atrial dilation and linear ablation for perpetuation of sustained atrial fibrillation

Introduction: Atrial dilation associated with increasing atrial pressure plays an apparent role in the development of atrial fibrillation (AF). We characterized a new model of separate and biatrial dilation in the Langendorff-perfused rabbit heart. The aim of this study was to examine if sustained AF in this model (1) would be inducible by separate right atrial (RA) and left atrial (LA) dilation; (2) would be reproducibly inducible at the same pressure level; and (3) could be suppressed by RA, LA, or biatrial ablation. Methods and Results: Intra-atrial pressure was increased stepwise in the RA (n = 13), LA (n = 12), or both atria (n = 25) until sustained AF could be induced or a pressure of 20 cm H2O was reached. The stimulation protocol was repeated once in RA and LA dilation (n = 9) and three times In biatrial dilation (n = 7). Then, RA orifices (superior and inferior caval veins, tricuspid valve annulus, and foramen ovale) or LA orifices (pulmonary veins, mitral valve annulus, and foramen ovale) were connected by radiofrequency (RF) lesions. Sustained AF was rendered inducible in 100% of hearts with biatrial dilation, but in only 92% of hearts with RA dilation and 67% with LA dilation. Inducibility of sustained AF was reproducible. Under biatrial dilation, not RA ablation (0/10 hearts; P = NS) but LA ablation (4/11 hearts; P < 0.05) and biatrial ablation (16/21; P < 0.01) reduced the inducibility of sustained AF. Conclusion: The inducibility of sustained AF due to increased intra-atrial pressure differs between the RA and LA. LA and biatrial lesions, not RA RF lesions, reduce the ability to perpetuate sustained AF.