New atrial fibrillation model with endocardial approach by CRT bi-electrode atrial pacing in mini-pigs

Objective: To evaluate the model of atrial fibrillation (AF) in mini-pigs with endocardial approach implantation of CRT-P using bi-electrodes pacing through RV/LV connectors.Methods: All surgical interventions were minimally invasive and conducted under general anaesthesia. CRT-P was implanted endocardially, using X-ray. First electrode was fixed in the right atrial appendage. The second one — in the interatrial septum or the right atrial free wall. Both of them were connected with CRT-P through RV/LV. Bi-electrode atrial stimulation was realized during a week with a basic heart rate of 150 bpm and a delay between electrodes of 80 ms (mean 450 bpm), which corresponds to the heart rate (HR) of AF. Electrophysiological study was performed during the experiment to analyze the cardiac conduction system. AF inducibility was evaluated before and after stimulation.Results: A series of experiments demonstrated that there were no complications following the device and electrodes implantation. There was a non-sustained paroxysm of AF before permanent pacing in one of three pigs. After pacing we noted a tendency to increase the baseline HR (average frequency from 94 ± 4 to 98 ± 6 bpm). Non-sustained paroxysm of AF was induced in all cases. The sustained AF with 92 min burden was induced in one pig.Conclusion: Endocardial bi-electrode atrial pacing in mini-pigs has proven to be safe. This AF model improves AF inducibility and can be considered as an alternative to epicardial stimulation for experiments employing AF models. Received 4 December 2022. Revised 17 January 2023. Accepted 18 January 2023. Funding: The study was supported by Russian Science Foundation (project No. 22-25-00672). Conflict of interest: The authors declare no conflict of interest. Contribution of the authorsConception and study design: V.V. Beloborodov, D.V. Losik, E.V. FisherData collection and analysis: E.V. Fisher, V.V. Beloborodov, D.V. Losik, A.G. FilippenkoDrafting the article: D.V. Losik, E.V. Fisher, V.I. Murtazin, V.V. BeloborodovCritical revision of the article: A.B. Romanov, D.V. Losik, V.V. Shabanov, I.L. MikheenkoFinal approval of the version to be published: D.V. Losik, V.V. Beloborodov, E.V. Fisher, V.I. Murtazin, A.G. Filippenko, I.L. Mikheenko, V.V. Shabanov, A.B. Romanov