Relationship between atrial fibrillatory rate based on analysis of a modified base-apex surface electrocardiogram analysis and the results of transvenous electrical cardioversion in horses with spontaneous atrial fibrillation

Objectives: To compare the atrial fibrillatory rate (AFR) derived from a local right atrial intracardiac recording (RA-FR) and from a single-lead surface elec-trocardiogram (ECG) during atrial fibrillation (AF) and to evaluate the correlation with transvenous electrical cardioversion (TVEC) threshold (in Joules), number of shocks and cardioversion success rate in horses. Animals: ECGs and clinical records of horses with AF treated by TVEC. Horses were included if a simultaneous recording of the right atrial intracardiac electrogram and a modified base-apex ECG were available. Materials and methods: Clinical records of horses with AF treated by TVEC were re-viewed. Three-minute long episodes of simultaneous electrograms and surface ECG during AF were selected for analysis and compared using Bland-Altman analysis. The mean RA-FR was measured from the deflections on the intracardiac electro-gram, while the AFR was extracted from the surface ECG using spatiotemporal QRS and T-wave cancellation. Results: Seventy-three horses satisfied the inclusion criteria. The mean difference be-tween RA-FR and AFR was -13 fibrillations per minute (fpm), the 95% limits of agree-ment were between -66 and 40 fpm, and there was a moderate (r 1/4 0.65) correlation between RA-FR and AFR (p < 0.001). Neither RA-FR nor AFR appeared to influence the TVEC cardioversion threshold or the number of TVEC shocks applied. Conclusions: The AFR may allow non-invasive long-term monitoring of AF dynamics. Neither RA-FR nor AFR could be used to predict the minimal defibrillation threshold for TVEC. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study compared atrial fibrillatory rate derived from a local right atrial intracardiac recording and a single-lead surface electrocardiogram during atrial fibrillation in horses. The results showed a moderate correlation between the two methods, but neither could predict the minimal defibrillation threshold for transvenous electrical cardioversion (TVEC).