Time-dependent antiarrhythmic effects of flecainide on induced atrial fibrillation in horses

Figures

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  Figure 1. Overview of the study protocol. The flowchart shows the order of interventions for the horses in the two groups. AF = atrial fibrillation

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  Figure 2. Time to cardioversion as a function of the cumulative duration of atrial fibrillation. Time to cardioversion (in min) was log transformed and plotted against the cumulative duration of self‐sustained atrial fibrillation (AF) for all flecainide infusions in horses with AF. Linear regression revealed a slope of 0.04 (95% CI 0.02, 0.05) with a coefficient of determination of 0.80

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  Figure 3. Transition from fine to coarse AF. The ECG sections (lead II) should be viewed in succession. The ECG was recorded 12 min after the end of flecainide infusion on day 27. It is evident that the atrial fibrillation becomes coarse, with distinct fibrillatory waves. The atrial rate is 170/min (352 ms interval) in the last part of the ECG. The horse cardioverts to sinus rhythm 40 min later

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  Figure 4. Mean heart rate at rest. Mean heart rate at rest (HRrest) for the individual horses measured on surface baseline ECG “start” and after pacing “end” in control and AF groups. The line and error bars reflect the mean ± SD. *** = P < 0.001

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  Figure 5. Ventricular effects of flecainide administration. QRS duration (A) and corrected QT intervals (QTc) (B) before and after flecainide treatment in all horses (n = 9) presented in box plots with whiskers from minimum to maximum values. # Represents the significance level of the comparison between the time points after flecainide infusion and the baseline (### = P < 0.001). * = P < 0.05, *** = P < 0.001

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  Figure 6. Abnormal ECG findings after flecainide infusion. Single abnormal QRS complexes (A) and an episode of consecutive abnormal QRS complexes (B). The QRS complexes were classified as abnormal because they display the R‐on‐T phenomenon. All ECG examples are lead II. * indicates abnormal complexes

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  Figure 7. Electrocardiogram obtained during flecainide infusion resulting in cardiac arrest. The ECG (lead II) is from a horse receiving a second dose of flecainide in an attempt to cardiovert atrial fibrillation with a duration of 59 days. After several episodes of torsades‐like ventricular tachycardia with preceding short‐long‐short coupling initiation (*) the horse develops ventricular fibrillation (VFib). A) Is an overview of the last 6 min leading up to cardiac arrest and B) is a section of the ECG where distinct fibrillatory waves appear at a rate of 163/min (368 ms interval)