Risk Factors for Recurrence of Atrial Fibrillation in Horses After Cardioversion to Sinus Rhythm

Abstract

BackgroundAlthough atrial fibrillation (AF) can be successfully treated in horses, recurrence occurs frequently. In humans, atrial function after cardioversion can predict recurrence.ObjectivesTo examine the prognostic value of atrial mechanical function at 24 hours after cardioversion and other potential predictor variables for AF recurrence in horses.Animals117 horses treated for AF at 4 referral centers.MethodsRetrospective study. Inclusion criteria were successful cardioversion, echocardiography at 24 hours after cardioversion and ≥4 months follow‐up. To determine factors associated with AF recurrence, a multivariable survival model was built.Results133 AF episodes in 117 horses were included. AF recurred in 36/100 horses with a first AF episode and in 57/133 AF episodes overall. Factors associated with recurrence in horses with a first episode were previous unsuccessful treatment attempt (hazard ratio HR 2.36, 95% confidence interval CI 1.11–4.99, P = .025) and mild or moderate mitral regurgitation (HR 2.70, 95% CI 1.23–5.91, P = .013). When the last AF episode of all horses was included, previous AF (HR 2.53, 1.33–4.82, P = .005) and active left atrial fractional area change ≤9.6% (HR 3.43, 1.22–9.67, P = .020) were significant predictors.Conclusions and Clinical ImportanceThe only echocardiographic variable of left atrial function with significant prognostic value for recurrence was low active left atrial fractional area change. Further research is necessary to evaluate whether echocardiography at a later timepoint could provide more prognostic information.

Echocardiographic Assessment of Left Atrial Size and Function in Warmblood Horses: Reference Intervals, Allometric Scaling, and Agreement of Different Echocardiographic Variables

“…Echocardiographic indices of LA mechanical function have previously been described in horses . They are sufficiently reliable for routine clinical use, allow documenting LA mechanical dysfunction after conversion of atrial fibrillation to sinus rhythm and could have prognostic implications in horses recovering from atrial fibrillation . However, the use of these indices in horses with MR and AR has not been described.…”

“…However, the population size of this study does not allow more detailed subgroup analyses and comprehensive investigation of the influence of different stages or causes of MR and AR on LA mechanical function. One could argue that assessment of active LA contraction by 2DE should be based on measurement of LA area at the time of maximum atrial contraction (determined subjectively), since at the time of MV closure (which occurs some time after maximum atrial contraction) the LA dimensions have again slightly increased because of pulmonary venous return and beginning LA relaxation. However, measurement of LA dimensions at the time of maximum LA contraction can be difficult in horses with less vigorous or complete lack of active atrial contraction, such as horses with atrial stunning.…”

Effect of sotalol on heart rate, QT interval, and atrial fibrillation cycle length in horses with atrial fibrillation

“…Even at lower levels of exercise intensity, horses in AF might exhibit extremely high heart rates (HRs), and collapse has been described . The success rate for both pharmacological cardioversion and TVEC is very high, but AF recurrence after treatment is common with an overall rate of recurrence up to 39% at 1 year after cardioversion . The pathophysiology of AF initiation and perpetuation in horses has not yet been completely elucidated.…”

“…The pathophysiology of AF initiation and perpetuation in horses has not yet been completely elucidated. Factors that might be associated with AF recurrence include structural changes to the atrial myocardium, atrial size and stretch, short atrial effective refractory period (AERP), and supraventricular ectopic foci . Long‐term antiarrhythmic treatment could be used to prevent AF recurrence after cardioversion through different mechanisms such as increasing AERP, decreasing supraventricular ectopy, and decreasing vulnerability to AF initiation.…”

“…1 The success rate for both pharmacological cardioversion and TVEC is very high, but AF recurrence after treatment is common with an overall rate of recurrence up to 39% at 1 year after cardioversion. [2][3][4][5] The pathophysiology of AF initiation and perpetuation in horses has not yet been completely elucidated. Factors that might be associated with AF recurrence include structural changes to the atrial myocardium, atrial size and stretch, short atrial effective refractory period (AERP), and supraventricular ectopic foci.…”