# Application of Acoustic Cardiography in Assessment of Cardiac Function in Horses with Atrial Fibrillation Before and After Cardioversion

## TL;DR

The study evaluates acoustic cardiography in horses with atrial fibrillation before and after treatment, finding it useful for assessing ventricular function but not left atrial function.

## Contribution

The study introduces the use of acoustic cardiography as an adjunct to echocardiography for evaluating cardiac function in horses with AF.

## Key findings

- Acoustic cardiography showed significant improvements in ventricular systolic function after cardioversion.
- S4 quantification was not clinically useful for assessing left atrial function post-cardioversion.
- Strong agreement was found between acoustic cardiography and echocardiographic measures of ventricular function.

## Abstract

Atrial fibrillation (AF) in horses reduces exercise capacity due to atrial contractile dysfunction, impaired ventricular systolic function, disproportionate ventricular rate response and reduced cardiac output. Atrial dysfunction can persist even after treatment and is considered a risk factor for recurrence. Ambulatory acoustic cardiography (Audicor® (Beaverton, OR, USA)) provides qualitative and quantitative information on hemodynamics and cardiac mechanical function and may aid in the clinical diagnosis of impaired heart function after AF treatment. This study aimed to evaluate the use of an acoustic cardiography monitor to assess cardiac mechanical function and its benefits as an adjunct to echocardiography in horses with AF before and after successful cardioversion to sinus rhythm. Audicor® snapshot analyses provided additional information on left ventricular systolic function and reflected changes seen in echocardiography. However, the Audicor® device did not seem clinically useful as a tool to directly assess left atrial mechanical function after cardioversion to sinus rhythm.

Left atrial mechanical dysfunction is common in horses following the treatment of atrial fibrillation (AF). This study aimed to evaluate the use of an acoustic cardiography monitor (Audicor®) in quantifying cardiac mechanical and hemodynamic function in horses with AF before and after treatment and to correlate these findings with echocardiographic measures. Twenty-eight horses with AF and successful transvenous electrical cardioversion were included. Audicor® recordings with concomitant echocardiographic examinations were performed one day before, one day after, and two to seven days after cardioversion. Key variables measured by Audicor® included electromechanical activating time (EMAT), heart rate-corrected EMATc, left ventricular systolic time (LVST), heart rate-corrected LVSTc, systolic dysfunction index (SDI), and intensity and persistence of the third and fourth heart sound (S3, S4). A repeated-measures ANOVA with Tukey’s test was used to compare these variables over time, and linear regression and Bland–Altman analyses were applied to assess associations with echocardiographic findings. Following conversion to sinus rhythm, there was a significant decrease in EMATc and LVSTc (p < 0.0001) and a significant increase in LVST (p = 0.0001), indicating improved ventricular systolic function, with strong agreement between Audicor® snapshot and echocardiographic measures. However, S4 quantification did not show clinical value for assessing left atrial function after conversion.