[Echocardiography and therapy of atrial fibrillation in horses].

This research study investigates the use of echocardiography to evaluate the condition of 45 horses with atrial fibrillation, a heart rhythm disorder, and assesses the effectiveness of their treatment with Quinidine sulfate. The study reveals a correlation between atrial and ventricular dilation, and suggests echocardiographic evaluation as a reliable method for predicting treatment success.

Research Study Overview and Methodology

• The study was performed on 45 horses, with 43 of them being warm-blooded, one thoroughbred, and one standardbred. All these horses were diagnosed with atrial fibrillation, a heart condition characterized by irregular heart rhythm.
• Echocardiographic evaluations were conducted using M-mode, B-mode and pulsed-wave Doppler echocardiography. These methods provide a detailed view of the heart’s structure and function, allowing the researchers to assess atrial dilatation, the absence of A-peak, diastolic undulation, and left ventricular shortening fraction among other things.

Key Findings

• Among the studied horses, 17 (38%) had a history of poor performance, indicating a likely connection between their athletic ability and heart condition.
• An increase of left ventricular shortening fraction was observed in 25 horses (56%). This condition refers to the degree of contraction of the left ventricle during each heartbeat.
• Atrial dilation, an increase in the size of the atria, was observed in 37 horses (82%). In contrast, 8 horses (18%) had normal atrial dimensions.
• A notable finding was that in some horses, only the left or the right atrium was enlarged. However, in the majority (22 horses), both atria were dilated.
• The study found a correlation between atrial dilatation and ventricular dilatation.
• Through echocardiograms and pulse-wave Doppler spectral tracings, the researchers found the absence of A-peak, a characteristic associated with healthy atria activity.

Treatment and its Effectiveness

• Quinidine sulfate, a medication used to restore normal heart rhythm, was used to treat 19 of the horses.
• Of these, nine horses returned to normal heart rhythm (sinus rhythm), with eight of them having normal atrial dimensions. This implies treatment tends to be more effective in horses with normal atrial measurements.
• Treatment was unsuccessful in nine horses with severe atrial dilatation and in one horse that had normal atrial dimensions, but suffered from mitral valve insufficiency.

Conclusion and Implications

• Echocardiographic evaluation, especially the measurement of atrial diameters, was found to be a reliable method to predict therapeutic success in horses with atrial fibrillation.
• This could mean that horses with atrial dilation may require a different therapeutic approach compared to those with normal atrial dimensions.
• This discovery could potentially lead to more personalized and effective treatment plans for horses suffering from atrial fibrillation.