Atrial fibrillation in horses: difficult diagnosis for a therapeutic orphan.

The research article explores atrial fibrillation (AF) in horses, a common heart disorder often diagnosed by chance. It discusses the ongoing debate on whether AF is a result of other cardiac conditions or can occur independently in horses. The treatment and outlook of AF in horses rely heavily on an accurate diagnosis. The article also explores different treatment methods and their associated risks.

Understanding Atrial Fibrillation in Horses

• AF is a prevalent pathological heart arrhythmia in horses. In most situations, it arises and develops without showing any symptoms, which often leads to its accidental discovery during a clinical examination.
• The research highlights a debate regarding whether AF can occur independently in a horse, or it’s a result of other heart conditions.
• AF in healthy horses, without underlying cardiac diseases, can often be successfully corrected by medical cardioversion, keeping the likelihood of a return to prior athletic performance quite high.

Challenges in Treatment

• AF’s treatment becomes increasingly difficult when it persists for a long time, requiring higher doses of anti-arrhythmic drugs—which might result in unwanted side effects.
• The practitioner often hesitates to use cardioversion due to limited therapeutic choices and high treatment-related risks.
• The major drawback is that while there are many potent anti-arrhythmic drugs available for human treatment, quinidine sulphate is the only therapeutic option for AF in horses.
• This drug may also cause severe adverse effects, making it hard to manage.

New Treatments

• Over the past half-decade, alternative anti-arrhythmic treatments for AF have been emerging.
• In modern human treatments, electrical cardioversion is often preferred over pharmacological alternatives. The positive results of using biphasic electrical cardioversion in horses were encouraging.
• However, more research is needed to enhance this technique and gather additional data regarding its effectiveness, relative risk, and expense.

Pharmacological Cardioversion

• The use of flecainide, a class I anti-arrhythmic drug similar to quinidine, has been suggested for pharmacological cardioversion of AF in horses.
  In experimentally induced acute AF, the drug revealed promising results.

• However, it had limited value in treating naturally occurring AF and could induce potentially dangerous dysrhythmias.
• Amiodarone, a class III anti-arrhythmic drug, offers a different pharmacodynamic approach to that of quinidine and flecainide. This drug’s effectiveness and tolerance in horses with chronic AF are described for the first time in this study.