What is Atrial Fibrillation?
Atrial fibrillation in horses is a condition in which a pronounced electrical abnormality of the rhythm of the heart occurs. Atrial fibrillation is a result of the atria failing to fully contract. The atria quivers, or fibrillates, as the electrical impulses from the atrioventricular mode occur inconsistently and at intermittent rates to the ventricles.
The heart has two atria where blood enters in, and then two ventricles in which the blood exits. This is the start of the process of oxygenated blood flow to the body. The electrical abnormality of the rhythm of the heart is diagnosed frequently in horses of all types and ages. Oftentimes, atrial fibrillation occurs in horses which have heart disease, typically advanced heart disease. Horses with insufficient valves typically have atrial dilation. Atrial fibrillation in horses can also develop in horses that do not have any signs of abnormalities of the heart, or heart disease.
Atrial fibrillation in horses is caused by an electrical dysfunction of the heart rhythm. Horses with atrial fibrillation have atria that do not contract to the fullest extent, thus causing quivering.
Book First Walk Free!
Symptoms of Atrial Fibrillation in Horses
Atrial fibrillation has many symptoms that are quite characteristic to the disorder. Symptoms of this heart condition may include:
- Shortness of breath
- Poor performance
- Nasal discharge
- Irregular heartbeat
Atrial fibrillation often affects full-grown, athletic horses rather than very young horses. Although horses that are not athletic can still get atrial fibrillation, the following horses show signs more often:
- Athletic horses
- Polo ponies
- Barrel racers
- Fox hunters
- Show jumpers
Causes of Atrial Fibrillation in Horses
Studies, as well as new treatments, are still being conducted on this disorder. Causes of atrial fibrillation may consist of:
- Underlying heart condition
- A depletion of potassium
- Overly active horses that tend to sweat
- Mitral regurgitation
- Congestive heart failure
Diagnosis of Atrial Fibrillation in Horses
If you suspect your horse has a heart condition by showing the above symptoms, make an appointment with your veterinarian. The veterinarian will perform a complete physical examination, including blood work and any other preliminary testing before he focuses on the possible heart issue. The veterinarian will ask you questions pertaining to your horse’s health history and any other breeding question he may have. He will also want to know any information about your companion’s activity, such as whether he is a performance or working horse.
Your veterinarian will begin by listening to your horse’s heart. If your horse has a heart rhythm that is irregular, he may hear it via his stethoscope. He may then perform a test known as an electrocardiogram. An electrocardiogram will confirm your horse’s irregular heartbeat, or arrhythmia, and will aid him in his diagnosis. He will also be able to confirm the type of arrhythmia occurring after the ECG. This test also evaluates the ventricular complexes, if any. This will also give a great deal of information to the medical professional.
The veterinarian may also perform an echocardiogram, which utilizes sound waves that are high-pitched. This ultrasound test sends the sounds through a transducer, which picks up the echoing of these sound waves as they bounce off the various parts of the heart.
Both of these tests are very useful in confirming a diagnosis of atrial fibrillation in your horse, and will assist the veterinarian in deciding upon a method of treatment.
Treatment of Atrial Fibrillation in Horses
Atrial fibrillation in horses is treatable, and your medical professional will explain in detail the treatment options. Treatment methods may include:
Quinidine is the drug of choice to treat atrial fibrillation by many veterinarians. Your veterinarian will explain the dosage recommendations, as well as the possible side effects. Side effects of this effective medication may include colic, nasal edema, ataxia, hives, and laminitis.
Your veterinarian may be able to recommend a heart specialist who can treat the atrial fibrillation with electrocardioversion. Electrocardioversion may be effective in horses with this condition that do not respond well to quinidine. This is a costly procedure and highly selective. In electrocardioversion, the horse is placed under anesthesia, and a catheter is inserted into your horse’s jugular vein in order for electrical leads to be placed into the heart. A properly-timed, synchronized shock is delivered to aid the sinus rhythm to return back to normal. In some cases, the procedure needs to be repeated over time.
Recovery of Atrial Fibrillation in Horses
In terms of recovery, quinidine tends to work with a good success rate for many horses. The sooner the atrial fibrillation is diagnosed, the more effective treatment will be for your horse. If your horse has had atrial fibrillation for an extended period of time, treatment may be less effective, but may still work. Once your horse is home, your veterinarian will specifically explain to you how to administer the medication. He will also alert you to any new symptoms you need to be on the lookout for. As mentioned above, quinidine does have side effects, and it is important to be educated on those possible effects.
In terms of electrical cardioversion, this is a very new and revolutionary method of treatment and is only offered at specific medical centers. This method of treatment is also quite costly, and since quinidine is effective for many horses, it is often decided to attempt the medication at the beginning of your horse’s treatment.
If you see any new symptoms or any behavioral changes within your horse that may not be related to the medication he is taking, contact your veterinarian.