Heart Disease in Horses: Symptoms, Diagnosis, and Treatment Options

Quick Answer
  • Heart disease in horses is a broad term that includes valve problems, arrhythmias such as atrial fibrillation, heart muscle disease, congenital defects, and heart failure.
  • Many horses with a mild murmur have no obvious problems at rest, but poor performance, tiring early, swelling under the chest or belly, a strong jugular pulse, collapse, or breathing effort are more concerning signs.
  • Your vet usually starts with a physical exam and auscultation, then may recommend an ECG to define an arrhythmia and echocardiography to assess valves, chamber size, and pumping function.
  • Treatment depends on the exact problem. Options may include exercise restriction, monitoring, antiarrhythmic medication such as quinidine for selected atrial fibrillation cases, diuretics for fluid buildup, or referral for advanced cardiology procedures.
  • Prognosis varies widely. Some horses can return to light or athletic work after treatment, while others need long-term management or retirement for safety.
Estimated cost: $350–$4,500

What Is Heart Disease in Horses?

Heart disease in horses means there is a problem affecting the heart's structure, rhythm, or ability to move blood effectively. This can include valvular disease such as leaking valves, arrhythmias such as atrial fibrillation, myocardial disease affecting the heart muscle, congenital defects present from birth, and in more severe cases, heart failure. Some horses have a murmur or rhythm change with few outward signs, while others develop poor performance, weakness, or fluid buildup.

A heart murmur does not always mean a horse has dangerous heart disease. Horses can have murmurs or certain rhythm findings that are mild or even physiologic in some situations. Still, a new murmur, reduced stamina, collapse, or signs of fluid retention deserve a prompt veterinary workup because the underlying cause matters more than the sound alone.

For pet parents, the biggest question is usually whether the horse is safe to ride, train, breed, or compete. That answer depends on the diagnosis, severity, and intended workload. Your vet may recommend anything from periodic monitoring to exercise restriction, medication, or referral to an equine cardiology service.

Symptoms of Heart Disease in Horses

  • Exercise intolerance or poor performance
  • Fatiguing faster than expected during work
  • Irregular heartbeat or unusually fast heart rate
  • Increased breathing effort or respiratory rate
  • Visible jugular pulse extending up the neck
  • Swelling under the chest, abdomen, or limbs
  • Weight loss, depression, or reduced stamina
  • Weakness, collapse, or fainting episodes
  • Cough associated with fluid backup or advanced disease
  • Sudden death during exercise

See your vet immediately if your horse collapses, struggles to breathe, develops marked swelling, or seems unsafe during exercise. More subtle signs, like a drop in performance or a newly detected murmur, still deserve attention because horses often hide cardiovascular disease until workload increases. Until your vet has examined your horse, it is safest to reduce or stop strenuous exercise.

What Causes Heart Disease in Horses?

Equine heart disease has several possible causes. In adult horses, valvular disease is common, especially when a valve does not close tightly and blood leaks backward. Arrhythmias are another major category. Atrial fibrillation is one of the best-known rhythm disorders in horses and may occur on its own or secondary to underlying heart disease. Some horses also develop disease of the heart muscle or the sac around the heart.

Foals can be born with congenital heart defects, including abnormal openings or blood vessel connections that change normal blood flow. The effect depends on the defect and its severity. Mild defects may be found incidentally, while more significant ones can lead to poor growth, tiring easily, collapse, or signs of heart failure.

Less commonly, heart disease can be linked to systemic illness, inflammation, toxin exposure, mineral imbalance, or changes that place strain on the cardiovascular system. Because the same outward sign can come from very different problems, your vet usually needs imaging and rhythm testing to sort out the cause and estimate risk.

How Is Heart Disease in Horses Diagnosed?

Diagnosis starts with a careful history and physical exam. Your vet will listen for murmurs, extra heart sounds, or rhythm changes, check pulses and jugular veins, and look for swelling, poor body condition, or breathing changes. This first step helps determine whether the finding may be mild and incidental or more likely to affect circulation and safety.

If your vet suspects true cardiac disease, the next tests often include electrocardiography (ECG) and echocardiography. In horses, ECG is especially useful for identifying and characterizing arrhythmias rather than screening for all heart disease. Echocardiography is the key imaging test because it shows valve motion, chamber size, wall thickness, and pumping function.

Additional testing may include bloodwork, cardiac biomarkers in selected cases, thoracic ultrasound or radiographs when fluid or concurrent disease is suspected, and exercise-based evaluation for performance horses. In referral settings, horses with difficult arrhythmias may need prolonged rhythm monitoring or advanced procedures such as transvenous electrical cardioversion. Once your vet knows the exact diagnosis, they can discuss work restrictions, treatment options, and realistic expectations.

Treatment Options for Heart Disease in Horses

Spectrum of Care means you have options. Here are treatment tiers at different price points.

Budget-Conscious Care

$350–$900
Best for: Horses with a newly heard murmur but mild or no symptoms, pet parents needing a stepwise plan, or situations where referral testing is not immediately possible.
  • Farm call or clinic exam with cardiac auscultation
  • Basic bloodwork if indicated
  • Short-term exercise restriction or retirement from strenuous work while monitoring
  • Repeat exams to track murmur intensity, heart rate, rhythm, swelling, and stamina
  • Referral discussion if signs worsen or safety concerns develop
Expected outcome: Often fair when signs are mild and the horse is kept at an appropriate activity level, but prognosis remains uncertain until the exact diagnosis is confirmed.
Consider: Lower upfront cost, but less diagnostic certainty. Important problems such as significant valve disease or atrial fibrillation may be missed or identified later.
Most Common

Recommended Standard Treatment

$900–$2,500
Best for: Most horses with poor performance, an irregular rhythm, a significant murmur, or signs suggesting clinically important heart disease.
  • Complete veterinary exam and targeted cardiovascular workup
  • ECG to define arrhythmias
  • Echocardiography to assess valves, chamber size, and function
  • Medication when appropriate, such as quinidine for selected atrial fibrillation cases or diuretics for fluid buildup under veterinary supervision
  • Workload recommendations, recheck imaging, and monitoring plan
Expected outcome: Variable. Some horses with manageable valve disease or successfully treated atrial fibrillation can return to useful work, while others need long-term restrictions or retirement.
Consider: Provides much better diagnostic clarity and a safer plan for exercise decisions, but costs more and may still lead to referral if the case is complex.

Advanced / Critical Care

$2,500–$4,500
Best for: Horses with atrial fibrillation that may benefit from conversion, severe or recurrent arrhythmias, collapse, heart failure, or high-value performance horses needing the fullest evaluation.
  • Referral to an equine hospital or cardiology service
  • Comprehensive echocardiography and advanced rhythm assessment
  • Hospital-based antiarrhythmic treatment with close monitoring
  • Transvenous electrical cardioversion for selected atrial fibrillation cases
  • Critical care for heart failure, severe arrhythmias, collapse episodes, or unstable horses
Expected outcome: Best when the underlying problem is treatable and addressed early. Some horses return to athletic work after advanced arrhythmia treatment, while others have guarded to poor long-term outlooks.
Consider: Highest cost and travel burden, and not every horse is a candidate for advanced procedures. Even with referral care, recurrence or exercise limitations may remain.

Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.

Questions to Ask Your Vet About Heart Disease in Horses

Bring these questions to your vet appointment to get the most out of your visit.

  1. What type of heart problem do you suspect: valve disease, arrhythmia, congenital disease, or heart failure?
  2. Is my horse safe to ride, train, breed, or compete while we are figuring this out?
  3. Do you recommend an ECG, echocardiogram, or both, and what will each test tell us?
  4. If this is atrial fibrillation, is my horse a candidate for quinidine treatment or referral for cardioversion?
  5. Are there signs of fluid buildup or heart failure that mean we should act more urgently?
  6. What activity restrictions should I follow right now, and for how long?
  7. What recheck schedule do you recommend to monitor progression or recurrence?
  8. Based on this diagnosis, what is the realistic outlook for comfort, safety, and future workload?

How to Prevent Heart Disease in Horses

Not every form of heart disease can be prevented. Congenital defects are present from birth, and some arrhythmias or valve changes develop despite excellent care. Still, regular wellness exams matter because your vet may detect a murmur or rhythm change before your horse shows obvious signs.

Good prevention focuses on early detection and sensible workload decisions. If your horse has reduced stamina, a prolonged recovery after exercise, or an irregular heartbeat, stop pushing through training and schedule an exam. Performance horses benefit from prompt evaluation of poor performance rather than assuming the issue is conditioning alone.

General health support also helps. Keep vaccinations, dental care, parasite control, nutrition, and body condition on track, and work with your vet to investigate systemic illness quickly. If a heart problem is already known, follow exercise restrictions, medication instructions, and recheck plans closely. Matching the horse's job to the diagnosis is one of the most important ways to reduce risk.

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