Aortic Regurgitation in Horses: Murmurs, Risks, and Monitoring

Quick Answer
  • Aortic regurgitation, also called aortic insufficiency, happens when the aortic valve leaks and lets blood flow backward into the left ventricle after each heartbeat.
  • Many horses have no obvious signs at first. The condition is often found when your vet hears a diastolic heart murmur during a routine exam.
  • Mild cases may stay stable for months to years with repeat exams and echocardiograms, while more severe cases can enlarge the heart and raise the risk of poor performance, arrhythmias, fainting, or heart failure.
  • See your vet promptly if your horse shows exercise intolerance, weakness, collapse, breathing changes, or a new drop in performance.
  • Typical US cost range for workup and monitoring is about $400-$1,500 for an exam, ECG if needed, and echocardiography, with emergency or referral-hospital care costing more.
Estimated cost: $400–$1,500

What Is Aortic Regurgitation in Horses?

Aortic regurgitation in horses means the aortic valve does not close tightly after blood leaves the heart. Because of that leak, some blood flows backward from the aorta into the left ventricle during diastole. Your vet may also call this aortic insufficiency. In older horses, it is one of the more common causes of a heart murmur, especially a diastolic murmur heard on the left side of the chest.

The heart can often compensate for a while, so some horses feel normal and continue working without obvious problems early on. Over time, though, the extra volume load can stretch the left ventricle and increase the heart's workload. That is why monitoring matters even when a horse seems comfortable.

Severity varies. A small leak may only need periodic rechecks, while a larger leak can affect exercise tolerance and increase the chance of rhythm disturbances or, less commonly, congestive heart failure. The main goal is not to label every murmur as dangerous, but to understand how much leakage is present and whether the heart is changing over time.

Symptoms of Aortic Regurgitation in Horses

  • No obvious signs in mild or early cases
  • Diastolic heart murmur found on routine exam
  • Reduced stamina or exercise intolerance
  • Poor performance or tiring sooner than expected
  • Occasional weakness after exertion
  • Irregular heartbeat or suspected arrhythmia
  • Bounding pulses in some horses with more significant leakage
  • Fainting, collapse, or near-collapse in severe cases
  • Breathing effort, fluid buildup, or other signs of heart failure in advanced disease

Many horses with mild aortic regurgitation do not look sick at home. The first clue is often a murmur your vet hears during a wellness, prepurchase, or performance exam. As the leak becomes more important, signs may include reduced stamina, slower recovery after work, or an irregular rhythm.

See your vet immediately if your horse collapses, seems weak during exercise, develops labored breathing, or suddenly cannot perform at a usual level. Those signs do not always mean severe aortic regurgitation, but they do mean your horse needs prompt evaluation.

What Causes Aortic Regurgitation in Horses?

In horses, aortic regurgitation is most often an acquired valve problem. The most common cause is degenerative change in the aortic valve as a horse ages. This wear-and-tear process can make the valve leaflets less able to seal tightly, leading to backward blood flow.

Less commonly, infection of the valve, called endocarditis, can damage the valve and create or worsen regurgitation. In those cases, your vet may also look for fever, weight loss, fatigue, or other signs of systemic illness. Rarely, other structural heart changes may contribute to the murmur pattern or complicate the picture.

Not every murmur means the same thing. Some horses, especially fit horses, can have flow murmurs that are not caused by important valve disease. That is why the cause cannot be confirmed by listening alone. Your vet uses the murmur's timing, location, intensity, and follow-up imaging to sort out whether the finding is mild, significant, or unrelated to aortic valve leakage.

How Is Aortic Regurgitation in Horses Diagnosed?

Diagnosis starts with a careful physical exam. Your vet listens for the timing and character of the murmur, checks pulse quality, and asks about exercise tolerance, performance changes, collapse episodes, and any history of fever or illness. Aortic regurgitation typically creates a diastolic murmur, and clinically important cases usually have a murmur that can be heard with a stethoscope.

The key test is echocardiography with Doppler. This ultrasound lets your vet see the valve, measure heart chamber size, and assess how much blood is leaking backward. It also helps track whether the left ventricle is enlarging over time. In some horses, your vet may add an ECG to look for arrhythmias, especially if there is poor performance, an irregular rhythm, or collapse.

Additional testing depends on the case. Blood work may be used if infection, anemia, or another illness is on the list. Chest imaging is used less often in field cases but may be part of a referral workup. Because severity can change, one normal-looking day does not replace follow-up. Serial exams are often the safest way to understand risk.

Treatment Options for Aortic Regurgitation in Horses

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

Budget-Conscious Care

$250–$700
Best for: Horses with a newly detected murmur, mild suspected disease, limited budget, or cases where your vet feels immediate referral is not necessary.
  • Farm-call or clinic physical exam
  • Cardiac auscultation and pulse assessment
  • Basic exercise history and risk discussion
  • Activity modification based on your vet's findings
  • Scheduled recheck exams every 3-12 months depending on severity
Expected outcome: Often fair to good in mild cases if the horse remains symptom-free and the murmur is monitored closely.
Consider: Lower upfront cost, but less detail. Without echocardiography, it is harder to know the true severity or detect early heart enlargement.
Most Common

Recommended Standard Treatment

$600–$1,500
Best for: Most horses with a confirmed or strongly suspected aortic regurgitation murmur, especially performance horses or horses with any decline in stamina.
  • Full veterinary exam
  • Echocardiogram with Doppler to confirm aortic regurgitation
  • ECG if an irregular rhythm is heard or performance has changed
  • Written exercise and monitoring plan
  • Repeat echocardiography every 6-12 months, or sooner if signs change
Expected outcome: Variable. Many horses with mild to moderate disease can remain comfortable for long periods, while severe leakage or chamber enlargement carries a more guarded outlook.
Consider: Provides the clearest picture for decision-making, but costs more and may require referral or haul-in imaging.

Advanced / Critical Care

$1,500–$4,000
Best for: Horses with severe murmurs, collapse, suspected arrhythmias, poor performance with structural heart change, or concern for infectious valve disease.
  • Referral-hospital cardiology consultation
  • Detailed echocardiography and repeat imaging
  • Continuous or serial ECG monitoring for arrhythmias
  • Blood work and infectious disease evaluation if endocarditis is suspected
  • Hospitalization and supportive care for collapse, heart failure, or unstable rhythm problems
Expected outcome: Guarded in horses with severe regurgitation, progressive heart enlargement, heart failure, or clinically important arrhythmias.
Consider: Most complete information and monitoring, but the highest cost range. It may also confirm limits on athletic use that some pet parents were hoping to avoid.

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

Questions to Ask Your Vet About Aortic Regurgitation in Horses

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

  1. Does this murmur sound most consistent with aortic regurgitation, or could it be a different type of murmur?
  2. How severe does the leakage appear, and is the left ventricle enlarged yet?
  3. Does my horse need an echocardiogram now, or is short-term monitoring reasonable first?
  4. Is my horse safe for current work, and are there exercise limits you recommend?
  5. Should we screen for arrhythmias with an ECG because of performance changes or an irregular rhythm?
  6. What warning signs at home would mean I should stop riding and call right away?
  7. How often should we repeat the exam or echocardiogram to watch for progression?
  8. If infection of the valve is a concern, what tests would help rule that in or out?

How to Prevent Aortic Regurgitation in Horses

There is no guaranteed way to prevent degenerative aortic regurgitation in horses, especially when it develops with age-related valve change. Still, regular wellness exams matter because they help your vet detect a new murmur before your horse shows obvious signs. Early detection gives you more options for safe monitoring and exercise planning.

Good general health care also helps reduce avoidable complications. Prompt attention to fever, unexplained weight loss, poor performance, or signs of infection may help your vet catch conditions like endocarditis earlier. Keeping dental care, vaccination, parasite control, and routine medical care on schedule supports overall health, even though these steps do not directly prevent valve degeneration.

If your horse already has a murmur, prevention shifts toward preventing progression-related problems. Follow your vet's recheck schedule, ask whether workload changes are needed, and keep notes on stamina, recovery time, and any fainting or rhythm concerns. Thoughtful monitoring is often the most practical and protective step.

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