Vet Tips 2025: Heart Murmurs in Horses—Understanding the Sound of Trouble 🐴🫀

By Dr Duncan Houston BVSc

While heart murmurs are fairly common in small dogs and often harmless, murmurs in horses are far less routine—and when detected, they deserve careful attention. Whether your horse is a senior or a competitive athlete, understanding what a murmur means can make all the difference in long-term care. 🎧🐎

What Is a Heart Murmur? 🩺🔊

A heart murmur is the sound of turbulent blood flow through the heart, typically due to leaky or narrowed valves. The murmur is identified by:

• 📍 Location (left or right side of chest)
• 🕰️ Timing in the cardiac cycle (systolic or diastolic)
• 🎚️ Intensity or loudness (graded on a scale from 1–6)

Unlike in cats—where any murmur is often serious—in horses, murmurs can range from inconsequential to potentially life-threatening. 🧠

The Two Most Common Murmurs in Horses 🧬🐴

1. Diastolic Murmur (Aortic Regurgitation) 🔁

• 💢
• 🧓 Most common in older horses
• 💉 Caused by degeneration of the aortic valve, leading to blood flowing backward into the heart

If your vet hears this murmur, they’ll often check the strength of the horse’s pulse. A bounding or forceful pulse may indicate the heart is compensating and under more strain than it should be. 📈

Potential Risks:

• ⚡ Susceptibility to ventricular arrhythmias
• 💥 Collapse or fainting episodes—especially under exertion, posing risk to both horse and rider

Fortunately, many horses live full, active lives with this murmur, but regular monitoring is key. 📋

2. Systolic Murmur (Mitral Regurgitation) 💨

• 🕰️ Heard after the first heart sound
• 📍 Usually on the left side of the chest
• 🔁 Caused by backflow of blood through the mitral valve

This murmur is similar to those found in small dogs and is more likely to progress to heart failure if severe. 🧬

Signs to Watch For:

• 📉 Exercise intolerance
• 💨 Labored breathing or increased respiratory rate
• ❤️ Rapid heartbeat
• 🫧 Foam at the nostrils (from pulmonary edema)

This type of murmur requires closer attention, especially in performance horses. 🏇

How Are Murmurs Diagnosed? 🔍🩺

Your vet will typically detect a murmur using a stethoscope during a routine exam. From there, additional diagnostics may include:

• 📊 Electrocardiogram (ECG) to check for rhythm abnormalities
• 🖼️ Echocardiogram (ultrasound of the heart) to evaluate valve structure and blood flow

These tests help assess whether the murmur is harmless or performance-limiting. 🎯

Should You Be Worried? 🤷‍♂️🧠

Not always. Some murmurs—especially low-grade or age-related ones—may not impact your horse at all. But if you notice changes in performance, breathing, or behavior, it's time for a workup. 🚩

When to Monitor and When to Treat 🩺📋

Monitor If:

• 🎚️ Murmur is low-grade (1–3/6)
• 📈 No signs of exercise intolerance
• 💨 Breathing and pulse remain normal at rest and during work

Act Quickly If:

• 📉 Your horse is less energetic or tires quickly
• 💥 Collapsing, fainting, or disorientation occurs
• 🫧 You notice respiratory distress or foaming from the nostrils

Your vet may recommend rest, medications, or adjusting your horse’s exercise routine based on their findings. 🏥

What Can Be Done? 🧠💊

There’s no way to “fix” a murmur, but treatment can help manage symptoms or complications:

• 💊 Diuretics or antiarrhythmics if heart failure signs are present
• 📉 Adjusted training or retirement for high-risk horses
• 📆 Regular follow-up exams and imaging to track progression

Staying informed and proactive can help extend your horse’s quality of life. 🧘‍♂️

Need Help Understanding a Murmur Diagnosis? Ask A Vet 📱🐴

If your vet just told you your horse has a murmur and you’re unsure what that means, connect with an equine cardiac expert at Ask A Vet.

Download the Ask A Vet app for 24/7 support on equine murmurs, performance concerns, and heart-safe care plans. 🐎🩺

Final Thoughts: Don’t Miss a Beat ❤️🐴

Heart murmurs in horses can be mild or severe—but all deserve attention. Know the signs, ask your vet the right questions, and schedule regular checks to ensure your horse stays strong from the inside out. 🧠💪

Need guidance now? Visit Ask A Vet today. 🐴📱