UF Large Animal Hospital
Heart Murmurs in Horses: What You Need to Know
Just like in humans, heart murmurs in horses can be a normal part of life—or a sign of something more serious. These murmurs are sounds caused by turbulent or high-velocity blood flow and may be heard during a routine veterinary exam.
What Is a Heart Murmur?
Heart murmurs are extra sounds heard during the heartbeat cycle. In horses, they’re often linked to heart disease, but not always. Some murmurs occur in completely healthy horses and are known as physiologic-flow murmurs.
How Veterinarians Diagnose Murmurs
Understanding how the heart sounds correlate to underlying anatomy, physiology, and pathophysiology allows your veterinarian to determine reasonable differential diagnoses and sometimes even a definitive diagnosis. All areas of the chest overlying the heart, including the apex and base on the left and right sides of the chest are carefully auscultated in order to fully assess the heart rate, rhythm, and sounds without missing any abnormalities.
Key aspects include:
- Location: Where the murmur is loudest (Point of Maximal Intensity, PMI), which can be left or right, apical or basilar.
- Timing: Murmurs can be systolic (during heart contraction), diastolic (between contractions), or continuous.
- Association with pulse: A systolic murmur coincides with the pulse, while a diastolic murmur occurs without the pulse.
- Intensity: The intensity or loudness of a murmur is graded on a scale of 1 to 6.
- 1 = Very soft, focal murmur only detected in a quiet area after extended auscultation
- 2 = Soft, focal murmur that is readily audible
- 3 = Moderately loud murmur with some radiation
- 4 = Very loud murmur that radiates widely
- 5 = Very loud murmur with a palpable thrill
- 6 = Very loud murmur with a thrill that is audible with the stethoscope off the chest wall
Causes of Heart Murmurs in Horses
Below are possible causes of heart murmurs in horses:
- Aortic Regurgitation: A leak at the valve between the left ventricle and aorta usually caused by age related degeneration or infection of the valve
- Mitral Regurgitation: A leak at the valve between the left ventricle and atrium usually caused by age related degeneration or infection of the valve
- Tricuspid Regurgitation: A leak at the valve between the right ventricle and atrium which may be seen in normal horses or may be caused by age related degeneration
- Pulmonic Regurgitation: A leak at the valve between the right ventricle and pulmonary artery which may be seen in normal horses
- Physiologic Murmur (low grade): No heart abnormalities, normal blood flow is heard across the aortic, pulmonic valve, or occasionally the mitral valve
- Ventricular Septal Defect: A congenital heart defect where there is a hole between the two ventricles (most common congenital heart defect of horses)
- PDA (normal in first week of life): An normal vessel in the developing fetus that connects the aorta and pulmonary artery, but should close shortly after birth
- Aortic Stenosis (rare): Congenital malformation of the aortic valve (between the left ventricle and aorta)
- Pulmonic Stenosis (rare): Congenital malformation of the pulmonic valve (between the right ventricle and pulmonary artery)
- Aorto-Cardiac Fistula: Acquired defect where a hole forms between the aorta just above the aortic valve and the right ventricle or atrium
Even though some murmurs are benign, others can affect your horse’s health and performance. That’s why it’s essential to get any murmur checked and monitored over time.
Don’t Leave It to Chance—Act Now
If you suspect your horse has a heart murmur—or you’re concerned about their heart health—schedule an evaluation with the cardiology experts at UF Large Animal Hospital by calling (352) 392-2229. Their specialized team has the experience and tools to diagnose and manage a wide range of equine cardiac conditions.
Your horse’s heart matters—take the next step in protecting it today.
