Cardiac Murmurs in Older Horses

This article can help you understand what it means if your horse is diagnosed with a cardiac murmur and what to expect.

heart murmur ultrasound — This image shows an ultrasound of a horse's heart. The green depicts blood flow in the wrong direction.Courtesy Dr. Amy Polkes

Cardiac murmurs are often detected in older horses due to the normal aging process and valve degeneration. This article can help you understand what it means if your horse is diagnosed with a heart murmur.

What Is a Cardiac Murmur in a Horse?

A murmur is blood flow that is going in the wrong direction during either the pumping phase (systole) or filling phase (diastole) of the heart cycle.

The most common type of murmur in an older horse is aortic regurgitation from degeneration of the aortic valve with age. Aortic regurgitation occurs during the filling phase of the cycle (diastole). This is when the left side of the heart is relaxed and refilling. The aortic valve should have a tight seal during filling. With aortic regurgitation, there is leaking of blood back into the left ventricle causing a diastolic murmur.

Aortic regurgitation murmurs can be very soft and quiet at first. However, they can become quite loud if there is any vibration at the leaking aortic valve.

Diagnosing Cardiac Murmurs

The diagnosis is made by cardiac ultrasound (echocardiography) done by an equine internal medicine specialist or cardiologist trained in equine cardiology.

There are several important things that are looked for during the echocardiography. Those include examination of the aortic valve with color flow doppler to confirm the diagnosis, determine the size and direction of the regurgitant jet, and most importantly to measure the size and function of the heart.

Abnormal blood flow is not the concern, it is the consequence of that abnormal flow that can lead to enlargement of the heart that is of concern.

Understanding What the Heart Murmur Means

It is important to have your horse evaluated by a qualified equine veterinarian if a murmur is detected. This allows you to understand the cause of the murmur and if there are cardiac changes of concern.

In horses with cardiac chamber enlargement, there is the potential for rhythm disturbances (arrhythmias) that could make the horse unsafe to ride. Horses that are still being ridden might need additional diagnostics. Those might include an exercising ECG to be sure there are no concerning arrhythmias during exercise.

Medications might also be recommended in horses with cardiac enlargement. These can improve blood flow and decrease the workload of the heart. These are generally inexpensive, easy to administer, and well tolerated.

Final Words

Cardiac murmurs are not always clinically significant. Your veterinarian might simply monitor the murmur over time for changes that could be cause for concern. They can become louder over time as they progress or transiently during times of stress and illness (colic, fever, dehydration, etc). Many murmurs remain stable for years and might not have an impact on the horses general health.

It is very important to have your veterinarian include cardiac auscultation as part of a routine annual examination.

Mars Horsecare, directly or through affiliated companies is the owner of a portfolio of equine-focused products and services under the brands BUCKEYE™, SPILLERS™, WALTHAM™ Equine Studies Group, ANTECH™, SOUND® and MARS EQUESTRIAN™, and is not responsible nor does it endorse any content unless so acknowledged within the individual article or material as the source. We recommend you seek advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.

My Senior Horse’s mission is to educate and assist owners and managers of horses, ponies, donkeys, and mules that are 15 years of age or older to improve the health and welfare of senior equids.