Understanding Cardiac Murmurs in Senior Horses

Cardiac murmurs are relatively common in older horses due to valve degeneration and the normal aging process. 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 goes 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 caused by age-related degeneration of the aortic valve. 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, blood leaks back into the left ventricle, causing a diastolic murmur.

Aortic regurgitation murmurs can be very soft and quiet at first. However, they can become 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 cardiologists look for during the echocardiography. They will examine the aortic valve with color flow doppler to confirm the diagnosis, determine the size and direction of the regurgitant jet and, most importantly, measure the size and function of the heart.

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

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 such as an exercising ECG to ensure 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 heart’s workload. They 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. Murmurs 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 impact the horse’s general health.

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