heart disease

Heart disease may not occur in horses as often as other health conditions, but the effects can be devastating when it does. Take a look at several common heart conditions and what to watch out for.

While heart disease is not as common as other health conditions in horses, it’s the third most common cause of performance issues in horses. That alone justifies the diagnosis of any heart abnormality in a horse. A normal, healthy heart beats over 630 million times in the average horse’s life and weighs close to ten pounds in the adult equine. This vital organ is tucked up under the horse’s left elbow, making it hard to access when he’s standing.

The normal resting heart rate for an adult horse is between 25 and 50 beats per minute (bpm). The heart rate will increase to 80 to 120 bpm at the trot, 120 to 150 bpm at the canter, 150 to 180 at the gallop, and can be as high as 240 beats per minute when a horse is running all out. Within five minutes of stopping exercise, the heart rate should drop back below 100 bpm.

A fit horse will have three clearly audible heart sounds when the heart is at rest; the third beat is a “physiologic” murmur and is not audible when the horse begins exercise. (Each heart sound is the noise made when a valve closes. Technically, there should be four sounds, as there are four heart valves, but the sound of two of the beats is usually obscured by the sound of the louder, bigger valves closing.)

Equine heart conditions

The range and type of heart conditions horses suffer from can be fairly similar to those we experience as humans, with some variations.

  • Just as with any other species, foals can be born with heart defects – this is called congenital heart disease. A heart defect will make vigorous physical exercise difficult for a growing foal and is one clue the foal needs medical evaluation.
  • Dysrhythmias (irregular heartbeats) are common in horses; however, most are physiologic and happen at rest. These must be differentiated from true dysrhythmias – a brief stretch of exercise should remove the irregular sounds, in most cases. If the heart murmur remains, then causes to consider would be AV block or atrial fibrillation. Both indicate a problem with the electrical conduction of the heartbeat’s symbol signal, which disallows the beat to progress across the heart as normal. An electrocardiogram can diagnose these heart conditions.
  • Valvular heart disease can lead to heart murmurs, which in advanced cases may sound like a washing machine. Essentially, one of the heart valves does not close properly, either due to genetic defect, trauma from health issues (infection), or aging. This can lead to right- or left-sided heart failure, depending on which valve is involved. Right-sided heart failure may lead to ascites and/or edema, especially in the lower legs and abdomen. Left-sided heart failure can lead to low blood volume and buildup of fluid in the lungs, which can potentially develop into pneumonia.
  • Myocardial disease is a disease of the heart muscle itself. While horses don’t usually get hardening of the arteries like humans do, the result of disease in the heart muscle is just like when a blood vessel to the human heart is occluded – the heart muscle dies and the horse suffers an event just like a heart attack in humans. Once there is a failure of the heart muscle to contract, blood will not flow, resulting in a grave prognosis.
  • Horses can also develop pericarditis, which is an inflammation of the pericardium, a thin fibrous sack surrounding the heart. Pericarditis is most common after respiratory disease and some viruses, and can be associated with heart failure. It can be diagnosed with ultrasound. These horses have chest pain and do not take deep breaths.
  • Aortic disease includes aneurysms and fistulas, which can be just as fatal in horses as in humans. In either case, the result is a tear in the aorta (the primary outflow from the heart). This causes sudden death as all the blood leaves the heart and drains into the chest cavity. These horses die suddenly, which is very traumatic to the owners, especially since the animals never display any signs of a problem prior to death.

The equine heart in Traditional Chinese Veterinary Medicine (TCVM)

In TCVM, the Heart is the Emperor of the organ systems and is closely related to the Blood, vessels, and other organs of the body (capitalization denotes the Chinese organs – not necessarily the same as in conventional medical systems). The Heart uses Qi to pump and move the Blood, thereby circulating nutrients to all parts of the body. Working with the other organs, the Heart regulates the volume of Body Fluids to keep the Blood in optimal condition.

Additionally, the Heart houses the Shen (spirit). When a horse has good Shen, he has bright eyes, is alert and feels well; poor Shen results in dull eyes, droopy ears and poor performance. A stall walker or a cribber has a disturbance of the Shen.

The Heart also controls the sweat. Body Fluids and Heart Blood are interchangeably related — deficiency of either will decrease production of sweat. Similarly, excess sweat can deplete Body Fluids and Heart Blood. Abnormal sweat can be an early indicator of heart issues. This is important, as most horse owners would prefer to know their horses have heart issues as early as possible, when the chances for treatment are better. Early detection is a great strength of TCVM.

Finally, the Heart in TCVM opens to the tongue. The tongue gives a good view to Heart function. A pale tongue suggests a weakness (deficiency) of the Heart, a red tongue is an excess condition and suggests Heat (Heat sometimes relates to infection). A small or enlarged tongue also suggests changes in blood volume or Heart Qi and warrants further investigation.

Not only can medical conditions of the heart be treated with TCVM, but so can heart conditions that may manifest as Shen disorders. TCVM treatment for horses includes acupuncture (including Moxa), Tui-na (massage), herbal therapy and food therapy. Because Chinese theory addresses the whole body, all organ systems can be addressed to aid the Heart in better function and improve quality of life for the horse.

Just as in humans, heart disease in horses is nothing to mess around with. Know and understand the basic signs of heart disease and involve your veterinarian straight away if you have reason to suspect your horse has, or is developing, a cardiac issue. Thankfully, in many cases, early detection and treatment can go a long way to ensuring these horses have long and healthy lives.