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In general, most horses that collapse and die suddenly are the victims of an aortic aneurysm, which is a weakening in the wall of the aorta--the major vessel leading from the heart. This area of weakened wall can rupture and the horse then bleeds out internally. In other words, there are no external signs of bleeding, except that the mucous membranes of the mouth, nose, eyes, rectum, and genitalia become very pale. People can develop a similar weakening of the wall of major vessels, and surgical intervention to strengthen the area is usually indicated if the aneurysm is diagnosed prior to its rupture. So far, we have been unsuccessful in developing successful ways to either diagnose or treat these aneurysms in the horse. Alternatively, horses can develop a rhythm abnormality in the heart beat, most often atrial fibrillation, which is an irregular contraction of the collecting chambers of the heart. Under circumstances of great stress, this rhythm abnormality can lead to collapse and possible death, although more often it results in exercise intolerance.
Heart Attacks in Horses
I have heard many people say that their horse died of a heart attack and although that's possible, heart attacks are really rare in horses. A heart attack is a human medical diagnosis of myocardial infarction that is due to clogged arteries that lead to the heart in humans. Dr. Alan Loynachan reports in Equine Disease Quarterly that since horses do not suffer from coronary artery disease, heart attacks like those that occur in people rarely occur in horses. Racehorses that unexpectedly drop dead due to sudden death syndrome are said to have heart attacks, but this is not correct. Equine heart disease can develop quickly or can be a gradual progression. Acute heart disease results from a direct insult to the heart or disruption of the electrical signaling system. This disruption to the electrical system can occur with the use of drugs such as those used in routine equine dentistry. This is another reason a vet should examine your horse's heart before any sedatives are used because they have an effect on electrical conduction of the heart. Also, other poisons, snakebites, infections, or nutritional deficiencies can affect the heart.
Chronic heart disease can also develop due to birth defects, cancer of the heart, or previous injury to the heart or valves from infection. Eventually, the horse's heart becomes overworked and cannot keep up with the oxygen demand and heart failure occurs. Heart failure and heart attacks are two very different syndromes in people and animals. The most common heart disease noted in horses in a University of Kentucky study was infection and inflammation of the heart muscle, valves, and surrounding tissue.
Heart Attacks in Horses
I have heard many people say that their horse died of a heart attack and although that's possible, heart attacks are really rare in horses. A heart attack is a human medical diagnosis of myocardial infarction that is due to clogged arteries that lead to the heart in humans. Dr. Alan Loynachan reports in Equine Disease Quarterly that since horses do not suffer from coronary artery disease, heart attacks like those that occur in people rarely occur in horses. Racehorses that unexpectedly drop dead due to sudden death syndrome are said to have heart attacks, but this is not correct. Equine heart disease can develop quickly or can be a gradual progression. Acute heart disease results from a direct insult to the heart or disruption of the electrical signaling system. This disruption to the electrical system can occur with the use of drugs such as those used in routine equine dentistry. This is another reason a vet should examine your horse's heart before any sedatives are used because they have an effect on electrical conduction of the heart. Also, other poisons, snakebites, infections, or nutritional deficiencies can affect the heart.
Chronic heart disease can also develop due to birth defects, cancer of the heart, or previous injury to the heart or valves from infection. Eventually, the horse's heart becomes overworked and cannot keep up with the oxygen demand and heart failure occurs. Heart failure and heart attacks are two very different syndromes in people and animals. The most common heart disease noted in horses in a University of Kentucky study was infection and inflammation of the heart muscle, valves, and surrounding tissue.