If you are wondering why do dogs get heart attacks (myocardial infarction), you may suspect your dog suffered from one or you perhaps heard about it happening to some dog.
Fortunately, heart attacks are not common in the canine world as they are in humans.
Indeed, dogs can eat a diet chock full of meat without worrying about their arteries hardening and shutting off blood flow to their hearts.
If having a heart attack is unlikely in your dog, consider that there are several other conditions that may look like a heart attack when they are not.
A Lesson in Anatomy
Just as humans, a dog's heart is made of several chambers along with veins and arteries. In particular, the coronary arteries are responsible for delivering oxygen-rich blood to the myocardium, the muscular tissue of the heart.
When the coronary arteries are squeaky clean and free of deposits, oxygen is successfully transferred to the heart so it can perform all of its important duties.
Problems start though when these arteries become clogged which can lead to serious complications such as a heart attack.
A Matter of Fats
The technical term for a heart attack is myocardial infarction (MI). A heart attack takes place when the myocardium fails to receive enough oxygen because of clogged coronary arteries.
In humans, the arteries become clogged because of hardened deposits of fat which often derive from years of consuming a diet high in saturated fats. Just like the drain pipe of a sink gets clogged when oily products accumulate, the arteries of humans become narrowed and blocked by fats, causing the heart to no longer receive its vital amounts of oxygen.
What happens next depends on whether the blockage is partial of complete. A partial blockage may cause chest pain, while a complete blockage can lead to death.
A heart attacks therefore takes place when the the blood flow through the coronary artery is totally blocked, starving the heart of oxygen and nutrients.
Processing of Fats
While dogs share a similar anatomy as humans, when it comes to their hearts, heart attacks in dogs are quite uncommon because dogs process fat in a different way compared to humans.
Dogs can eat meat and a diet rich in fats and their arteries will not develop atherosclerosis as it happens in humans. This is because, normally, when a dog eats, the fat content of the food splits (into triglycerides and cholesterol) and it is absorbed.
More than developing a heart attack, dogs who eat diets high in fat are more likely to develop pancreatitis, an inflammation of the pancreas that leads to severe vomiting and loss of appetite.
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Exceptions to the Rule
There are however some cases of dogs developing coronary artery disease, but in these cases, fats are not the main culprit.
Rather, contributing factors are medical conditions such as hypothyroidism. The thyroid gland indeed in dogs is known for producing hormones that help control metabolism and help regulate cholesterol.
Cholesterol accumulations in the arteries (condition known as atherosclerosis) leads to reduced blood flow which can potentially result in severe and even life-threatening conditions such as heart attacks, circulatory issues and hemorrhages, explain Dr. Crnec in an article on what to do when dogs eat grease.
However, even then, the risks of developing a heart attack in dogs suffering from this condition are minuscule, explains veterinarian Dr. Nancy Laste in an article for Pet Place. Heart attacks in dogs are therefore are rarely reported.
What Was it Then?
If heart attacks are so uncommon in dogs, then what causes a dog to collapse? There are several other conditions that may look like a heart attack, but that in reality are something else.
These often fall under the "seizure," "syncope" or "sudden death" category.
Seizures are characterized by jerky movements of the limbs from a dog who appears unresponsive. After the seizure is over, dogs may appear abnormal for several minutes or hours (post-ictal state).
Typically, seizures last less than 5 minutes. A seizure lasting more than 3 to 5 minutes warrants a trip to the emergency vet.
Syncopal episodes in dogs are brief periods during which the dog loses consciousness because of lack of oxygen flowing to the brain. These brief blackouts can be caused by conditions such as heart rhythm abnormalities, respiratory disease, hormonal disorders, anemia or low blood pressure arising as a side effect from certain medications.
Vestibular disease in dogs may also cause a drunk-like gait with the dog falling at times.
Syncopes generally last between seconds or minutes.
Sudden death. There are several conditions that may cause sudden death in dogs, but heart attacks due to clogged arteries as mentioned are unlikely. Dogs however aren't immune to heart problems and get their fair share of cardiac conditions.
Causes of sudden death in dogs include heart arrhythmias, heart valve defects, a hemorrhaging, ruptured spleen as seen in hemangiosarcomas, or presence of blood clots in the lungs.
There can be other causes and the only true way to know what may have caused sudden death in dogs is asking the vet to perform an necropsy.
Did you know? According to doctor William C. Roberts in an article published in the American Journal of Cardiology, 1990 vol. 66,896, it was impossible to cause atherosclerosis in a dog even when given 100 grams of cholesterol (that's 200 times the amount the average American eats every day) and 120 grams of butter fat added to its meat ration.