Why Dogs Don't Get Heart Attacks

Your dog can get hit by a car, he can be poisoned by the neighbour and he can choke on a bone. Nevertheless, you will never see your dog die from a heart attack. Wonder why?

Why Dogs Don't Get Heart Attacks

The number one killer in western society is Cardiovascular Disease (e.g., heart attack, cardiac arrhythmia) [1]. A significant fraction comes from heart attacks, which means that blood flow to the heart is blocked. Around 49.000 patients per year die from myocardial infarctions just in Germany [2].

Dogs on the other hand seem to have more problems with cancers than with Cardiovascular Diseases. If they have a problem with their heart, most of them either have some congenital defect (i.e., born with a heart defect) or develop some cardiomyopathy (e.g., stiff heart, enlarged heart) during their lifetime. When you take a closer look at the data, almost no dog dies from an acute heart attack [3].

But why is that?

Let's compare the anatomy.

A human heart has a left and right coronary artery. They have to work together to supply the heart with blood. If one of them gets clogged for any reason (e.g., atherosclerosis), part of the heart will start dying after 20 minutes. That damage will be permanent and this gives doctors job security :) [4].

Comparison of the coronary arterial circulation in the dog (A), pig (B) and human (C)

A dog heart has the same left and right coronary artery. Yet there is one major difference. These arteries have significantly more coronary collateralization (i.e., growth of new blood vessels serving the heart), including many arterial anastomoses (i.e., a connection between arterial blood vessels). This means that each segment of the dog heart has numerous sources of blood supply [4].

What happens if one artery gets blocked?

Simple. The other arteries take over. It is extremely unlikely that multiple arteries get occluded at the same time. This makes it almost impossible for a dog to experience a heart attack as you would expect in a human [4].

Why should you care about that?

Dogs used to be the primary animal models during the 1970s and 1980s in multiple studies to identify better pharmacological therapies (drugs). The goal of these drugs was to decrease the size of the infarct in humans. However, these nuanced differences in human and dog anatomy were overlooked. This led to less than optimal results in humans later on.

In other words: Only dogs profited from such new drugs since the efficacy of those therapies was falsely claimed to be higher than real [4]. But at least my dog can enjoy a happier and healthier life now :).

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References

  1. Ritchie, H. (2018, February 14). Causes of Death. Our World in Data. https://ourworldindata.org/causes-of-death
  2. Myokardinfarkt. (2021, February 6). Amboss. https://www.amboss.com/de/wissen/Myokardinfarkt
  3. Stalker, M. (n.d.). Causes of sudden unexpected death in dogs and cats – it’s not the neighbour! | Animal Health Laboratory. Uoguelph. Retrieved May 2, 2021, from https://www.uoguelph.ca/ahl/content/causes-sudden-unexpected-death-dogs-and-cats-%E2%80%93-it%E2%80%99s-not-neighbour
  4. Hill A.J., Iaizzo P.A. (2005) Comparative Cardiac Anatomy. In: Iaizzo P.A. (eds) Handbook of Cardiac Anatomy, Physiology, and Devices. Humana Press, 82–83. https://doi.org/10.1007/978-1-59259-835-9_5

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