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About Canine Heart Disease

Canine heart disease is just as dangerous in dogs as it is in people. The heart is an amazing organ that runs 24 hours a day, 7 days a week, but in order for your dog's heart to run good. . . it must be taken good care of.

Before we talk about various types of heart disease in dogs, let's talk about how the heart actually works.

A dog's heart works exactly the same way as the human's heart, although it beats a little faster. Let's take a look at the different parts, and how they work together like a well oiled machine:

The heart is a combination of 2 pumps, and each of those pumps have 2 parts (or chambers). The 2 pumps are divided by Left and Right sides.

Blood flows into the right side of the heart, which is slightly smaller and lower pressure than the left.

The blood enters the right side and is then pumped to the lungs, where it drops off carbon dioxide, and picks up oxygen.

The freshly oxygenated blood then flows into the left side of the heart, which is larger and higher pressure than the right.

The left side then pumps all that fresh blood through the Aorta and into the veins, which then carry it to the entire body.

As you can see from the picture, there are 4 valves in the dog's heart that let blood pass between the different chambers. They are one-way valves and keep the blood flowing in the right direction.

Canine Heart Disease:
On this page you’ll find short summaries of different types of canine heart disease. For in-depth information on a particular dog heart problems, click the links under each headline to learn more about that topic.

How Blood flows through the Dogs Heart

Right Side:

  • Blood flows into the Right Atrium of the heart through the Inferior and Superior Vena Cava's (2 very large veins)
  • The blood then flows through the Tricuspid Valve into the Right Ventricle until it's full (the Tricuspid Valve keeps the blood from going back the wrong direction)
  • The blood then flows from the Right Ventricle through the Pulmonary Valve into the Pulmonary Artery.
  • The Pulmonary Artery delivers the blood to the lungs where it picks up fresh oxygen

Left Side:

  • Blood flows from the lungs (after being filled with fresh oxygen) through the Pulmonary Vein into the Left Atrium
  • Blood then flows from the Left Atrium into the Left Ventricle through the Mitral Valve (Just like on the Right side, the Mitral Valve keeps blood from flowing back the wrong way)
  • The blood leaves the Left Ventricle through the Aortic Valve and is delivered to the Aorta
  • From the Aorta, the blood is transported to the entire body through the veins

Types of Canine Heart Disease

Now that we know how the heart is supposed to work, we can talk about what things cause problems in the heart, such as faulty valves.

If any one of the intricate pieces of the heart stops functioning properly, it causes problems. There are several common heart conditions that can make one or more of the pieces not work like they're supposed to.

The result is one or more types of canine heart disease, or other dog heart problems:

Canine Congestive Heart Failure

Congestive heart failure in dogs means that the blood is not flowing to and from the lungs & body at the correct pressure and volume.

If the blood is not being pumped from the heart at the rate it should be, then it causes a back-up in the blood flow into the heart.

When pressure is increased upstream from the heart, then the blood will leave the blood vessels and congest in other tissues of the body.

The two most common causes of this type of canine heart disease are:

  • DVD (Degenerative Valvular Disease) - Happens when the heart valves don't work properly, and allow the blood to flow in backwards in the wrong direction. In dogs, the most common valve to be affected is the Mitral Valve (the valve between the Left Atrium and Left Ventricle)
  • DCM (Dilated cardiomyopathy) - Happens when the Ventricle chamber enlarges, and loses strength. The loss of strength means that it cannot pump (contract) as strong as it's supposed to. Because it can't pump as much blood, it causes a back-up of blood upstream to the heart and congestion in the surrounding tissue.

When one of the above problems occurs on the Right side of the heart, congestion usually happens in the abdomen area.

When a problem happens on the Left side of the heart, the congestion is usually in the lungs, which results in Pulmonary Edema (build-up of fluid in the lungs).

Enlarged Heart in Dogs

Canine enlarged heart is also known as DCM (Dilated cardiomyopathy), and as noted above it's one of the major causes of Canine Congestive Heart Failure.

So, to really understand we need to know what causes the heart to become enlarged. In most cases, the cause of DCM in dogs is not known, but genetics can definitely play a part.

This is the most common heart condition to affect some large breed dogs such as:

  • Great Danes 
  • Mastiffs
  • Boxers
  • Irish wolfhounds
  • Dobermans

It usually effects dogs when they are middle aged, and males are affected more often than females. There are other things that can contribute to the condition, such as insufficient nutrition, toxins, parasites and infections.

Canine Heart Murmur

A heart murmur in dogs is basically an irregular heartbeat and is caused when the blood is not flowing normally. Essentially, it causes a communication disconnect between the Right and Left sides of the heart.

A dog heart murmur can caused by numerous things. They can sometimes develop as a result of other types of canine heart disease, or a puppy can be born with it and live his entire life without any issues.

They can often be treated by surgery, medicine or diet changes. But only a veterinarian can diagnose your dog with a heart murmur, and determine what the cause of it is.

High Blood Pressure in Dogs

High canine blood pressure is also known as hypertension, and it's basically the same as in humans. Although a normal blood pressure range in dogs is higher than people.

Measuring a dog's blood pressure is not nearly as easy as it is in humans, and it can vary by breed. For humans, the ideal blood pressure is 120/80, often stated 120 over 80.

For dogs the top number is considered high if it's consistently over 170. And the bottom number is considered high if it's over 100 consistently.

I for one get a little stressed out when I go to the doctor, and tend to have a slightly elevated blood pressure -- the same things often happens to dogs. So, just because your dog's blood pressure may be slightly high on a visit to the vet, isn't necessary cause for alarm.

Veterinarians don't normally measure a dog's blood pressure on routine visits, like our doctors do. If however, there are other symptoms that cause you or your vet to suspect something related to canine heart disease, then of course blood pressure will be an important measurement.

Heartworm in Dogs

Heart worms in dogs are one of the most dangerous parasites a dog can deal with.

These pesky little parasites are one of the major causes of canine heart disease. They are very dangerous and often fatal.

The reason they're called heartworms is because in their adult form, they infest the right atrium of a dogs heart, and start to reproduce.

Once they're at this stage, the heart can become seriously damaged. Treatment for a bad infestation of heartworm can cause serious side-effects for a dog, and even be fatal.

The very best thing you can do to protect your dog from a heart worm infestation is to prevent it. There are a lot of products on the market to prevent heart worms in dogs, some are better and safer than others.

Heart worms are contagious, but not in same way as other parasites. The most common way a dog contracts them, is by being bitten by a mosquito that has also bitten another infected dog.

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