What Is Heart Failure?

Heart failure occurs when the heart, weakened by disease, fails to pump enough blood to meet the body's needs.

What is the difference between heart disease and heart failure?

In the early stages of heart disease, your dog’s body may make adjustments to allow him/her to cope with the disease. During this stage of the disease, your dog may show no visible signs of being unwell or the signs could be mistaken for normal aging.


In time, heart disease can lead to heart failure, which means that the heart has to work harder to do its job, and this can cause more damage to occur. You may also see or hear the term congestive heart failure. The word “congestive” indicates that heart failure is linked to increased fluid buildup, or congestion, in areas such as the lungs, liver, or abdominal cavity. If your dog has heart failure, you will likely notice your dog’s health getting worse.


But even if your dog is at risk, do not lose hope. In dogs with heart disease, the body will adapt to the condition, and it can take some time before heart failure develops. In some dogs, heart disease may not lead to heart failure. But it is important to understand your dog’s heart condition and watch for the signs of early heart failure.

How to think of heart failure

How the healthy heart works

= Oxygenated blood

= Deoxygenated blood

= The heart

= The body

= The lungs

The cardiovascular system can be thought of as a series of train tracks in which the tracks represent the blood vessels extending to and from the main train station, or heart.


Think of the red train as your dog’s oxygenated blood. Just as a train drops off commuters at their offices, so does oxygenated blood exit the lungs and drop off essential nutrients and oxygen that the body needs to do its job.


The blue train is your dog’s deoxygenated blood. When the blue train heads back from the city, it passes through the train station again on its way to drop off its passengers at home. Similarly, deoxygenated blood passes through the heart and enters the lungs where it gets reoxygenated, so it can go back to work.


In a healthy dog, these trains move in the right direction.


What happens during heart failure

When a heart becomes diseased, however, things go wrong. Because the heart is one interconnected system, when one thing breaks down, it affects everything else. The blue train can start heading in the wrong direction, getting in the way of the red train. Because neither train can get where it needs to go, a backup occurs on the tracks. This is similar to what happens when a leaky mitral valve causes blood to leak backwards.



Think of what happens when there’s a train backup. People either get stuck at home and cannot get to work or they are slowed down somewhere along the tracks. This is similar to the congestion and fluid overload that can build up in a dog’s lungs. Notice how there are no red trains or people over by the city. That means work is not getting done (no nutrients or oxygen are getting to the body so it struggles to do its job).