Dogs are less likely to suffer heart failure than humans. But, many of the same risk factors are involved and may increase the likelihood of an acute—and possibly fatal—cardiac event. These factors include obesity, diabetes, high blood pressure, poisoning, or serious bacterial infection. While there are many forms of canine heart disease, all can ultimately cause heart failure.

What Is Heart Failure?

Heart failure is the result of severe cardiac disease that impairs the heart's blood flow and stops it from functioning. Blood flow is restricted and therefore unable to adequately supply the dog's organs with oxygen. Another form of heart failure, called congestive heart failure, happens when blood flow is constricted or blocked, so blood pools in the dog's body and organs.

Symptoms of Heart Failure in Dogs

Dogs with heart disease may be asymptomatic (free of any signs of illness) if the heart disease is mild enough to allow the heart and the rest of the body to compensate. However, if heart disease progresses without treatment, signs of heart failure will develop.

Heart failure can affect one or both sides of the heart, with some symptoms specific to the side that is damaged. While many of these symptoms can indicate other conditions, even the subtlest sign may indicate impending heart failure or congestive heart failure in a dog.

Right-sided heart failure results in a backup of blood, which accumulates in the abdominal and chest cavities, liver, and limbs. The pooling of blood may cause visible swelling in a dog's torso or legs.

In the case of left-sided heart failure, the blood returning from the lungs to the heart backs up, and fluid accumulates in the lungs. This causes the dog to experience labored breathing, tiredness or weakness, and coughing.

In some dogs, both sides of the heart fail, causing a combination of symptoms associated with unilateral failures.

Causes of Heart Failure

Heart failure is a culmination of damage that occurs throughout heart disease progression. There are four distinct causes of acute heart failure, as follows:

• Systolic myocardial failure: This is the inability of the heart to contract fully or as powerfully as it should. It can be caused by genetics, injury, infection, drugs or poisons, electric shock, heatstroke, tumors, or unidentifiable factors.
• Obstruction of cardiac inflow: This obstruction of blood flow can be the result of surrounding fluid pressure, tumors, ventricular stiffening due to diastolic dysfunction, or physical abnormalities.
• Pressure overload: This problem occurs due to long-term constriction of vessels and increased blood pressure.
• Volume overload: This is the marked increase in blood volume in one or both ventricles due to valve disease, physical abnormalities that cause left-to-right shunts, hyperthyroidism, or anemia.

Diagnosing Heart Failure in Dogs

The vet will probably want to rule out heartworms, and in addition to blood and urine tests, may order a chest x-ray and an ultrasound scan of the heart called an echocardiogram. An electrocardiogram (EKG) that measures your dog's heart rhythm can also be helpful. One or more of these tests will be necessary to determine what type of heart disease your dog has.

Treatment of Heart Failure

If caught in time, heart failure may be treated with a variety of drugs, based on the exact cause, manifestation, and severity of the particular case. Some medications can help the heart contract; others help widen blood vessels. Diuretic drugs can help a dog excrete accumulated fluid, relieving discomfort and pressure on the heart. Your veterinarian will establish a treatment plan that will require strict adherence to improve your dog's quality of life and reduce risks associated with some of the drugs that may be prescribed.

Prognosis for Dogs with Heart Failure

The prognosis for a dog with heart failure depends on the severity of its heart condition and associated health issues. A dog with advanced heart failure, obesity, and diabetes is unlikely to rebound fully. However, if the dog's heart is in the early stages of failure, and the owner is committed to improving the dog's health and fitness, then chances are good that the dog may enjoy a happy and fairly active life for months or years.

How to Prevent Heart Failure

In some cases, heart failure can be avoided for months or even years if the underlying disease is managed using medications that improve heart function and reduce fluid build-up. Close monitoring is important because medication adjustments may be necessary over time.

The best way to prevent canine heart failure is to reduce its risk factors: Make sure your dog doesn't become overweight, and work with your vet to treat ongoing health conditions such as diabetes.