Understanding heart failure in dogs

Dogs don’t experience heart attacks the way humans do, but this doesn’t mean they don’t die of heart disease. Heart failure in dogs is increasingly common in present scenario, with many showing symptoms by age seven or eight. Even some young dogs develop congestive heart failure, inheriting the propensity for the disease from their parents. Here’s more on heart failure in dogs.

Dr. K Satish Kumar

Dr. K Satish Kumar

Veterinarians with present technology know that in many cases, heart disease can be slowed, reversed and even cured. Heart failure is a common end result of heart disease in dogs. Though canine heart disease includes many different types of conditions, all forms of heart disease can ultimately cause heart failure.

Heart failure – classification

  • Heart failure in dogs may take on two different forms. Right-sided heart failure occurs when the right side of heart fails to pump blood properly. This failure results in blood which should be returning from other parts of the body backing up in those body organs rather than returning normally to the heart. This results in accumulation of fluid in other parts of the body, most noticeably in the abdominal cavity, the liver and the limbs.
  • Left-sided heart failure occurs when the pumping mechanism in the left side of heart fails. In this instance, the blood returning from the lungs to the heart backs up and fluid accumulates in the lungs.
    In some dogs, both sides of the heart are involved. This may lead to failure of both the left and right sides of the heart and result in signs of both right- and left-sided heart failures occurring simultaneously.

Heart failure – signs
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 for the disease. However, if the heart disease is severe enough that the heart cannot compensate for the disease, heart failure will occur and will lead to signs of heart failure. The types of signs seen in heart failure will vary depending on how severe the disease is and which side of the heart is affected. However, the signs most commonly encountered with heart failure include:

  • Generalised weakness
  • Exercise intolerance
  • Lethargy
  • In appetence
  • Weight loss
  • Coughing (most often seen with left-sided heart failure)
  • Dyspnoea at rest (most often seen with left-sided heart failure)
  • Pedal edema (most often seen with right-sided heart failure)
  • Ascites (most often seen with right-sided heart failure)
  • Cyanosis (a bluish colouration of the gums)
  • Syncope (fainting episodes)

Congestive heart failure is the inability of the heart to provide adequate circulation to meet the body’s needs. It is the end result of a weakened heart muscle. The health of the liver, kidneys, lungs and other organs is impaired by the circulatory failure, resulting in a problem involving multiple organs. A diseased heart can compensate for many months or years without signs of failure. When failure does occur, it may appear suddenly and unexpectedly-sometimes immediately after strenuous exercise, when the heart is unable to keep up with the body’s demands.
In toy and small-breed dogs, chronic valvular disease is the most common cause of heart failure and in large-breed dogs it is dilated cardiomyopathy. The early signs of heart failure are tiring easily, a decrease in activity level and intermittent coughing. The coughing occurs during periods of exertion or excitation. It also tends to occur at night. Dogs may be restless – pacing instead of quickly settling down to sleep. These early signs are non-specific and may even be considered normal for the dog’s age. As heart failure progresses, the dog develops other signs, such as lack of appetite, rapid breathing, abdominal swelling and a marked loss of weight. Because the heart no longer pumps effectively, blood backs up in the lungs, liver, legs and other organs. Increased pressure in the veins causes fluid to leak into the lungs and peritoneal cavity. An accumulation of fluid in the chest cavity (pleural effusion) also occurs with right-sided heart failure. In the late stages of heart failure the dog sits with his elbows spread and his head extended. Breathing is laboured. The pulse is rapid, thready and often irregular. The mucous membranes of the gums and tongue are bluish-grey and cool. A thrill may be felt over the chest. Fainting can occur with stress or exertion.
Diagnosis
An accurate diagnosis is established through chest X-rays, ECG, echocardiography and other tests, such as a heartworm antigen test. In dogs as in humans, there are four functional classifications of heart failure.

  • Class 1 has no obvious signs. This early phase, during which the heart begins to malfunction, can last for years.
  • In Class 2, fatigue and shortness of breath begin to accompany active exercise or heavy physical activity. There are no symptoms when the dog is sitting still or lying down.
  • In Class 3, even slow walking on a level surface can produce shortness of breath and fatigue. Other possible signs include a persistent dry or hacking cough, wheezing, sudden collapse and a bluish discolouration of the tongue and gums during exercise.
  • In Class 4, the patient is uncomfortable at all times, even while resting. Edema can affect the legs and feet as well as abdomen and chest area. In advanced cases, fluid collecting in the chest cavity can push on the heart and collapse the lungs. In contrast to the long time lag between Class 1 and Class 2, the illness progresses quickly from Class 3 to Class 4, so that a dog who seemed healthy and active may suddenly enter a critical condition.

Heart failure management
It is important to correct any underlying cause whenever possible. Heartworms, bacterial endocarditis and some forms of congenital cardiac diseases are potentially curable if they are treated before the heart is damaged.
Treatment of congestive heart failure involves feeding the dog a low-salt diet, restricting exercise, and giving appropriate medications to increase heart function and prevent cardiac arrhythmias. In dogs with mild symptoms, salt restriction may be the only treatment required. Exercise is beneficial, but only for dogs who are not symptomatic.
If symptoms such as easy tiring, coughing, or rapid breathing appear with exercise, do not allow your dog to engage in activities that elicit these symptoms.
Various drugs are available that increase the force and contraction of the heart muscle or decrease the workload. They include the digitalis glycosides, calcium channel blockers, angiotensin-converting enzyme (ACE) inhibitors, beta blockers, and anti-arrhythmics. ACE inhibitors such as enalapril maleate and benazepril may prolong the life of dogs with valvular heart disease and cardiomyopathy and are commonly used in dogs with these diseases. Fluid accumulation in the lungs and elsewhere is managed by diuretics such as furosemide.  Dogs with congestive heart failure may benefit from vitamin-B supplements and taurine or carnitine. Coenzyme Q is another supplement that may help dogs with cardiac problems.
With proper treatment, a dog with heart failure can live a longer and more comfortable life. However, the patient requires close monitoring.
(Dr K Satish Kumar is Associate Professor and Head, Sri Venkateswara Veterinary University, Veterinary Hospital, Warangal while Dr D Srikala is Assistant Professor, Veterinary Medicine, CVSc, Tirupati).