Heart Disease in Cats

By Tammy Hunter, DVM; Ryan Llera, BSc, DVM; Ernest Ward, DVM

What types of heart disease do cats get?

Heart disease is a serious medical condition in dogs, cats, and humans. In general terms, heart disease in cats can be divided into two categories: congenital and adult onset.

In congenital disease, the heart defect is present at birth. Signs of congenital disease are often seen at a young age, but in some cases, congenital heart disease can go undetected for many years.

Congenital heart disease may be caused by a developmental problem that causes malformation of the heart as the embryo develops. This type of congenital heart disease may affect only a single kitten in the litter. Congenital heart disease may also involve a genetic or hereditary disorder, in which case the problem may develop in more than one kitten in the litter.

Adult-onset heart disease can occur as the result of damage to the heart structure at some time during the cat's life, resulting in abnormal function. Some cases of apparent adult-onset heart disease can be due to a hereditary condition that progresses as the cat ages, eventually causing problems. The most common type of adult-onset disease in cats is cardiomyopathy, a disease affecting the heart muscle.

"The most common type of adult-onset disease in cats is cardiomyopathy, a disease affecting the heart muscle."

The exact cause of most types of adult-onset heart disease is unknown, although genetics and lifestyle (weight, physical activity, and diet) may play an important role. In some cases, adult-onset heart disease develops as a secondary problem, with the primary problem being in some other area of the body. A common primary problem in cats is hyperthyroidism (overactive thyroid gland).

What is the structure of the heart and how is it affected by heart disease?

The heart can be divided into four functional components:

  • the heart muscle, which pumps the blood around the body
  • the heart valves, which act to prevent the blood going in the wrong direction,
  • the pericardium, which is a tough membrane surrounding and protecting the heart, and
  • the electrical conducting system, which initiates and transfers electrical impulses around the heart, allowing it to contract or beat in a systematic and coordinated fashion.

Heart disease can affect any or all of these parts.

How common is heart disease in cats?

Heart disease is less common in cats than in dogs. The most common type of heart disease in cats is adult-onset hypertrophic (enlargement or thickening of the heart) cardiomyopathy (see handout "Cardiomyopathy in Cats").

What are the signs of heart disease in cats?

Most cats display no clinical signs until the disease is advanced. Unlike humans and dogs, cats rarely cough if they have heart disease. Exercise intolerance occurs but can be difficult to recognize, since cats rarely go for walks or engage in sustained physical activity with their owners. With advancing disease and declining exercise tolerance, cats tend to become more withdrawn, hide under furniture, and sleep more.

The most common signs of heart disease in cats are:

  • poor appetite
  • weight loss
  • lethargy
  • increased respiratory rate and effort
  • sudden collapse
  • sudden hind-leg paralysis accompanied by pain due to thromboembolism (blood clots), which may be referred to as a “saddle thrombus”
  • stunted growth (kittens)

What types of congenital heart disease occurs in cats?

The two most common types of congenital heart disease are 1) malformations of a valve or 2) a septal defect in the wall that divides the right and left sides of the heart (a “hole in the heart”). In both circumstances, blood flows abnormally through the defect, causing turbulence.

This turbulence causes a heart murmur that is often detected during a routine physical examination of the kitten. The loudness of the murmur reflects the amount of turbulence but is not indicative of the severity of the disease. Not all heart murmurs are associated with heart disease. Some may reflect another disease process such as anemia. Normal cats can have intermittent heart murmurs, often when their heart rate is increased due to stress, and these physiologic murmurs have no impact on their health.

How is congenital heart disease diagnosed?

Depending on the murmur and the degree of clinical signs, further testing may be advised to determine the cause. The additional testing generally involves X-rays, electrical recording of the heart (ECG), and ultrasound examination (echocardiography). If your veterinarian suspects that the heart murmur is secondary to another disease, more extensive tests such as blood screening may be recommended.

How is congenital heart disease treated?

Treatment will depend on the cause of the heart disease. At this time, few congenital heart abnormalities in the cat can be surgically corrected, other than patent ductus arteriosus (see below). When a young kitten is diagnosed with heart disease, diagnostic testing will help determine the prognosis and whether medical treatment is necessary. If a heart murmur is detected on a routine examination but the cat is not showing signs of problems, careful monitoring is often the best option.

The presence of a heart murmur does not necessarily mean that your cat's quality of life or life expectancy will be affected.

Are some cat breeds predisposed to heart disease?

Yes, certain breeds of cats are predisposed to some types of heart disease.

  • Maine coon: A severe form of heart muscle disease (hypertrophic cardiomyopathy) is seen in some Maine coon cats. Affected cats may develop problems as early as three months of age, while less affected cats show signs of heart failure by two to four years of age. A recent study showed that 33% of Maine Coon cats had a genetic abnormality related to hypertrophic cardiomyopathy.
  • American and British shorthair: A less serious form of hypertrophic cardiomyopathy is seen in these breeds.
  • Persian cats (domestic long hair): This breed also has a high incidence of hypertrophic cardiomyopathy.
  • Siamese cats: This breed is more commonly affected by patent ductus arteriosus (PDA). The ductus arteriosus shunts blood away from the lungs during prenatal life, and normally closes at birth. If the ductus arteriosus fails to close, or is “patent”, blood flow to the chest, abdomen, and hind limbs is affected. Siamese cats have also been diagnosed with dilated cardiomyopathy, where the heart muscle gets thinner as the heart enlarges.

What heart diseases do cats get in adulthood?

The most common heart disease that adult cats develop is cardiomyopathy, usually of the hypertrophic form (see handout "Cardiomyopathy in Cats). Diseases that primarily affect the heart valves and pericardium are rare in adult cats.

Several conditions can affect heart rhythm in cats. Many cats with rhythm disturbances show relatively few signs of disease. In some cases, the cat will require drugs to restore a normal heart rate and rhythm.

Will my cat have any dietary restrictions?

Cats with heart disease have no specific dietary requirements, as long as they are able to maintain a normal body weight and as long as their diet contains adequate levels of the amino acid taurine. Taurine is essential for cat diets to prevent dilated cardiomyopathy. It is important that your cat's body weight be maintained in an optimal range, neither overweight nor underweight. It may be necessary to adjust the calorie content of the cat's diet in order to do this.

Low-salt diets are unlikely to be helpful unless the heart disease is associated with high blood pressure (hypertension). Dietary supplementation with vitamin E, Coenzyme Q10, or other medications or dietary additives may be helpful. Your veterinarian will make specific recommendations based on your cat's needs.

If my cat is put on heart medication, are there any special concerns?

It is essential that you follow the instructions for your cat's heart medication. For drugs given more than once daily, doses should be spread out over the day as evenly as possible. Some heart medications can have serious adverse effects if stopped suddenly, so it is important that your cat receives the medication regularly and that prescription refills are requested ahead of time.

Your veterinarian will discuss specific drugs for your cat if needed. Some commonly used medications for cats include ACE inhibitors such as enalapril (Enacard®) or benazepril (Fortekor®); beta blockers (i.e., atenolol); pimobendan (Vetmedin®); and diuretics such as furosemide or spironolactone. A very low dose of aspirin or a medication called clopidogrel (brand name Plavix® in the US) may be used if blood clotting is a problem. Routine examinations and testing are important to monitor the effects of these drugs. Regular blood and urine screening may also be required to monitor the effects of these drugs on other organs in the body.

Prognosis can vary depending on when the heart disease is identified, what the condition is, and how effective treatment is.

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