Heart disease is becoming increasingly common in our pets. Around 16% of cats and 10% of dogs have a heart murmur, with these figures increasing substantially as your pet becomes senior.

How does the heart work?

The heart consiHeartbeatsts of four muscular chambers which pump blood when stimulated by electrical impulses. The right side of the heart pumps blood around the lungs and the left side pumps blood around the rest of the body. The chambers of the heart are separated by valves which keep the blood flowing in the right direction.

What causes heart disease?

Heart disease does not have a single cause. Broadly speaking, it can affect the heart valves, the heart muscle, the electrical conduction within the heart, or the pericardium (a strong sac that surrounds the heart). Some problems with the heart can be present from birth (congenital defects) but more commonly, disease will develop in later life (acquired heart disease).

Congenital heart disease is much less common than acquired heart disease and is mainly seen in young animals. The symptoms are not always seen straight away at birth, as it can take time for subsequent damage to develop enough to cause symptoms. The common causes of acquired heart disease vary between cats and dogs, as well as between dog breeds.

It is important to recognize that heart disease is not the same as congestive heart failure. Dogs can have heart disease for years without showing outward signs. But as the heart becomes more inefficient, it can result in poor oxygenation of the body and fluid build up in the lungs and other areas. This is congestive heart failure.

Common causes in cats

Hypertrophic cardiomyopathy (HCM)

  • Often affects: Maine Coons and Ragdolls, but all cats can develop the condition.
  • The heart wall becomes thickened without the heart increasing much in size. Consequently, the chambers of the heart become very small and can pump only a small volume of blood. The heart also struggles to relax properly between beats. Most cases of this condition are either genetic or of unknown cause, but occasionally can be secondary to conditions such as hyperthyroidism, anaemia or high blood pressure.
  • Cats with heart disease are at high risk of developing thromboembolisms (clots) which can travel around the body and become lodged in blood vessels – often those supplying the back legs or lungs.

Common causes in dogs

Mitral valve disease (MVD)

  • Heart 2Most common cause of heart disease in smaller dogs.
  • Often affects: Cavalier King Charles Spaniels.
  • The mitral valve, on the left side of the heart, degenerates and becomes leaky. This allows some blood to flow in backwards direction within the heart and results in a heart murmur. As it worsens, this will reduce the pumping ability of the heart.

Dilated cardiomyopathy (DCM)

  • Most common cause of heart disease in larger dogs.
  • Often affects: Dobermanns, Great Danes and Irish Wolfhounds.
  • The heart muscle itself is diseased, and becomes weak and stretched. Over time, the heart becomes very large with thin walls, which are unable to contract properly to pump blood. This condition can become severe without the presence of a murmur, and research recommends testing at risk breeds for signs of the disease before serious symptoms appear.


Signs to look for in dogs:

  • Faster breathing
  • Tiring easily on walks/less playful
  • Coughing – during/after exercise/before bedtime
  • Weakness
  • Weight loss
  • Drinking more and urinating more
  • Lethargy/fatigue
  • Fainting (syncope)
  • Swollen belly/pot bellied

Signs to look for in cats:

Possibly no signs at all. Many cats show no outward signs until it becomes severe and sudden signs develop. These can include sudden death, loss of use of back legs and breathing difficulties.

Other signs include:

  • Vomiting
  • Depressed or agitated
  • Poor appetite
  • Weight loss
  • Swollen belly/Pot-bellied
  • Weakness

Signs of severe congestive heart failure:

  • Severe panting/struggling to breath
  • Collapse
  • Blue/dark red/purple gums and tongue



  • Heart 3Auscultation – listening for murmurs/abnormal rhythm.
  • Echocardiography (heart ultrasound) – assess valve function, contraction and heart shape/size.
  • Chest X-rays – assess heart size and fluid build up in lungs.
  • Electrocardiogram (ECG) – assess electrical impulses within the heart.
  • ProBNP Blood test – identifies damaged heart muscle.
  • Blood and urine tests – identify conditions that can cause heart damage/the impact of heart disease.


In the early stages of heart disease, your pet may just need regular checks by your vet. If signs develop, medication can reduce the symptoms. Heart disease cannot be cured, but progression can be slowed down.


  • Beta-blockers
  • Calcium-channel blocker
  • Anti-clotting drugs
  • Diuretics
  • ACE inhibitors


  • Pimobendan
  • Diuretics
  • ACE inhibitors
  • Anti-arrhythmic drugs

In addition to medication, weight and exercise control are also important in the management of heart disease.

If you have any concerns about heart disease in your pet, contact the practice on 01626 835 002.

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