Heart disease is very common in dogs affecting approximately 10% of the population.
Early-stage heart disease is often symptom free but could be detected by your vet at a routine vaccination or visit for another problem. The vet may detect a heart murmur (the noise made when there is an abnormal flow of blood in the heart) or abnormal heart rhythm. If your vet is concerned, they may advise further tests to assess the heart or they may be happy to wait and re-examine the pet in 3- 6 months to assess any changes.
Signs of more significant heart disease include; coughing, panting, lack of exercise tolerance, weight loss, poor appetite and an abdominal distention. Once your dog has developed heart disease there is no cure, but most cases can be managed well with lifelong medication although life expectancy varies considerably depending on the stage and type of heart disease.
The most common form of heart disease in small dogs is Valvular Disease. This is essentially due to wear and tear on the heart valves with the Mitral valve being the most commonly affected. This is the valve on the high pressure or left side of the heart. Some breeds such as the Cavalier King Charles Spaniel are predisposed. They will most commonly develop a leaky valve in middle age which can be picked up by the vet as a heart murmur on the left-hand side. In the early stage, a small grade 1 or 2 murmur represents a small leak and will often not require treatment. However, this can progress to a larger leak and means the heart has to work harder to pump the same volume of blood around the body. This larger leak corresponds to a grade 5 or 6 murmur which can often be detected without a stethoscope. Eventually the extra work load on the heart results in heart failure and the dog’s lungs and/ or abdomen fill with fluid. Dogs go into heart failure rather than having heart attacks like humans.
In large breed dogs a form of heart disease called Dilated Cardiomyopathy is common. This is a disease of the large heart chambers (the ventricles) and results in the muscular walls of these chambers becoming weak and stretched. This results in the heart struggling to pump blood round the body efficiently. Again, some breeds are over represented, such as Dobermans. The clinical symptoms of heart failure are the same as seen in small dogs, but this disease carries a poorer long-term prognosis and does not respond to medication as well.
The third most common form of heart disease is a Congenital Defect. This can be anything from a hole in the heart (a defect in the heart wall which allows blood to flow from the left to the right side) or a more complicated defect involving more of the heart structures. Some small defects correct themselves after birth, some can be lived with, some can be surgically corrected and some are life limiting.
The first test for heart disease is using the stethoscope - this can allow the vet to assess a murmur, abnormal rhythm or fluid on the chest. Further tests include; x-ray to assess heart size and lung health, an ultrasound to look at heart filling, muscle thickness and valve efficiency and an ECG to assess electrical activity in the heart and rhythm.
There are 3 main classes of drugs available to treat heart problems and most dogs will be on a combination of these. Vasodilators open blood vessels allowing a greater volume of blood through. Positive Inotropes improve the efficiency and strength of the heart contractions so pushing more blood forward. Finally, diuretics which help clear any fluid built up in the chest or abdomen.
If you see any of the symptoms develop, make an appointment with your vet as soon as possible. Early detection can make all the difference