Heart Disease in Dogs

Heart disease occurs in approximately 10% of dogs in both large breed and small breeds.

There are 2 common causes of heart disease:

1. Caused by a leaking valve.  This is the most common form of heart disease especially in small breed dogs eg  Poodles, Chihuahuas. The heart is made up of 4 chambers -the left and right atrium and the left and right ventricles.  A series of valves between the chambers form a seal to prevent the back flow of blood when the heart pumps.  If any of these valves are defective, then blood leaks backwards when the heart pumps, and creates a noise called a murmur.  The most common valve to leak is the mitral valve, which sits between the left atrium and left ventricle. This leak known as mitral valve regurgitation. 
2. An ineffective heart pump.  This is called Dilated Cardiomyopathy and commonly is seen in large breed dogs eg  Dobermans, Great Danes.  The heart muscle becomes thin and flabby and the muscle can no long beat effectively for blood to flow properly through the heart.

In the early stages of heart disease the heart will beat faster to compensate for decreased output of blood. With leaking valves the heart muscle enlarges to pump harder – rather like your biceps increasing in size with an increase in weight lifting. For this reason you may not see any obvious signs of heart disease until the disease become quite advanced.  When this happens the heart can no longer pump enough blood to meet the body’s needs, and your dog may go into congestive heart failure.  This happens when blood queues up to go through the damaged heart and causes a congestion of blood in various organs, especially the lungs.  This ultimately leads to fluid leaking out of the vessels and into the lungs, or other organs.

Clinical signs of heart disease

1. Tiring easily, reluctance to play or exercise (may be mistaken as normal aging)
2. Coughing – especially at night (fluid in the lungs – pulmonary oedema)
3. Rapid breathing or a difficulty in breathing (fluid in the lungs – pulmonary oedema)
4. Poor appetite
5. Swollen abdomen (due to fluid build-up in the abdomen)
6. Fainting/collapse
7. Pale grey/blue gums (cyanosis) often with very advanced heart failure

Diagnosis

If you notice any of these symptoms then it’s important that you bring your dog to the vets for a check-up.  Your vet will give your dog a thorough examination which may include:

1. Listening to your dog’s heart with a stethoscope.  He/she may notice a heart murmer (indicating a leaky valve), a fast heart rate and/or an abnormal heart rhythm.
2. Listening to your dog’s chest with a stethoscope to detect evidence of fluid in the chest/lungs.
3. X-raying your dog’s chest to look for evidence of heart enlargement or fluid within the lungs/chest.
4. Ultrasounding your dog’s heart (echocardiography) to look for leaking valves, or thickened/thin walled heart chambers.
5. Performing an ECG (electrocardiogram) to check for abnormal electrical activity across the heart – this is seen with arrhythmias (abnormal heart rhythm) when the normal pacemaker of the heart is faulty.
6. Checking your dog’s blood pressure – which can be low with heart disease
7. Taking a blood test for cardiopet Pro BNP.  This detects evidence of cardiac muscle damage.

Treatment Options

There are various medications that we can use to help with heart disease.                                            

The most common ones are:

1. Diuretics eg furosemide/spironolactone – drugs to remove excess fluids from the lungs/tissues. Initially given at a higher dose to clear away fluid and then the dose is dropped to a maintenance level to prevent fluid retention.
2. ACE Inhibitors eg benzalpril/enalapril  – this is a group of heart medications that dilates both arteries (vessels that flow away from the heart), and veins (vessels that flow towards the heart) to ensure a smooth blood flow and prevent fluid leaking from  the vessels due to increased pressure.  They also have a mild diuretic effect. 
3. Positive inotopes eg pimebendin (Vetmedin)  - this drug increases heart muscle contraction and dilates the arteries. This is a very important drug for dilated cardiomyopathy. 
4. Antiarrhythmic drugs eg procainamide, atenolol, digoxin – these drugs help the heart to beat with a normal rhythm.

Your vet will decide which drugs may be the best option for your dog.

In addition it’s really important for your dog to maintain a healthy body weight.  If your dog is overweight then the heart has to pump harder to circulate blood.  Talk to your vet about a suitable diet regime.

Your vet may also suggest changing your dog’s diet to a low salt food.   High levels of salt will increase your dog’s fluid retention and increase the load on their heart.  Avoid any salty treats.

It is also important to maintain exercise with your dog, however speak to your vet to determine the level that is appropriate. 

Annual health checks are very important for early detection of heart disease and this combined with a specialised treatment plan, diet and exercise can all help to prolong and dramatically improve your dog’s quality of life, bringing you many more happy years together.