Heart Disease in Dogs

Heart Disease in dogs

Heart disease affects an estimated 15% of dogs in the UK, making it the second most common cause of death after cancer.
 

But science has been coming along in leaps and bounds over the last few years, and the outlook for a dog with heart failure is often not as gloomy as it once was.
 

The canine heart

The heart is simply a muscular pump divided into four chambers; two on the left and two on the right.

The common heart diseases suffered by dogs often lead to heart failure. That's not to be confused with heart attacks experienced by people. Dogs will generally suffer what is called Congestive Heart Failure (CHF), a relatively slow worsening of symptoms - also suffered by people - as the heart struggles to compensate for whatever defect or disease is present. As the condition develops, it will affect all other organs in the body that rely on the efficient supply of nutrient-rich blood.

Types of Heart Failure

Experts classify canine heart diseases in one of two categories (Acquired & Congenital Heart Disease):

Acquired Heart Disease

Acquired heart diseases are those that a dog acquires during its lifetime, usually as a result of normal wear and tear, infection or injury.
 

Acquired heart disease accounts for 95% of all heart disease seen in dogs, and usually appears after they reach middle age.
 

By the time a dog shows obvious symptoms of acquired heart disease, it is likely that irreversible damage has already been done. Usually, the earlier heart disease is diagnosed, the better your vet will be able to manage the condition.
 

So, it's worth asking your vet to give your dog an annual health check regardless. In this way, they'll stand the best chance of picking up any signs that you would not be able to spot yourself.
 

If your dog is diagnosed with an acquired heart disease, the outlook is not necessarily all bad. With the latest drug therapy, he may be able to live a comfortable life for some time to come.
 

Common acquired heart diseases:

* Chronic Valvular Disease when the valves within the heart degenerate with age and start to leak.

* Myocardial Disease when the heart muscle itself weakens, causing the heart to enlarge.

* Pericardial Disease when the protective sac that surrounds the heart fills with fluid, preventing it from pumping efficiently

* Arrhythmias a failure of the electrical system which tells the heart when to beat.

Congenital Heart Disease

Congenital defects are those that have been present since birth. Thankfully, they are comparatively rare, accounting for only 5% of the cases seen by vets.
 

Congenital defects will usually cause the blood flow through the heart to become turbulent; making a distinctive whooshing noise that vets can hear using a stethoscope. That's what is meant by a 'heart murmur'. However, if your vet tells you they've detected a heart murmur in your dog, it's not necessarily cause for concern.
 

Many puppies are born with a slight heart murmur (or puppy murmur) that clears up by itself after 4-6 months. In many cases, vets will simply recommend a later check up, just to be sure that the condition has resolved itself.
 

Pronounced heart murmur is quite rare, but may be indicative of a serious congenital defect. However, without specialist experience and equipment, it can be difficult for a GP vet to know what defect is causing the murmur. For this reason, if the murmur is pronounced, or persists beyond puppyhood, patients will often be referred to a specialist veterinary cardiologist.
 

Common congenital defects:

* Patent Ductus Arteriosus a blood vessel used to bypass the lungs of pups as they develop in the womb fails to close after birth.

* Pulmonic Stenosis the flow of blood from the right heart to the lungs is hampered or blocked.

* Aortic Stenosis the flow of blood from the left heart to the body is hampered or blocked.

* Hole In The Heart a hole between the pumping chambers of the heart.

Other Conditions a number of other rare defects of the heart that occur in puppies.

Treatments

It's important to distinguish between heart disease and heart failure. Heart disease is the underlying condition. It can rarely be cured. Heart failure is the consequence of heart disease.
 

Heart failure is rarely a sudden cessation of the heart's function, but a slow complex process in which its decline affects the performance of almost every part of the body. Unlike the underlying disease, heart failure can often be managed with drugs that improve and extend the dog's life.
 

Chief amongst these are ACE inhibitors. First used in man, ACE inhibitors reduce blood volume and pressure, thereby relieving stress on the heart. They are also thought to slow the deterioration of the heart muscles.
 

There are many other drugs, diets and surgical techniques used to treat heart disease or manage heart failure. A special exercise regime for your dog will also be very important.

Drugs

ACE inhibitors

One class of drug, called ACE inhibitors, is recommended as the mainstay of treatment in nearly all cases of heart failure in dogs. ACE inhibitors work at a number of different levels, primarily suppressing the body's compensation system to relieve stress on the heart. There has been no other drug in the history of veterinary cardiology that has undergone such extensive controlled clinical trials proving its value.

Diuretics

Diuretics are usually used, often long term, to stimulate the kidneys in removing excess fluid from the body.

Other Drugs

Nitroglycerin is used short term to dilate the veins throughout the body, thereby redistributing fluids and easing pressure on the heart or lungs. Nitroglycerin is only effective for a day or two, after which the body builds a tolerance. It is commonly administered by the veterinary surgeon.
 

Digitalis is primarily used to control an excessively fast heart rate. It needs to be prescribed with care as it is relatively easy to overdose. Concurrent regular blood testing is often recommended to reduce the risk of overdose.
  

Inodilators directly stimulate the heart muscle and are therefore used when the heart muscle fails, i.e. in dilated cardiomyopathy or in end stage valvular disease.
 

Note that in the treatment of congestive heart failure, other drugs should always be used in addition to, rather than in place of ACE inhibitors.

Diets

One of the effects of heart failure is fluid retention, which in turn causes increased pressure on the heart, and symptoms such as coughing and abdominal swelling.

One of the priorities in the management of heart failure is to reduce fluid retention. The most important thing is that you do NOT feed your pet any food with a high salt content. Especially snack foods prepared for human consumption, such as sausages & pork pies.

Exercise

By the time heart failure is diagnosed, the body's compensation system may have kicked in already, with the effect of placing added stress on the heart. Until the compensation system can be controlled with drug therapy, your vet may recommend a period of complete rest for your dog.
 

Once drug therapy has started to work, it's likely that your vet will recommend a return to normal or near-normal exercise, as it remains important to promote good circulation and exercise the heart.

Surgery

Heart surgery for dogs will only be appropriate for the relatively small number of dogs that have very specific, usually congenital heart problems. However, where appropriate, the success rate is very high, and your dog should benefit from a markedly improved quality and quantity of life. It is worth noting that surgical intervention in the cardiac case is almost always best performed by a specialist cardiologist, although some general vet’s are able to carry out a pericardial drainage.

Procedures

Patent Ductus Arteriosus (keyhole vs traditional surgery).For those dogs with PDA, traditional surgery to seal the blood vessel has a very high success rate. However, relatively new keyhole techniques are less invasive, and generally offer a quicker recovery.
 

Pacemakers
First developed for people, the technique of inserting a pacemaker has now been successfully applied in the veterinary world. A dog fitted with a pacemaker has every chance of living a long and healthy life.
 

Balloon ValvuloplastyThis technique involves the insertion of a balloon tipped catheter into the constricted area of the heart, and inflating to reduce the constriction. About 85% of animals show an improvement in health following the treatment, but it is not without risk. 5-10% of animals will not survive treatment.
 

Pericardial Drainage / Pericardiectomy
Pericardial drainage involves the insertion of a catheter into the pericardium to drain excess fluid and thereby relieve pressure on the heart. In some cases, the problem of fluid build-up is recurrent, and surgery to remove up to half of the pericardium may be called for.

Canine Cardiologists

The most appropriate person to oversee the care of your animal is always your usual veterinary surgeon. They will be familiar with your pet's medical history, and will be best placed to monitor the results of treatment.
 

However, as in human medicine, some veterinary surgeons decide to specialise in certain areas of care, such as cardiology.  In some cases, your vet may decide to refer your pet to such a specialist for advanced treatment or a second opinion.

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