Category: heart diseases

Ventricular septal defect (VSD) is a congenital heart defect, i.e. it is caused by abnormal development of the puppy before birth. The dog’s heart, like that of humans, is a muscular pump with four separate chambers. The right side of the heart sends blood to the lungs where it picks up oxygen. The left side of the heart pumps the blood around the body. The heart is divided into left and right halves by a muscular wall (the septum). The ventricular septum separates the right and left ventricle.

In a VSD the septum doesnt develop properly resulting in a small hole in the septum allowing some blood to divert from the left side of the heart to the right side. The effects of this on the dog depend on the size and location of the defect. Most dogs have small defects that are well tolerated. In some cases, very small VSD holes may close spontaneously. Larger defects can lead to congestive heart failure.

Although the condition is present from birth, signs of a Ventricular septal defect (VSD) are usually not noticed until later in life. Many dogs with VSD have no outward signs of illness. The murmur caused by a VSD is often detected by a vet (often during a routine health check). When you bring home a new puppy it is always advisable to ask your vet to check for any heart murmurs. VSDs are seen most commonly in certain breeds of dog (English Bulldog, English Springer Spaniel and West Highland White Terrier and the Keeshond).

If the defect is large, clinical signs may be seen when the dog is less than two years of age. Severely affected animals may have stunted growth, although this can be difficult to recognise without direct comparison to their littermates. If the condition goes unrecognised and heart failure develops the affected animal may be reluctant to exercise, cough, or have difficulty breathing.

If your vet hears a murmur when listening to your dogs heart they will want to do some other tests. Heart murmurs are caused by the sound of abnormal and high-speed blood flow and are very common findings in dogs with VSD. Very quiet heart murmurs can be present in an otherwise healthy pet so a diagnosis of VSD or other congenital heart disease is not necessarily inevitable.

Ultrasound is the method of choice for finding the cause of a heart murmur. If a heart murmur is heard, an ultrasound examination is recommended. Ultrasound examination of the heart requires considerable knowledge and experience and should be performed by someone with experience in examining young dogs.

X-rays are important in the diagnosis and monitoring of heart disease. In dogs with severe VSD, evidence of heart enlargement on the left side is often evident. X-rays are also used to see if signs of heart failure are present, if there any signs of further heart failure treatment is usually started immediately.

If the VSD is very small, then your dog may lead a normal life with no treatment being necessary. However, if the defect is large, the outlook is worse and your dog may have a significantly reduced life expectancy. Your vet will discuss the outlook and long term management of your dog with you.

If the ventricular septal defect is small, then no treatment is needed and the hole may spontaneously close. Large VSDs may need medical management to treat heart failure if it develops. Some surgical options are available to help reduce the flow of blood across the hole but definitive repair to actually close the hole is typically not possible.

Many animals with ventricular septal defect live a normal life with no signs of heart disease but this depends on the size and location of the defect. Affected dogs and their parents (who could be genetic carriers of the condition) should be not be allowed to have puppies.

Dogs with more severe defects are likely to develop heart failure at a relatively early age and the long term outlook is poor. Life-expectancy may be reduced and long term medication will be required.

Pulmonic stenosis is a congenital heart disease, i.e. it is caused by abnormal development of the puppy before birth. The dog’s heart, like that of humans, is a muscular pump. The right side of the heart sends blood to the lungs where it picks up oxygen. The left side of the heart pumps the blood around the body.

Pulmonic stenosis occurs when there is an obstruction to blood flowing out of the heart on the right side. In most cases, the obstruction is caused by a narrowed valve (pulmonic valve) that separates the right side of the heart and the pulmonary artery. This narrowing forces the heart to work harder to pump blood to the lungs. The signs shown by the dog depend upon the amount of narrowing (stenosis).

Although the condition is present from birth, signs may not be noticed until later in life. Many dogs with pulmonic stenosis have no outward signs of illness – although their growth may be stunted this may not be obvious without direct comparison to a littermate. If your dog is severely affected they may suddenly faint during/after exercise or show signs of heart failure.

It is most commonly seen in small breeds of dog (Bulldog, Scottish Terrier, Wire-haired Fox Terrier, miniature Schnauzer, West Highland White Terrier, Beagle, Boxer, Chihuahua, Samoyed and German Shepherd Dog).

If your vet hears a murmur when listening to your dogs heart they will want to do some other tests. Heart murmurs are caused by the sound of abnormal and high-speed blood flow and are very common findings in dogs with pulmonic stenosis. Very quiet heart murmurs can be present in an otherwise healthy pet so a diagnosis of pulmonic stenosis or other congenital heart disease is not necessarily inevitable.

Ultrasound is the method of choice for finding the cause of a heart murmur. If a heart murmur is heard, an ultrasound examination is recommended. Ultrasound examination of the heart requires considerable knowledge and experience and should be performed by someone with experience in examining young dogs.

X-rays are important in the diagnosis and monitoring of heart disease. In dogs with severe pulmonic stenosis, evidence of heart enlargement on the right side is often evident. X-rays are also used to see if signs of heart failure are present, if there any signs of further heart failure treatment is usually started immediately.

If the pulmonic stenosis is mild then your pet may live a normal life without any treatment. In some cases your vet may advise exercise restriction. In more severe cases (with clinical signs from an early age) the outlook is poor. Your vet will discuss the outlook and long term management of your dog with you.

In mild cases, treatment may not be necessary. If signs heart failure or intolerance to activity are present, your vet may prescribe medical management to assist heart function and reduce water retention.

In severe cases your vet may advise surgery. A catheter with a balloon tip can be passed into the narrowed artery and when the balloon is inflated it opens the vessel to allow more blood to flow. This is called balloon valvuloplasty, and typically helps relieve the severity of severe disease.

Many animals with pulmonic stenosis have a normal life span with no signs of heart disease. In affected animals annual monitoring of ECG and echocardiogram is advisable for early detection of signs of heart failure. Lifespan in severely affected animals may be significantly reduced.

Affected dogs and their parents (who could be genetic carriers of the condition) should be not be allowed to breed.

The dog’s heart, like that of humans, is a muscular pump with four separate chambers. The right side of the heart sends blood to the lungs where it picks up oxygen. The left side of the heart pumps the blood around the body.

The ductus arteriosus is a blood vessel used to bypass the puppys lungs in the womb and this normally closes within a few days after birth. In dogs with a patent ductus arteriosus, this bypass fails to close and some blood is therefore able to re-enter the circulation in the lungs without passing through the body. This can lead to a condition where the lungs are receiving extra blood flow.

Patent ductus arteriosus (PDA) is a congenital heart defect, i.e. it is caused by abnormal development of the puppy after birth. In many cases the first sign of disease is a murmur that is detected by their vet during a routine health check. When you bring home a new puppy it is always advisable to ask your vet to check for any heart murmurs.

PDA is seen in many small breeds of dog (Bichon Frise, Keeshund, Maltese Terrier, Poodle among others) and is also more common in female dogs. The initial signs of a PDA may include reluctance to exercise, shortness of breath or coughing. Heart failure may occur in dogs with unrecognised or untreated PDA.

If your vet hears a murmur when listening to your dog’s heart they will want to do some other tests. Heart murmurs are caused by abnormal blood flow and the murmur of a PDA is very characteristic. Often, the vet will be able to predict the presence of a PDA by listening carefully to the murmur. Very quiet heart murmurs can be present in an otherwise healthy pet so a diagnosis of PDA or other congenital heart disease is not necessarily inevitable.

Ultrasound is the method of choice for finding the cause of a heart murmur. If a heart murmur is heard, an ultrasound examination is recommended. Ultrasound examination of the heart requires considerable knowledge and experience and should always be performed by someone experienced in examining young dogs.

X-rays are important in the diagnosis and monitoring of heart disease but will not always identify the cause of a heart murmur. In dogs with PDA, several characteristic findings are typically present on X-rays, and your vet may be able to predict the presence of PDA by carefully examining the X-rays. X-rays are also used to see if signs of heart failure are present. If there are signs of heart failure, treatment should be started.

Your vet will discuss the outlook and long term management of your dog with you. They will typically recommend surgery to correct the condition and with successful treatment, your dog can lead a full and long life.

The unsealed blood vessel can be closed using traditional open-chest surgery to tie off the PDA. Alternatively the vessel can be closed by PDA coil or device occlusion. This involves placement of a metal device that induces the formation of a clot, effectively closing off the blood vessel. The PDA closure device is usually delivered through a catheter placed in an artery in the leg and then guided into the PDA. This surgical technique is highly specialised and is usually only available at large referral centers or veterinary schools. However, it is a relatively non-invasive approach and your dog should be discharged 24-48 hours after the procedure.

Many animals with patent ductus arteriosus live a normal life span with no signs of heart disease provided surgery (or coil occlusion) is carried out when they are young and before the development of heart failure. If the surgery is carried out in an older dog or in an animal with congestive heart failure, then the outlook is less favorable.

Affected dogs and their parents (who could be genetic carriers of the condition) should be not be allowed to breed.

The dog’s heart, like that of humans, is a muscular pump with four separate chambers. The right side of the heart sends blood to the lungs where it picks up oxygen. The left side of the heart pumps the blood around the body. The four areas of the heart are separated by valves that ensure the blood always flows in the correct direction through the heart. The mitral valve lies between the 2 chambers on the left side of the heart. It prevents blood from flowing backwards (towards the lungs) rather than around the body when the heart contracts.

Damage to the mitral valves can occur in a number of ways. The most common disease is degeneration of the valve as a result of ageing (this is called endocardiosis). In other cases the valves may fail to develop properly, e.g. mitral dysplasia, or can be affected by infections carried in the blood (endocarditis).

Damaged valves do not work properly – abnormal valves allow leakage of blood between the heart chambers. When valves are leaking the abnormal blood flow can be detected when listening to the heart (a murmur).

If the valve is leaking not all the blood leaves the heart with each contraction and so the heart has to beat faster and harder to pump the same amount of blood out into the circulation. The increased work eventually leads to heart failure.

Many dogs with mitral valve disease have no outward signs of illness. The murmur is often detected by a vet after a routine examination (often at a health check at the time of vaccination). Degeneration of the valve is more common in certain breeds of dog, particularly small breeds. In some breeds – notably the Cavalier King Charles Spaniel (CKCS) – dogs often inherit the condition from their parents.

If your dog is from a breed with a high risk of developing mitral valve disease you might ask your vet to check them for the presence of a murmur. Most animals with mitral valve disease are middle-aged or older but young animals can be affected.

The initial sign of mitral valve disease may be reluctance to exercise, or coughing due to heart failure or direct pressure on the large airways by an enlarged heart.

If your vet hears a murmur when listening to your dog’s heart they may want to do some other tests. Murmurs are very common findings and if your pet is well there may be nothing to worry about. However, even if your pet has a problem such as coughing your vet may find that the cough is caused by something else and the disease of the mitral valve is not causing any problems.

X-rays are very important in the diagnosis and monitoring of heart disease. On the X-ray of your dog’s chest your vet will be able to see the size of the heart and also any effects on the lungs and blood vessels. Enlargement of the blood vessels in the lungs or evidence of fluid in the chest may be the first indication of heart failure and, if these changes are present, treatment should be started immediately. One of the important benefits of chest X-rays is that they will help your vet to rule out respiratory disease as a cause of coughing.

Although examination and other tests may make your vet suspect that your dog has heart disease ultrasound is the method of choice for finding the actual cause. With ultrasound you vet will be able to see the heart valves and it may be clear that they are not meeting correctly. With some special ultrasound machines patterns of abnormal blood flow around the valve can be seen. Ultrasound examination of the heart requires considerable knowledge and experience and should always be performed by experts.

Your vet may also want to do some blood tests (particularly to check that their kidneys are working properly) before starting your pet on treatment.

If your dog has damaged heart valves these will not repair. The only permanent solution is to replace the valves. In man, replacement of damaged heart valves is possible and whilst this procedure has been carried out successfully in dogs (usually those born with a malformed valve) it is certainly not considered standard practice in pets. However, since the disease often causes few problems your pet may be able to live quite happily with the disease. If heart failure develops medication can help your pet to lead a happy life.

Many animals with mitral valve disease show no signs of heart disease and these patients require no specific treatment. If your pet is not showing any signs of ill health your vet will just monitor them regularly to detect any progression of disease. If heart failure develops then appropriate treatment can be started.

There are many drugs that can help animals with heart failure and these include:

• Diuretics (usually furosemide and spironalactone) to stop fluid retention in the circulation and the lungs
• ACE inhibitors to help to prevent fluid retention and make it easier for the heart to pump blood
• Pimobendan – to improve efficiency of heart function
• Digoxin to slow the heart rate and may help it to function more effectively.

Not all these drugs are appropriate in every animal and your vet will decide on the best treatment programme for your pet and will discuss these choices with you. Often a combination of drugs is needed and the doses of drugs may change with time. Usually once treatment has started it will need to be continued for the rest of your pets life.

There is no evidence that it is beneficial to start treatment before signs of heart failure develop in dogs with mitral valve disease.

Many animals with degenerative mitral valve disease live out a normal life span with no signs of heart disease. Some CKCS may develop heart murmurs at only a few years of age but not even all of these will develop clinical signs associated with the condition. Animals with significant heart failure require therapy and the outcome will depend upon how well they respond to this therapy.

When heart function is compromised there are many mechanisms that come into play to reduce the impact on the animal. Since few pets are athletic, heart disease can be present in many without their owner noticing any ill effects. Many cases of heart disease are detected by the vet at routine examination, e.g. before vaccination. Abnormalities are often detected in the first 2 years of life, if congenital lesions are present; or in middle-aged to older pets when acquired degenerative changes develop. Owners generally notice signs once heart failure has developed or if their pet has problems during periods of stress or excitement.

Clinical signs of heart disease vary according to the area of the heart affected. They range from coughing and weight loss to abdominal distension (ascites) or collapse.

Clinical examination

A full clinical examination is essential in all patients with suspected heart disease. Abnormalities in the heart may cause changes to the pulse rate, rhythm or strength. The pulse should be assessed at the same time as listening to the heart to confirm that every heartbeat generates a strong pulse. Poor heart function may also result in congestion of the veins (fluid retention). By listening to your pet’s heart with a stethoscope your vet can determine the rate and rhythm of heartbeats and hear murmurs or other abnormal heart sounds. Ideally blood pressure should be measured in all patients with heart disease.

X-rays

X-rays are very important in the diagnosis and monitoring of heart disease. Assessment of the heart size and shape itself is important but the lungs and blood vessels visible on the radiograph are also examined. At least two pictures of the chest (one with the animal lying on its side and one lying on its belly) are needed for complete x-ray assessment of the heart. In almost all cases it is safer to administer a low dose of an appropriate sedative than to risk a patient struggling when x-rays are being taken.

Echocardiography

Ultrasound is the method of choice for determining the cause of structural heart disease. It allows the vet to see the heart structures, ie myocardial thickness, the relative sizes of the heart chambers, and the position of the valves and major blood vessels. Echocardiography also allows the vet to watch the heart beating. The motion of the valves, contraction of heart walls and abnormal patterns of blood flow can be seen. Echocardiography requires considerable knowledge and experience and should always be performed by experts.

Laboratory tests

Routine laboratory tests (particularly assessment of liver and kidney function) are important for monitoring of animals with heart disease. The dose of many drugs used in the treatment of heart disease may need to be altered in patients with reduced liver or kidney function. It is important to assess kidney function in all patients before they start on long-term therapy for heart failure.

Electrolyte abnormalities are common in patients with heart failure and some drugs can make these imbalances worse. Low potassium levels can develop as a result of inappetence and the use of some diuretics, e.g. furosemide.

There are now some laboratory tests which allow us to measure substances produced by damaged hearts and these tests are likely to become increasingly important in the diagnosis and management of heart disease in the future.

Electrocardiography

The electrocardiogram (ECG) measures the electrical activity in the heart. Although measurements made on ECG can provide an approximate guide to the size of specific heart chambers, x-ray or ultrasound are better for assessing heart size. The most important use of ECGs is in the monitoring of abnormal heart rhythms (arrhythmia).

When the heart contracts a pulse of blood is forced through the arteries. This pulse generates thesystolicblood pressure. In between the heart contractions the pressure in the arteries falls this is thediastolicblood pressure. In animals we mostly measure systolic blood pressure.

Systolic pressure does not stay the same at all times. Arteries are constantly being constricted (narrowed) or dilated (widened) so that blood can be diverted to whichever organs are most active at the time. A dilated artery has a larger diameter, making it easier for blood to flow through. Less pressure is needed to pump blood through the dilated artery and so blood pressure is lower if arteries are dilated.

Blood pressure also tends to increase a little with age. The arteries of older pets tend not to be as elastic as in younger animals. These arteries do not dilate easily so the overall resistance to blood flow is increased, resulting in higher blood pressure.

Hypertension in animals is almost always secondary to other problems. In dogs the main causes of hypertension are kidney disease and hormonal conditions such as diabetes mellitus and hyperadrenocorticism (Cushings disease).

In hypertension the increased pressure in the blood vessels damages the vessel walls, causing bleeding and blood clot formation. This causes particularly severe problems if blood vessels in the eye, kidney, heart or brain are affected. In addition when blood pressure is high the heart has to pump against a greater resistance and this places increased strain on the heart muscle.

In the early stages of disease there are few, if any, signs of hypertension itself, but because hypertension is commonly associated with an underlying disease you may notice signs of that disease in your pet. Appetite may be decreased in kidney failure, or may be increased in diabetes, and both conditions can cause weight loss, excessive drinking and occasionally vomiting.

Signs related to secondary damage to blood vessels will depend upon the organ affected. Damage to the blood vessels in the eye may cause sudden onset blindness, and this is often the first recognisable indication of hypertension in cats. Damage to blood vessels in the brain can cause strokes and other neurological disorders, and increased blood pressure in the blood vessels that supply the kidney can cause further deterioration in kidney function.

If your vet suspects hypertension they will want to examine your dogs eyes for areas of haemorrhage (bleeding) or detachment of the retina (at the back of the eye). Examination of the eyes can be a very useful way to identify the disease but the best way to confirm the diagnosis, and to monitor the response to any treatment, is by measurement of blood pressure.

Measurement of blood pressure is becoming more common in veterinary practice although it is not yet part of the routine examination in most cases.

The method used to measure blood pressure is very similar to that used routinely in people, but because of the small size of the arteries more specialised equipment is needed. An inflatable cuff is placed around one of the dog’s legs (or sometimes round its tail) and the vet uses a small receiver held against the arteries in the foot (or tail) to detect the pulse. The cuff is then inflated and deflated a number of times and the vet listens for changes in the sound of the pulse as the pressure in the cuff increases and decreases.

The process only takes a few minutes; does not hurt and most animals do not object at all. Blood pressure needs to be monitored regularly in animals that have been diagnosed with hypertension and most pets soon become used to the procedure.

Most healthy dogs have a systolic blood pressure of between 120 and 180 mmHg. A dog with a blood pressure that is consistently over 180 – 190 mmHg is considered to be hypertensive, although older animals do tend to have slightly higher blood pressure than young dogs. Sight hounds, e.g. Greyhounds and overweight dogs tend to have higher blood pressure.

If an underlying cause of hypertension can be identified this disease should be treated, and if the blood pressure is only slightly elevated then this may be sufficient to bring blood pressure down into the normal range. However in most cases it will be necessary to use additional treatments which are specifically aimed at lowering the blood pressure.

For long-term management of hypertension in dogs ACE-inhibitors e.g. enalopril or benazapril may be used, but if these are not producing enough effect other drugs may be added. Other groups of drugs which may be effective include calcium-channel blockers and beta-blockers. Animals with hypertension have individual responses to treatment and it is important to monitor the blood pressure closely once treatment has been started, altering the dose of the drugs, or altering the medication as necessary. In patients with kidney failure, it is also important to monitor kidney function when using anti-hypertensive drugs.

Feeding a low salt diet may also be of value, although it is unlikely to be sufficient as a sole treatment of hypertension. You should avoid feeding pet treats to dogs with high blood pressure since most of these are quite high in salt. Most hypertensive dogs can be fed a normal commercial dog food, although your vet may recommend the use of a prescription diet for management of underlying disease, e.g. chronic kidney failure.

If your dog has suffered sudden onset blindness emergency treatment to rapidly lower the blood pressure may be recommended. Blood pressure must be measured regularly whilst this emergency treatment is given to ensure blood pressure does not drop too low so your dog may need to be admitted to hospital during the first stages of emergency treatment. If treatment can be started at an early stage of the disease then there is a chance that your dog may regain its sight.

If an underlying cause can be identified and treated then blood pressure may return to normal without the need for any specific medication. Unfortunately in most cases this is not possible and additional drugs are needed to reduce blood pressure. Fortunately in most cases treatment is effective, and blood pressure can be brought into the normal range within a few weeks of starting treatment.

For the majority of animals treatment will be required lifelong and in all cases it remains important to continue to monitor blood pressure as accurately as possible in order to identify any recurrence of the problem.

Atrial fibrillation is one type of disturbance of the normal heart rhythm (dysrhythmia). To understand this condition we first need to know how the normal heart functions:

In the normal heart electrical activity is initiated from a natural pacemaker in the heart and follows a set path around the heart muscle. As the electrical activity moves through the muscle the muscle begins to contract. The electrical signals move in an ordered way like a wave over the heart surface, from the chambers at the top of the heart (atria) to the lower chambers (ventricles). As the electrical signals pass through the heart muscle contracts in a synchronised fashion, like squeezing a tube of toothpaste.

The heart is divided into a left and right side and there are 2 chambers on each side (one atrium and one ventricle, linked together through a valve). In the normal heart the upper chambers (the atria) contract first squeezing the blood out of the atria and into the main pumping chambers, the ventricles. When the ventricles are full they begin to contract to pump blood around the body (from the left side of the heart) or around the lungs (from the right side).

Atrial fibrillation normally occurs in enlarged hearts where the atrial muscle is already stretched. Damage to the muscle caused by the stretching can make it more likely that a spontaneous electrical pulse will be generated in an area outside the pacemaker.

In atrial fibrillation there is disruption of the normal electrical activity throughout the atria resulting in random and chaotic atrial muscle contractions and preventing normal atrial contraction. The electrical pathways in the ventricles are still intact, allowing the ventricular muscle to contract in an organised manner. But because the electrical signals that the ventricles receive from the atria are random and so much more frequent and chaotic than normal, the ventricles often do not have time to contract and relax before a new signal arrives telling them to contract again.

Hence the contractions are not regular and there is a variable time between each heart beat. When you listen to a heart in atrial fibrillation you hear an erratic jungle drum beat rather than the regular lup-dup sound. Some people say that atrial fibrillation sounds like shoes in a tumble dryer.

Atrial fibrillation is normally a rapid heart rhythm and because the ventricles are contracting so often they do not have time to fully fill with blood between each beat. The amount of blood leaving the heart is therefore reduced and this poor blood supply can result in signs of lethargy and exercise intolerance and even exacerbate heart failure.

Atrial fibrillation is much more common in large and giant breeds of dog and in these breeds may even occur with an apparently normal heart. This may be due to the fact that these giant dogs naturally have such large hearts.

In smaller breeds of dogs atrial fibrillation usually only occurs in dogs with enlargement of the upper chambers of the heart (the atria). This enlargement of the heart can be caused by a variety of diseases but most commonly is caused by some congenital heart diseases (where the heart develops abnormally from birth), and dilated cardiomyopathy (DCM) or leaky heart valves (mitral valve disease) in older animals.

A few drugs (most notably digoxin, which may be used in the treatment of some heart diseases) can also cause atrial fibrillation. If your dog is receiving any medication make sure you mention this to your vet even if you think they already know.

In large and giant breed dogs atrial fibrillation may occur in apparently normal animals and there may be no outward signs of disease. Often in these breeds the condition is detected at a routine examination at the vets for an unrelated problem or at a routine health check. If underlying heart disease is present then you may first notice signs of this. Signs of heart disease can vary but may include: unwillingness to exercise; coughing at night or breathlessness on exercise.

Your vet will probably recognise that your dog has an abnormal heart rhythm when they listen to your dog’s heart. However, in order to confirm the diagnosis an ECG examination is essential to distinguish it from other types of abnormal heart rhythm.

An ECG is a simple test which records the electrical activity from your dog’s heart. If atrial fibrillation is detected then other tests are indicated to look for underlying heart disease. These tests will almost certainly include X-rays and ultrasound examination of the heart but sometimes blood tests are also required.

Even for a vet, it is very difficult to accurately assess heart rate in atrial fibrillation without an ECG. This is because some of the heart beats are so weak that they are very hard to hear with a stethoscope and do not result in a pulse that is strong enough to feel.

Although in people there are some treatments specifically aimed at converting the heart rhythm back to normal this is rarely undertaken in dogs. If there is an underlying heart disease then this requires management. Provided the heart rate is not too fast, dogs can perform reasonably well despite atrial fibrillation. If the average heart rate is rapid in a dog with atrial fibrillation, specific medications will be required to reduce the heart rate.

If the heart rate can be maintained at a roughly normal rate and the ventricles are able to fill properly before contraction they can deliver an adequate blood supply to the body tissues. In large or giant breed dogs with atrial fibrillation that is not too fast and no evidence for a heart condition can be found (this is sometimes referred to as “lone” atrial fibrillation), periodic retesting of heart size and function will be required. This is because in some of these dogs, especially Irish Wolfhounds, the atrial fibrillation is a warning that development of dilated cardiomyopathy is likely at some stage in the future (although it is much harder to predict when it will become obvious – this may be months or years from the time the atrial fibrillation was first detected).

It is unusual for dogs with atrial fibrillation to ever go back to having a normal heart rhythm. However, those dogs with “lone” atrial fibrillation (no detected underlying heart disease) sometimes live many years after diagnosis with no signs of disease, although they should be monitored periodically by your vet.

The outcome is not so good for those dogs with an obvious underlying heart problem. In these cases the heart disease is often severe enough that the dog will require cardiac medications for life and life span will be reduced.

If you have any concerns about our dog contact your own vet for further advice.

In early stages of heart disease there may be no signs and your dog may just need to be checked regularly by your vet. However, in most cases heart disease does get worse and treatment may be necessary to relieve the signs of disease and slow down the rate of disease progression.

Management of heart disease requires a combination of:

• Changes to your dog’s lifestyle, ie he may not be able to exercise as much and it is very important that he is always allowed to rest whenever he wishes.
• Drugs to remove excess fluid retention (ACE inhibitors and diuretics).
• Drugs to improve the strength of the heart beat (pimobendan) or change the heart rate (digoxin, other antiarrhythmics).
• Dietary changes may be recommended by your vet depending on the type of heart disease present.

Heart valve disease

Many animals with mitral valve disease show no signs of heart disease and these patients require no specific treatment. However, heart failure may develop and then appropriate treatment can be started.

Heart muscle failure

In some heart disease the heart muscle itself is affected. It may become thin and weak, in which case drugs can be used to improve heart muscle contraction. In some disease the heart muscle becomes thickened and tense and drugs may be used to help the muscle relax so the heart can expand and fill with blood between contractions. In both cases it may be useful to also give drugs that reduce the resistance in the circulation so that it is easier for the heart to pump blood around the body.

Heart failure

Once the heart has failed for whatever reason, fluid will start to build up. If the right side of the heart is failing fluid may accumulate in the abdomen or in the chest (outside the lungs). More commonly the left side of the heart fails and then fluid builds up within the lung itself.

Heart rhythm disturbance

Sometimes the diseased heart develops an abnormal rhythm. If the average heart rate is rapid, specific medications will be required to reduce the heart rate. If the heart rate is too slow then drugs that increase the heart rate or an artificial pacemaker may be necessary.

Not all drugs are appropriate in every animal and your vet will decide on the best treatment programme for your pet and will discuss treatment options with you. Often a combination of drugs is needed and the doses of drugs may change with time. Usually once treatment has started it will need to be continued for the rest of your pet’s life. All drugs have some side effects and if you are worried about any aspect of your pet’s treatment or any of the signs it is showing you should contact your own vet for further advice.

For most diseases, there is no evidence that it is beneficial to start treatment before signs of heart failure develop.

There are many drugs that can be used to help animals with heart failure. Most commonly a combination of a diuretic, an ACE inhibitor and pimobendan is used.

Diuretics (also sometimes known as ‘water tablets’)

These are used to stop fluid retention, which can cause breathing difficulty if it builds up in the lungs. Diuretics help to remove water from the body by increasing the production of urine.

The most commonly used diuretic is furosemide. Furosemide is usually given 2 or 3 times daily. In some more advanced cases other weaker diuretics may be used in combination with furosemide to improve the effect (i.e. spironolactone, hydrochlorothyazide).

Since animals on diuretics will produce more urine they will also need to drink more water. It is important that you do not restrict the water intake of your pet as they may become dehydrated. Animals receiving diuretics will need to urinate more frequently and sometimes can develop urinary incontinence – either making puddles in the house or leaking small amounts of urine when lying down. As the excess water is washed out of the body it also carries with it some salts and animals receiving diuretics for a long time may become a bit deficient in some salts.

Your vet will want to test blood samples from your pet to ensure that they are not developing problems as a consequence of the diuretics but you should not give any other supplements without veterinary advice. If you notice any side effects when your pet is given diuretics you should discuss these with your vet.

ACE inhibitors

There are many drugs in this group and they act by dilating blood vessels, which results in a lowering of blood pressure. In people these drugs are used frequently to treat high blood pressure – in pets they are most often used in heart failure to help prevent fluid retention and make it easier for the heart to pump blood. The most commonly used drugs in this group are enalapril, benazepril, lisinopril and ramipril. These are usually given once or twice daily.

When these drugs are first given it may take your pet some time to get used to the medication, Since these drugs lower blood pressure your pet may suffer signs of lethargy or weakness and very rarely even collapse. If these signs develop when you start the medication, contact your vet immediately to get further advice.

The most serious side effect usually seen with these drugs are effects on kidney function. For this reason, if your pet is prescribed ACE inhibitors, your vet will probably recommend some routine blood tests to make sure your pet’s kidneys are working normally before, and during treatment. Vomiting and diarrhea may also be seen in some animals.

ACE inhibitors should not be given to pregnant animals as they can cause birth defects.

Drugs to improve heart function

Pimobendan is most often used in dogs with heart valve disease or those with dilated cardiomyopathy. It improves the efficiency of heart function by increasing the force of heart contraction (without increasing the use of energy and oxygen by the heart muscle) and causes blood vessel dilation (which makes it easier for the heart to pump blood around the circulation).

It is often used in conjunction with other drugs in the management of heart failure. Side effects are rare but may include vomiting or irregular heart rhythms and if these occur the dose may need to be reduced. It is usually given twice daily, ideally 1 hour before feeding.

Antiarrhythmic drugs

Beta Blockers

Beta blockers slow the heart rate and therefore reduce the amount of oxygen needed by the heart muscle. They can also be used to slow the heart in some rhythm disturbances. The most commonly used beta blockers are propranolol and atenolol and these are given once or twice daily.

Beta-blockers may cause low blood pressure, low heart rate and worsen heart failure. Diarrhea may also occur. To reduce the risk of side effects beta blockers are usually given at a low dose to start with and the dose is increased slowly until it has the required effect. Signs to look out for that might indicate an overdose of beta blockers are lethargy, weakness or collapse, or a worsening of signs of heart failure. If you are worried about any signs in your pet call your vet for advice.

Digoxin

Digoxin has mild effects on the heart muscle making it contract more strongly. In the past this drug was used commonly to treat heart failure for this property. However these effects are so mild that nowadays this drug is used mainly for the treatment of heart rhythm disturbances, particularly one called atrial fibrillation. It causes the heart to slow down. This drug is usually given twice a day and a liquid form is available as well as tablets.

A few days after starting digoxin your vet will want to test the drug levels in the blood. The sample has to be taken 6-8 hours after administration depending on the lab analyzing the sample. Side effects of digoxin commonly include a loss of appetite and vomiting, diarrhoea and depression. If these signs develop you should contact your vet immediately for advice. Drug levels and kidney function must be routinely monitored (i.e. every 3 months) to make sure they are not above the therapeutic range and that your pet is not at risk of side effects.

Diltiazem

Diltiazem is used in some pets with an abnormal heart rhythm to slow the heart rate. It is commonly combined with digoxin to treat atrial fibrillation. Your vet may want to check that your pet’s liver and kidneys are working normally before they prescribe this drug. Tablets are usually given 3 times daily.

Solatol

Sotalol is used in some pets with an abnormal heart rhythm to slow the heart rate. Side effects may include low blood pressure, low heart rate, depression, nausea, vomiting and diarrhea. If these signs develop you should contact your vet immediately for advice. Your vet will want to check kidney function before prescribing this drug. Tablets are given twice daily.

Amiodarone

Amiodarone is used in some pets with an abnormal heart rhythm to slow the heart rate. In most cases it is used when other antiarrhythmic drugs have failed. Dogs on this drug may lose appetite and vomit. Other side effects may include low blood pressure, low heart rate, low thyroid hormone levels and liver toxicity. Your vet will want to do some blood tests to check that your pet does not have liver disease before prescribing this drug and will want to repeat these tests periodically while on treatment. Tablets are usually given twice daily.

The dog’s heart, like that of humans, is a muscular pump with four separate chambers. The right side of the heart sends blood to the lungs where it picks up oxygen. The left side of the heart pumps the blood around the body. The four areas of the heart are separated by valves which ensure that blood always flows in the correct direction through the heart.

Heart disease may affect any area of the heart:

Heart valves

The valves within the heart may fail to develop properly, e.g. mitral dysplasia, or may degenerate as a result of ageing (endocardiosis). Specific infections can affect the heart valves (endocarditis). Abnormal valves allow leakage of blood between heart chambers even when they are closed. When valves leak abnormal blood flow can be detected when listening to the heart (a murmur) and on ultrasound.

Heart muscle

In general terms the heart muscle may be either too thick or too thin. If the muscle is too thin the heart is unable to contract properly and if the muscle is thick the heart cannot relax and therefore does not fill with blood between contractions. In either case the heart is unable to pump sufficient blood out.

Electrical conduction

Abnormal electrical conduction affects the rate and rhythm of the heart. Electrical abnormalities can be caused by disease outside the heart. If the heart beats too quickly there is not enough time for it to fill properly between beats and so it pumps less blood with each beat. If the heart beats too slowly there are not enough pulses to supply enough blood to the body. Chaotic rhythms occur where contractions of different parts of the heart are not synchronised and so pulse volume is reduced.

Pericardium

The pericardium is a strong sac that surrounds and supports the heart. Changes to the pericardium usually result in constriction of the heart, preventing it from filling properly between contractions. The right side of the heart (because it has thinner walls) is usually more easily compressed than the left.

Heart disease in older dogs is usually caused by damage to the heart valves or stretching of the heart muscle. Particular breeds of dog are more prone to certain types of heart disease.

The two most common types of heart disease in the adult dog are:

Valvular heart disease

This is particularly common in Cavalier King Charles Spaniels (CKCS) but can occur in almost any breed. As a dog ages its valves may become worn and degenerate and therefore get more and more leaky. Instead of closing properly each time the heart pumps, the valves flop open allowing blood to move backwards as well as forwards through the heart chambers. This results in a reduced blood supply to the body. More about mitral valve disease.

Dilated cardiomyopathy (DCM)

This form of heart disease is seen most commonly in large and giant breeds, particularly Dobermann pinschers, Great Danes and Irish Wolfhounds. Some spaniels are also affected and it could rarely affect dogs of any breed. The disease causes a stretching of the heart muscle walls so that the heart swells (like a balloon filled with water). The contractions of the heart muscle become very weak so blood is not pumped around the body effectively. More about dilated cardiomyopathy (DCM).

In humans, heart disease is the result of damage to the heart muscle caused by blood clots (myocardial infarction) anf this causes the signs of a heart attack. However, dogs do not get this kind of heart disease.

The signs of heart disease are often very similar whatever the cause. Many of the signs of heart disease can be confused with natural ageing changes. Reduced energy and less desire to exercise are common. Dogs with severe heart disease often have poor appetites and may lose weight. If water retention occurs as a result of the heart failure you might not notice that your dog is losing weight.

Other common signs of heart failure are panting and coughing due to fluid build up in the lungs – but remember these signs may be seen with many other diseases too. Less commonly, dogs with heart disease may faint or collapse.

When your vet examines your dog he will use a stethoscope to listen to your dog’s heart. If heart disease is present, your vet may hear a change in the heart sounds. The heartbeat may be fast (or occasionally slow), irregular or there may be an unusual noise (a murmur).

X-rays may show that the heart is enlarged and ultrasound can be used to see whether the heart muscle and valves are working normally. An electrocardiogram (ECG), records the electrical activity that causes the heart muscle to beat and can be used to see if the beat is irregular.

Ask your vet to check a new puppy as soon as you get it and they will listen to its heart to detect any possible congenital heart problems. You may want to return the puppy to the breeder (if you are not already too attached to it) or, if possible, consider early correction of defects before signs of disease develop.

Heart disease does not necessarily mean heart failure. Many dogs with heart disease have no outward signs of illness and are able to lead relatively normal lives without any medication. However, most heart diseases will get worse and once symptoms start, treatment will probably be required for the remainder of your dog’s life.

In early stages of heart disease there may be no signs and your dog may just need to be checked regularly by your vet. If signs develop these can be treated. However, in most cases heart disease does get worse and treatment will only slow down the rate of disease progression. Such treatment includes:

• Changes to your dog’s lifestyle, i.e. more controlled exercise.
• Drugs to improve the strength of the heart beat or change the heart rate (digoxin, pimobendan or antiarrhythmics).
• Drugs to remove excess fluid retention (ACE inhibitors and diuretics).
• Dietary changes may be recommended by your vet depending on the type of heart disease present.

Some congenital heart defects can be corrected by surgery. If your vet recommends surgery it is well worth considering. If the problem is corrected at an early stage (before any signs develop) it may be that your dog could be cured and never require any further treatment.

This is an impossible question for your vet to answer. Some animals with heart disease may live normal lives with no symptoms at all. Other dogs do not respond to any treatment and may die quickly. It all depends on the type and severity of the heart disease. Your vet may be able to give you an idea of the likely lifespan of your pet on an individual basis.

The most important thing when managing any disease is the quality of life that your dog has. If you are concerned that your dog is feeling unwell, or consider that the treatment is not helping him, you must contact your vet for further advice.

Cardiomyopathy literally means disease of the heart muscle (cardio = heart, myopathy = muscle disease). In DCM the heart muscle becomes thin and weakened. The heart muscle can be damaged in a number of ways including viral infections.

Dietary deficiencies of taurine (an essential amino acid only found in meat protein) and carnitine have been reported as causes of DCM in some groups of dogs. Low levels of carnitine in the blood has been detected in some Boxers and springer spaniels with DCM, and some Cocker spaniels with DCM may have low blood taurine levels.

Since the disease is much more common in some breeds than others, genetic factors are probably important. In most cases of DCM there is no apparent cause of the damage to the heart and this is termed idiopathic cardiomyopathy.

Once the heart muscle is damaged it becomes weak and so does not contract well. Because heart contractions are weak the heart does not empty with each contraction and the blood supply to the body is reduced. Pulses are weak and the paws may feel cold. With time the heart muscle stretches and heart becomes a flabby sac.

DCM eventually results in heart failure with fluid build-up in the lungs (pulmonary oedema), the chest (pleural effusion) and belly (ascites).

Signs of heart disease are often not noticed by owners until their pet develops heart failure. Your vet may hear an irregular heart beat on a routine examination and this may be the first sign that your dog has heart disease.

Owners most commonly recognise exercise intolerance and breathlessness in their pet but anorexia, depression and excessive drinking are also common. The first sign in many dogs is coughing and collapse.

You may notice that your dog has recently lost weight – this may be due to cardiac cachexia. If ascites develops the abdomen may be distended and you must be careful not to misinterpret this swelling as weight gain. Some animals with DCM die suddenly.

From the changes that you describe and by examining your dog your vet may suspect that your pet has a heart problem. Other tests will be needed to confirm this. Chest X-rays may show that the heart outline is enlarged and there may be other changes (such as fluid in the chest) caused by heart failure. Y

our vet will need to examine your dog’s heart with ultrasound to make the diagnosis. With ultrasound it is possible to measure the thickness of the heart muscle and the size of the heart chambers. Ultrasound also allows us to see the heart beating and we can measure how much contractility it has.

Abnormal heart rhythms are common in DCM so an electrocardiogram (ECG) is useful in patients with DCM. A special type of rhythm (atrial fibrillation) is present in most giant breeds with DCM and other disturbances to the heart rhythm are particularly common in Dobermanns and Boxers.

Blood changes in DCM are not specific, but may indicate poor kidney function due to reduced blood supply to the kidneys. There is now a blood test (proANP) that can be used for early detection of heart disease in dogs and this may be useful in some cases if other diagnostic methods are not available.

In almost all cases there is no treatment for the underlying muscle disease. Signs of heart failure can be managed according to its severity. Patients in acute heart failure (collapsed and with breathing difficulties) should be taken into hospital for strict rest and immediately started on diuretics and a vasodilator (nitroglycerine cream rubbed onto the ear pinna). Intravenous diuretics are given to remove fluid on the lungs.

Long-term treatment includes controlling exercise and administering oral diuretics and ACE inhibitors to reduce lung fluid. If the heart rate is fast then dogs may benefit from drugs that slow the rate. Pimobendan has been shown to improve quality of life in some dogs with DCM.

If your vet thinks that a dietary deficiency is a possibility then supplementation with carnitine or taurine may be beneficial. However, these treatments can be expensive in giant breeds and are unlikely to beneficial in these breeds. If you can afford it, it is probably wise to try supplementation with L-carnitine in Boxers and Springer Spaniels and taurine in Cocker Spaniels and dogs on vegetarian diets.

If heart rhythm is abnormal drugs may be given to control this. It is very unusual to be able to convert the heart back to a normal rhythm if DCM is present but if the heart rate is slowed the heart may contract better with each beat and therefore give a better output of blood to the body.

Kidney function, and other blood tests should be performed regularly in patients receiving treatment.

The outlook for most dogs with DCM is not very good. Most animals with DCM develop heart failure and some die, as fluid builds up in the lungs, or are put to sleep as a result of poor quality of life. Many dogs with DCM die suddenly (probably as a result of developing severe cardiac rhythm disturbances).

The outlook for dogs with DCM is extremely variable depending on the severity of the disease and the breed of dog. Most dogs survive around 6 months and around one-third of dogs will be alive one year after diagnosis. Cocker Spaniels and giant breed dogs appear to survive better than other breeds. Some, with appropriate management, may live relatively normal lives for years after diagnosis.

Dogs with fluid in their chest at the time of diagnosis tend not to survive so long. The outlook for most Dobermanns is unfortunately extremely poor (with many only living a few weeks and most only living a few months after diagnosis).