Cardiology - Related Articles

To learn more about any of the subjects below, simply select the topic to reveal more information.

AV Block (Heart Block)

http://mdmedicine.wordpress.com/2011/04/24/heart-conduction-system/

Heart block in general is the delayed or absent conduction through the atrioventicular node (the communication point  between the upper and lower chambers of the heart).  The most likely underlying causes include alterations in the nervous  influence in this area or fibrous replacement tissue in this location although electrolyte abnormalities, some medications,  and inflammatory processes can cause this as well.  Alterations in nervous influence are typically due to another disease  process like diseases of the nervous system, respiratory system, or gastrointestinal system and are not a primary cardiac  issue.  If the heart block is due to a primary cardiac issue then the treatment depends on the severity of the condition.  If  the heart block is causing symptoms (decreased energy level or fainting episodes) then the treatment of choice is to place  a permanent pacemaker to control the heart rhythm and alleviate these symptoms.  See pacemaker implantation.  If a  permanent pacemaker is not an option, then medical management options can be considered although they are often less  successful than pacemaker therapy.

Click here to download PDF >

Dilated Cardiomyopathy

Your dog has been diagnosed with dilated cardiomyopathy (DCM). This disease is caused by a disease of the heart muscle that has led to diminished contractile function. There are many potential causes of the disease but the vast majority of clinical cases are “idiopathic” meaning that the cause is unknown. The only clinically significant cause we can identify is taurine deficiency. Taurine is an amino acid (building block of protein) that is metabolized aberrantly in some dogs. It is very rare but when identified, is partially treatable. Unfortunately, most other cases of DCM slowly progress to congestive heart failure despite treatment.

In order to understand how this disease may affect your dog, it is important to understand normal circulation in the heart. Blood drains from the body into the right atrium where it passes through the tricuspid valve and into the right ventricle. From here, blood is pumped into the pulmonary artery and subsequently to the lungs where it picks up oxygen. The oxygenated blood then drains passively into the left atrium, through the mitral valve, and into the left ventricle. The left ventricle then pumps the blood through the aorta and back to the body.

In dogs with DCM, the myocardial (heart muscle function) progressively worsens which leads to heart enlargement and increased intra-cardiac pressures. The disease often affects the left ventricle primarily although the right ventricle is often concurrently diseased. As the left ventricular pressure increases, the left atrial pressure increases. As the pressure in this chamber rises, it is transmitted back to the blood vessels in the lungs and, if the pressure is high enough, fluid can exude into the alveoli (air sacs) in the lungs. This is called pulmonary edema or congestive heart failure. In many dogs this causes a cough. However, some dogs don’t cough when this occurs. Instead, they breathe faster (more than 40 breaths per minute) or with too much effort.

Dogs with DCM should be monitored at home for a cough or an increase in respiratory rate (greater than 40 breaths per minute) or effort. If any of these occur, a chest x-ray should be taken to evaluate for the presence of pulmonary edema.

Depending on the stage of disease your dog is at, medications may be prescribed. Most cardiac medications can adversely affect the kidneys. For this reason, it is important to monitor kidney function with blood tests as new medications are introduced or dosage changes are made.

An echocardiogram (ultrasound of the heart) is necessary for definitive diagnosis of dilated cardiomyopathy. An echo allows us to look on the inside of the heart and assess the heart’s function. It will be repeated periodically over the course of your dog’s disease to monitor for significant changes in heart function. Chest x-rays are often taken to evaluate for the presence of pulmonary edema. Some dogs develop rhythm disturbances secondary to their enlarged hearts. In these cases, an electrocardiogram (ECG) is done.

Thankfully, most dogs with DCM feel good as long as their congestive heart failure is controlled. I will work closely with your veterinarian to ensure that your dog gets the best care possible.

Click here to download PDF >

Heartworm Disease

Heartworm disease is caused by a parasite called Dirofilaria immitus that is uses mosquitoes as the vector and dogs as the host. Cats can get heartworm disease but are considered an aberrant host so it behaves very differently in them. A dog that receives a bite from a mosquito that is carrying the larval stage of the heartworm receives this larval stage and it develops in to adult heartworms in the arteries of the lungs. This causes an inflammation as well as many other changes in the lungs. Eventually the blood pressure in these vessels can increase (pulmonary hypertension) which increases the workload on the right side of the heart which pumps blood to the lungs. Heartworms can cause a variety of symptoms including coughing, decreased exercise tolerance, increased breathing rate or effort, abdomen distended with fluid, discolored urine as well as many other symptoms depending on the severity of the disease process. Once there are live adults living in the pulmonary arteries, adulticide therapy needs to be performed after assessing the overall health of the pet. This is done with injections of an arsenic derivative medication over a month. The pet has to be strictly confined during this therapy period (for approximately 2 months) because activity can lead to complications. Some of the changes that occur with the heartworm therapy are not reversible with heartworm therapy.

Heartworm disease is easily prevented by administering a monthly heartworm preventative to your pet. Your veterinarian can assist you in selecting the best preventative for your pet.

Click to download PDF >

Hypertrophic Cardiomyopathy

Your cat has been diagnosed with Hypertrophic Cardiomyopathy (HCM). This is the most common heart disease seen in cats although it is relatively rare in the cat population as a whole. HCM is a disease that causes the heart muscle to abnormally thicken. The thickening primarily affects the left ventricular muscle and does so in a variety of patterns.

Some cat’s muscle is diffusely thickened while others only have focal areas of thickening. Regardless of which type your cat has, the end result can be the same.

In order for you to understand how this disease may affect your cat, it is important to understand how blood travels through the heart. The venous blood from the body drains into the right atrium, through the tricuspid valve, and into the right ventricle. The right ventricle then pumps this un-oxygenated blood to the lungs through the pulmonary artery.

Moving through capillaries, the blood picks up oxygen from the lungs. This blood then drains through large pulmonary veins into the left atrium, through the mitral valve and into the left ventricle where it is pumped through the aorta and back to the body.

Many cats with HCM are only mildly affected and never experience clinical problems with the disease. However, some cats slowly progress over time. Unfortunately, it is impossible to tell which type an individual cat has. As the disease progresses, scar tissue replaces the thickened muscle. This muscle eventually becomes very stiff as well as too thick. This causes the filling pressure of the left ventricle to rise. Imagine pouring water into a thick and thin walled balloon. The thinner walled balloon is easily distensible and would fill readily. In order to fill the thick walled balloon, the water pressure would need to be turned up. This is analogous to a stiff left ventricle. Left atrial pressure must rise in order to fill it. This causes the left atrium to enlarge and the pressure to back up further into the lungs.

There are three potential outcomes to HCM.

1. Congestive Heart Failure (CHF). The most common outcome in cats with severe HCM. This can happen if the left atrial pressure is high enough to cause fluid to leak into the lungs.

2. Clot formation. An enlarged left atrium is unfortunately an ideal location for a blood clot to form. Once formed, it is often released into the blood stream and lodges in the blood supply to the hind legs. This causes acute hind limb paralysis.

3. Sudden death. This is a RARE but possible outcome.

If your cat has only mild disease, there is no risk of CHF or clot formation. The risk of sudden death is miniscule. If your cat has moderate or severe disease, there is risk for both CHF and clot formation although clot formation is less common. These cats should be monitored for any change in breathing (too fast or labored). If this occurs, a chest x-ray should be taken as soon as possible to evaluate for the presence of CHF.

Unfortunately, there is not a proven therapy available to slow progression of this disease. There are many medications that have theoretical basis in slowing progression. When and if CHF develops, there is medication to help in controlling it. Aspirin is prescribed when the left atrium becomes enlarged although it is not always efficacious in preventing clot formation. I will work closely with your doctor in developing the treatment plan best for your cat and your family. Most cats with this disease have an excellent quality of life and don’t realize they are sick.

It is important to remember that many afflicted cats never develop problems with HCM. It is very important to monitor their echo so that if changes occur, appropriate therapy is prescribed.

Click here to download PDF >

Mitral Regurgitation

Your dog has been diagnosed with mitral regurgitation (MR). This disease is caused by a degenerative process that occurs in most dogs as they age. In your dog, this process has caused the valve to leak.

In order to understand how this disease may affect your dog, it is important to understand normal circulation in the heart. Blood drains from the body into the right atrium where it passes through the tricuspid valve and into the right ventricle. From here, blood is pumped into the pulmonary artery and subsequently to the lungs where it picks up oxygen. The oxygenated blood then drains passively into the left atrium, through the mitral valve, and into the left ventricle. The left ventricle then pumps the blood through the aorta and back to the body.

In dogs with MR, the leak in the valve can progressively worsen so that the left ventricle is pumping a significant amount of blood backwards through the leaky valve. Since it also has to pump a normal amount of blood forwards, the left ventricle slowly enlarges. Also, the left atrium enlarges to accommodate the backflow through the mitral valve. Left atrial enlargement is indicative of abnormally high pressure in the left atrium.

As the pressure in this chamber increases, it is transmitted back to along to the blood vessels in the lungs and, if the pressure is high enough, fluid can exude into the alveoli (air sacs) in the lungs. This is called pulmonary edema or congestive heart failure. In many dogs this causes a cough. However, some dogs don’t cough when this occurs. Instead, they breathe faster (more than 40 breaths per minute) or with too much effort.

Dogs with MR should be monitored at home for a cough or an increase in respiratory rate (greater than 40 breaths per minute) or effort. If any of these occur, a chest x-ray should be taken to evaluate for the presence of pulmonary edema.

Depending on the stage of disease your dog is at, medications may be prescribed. Most cardiac medications can adversely affect the kidneys. For this reason, it is important to monitor kidney function with blood tests as new medications are introduced or dosage changes are made.

An echocardiogram (ultrasound of the heart) is necessary for definitive diagnosis of mitral regurgitation. An echo allows us to look on the inside of the heart and assess the heart’s function. It will be repeated periodically over the course of your dog’s disease to monitor for significant changes in heart function. Chest x-rays are often taken to evaluate for the presence of pulmonary edema. Some dogs develop rhythm disturbances secondary to their enlarged hearts. In these cases, an electrocardiogram (ECG) is done.

Thankfully, most dogs with MR feel good as long as their congestive heart failure is controlled. We will work closely with you and your veterinarian to ensure that your dog gets the best care possible.

Click here to download PDF >

Patent Ductus Arteriosus

Your pet has been diagnosed with a patent ductus arteriosus (PDA). This vessel is present in fetal life so that blood can bypass the yet functioning lungs. Once exposed to oxygen after birth, this vessel should close. In your pet this closure did not occur.

In order for you to understand how this disease may affect your pet, it is important to understand how blood travels through the heart. The venous blood from the body drains into the right atrium, through the tricuspid valve, and into the right ventricle. The right ventricle then pumps this un-oxygenated blood to the lungs through the pulmonic valve into the pulmonary artery. Moving through capillaries, the blood picks up oxygen from the lungs. This blood then drains through large pulmonary veins into the left atrium, through the mitral valve and into the left ventricle where it is pumped through the aorta and back to the body.

In your pet’s case the open vessel (the PDA) causes a portion of the blood from the aorta to shunt to the pulmonary artery though the lungs and back to the left side of the heart. This causes overcirculation of the lungs and left heart. This overcirculation causes the left heart to dilate over time and increases the pressures in the left heart over time. The increase in pressure in the left heart and the pulmonary veins (the vessels that drain into the left heart from the lungs) eventually causes fluid to exude into the lungs which is a condition called congestive heart failure. This will make your pet breath harder, cough, or decrease exercise tolerance and can be fatal.

The good news is that this condition is repairable with an interventional or surgical procedure. If repair occurs early in life and is successful, your pet will have a normal life expectancy and quality of life. Most pets with this condition are candidates for interventional occlusion of the defect. This consists of anesthetizing your pet and placing a catheter into the femoral artery to deploy a device in the defect. The device then prohibits blood from crossing the defect. If your pet is too small or the defect is of a shape that is not amendable to interventional repair, surgical closure can be performed.

Occasionally the pressures in the lungs are high with this defect. If the pressures are high in the lungs it may prohibit closure of the defect. If this condition is present in your pet we will discuss therapeutic measures that can be performed.` more information: www.AlpenglowVets.com

Click here to download PDF >

Pericardial Effusion

Pericardial Effusion is when there is an inappropriately large volume of fluid in the sac around the heart. As this fluid volume increases it puts pressure on the heart and impacts the filling of the heart. There are a number of causes of pericardial effusion but many of these do not cause enough fluid to compress the heart. The most common causes of fluid that compresses the heart include neoplastic causes (hemangiosarcoma, chemodectoma, mesothelioma and less commonly lymphoma) and idiopathic causes (meaning the fluid occurs but the cause is unknown). Infectious and coagulopathic causes are possible but less likely. Pericardial effusion often presents as an emergency due to the impact on the heart.

The emergency treatment is to perform a pericardiocentesis. This is performed by inserting a catheter in the sac around the heart to remove the fluid to alleviate the compression on the heart. This fluid is often sent out for analysis to provide insight into the cause of this condition. The prognosis is variable depending on the underlying cause.

Idiopathic Pericardial Effusion: The underlying cause of this disease process is unknown. If the pericardial effusion recurs then removing part of the pericardium may be necessary to elimate the symptoms associated with this disease.

Hemangiosarcoma: This is a tumor that is typically associated with the right atrium/auricle in the heart. It is a fast growing tumor that metastasizes (spreads to other parts of the body) rapidly. If the tumor is surgically resectable then the best treatment option includes surgical resection of the tumor followed by chemotherapy. Chemotherapy alone, with our without removal of part of the pericardium, may decrease the tumor growth rate and effusion rate. Overall the prognosis is poor.

Chemodectoma: This tumor is slow growing and slow to spread. Brachycephalic breed dogs are overrepresented for this tumor type. Dogs with pericardial effusion due to a chemodectoma often require a partial removal of the pericardium to alleviate symptoms. The tumor itself is unlikely to be surgically resectable due to the type of cells that make up the tumor as well as the location of the tumor.

Click to download PDF >

Pulmonary Hypertension

Your dog has been diagnosed with pulmonary hypertension. Pulmonary hypertension is the term used to describe pathologically elevated pulmonary arterial pressure. It is a separate disease entity than systemic hypertension which describes high blood pressure in the rest of the body.

In order for you to understand how this disease may affect your dog, it is important to understand how blood travels through the heart. The venous blood from the body drains into the right atrium, through the tricuspid valve, and into the right ventricle. The right ventricle then pumps this un-oxygenated blood to the lungs through the pulmonary artery. Moving through capillaries, the blood picks up oxygen from the lungs. This blood then drains through large pulmonary veins into the left atrium, through the mitral valve and into the left ventricle where it is pumped through the aorta and back to the body.

When dogs develop significant pulmonary hypertension, the right side of the heart enlarges (sometimes dramatically) in order to pump blood into the elevated pulmonary arterial circulation. If the pressure on the right side rises enough, the enlarged right side can impede normal filling of the left side. Subsequently, the amount of blood pumped into the systemic circulation to the body is reduced which causes weakness, exercise intolerance, and sometimes fainting. Also, the elevation in right sided pressure can back up into the venous return from the body causing fluid to ooze out of the capillaries and into the abdominal cavity. This is called right sided congestive heart failure.

The causes of pulmonary hypertension are numerous. In some cases, it is secondary to chronic pulmonary thromboembolism (PTE). Diseases that predispose dogs to PTE include immune diseases, severe liver disease, kidney disease, endocrine disease (such as Cushings disease), and cancer. Other causes of pulmonary hypertension are chronic lung disease; chronic, severe left heart disease; Heartworm disease; and idiopathic. Idiopathic is a word used when the underlying cause cannot be identified. In most dogs, the underlying cause cannot be identified. An attempt should be made to identify the cause because in some cases, it can be treated or the disease process slowed.

The single most important test used to identify pulmonary hypertension and assess its severity is the echocardiogram. The echocardiogram is used to diagnose PH as well as to assess its severity. Dogs with mild PH do well and rarely experience clinical signs. Dogs with moderate PH are variably affected. Most don’t experience obvious clinical signs although they may be somewhat exercise intolerant or faint/collapse with exertion. Dogs with severe PH always experience clinical signs. They include trouble breathing, fainting with exertion, and/or right sided congestive heart failure. The tests used to identify the cause of pulmonary hypertension are labwork (complete biochemistry profile, complete blood count, and urinalysis, Heartworm test, and d-dimer) as well as abdominal u/s if cancer or other abdominal disease is suspected.

If the underlying cause can be identified, every attempt should be made to treat it. Many of the diseases that cause PH are unfortunately, not amenable to therapy. In most dogs, treatment is directed at lowering the blood pressure in the lungs. This is done medically. The most effective medication for the treatment of PH is Sildenafil (Viagra).

Approximately 65% of dogs respond to Viagra and although their pulmonary arterial pressure does not normalize, it is lowered enough to cause marked improvement in clinical signs. Viagra can be prohibitively expensive so it is only prescribed in cases of severe PH. There are other medications that can be beneficial that may be prescribed earlier.

Dogs with pulmonary hypertension should be monitored for a change in breathing pattern (increase abdominal effort with each breath; rapid, shallow breathing, etc), fainting or collapse, exercise intolerance, and abdominal swelling (which could indicate the onset of right sided congestive heart failure).

It is important to remember that many afflicted dogs never develop problems with Pulmonary Hypertension. It is very important to monitor their echo so that if changes occur, appropriate therapy is prescribed.

Click to download PDF >

Pulmonary Stenosis

Your dog has been diagnosed with Pulmonic Stenosis (PS). The term pulmonic stenosis usually implies that there is valvular pulmonic stenosis; however, supravalvular and subvalvular pulmonic stenosis share the same pathophysiology and are often used to describe the same disorder. Valvular PS is the most common type of PS and is most amenable to correction. Valvular PS is a congenital defect where the pulmonic valve leaflets open incompletely in the contraction phase (systole) of the cardiac cycle. Supravalvular PS is when there is a ring or ridge of tissue above the pulmonic valve causing obstruction of outflow while subvalvular PS refers to obstruction below the pulmonic valve. The rest of this discussion will focus on valvular PS but the pathophysiology is the same for all three types. It is commonly heritable so the breeder of your puppy should be notified if possible.

In order for you to understand how this disease may affect your dog, it is important to understand how blood travels through the heart. The venous blood from the body drains into the right atrium, through the tricuspid valve, and into the right ventricle. The right ventricle then pumps this un-oxygenated blood to the lungs through the pulmonic valve into the pulmonary artery. Moving through capillaries, the blood picks up oxygen from the lungs. This blood then drains through large pulmonary veins into the left atrium, through the mitral valve and into the left ventricle where it is pumped through the aorta and back to the body.

Dogs with PS have partial fusion of the valve leaflets that causes an acceleration of blood flow as it crosses the valve. The abnormal blood flow is what causes the heart murmur that was ausculted by your veterinarian. Because the outflow tract is abnormally narrowed, the pressure the right ventricle must overcome in order to pump blood into the pulmonary artery is elevated. This change in pressure is termed the pressure gradient – the degree of elevation of the pressure gradient is how PS is classified. The right ventricular muscle thickens in order to overcome the increase in pressure. The thickened muscle is inadequately perfused by the coronary circulation and becomes damaged. This damaged heart muscle can cause rhythm disturbances and also eventually lead to congestive heart failure.

In normal dogs, the pressure gradient across the pulmonic valve is less than 20mmHg. In dogs with mild PS, the pressure gradient is between 20 and 50mmHg. Dogs with moderate PS have a pressure gradient between 50 and 80mmHg and dogs with severe PS have a pressure gradient greater than 80mmHg.

An echocardiogram is used to make the diagnosis of PS and to classify its severity. It is also important to evaluate for concurrent defects. Many dogs with PS also have a patent foramen ovale (abnormal connection between the right and left atria) as well as a malformed tricuspid valve.

Dogs with mild PS have a good prognosis and generally live a full life. Dogs with moderate PS also have a good prognosis – a small percentage may go on to develop muscle failure late in life. In dogs with moderate PS that have concurrent tricuspid valve dysplasia or a patent foramen ovale, therapy should be considered. Dogs with severe PS are at risk for sudden death, fainting, as well as eventual muscle failure. Therapeutic options for valvular pulmonic stenosis include balloon valvuloplasty (BV) as well as surgical valvulotomy.

BV is the preferred treatment as it is minimally invasive and offers a good outcome. It is performed by a cardiologist in a catheterization laboratory. Surgical valvulotomy is performed by a surgeon and entails a thoracotomy (incision into the thoracic cavity).

Supra or sub valvular obstructions are less amenable to balloon valvuloplasty. Surgery is indicated in cases where the obstruction is severe. Few institutions are able to provide this option. With therapy, the prognosis for severe PS is good. Some dogs require lifelong therapy of a beta blocker while others can be maintained on no medication. Lifelong monitoring with echocardiograms is warranted in all cases of moderate or severe PS.

Click to download PDF >

Subaortic Stenosis

Your dog has been diagnosed with Subaortic Stenosis (SAS). SAS is a congenital defect that causes an abnormal narrowing of tissue just below the aortic valve. The region tends to progressively narrow over the first year of life. It is commonly heritable so the breeder of your puppy should be notified if possible.

In order for you to understand how this disease may affect your dog, it is important to understand how blood travels through the heart. The venous blood from the body drains into the right atrium, through the tricuspid valve, and into the right ventricle. The right ventricle then pumps this un-oxygenated blood to the lungs through the pulmonary artery. Moving through capillaries, the blood picks up oxygen from the lungs. This blood then drains through large pulmonary veins into the left atrium, through the mitral valve and into the left ventricle where it is pumped through the aorta and back to the body.

Dogs with SAS have a narrow region of tissue just below the aortic valve that causes an acceleration of blood flow as it crosses the region. The abnormal blood flow is what causes the heart murmur that was ausculted by your veterinarian. Because the outflow tract is abnormally narrowed, the pressure the left ventricle must overcome in order to pump blood into the aorta is elevated. This change in pressure is termed the pressure gradient – the degree of elevation of the pressure gradient is how SAS is classified. The left ventricular muscle thickens in order to overcome the increase in pressure. The thickened muscle is inadequately perfused by the coronary circulation and becomes damaged. This damaged heart muscle can cause rhythm disturbances and also eventually lead to congestive heart failure.

In normal dogs, the pressure gradient across the aortic valve is less than 20mmHg. In dogs with mild SAS, the pressure gradient is between 20 and 50mmHg. Dogs with moderate SAS have a pressure gradient between 50 and 80mmHg and dogs with severe SAS have a pressure gradient greater than 80mmHg.

An echocardiogram is used to make the diagnosis of SAS and to classify its severity. It is also important to evaluate for concurrent defects. Many dogs with SAS also have aortic insufficiency (leaky aortic valve) as well as an abnormally formed mitral valve (mitral valve dysplasia).

Dogs with mild SAS have a good prognosis and generally live a full life. They can develop late complications (endocardits, muscle failure) but this is rare. Dogs with moderate SAS have a good prognosis in the short term and fair to good long term. A small percentage of dogs with moderate SAS die suddenly. They are at higher risk than the first group of developing late complications but the risk is relatively low. Dogs with severe SAS are at a high risk for sudden death.

There is no definitive therapy for SAS. Dogs who have had open heart surgery to remove the abnormal tissue die suddenly at the same rate as though who don’t undergo surgery. Medical therapy with a beta blocker appears to reduce the incidence of sudden death in dogs with severe SAS.

Fortunately, most dogs with SAS are unaware that they are sick and feel like normal dogs.

Click here to download PDF >

Sick Sinus Syndrome

Sick sinus syndrome is a combination of a variety of electrical abnormalities that typically result in a heart rate that is too slow (sinus pauses, wandering pacemaker, atrioventricular block). Occasionally a pet will have a component of the syndrome that causes the heart rate to get too fast (“brady-tachy syndrome”). Miniature schnauzers and West Highland white terriers are overrepresented but it is certainly not limited to these two breeds. The symptoms of sick sinus syndrome include decreased exercise tolerance and fainting episodes. The therapy for sick sinus syndrome is to place a permanent pacemaker (see pacemaker implantation). If pacemaker implantation is not an option, medical management can be attempted but it is often not as successful as pacemaker implantation.

Click to download PDF >

Supraventricular Tachycardia

Supraventricular arrhythmias are abnormal beats that arise from the atria (the filling chambers of the heart). Three or more of these abnormal beats in a row is considered supraventricular tachycardia. Supraventricular tachycardia is often caused by underlying heart disease but sometimes can be related to disease processes of other organs. Occasionally the underlying cause of the arrhythmia cannot be determined. Supraventricular arrhythmias are managed medically. Sometimes this includes an acute period of hospitalization with intravenous medication but in general includes oral antiarrhythmic therapy at home. The arrhythmias are frequently monitored with Holter monitors (24 ECG monitoring).

Most dogs respond to anti-arrhythmic therapy; however, some patients are difficult to control and require multiple medication changes before good rhythm control is achieved. Untreated, SVT can cause profound myocardial systolic failure (pump failure) which can result in congestive heart failure.

Click to download PDF >

Tricuspid Valve Dysplasia

Tricuspid valve dysplasia is a congenital malformtion of the tricuspid valve.  This causes the valve to leak (tricuspid  regurgitation) and sometimes to restrict blood flow through the valve (tricuspid valve stenosis).  The malformation can be  mild and therefore does not cause the pet any clinical concerns or be more severe and predispose the pet to right heart  failure (fluid accumulation around the lungs or in the abdomen).  If it is more severe and causes clinical signs, it can be  managed for some period of time with medical management and sometimes periodic fluid removal.  Tricuspid valve  dysplasia is considered hereditary in many breeds and therefore pets with tricuspid valve dysplasia should not be bred and  the lineage should be carefully examined.  The murmur of tricuspid valve dysplasia can be very soft to absent so the best  screening tool for breeding pets of breeds overrepresented for tricuspid valve dysplasia (like the Labrador retriever) is an  echocardiogram.

Click to download PDF >

Click Here For Emergency Care Referring Veterinarians Click Here