SECTION 2 Cardiovascular System
Arrhythmogenic Right Ventricular/Cardiomyopathy in Boxers
Rebecca E. Gompf DVM, MS, DACVIM (Cardiology)
BASIC INFORMATION
Description
Boxer cardiomyopathy is a disease of the heart muscle of boxers. The condition causes abnormal heart rhythms (arrhythmias) that arise in the right ventricle, the large chamber on the right side of the heart. Because many people confuse this problem with dilated cardiomyopathy, the disease has been given a new name, arrhythmogenic right ventricular cardiomyopathy (ARVC).
Causes
The heart muscle cells of affected boxers, mainly in the right ventricle, are replaced by fatty or fibrofatty scar tissue. Sometimes these abnormal changes occur in the left ventricle also. These changes cause arrhythmias, such as ventricular premature contractions (VPCs) and ventricular tachycardia (VT). (See the handout on Ventricular Premature Contractions and Tachycardia.) The overall heart size and function are normal in these dogs. Later in the disease, however, some dogs develop dilated cardiomyopathy. (See also the handout on Dilated Cardiomyopathy in Dogs.)
Clinical Signs
Most boxers with ARVC are clinically normal and show signs only when the arrhythmias are severe. Sometimes arrhythmias are found on routine physical examination or when an electrocardiogram (ECG) is run as a screening test. Some dogs have fainting episodes or die suddenly from severe ventricular arrhythmias. Arrhythmias can develop at any age in these dogs.
Diagnostic Tests
In boxers with a family history of sudden death or ARVC, an ECG or Holter monitoring is often done yearly. (See handout on Electrocardiography.) The exact age at which screening ECGs and Holter monitoring should be done is often based on the dog’s family history.
If VPCs are detected and confirmed by ECG, the diagnosis of ARVC is made by eliminating all other causes of these arrhythmias. Since many problems can cause VPCs, extensive testing must be done to rule out other diseases. Chest and abdominal x-rays and laboratory tests (including thyroid tests and possibly titers for tick-borne diseases and others) are often recommended. An echocardiogram (heart ultrasound) is done to rule out other heart diseases.
TREATMENT AND FOLLOW-UP
Treatment Options
If fainting episodes, VT, or severe VPCs are present, hospitalization is often needed to treat the arrhythmias with injectable medications. The more severe the arrhythmia, the higher the possibility of sudden death.
Once the heart rhythm is stabilized, several different drugs or drug combinations can be used orally. Not every drug works in every dog, so changes may be needed in therapy to control the ventricular arrhythmia.
Side effects of antiarrhythmic drugs include lethargy, anorexia, vomiting, and diarrhea. The last three effects are more common with mexiletine. Occasionally these drugs can make the arrhythmia worse, so that the dog must be switched to another medication. Amiodarone has multiple side effects, including liver damage with elevated liver tests, decreased white blood cell counts, and damage to the thyroid gland.
Follow-up Care
Affected boxers require frequent ECGs until their VT or VPCs are controlled. Ideally, a Holter monitor is applied to dogs with non–life-threatening arrhythmias to document the frequency of the arrhythmias prior to treatment. Then another Holter recording is done after the drug has reached adequate blood levels to judge how effective it is in controlling the abnormal beats. Affected dogs require antiarrhythmic therapy for the rest of their lives.
Prognosis
Boxers whose arrhythmias are well controlled with medications can live a long time. No drug is 100% effective in preventing sudden death, however. Animals on medication can still die suddenly. The better the arrhythmia is controlled, the less likely it is for sudden death to occur. Holter monitors provide the best way to evaluate how well the medication is controlling the arrhythmias.
Because this problem has a genetic basis and runs in families, it is wise not to breed dogs that have ARVC.
Arterial Thromboembolism, Peripheral
Rebecca E. Gompf, DVM, MS, DACVIM (Cardiology)
BASIC INFORMATION
Description
Arterial thromboembolism occurs when a blood clot lodges in an artery. The place where the blood clot comes to rest depends on the size of the clot and the size of the artery. Most blood clots are small and lodge in smaller arteries. The clots can cause strokes if they cut off blood to certain areas of the brain. Clots can cause damage and eventual failure of any organ in the body. In cats, the clots usually lodge in a front leg or at the termination of the aorta where it divides into arteries that supply the rear legs. This disease occurs most often in cats; it is uncommon in dogs.
Causes
Dogs can develop clots secondary to kidney diseases, Cushing’s disease (excessive levels of circulating steroid hormones), infections of the left heart valves (bacterial endocarditis), and other conditions that affect clotting. Cats usually develop clots in the left atrium, the small chamber on the left side of the heart, when it becomes dilated from hypertrophic (HCM) or dilated (DCM) cardiomyopathy or other diseases of the heart muscle. Cats have sticky platelets, and clots may form if there is decreased blood flow in the big left atrium. Pieces of the clot can break off and travel in the bloodstream to other areas, especially to the end of the aorta.
Clinical Signs
Signs of the underlying diseases are usually present but can be subtle in cats. The first sign of a problem may be sudden paralysis of a front leg or both rear legs. If the incident is recent, the animal may be crying in pain. The affected limbs are cold and limp, with blue nail beds. Muscles in the affected legs may feel hard.
Diagnostic Tests
Numerous tests are required to find the underlying cause of the problem and to assess the extent of damage from the clot. Laboratory tests, chest x-rays, and an echocardiogram (heart ultrasound) are commonly performed. Abdominal x-rays and a Doppler ultrasound study of the aorta may also be recommended to assess other organs and the extent of the clot. Additional tests may be needed based on the results of initial procedures.
TREATMENT AND FOLLOW-UP
Treatment Options
Hospitalization is usually required for initial testing and therapy. Supportive care is started, with pain medications, sedatives, and intravenous (IV) fluids. Manual expression of the bladder and physical therapy for paralyzed legs are often needed. Specific treatments are given for the underlying disease.
Medications to break down the clot are rarely used in dogs and cats; they are often ineffective, perhaps because they must be given within a few hours of the arterial obstruction, and the event is not often witnessed in animals. Streptokinase and tissue plasminogen activator (TPA) are used in people, and both drugs have been used in cats, but with varying impact on survival. They have been used only infrequently in dogs, and there is little information about their effects.
Medications are started to prevent the clot from getting bigger and to try to prevent future clots. Injectable heparin is commonly used during hospitalization. Clopidogrel (Plavix) may be given orally in cats.
After discharge from the hospital, home care may involve the following:
Follow-up Care
Frequent, often weekly, monitoring of the underlying problem and effects of the clots (such as kidney dysfunction) are usually needed. Repeated blood clotting tests are needed if warfarin is used. After a few weeks, the frequency of rechecks may be modified, depending on the response to treatment.
Prognosis
Animals with blood clots in the legs have a guarded prognosis. If there is no return of blood flow to the rear legs within a couple of days, prognosis is very poor, and it is unlikely the animal will recover function of the legs. Future clots are likely to develop if the underlying problem cannot be controlled or the preventive medications do not work.
Overall prognosis also depends on the underlying heart disease. In cats, each form of cardiomyopathy has a different prognosis; however, the formation of clots always makes the prognosis much worse. In dogs, some underlying diseases are easier to treat than others, so prognosis depends on the disease that is causing the clots.
Atrial Fibrillation
Rebecca E. Gompf, DVM, MS, DACVIM (Cardiology)
BASIC INFORMATION
Description
Atrial fibrillation (AF) is an abnormal heart rhythm caused by rapid, irregular contractions of the upper chambers (atria) of the heart. Because the heart is beating faster and more irregularly than normal, it does not fill or pump blood properly. Failure to pump blood normally can result in fluid accumulation in the lungs, chest, or abdomen and can lead to weakness and heart failure.
Causes
The most common cause of AF is advanced heart disease, with enlargement of one or both atria. Advanced heart diseases in dogs may include degeneration and leakage of heart valves, diseases of heart muscle (cardiomyopathy), and certain congenital heart deformities.
AF can occur spontaneously for unknown reasons (idiopathic) in giant-breed dogs such as the Great Dane and Irish wolfhound. Occasionally the administration of narcotics has caused AF in large dogs.
Clinical Signs
Clinical signs of both heart disease and AF are usually present. Weakness and inability to exercise are common. Fainting episodes may occur, especially with exertion. Cats are often less active than usual. Breathing may be faster and labored, and coughing may be noted.
Giant-breed dogs usually have no symptoms at first, and the AF may be detected only when an irregular rhythm is heard with a stethoscope and an electrocardiogram (ECG) is performed. Some of these dogs eventually develop signs of heart disease.
Diagnostic Tests
An ECG is needed to confirm the presence of AF. Additional tests, such as chest x-rays and an echocardiogram (heart ultrasound), are then done to search for the underlying cause. Any fluid removed from the chest or abdomen may be sent for analysis. Laboratory tests are usually recommended to rule out other diseases that cause similar signs.
TREATMENT AND FOLLOW-UP
Treatment Options
Treatment is initially directed at any underlying heart disease or heart failure and may include drugs to increase contractility (such as pimobendan) or decrease fluid retention (diuretics).
Then medications such as the following are started to bring the heart rate down to a more normal range.
Follow-up Care
Once medications are started, ECGs are periodically repeated to monitor heart rate and make adjustments in medications. A Holter monitor, which is a 24-hour continuous monitor, may be recommended to ensure that the heart rate stays within an acceptable range during normal activities. Chest x-rays, echocardiograms, abdominal x-rays, and laboratory tests may be repeated until the animal is stable and then periodically, especially in giant-breed dogs, to monitor for any signs of significant heart disease or in any animal if signs of heart failure develop.
Prognosis
Dogs with advanced heart disease and AF may live 3-12 months, depending on the type and severity of their heart disease. Cats live an average of 3-6 months. Affected cats are prone to develop blood clots in their left atrium, so they are usually placed on blood thinners such as aspirin or clopidogrel (anticoagulation therapy). Giant-breed dogs with idiopathic AF can live for years; however, their AF can progress to serious heart disease (dilated cardiomyopathy).
Atrial Premature Contractions and Tachycardia
Rebecca E. Gompf, DVM, MS, DACVIM (Cardiology)
BASIC INFORMATION
Description
The normal heartbeat originates in the small upper chambers of the heart, the atria. When the atria become irritated, irregular, premature beats called atrial premature contractions (APCs) may be generated, and the heart may beat faster than usual (tachycardia). Atrial tachycardia (AT) is a sequence of four or more APCs, usually occurring at a fast rate. As the number of abnormal beats increases and the heart rate becomes higher, the heart may not fill and pump blood properly.
Causes
The most common cause is heart disease that results in enlargement of one or both atria. The stretching of the atria causes abnormal beats to occur. These arrhythmias can also arise with other problems in the body, such as bruising of heart muscle after blunt trauma (such as being hit by a car), or liver or kidney failure.
Clinical Signs
No clinical signs occur if only sporadic, infrequent APCs are present. Frequent APCs may lead to an inability to exercise, increased rate and effort of breathing, and coughing. AT can cause weakness and possibly fainting. Fainting due to AT can be hard to tell from seizures.
Diagnostic Tests
An electrocardiogram (ECG) is needed to confirm the presence of APCs or AT. If these abnormal rhythms are not present all the time, continuous ECG monitoring may be recommended. Such monitoring can be done in the hospital or with a 24-hour, continuous Holter monitor or an event monitor that the animal wears at home.
Because APCs and AT are usually associated with heart disease and other systemic problems, additional tests are often recommended. Such tests may include laboratory tests, chest x-rays, an echocardiogram (heart ultrasound), an abdominal ultrasound study, and other tests. Any fluid in the chest or abdomen may be removed and sent for analysis.
TREATMENT AND FOLLOW-UP
Treatment Options
Treatment is initially directed at any heart disease present. If the overall heart rate is close to normal and no signs are present, then the APCs or AT may not be treated. If the heart rate is too fast, medications (alone or in combinations) are used to slow it down and may include the following:
If other diseases are causing the APCs, then those diseases are usually treated first, and the arrhythmia is monitored with ECGs. If the APCs do not resolve and AT occurs, they are treated as outlined earlier.
Follow-up Care
Once medications are started, ECGs are periodically repeated to monitor heart rate and make adjustments in medications. A Holter monitor may be used to make sure the heart rate stays within an acceptable range during normal activity. If the patient is started on medications, periodic laboratory tests may be recommended to check kidney function and monitor resolution of other diseases. Chest x-rays and echocardiograms may be repeated if heart disease is present.
Atrioventricular Valve Degeneration in Dogs
Rebecca E. Gompf, DVM, MS, DACVIM (Cardiology)
BASIC INFORMATION
Description
The left atrioventricular (AV) or mitral valve lies between the left atrium and the left ventricle. The right AV or tricuspid valve lies between the right atrium and ventricle. These valves keep blood from flowing backward into the atria when the heart contracts.
As these valves age, deposits occur and they become scarred (myxomatous degeneration), which causes them to leak when the heart pumps. As a result, the heart is less efficient in pumping blood and slowly enlarges. If the leakage is minor, the heart usually compensates, but as the leakage worsens, heart failure can develop. The mitral valve is most commonly affected and mitral degeneration may eventually lead to left-sided heart failure.
Causes
The cause of the myxomatous degeneration is unknown. AV valvular disease is the most common heart disease in dogs. It most commonly affects small to medium-sized breeds, especially the papillon, poodle, Chihuahua, dachshund, and Cavalier King Charles spaniel.
AV valvular disease is common in older dogs. The disease tends to develop at a younger age and progresses more rapidly in male dogs than in females. Genetic factors play a role in this disease, but other conditions (level of exercise, obesity, diet) may influence the severity of the problem.
Clinical Signs
The leaking valve often causes a heart murmur that can be detected on a routine physical examination before signs occur. The first clinical sign is usually coughing that is triggered by excitement or exercise. As the left heart enlarges, signs of heart failure may develop, such as more severe coughing, restlessness and pacing at night, inability to exercise normally, and rapid, labored breathing.
Dogs that go into right heart failure may also cough, but more often they tire while exercising, lose weight and muscle mass, and develop fluid in their abdomen. Eventually fluid also builds up in the chest, and they have trouble breathing.
Diagnostic Tests
Heart murmurs are often graded in severity based on how loud they are. Low-grade murmurs require monitoring over the course of the dog’s life. If the murmur changes rapidly or reach a more severe grade, if the dog develops clinical signs, or if irregular heart rhythms are detected, then tests may be done to evaluate the heart and other organs, such as:
Some dogs that are in severe distress from left heart failure require stabilization before testing is done.
TREATMENT AND FOLLOW-UP
Treatment Options
Treatment is usually started after clinical signs develop, because no drugs have yet been found that stop progression of this disease. Dogs with mild signs may be treated on an outpatient basis, but more severely ill dogs require hospitalization. A number of drugs are available for stabilizing heart failure, including injectable diuretics (such as furosemide) to decrease fluid in the lungs, vasodilators (such as nitroglycerine ointment, nitroprusside, or hydralazine) that decrease the heart’s workload, and oxygen therapy. Some fluid may be drained from the chest cavity or abdomen.
After heart failure is stabilized, long-term oral medications are started. Some of these drugs may also be used in dogs with mild clinical signs.
In addition to drug therapy, dogs with heart failure should not be fed salty foods, and low-salt diets may be used to limit salt intake. Although strenuous exercise is avoided, mild to moderate exercise may be done based on guidelines from your veterinarian.
Follow-up Care
Dogs with no clinical signs are commonly monitored with physical examinations every 6-12 months and yearly chest x-rays. If your dog develops problems breathing, notify your veterinarian immediately. Intensive monitoring is needed during hospitalization for heart failure. Following discharge, periodic recheck visits and testing are needed for the rest of the dog’s life.
Prognosis
Dogs with asymptomatic disease may live for years without developing clinical problems. The more severe the leak in the valve and the bigger the left atrium, the more likely it is that the dog will develop heart failure. The average survival time for dogs with heart failure is 8-10 months, but every dog varies in how it responds to treatment. Dogs with other diseases, such as kidney failure, tend to do poorly.
Cavalier King Charles spaniels and other small dogs that develop AV valve degeneration before 5 years of age should not be used for breeding.
BASIC INFORMATION
Description
Cardiac tumors arise from heart tissues (primary tumors) or metastasize to the heart from another location (secondary tumors). These tumors can interfere with normal heart function or cause bleeding into the pericardial sac (the sac around the heart). Decreased heart function may result in poor circulation and heart failure.
Causes
Primary tumors of the heart include hemangiosarcoma, heart base tumors, mesothelioma, rhabdomyosarcoma, fibrosarcoma, and lymphosarcoma. These tumors can also originate from other areas and metastasize to the heart. The cause of these tumors is unknown.
Hemangiosarcomas are highly malignant tumors of blood vessels. They often invade the wall of the right atrium—the small, upper chamber of the right heart. The tumor destroys the wall of the atrium and may bleed into the pericardial sac, causing pericardial effusion. (See also the handout on Pericardial Effusion.) Golden retrievers and German shepherd dogs are prone to develop hemangiosarcoma. Primary cardiac hemangiosarcoma has been reported in only one cat.
Mesotheliomas are small tumors that spread over the pericardial sac and chest wall. They can cause pericardial effusion that is lethal to dogs, but they are rare in cats. Lymphosarcomas, rhabdomyosarcomas, and fibrosarcomas occur in both dogs and cats. They often invade the wall of the heart, which decreases its ability to contract. They can also cause the heart valves to leak, in which the end result is heart failure.
Clinical Signs
Most animals with significant effusion have a sudden onset of lethargy, weakness, and collapse. Trouble breathing occurs in about half of affected dogs, and 23% have abdominal swelling. Loss of appetite, vomiting, or coughing may be noted. Signs associated with cancer in other organs may be present.
Diagnostic Tests
X-rays of the chest and abdomen are usually recommended. If an enlarged heart is seen on the x-rays, an echocardiogram (heart ultrasound) and an electrocardiogram (ECG) are done to differentiate pericardial effusion from other cardiac diseases. The echocardiogram also helps identify the presence of a tumor and its effects on the heart.
Laboratory tests and an abdominal ultrasound are often done to look for tumors in other organs and to evaluate their systemic effects. Some of these tests may be delayed until fluid has been removed from the pericardial sac and the animal is stable. Fluid may be submitted for analysis. Additional tests may also be indicated.
TREATMENT AND FOLLOW-UP
Treatment Options
If pericardial effusion is causing symptoms, it is removed by pericardiocentesis, which involves insertion of a catheter into the pericardial sac to drain the fluid. Removal of fluid helps prevent sudden death from cardiac tamponade, which is caused by poor filling of the heart due to severe fluid pressure.
Dogs with right atrial hemangiosarcoma are difficult to treat. Pericardiocentesis provides temporary relief, but the effusion returns in a short time. Surgical removal of the tumor and chemotherapy may be attempted in some cases. Dogs with heart base tumors benefit from removal of the pericardial sac, because these tumors grow very slowly. Treatment of other tumors depends on the tumor type and may involve removal of the pericardial sac and chemotherapy.
Follow-up CarePrognosis
Dogs with right atrial hemangiosarcoma have a median survival time of 56 days (range, 0-229 days). Pericardial mesothelioma also carries a grave prognosis. Prognosis is better for heart base tumors; average survival time is 730 days after removal of the pericardial sac or 42 days if no surgery is performed.
Dogs with cardiac lymphosarcoma that is stage III or higher have a poor prognosis for remission and survival. In a study of 12 dogs treated with removal of the pericardial sac and chemotherapy, the median survival time was 41 days. Three dogs did live 328 days or longer, so not all of them did poorly.
Cardiopulmonary Resuscitation
Rebecca E. Gompf, DVM, MS, DACVIM (Cardiology)
BASIC INFORMATION
Description
Cardiopulmonary resuscitation (CPR) is a group of procedures that are done to try to revive an animal whose heart has gone into ventricular fibrillation (heart is just vibrating, not beating) or has totally stopped (cardiac arrest). Once the heart stops beating normally, the animal also stops breathing (respiratory arrest); sometimes breathing stops first.
The first step in CPR is placement of a tube into the animal’s throat, so that artificial respiration (assisted breathing) can be done. At the same time, chest compressions are started in an attempt to circulate blood throughout the body, and an intravenous catheter is inserted so that drugs can be given to help stimulate the heart. An electrical shock (defibrillation) may be applied to stop the fibrillation and stimulate the heart to beat normally. In extreme cases, your veterinarian may decide to open the animal’s chest and squeeze the heart by hand so that blood begins to circulate. When the chest is open, drugs can be administered directly into the heart.
Causes
Many factors can cause the heart to stop or go into ventricular fibrillation, including serious diseases, certain drugs, drowning, electrocution, being struck by a car, certain toxins, and general anesthesia, among others.
Clinical Signs
An animal that has gone into cardiac arrest will suddenly collapse and stop breathing. The animal may also become rigid or have muscle twitching. A few gasps of breath may be seen, but there is no continuous breathing.
Diagnostic Tests
Listening to your animal’s heart with a stethoscope will identify that the heart is not beating. A lack of breathing may also be noted. CPR is started immediately, and an electrocardiogram (ECG) is performed to determine what heart rhythm is present.
Laboratory tests may be run throughout CPR to monitor the response to the procedures. If your animal is successfully resuscitated, then numerous laboratory tests, chest and abdominal x-rays, and other tests may be recommended to determine why your animal went into cardiac arrest and its effects on other organs.
TREATMENT AND FOLLOW-UP
Treatment Options
If CPR is successful, additional therapy is usually needed for the underlying cause of the arrest and is based on results of additional tests. Hospitalization is often required for several days following CPR so that the animal can be stabilized and treated.
Successful CPR is difficult to perform on animals that are not hospitalized. Some owners have been able to revive their animals by breathing for them when the animal has suffered only respiratory arrest. If the heart stops, then multiple individuals are needed, working as a team, to perform CPR successfully.
Follow-up CarePrognosis
Animals that experience only respiratory arrest have a better chance of being successfully resuscitated than if their heart also stops. Following cardiac arrest, the survival rate for dogs is only 4%, and for cats it is only 2%. These rates are low because most affected animals have serious underlying medical problems that cannot be easily corrected. In addition, most animals that have arrested once will have another cardiac arrest within a short time.
People who experience a cardiac arrest have about a 30% chance of being resuscitated successfully, but fewer than 20% of those individuals ever leave the hospital, because they also have serious underlying medical problems. The most successful CPR outcomes occur in people who have suffered drug overdoses, electrocution, or drowning.
Fictional television programs have given people the wrong expectations with respect to successful CPR. In most television shows, the person who has arrested is saved and leaves the hospital at the end of the show healthy and happy. This is not a realistic depiction of CPR in animals, because most do not survive a cardiac arrest.
Because the success rate of CPR is low in seriously ill animals, consider discussing with your veterinarian what you would like to have done if your animal arrests. You may elect not to have CPR performed on your animal if the underlying disease is extremely serious. This is always a difficult decision to make and a very personal one. Your veterinarian can give you the information that you need to make a wise, informed decision on whether you want CPR performed if your animal goes into cardiac arrest while hospitalized.
BASIC INFORMATION
Description
Left heart failure occurs when the left side of the heart is no longer working properly and cannot pump blood effectively to the body. Blood accumulates in the lungs and interferes with the ability of oxygen to enter the bloodstream. If left heart failure is not treated or if your dog does not respond to treatment, then death may occur from this accumulation of blood.
Causes
A number of diseases can cause left heart failure in dogs (see also the handouts on each of these conditions):
Clinical Signs
Dogs with left heart failure cannot exercise; they cough when lying down, and they may get up and pace after lying down. As signs worsen, they eventually start breathing faster (more than 50 times per minute) and with more effort. A loud heart murmur that can be heard with a stethoscope is a common finding on physical examination.
Diagnostic TestsTREATMENT AND FOLLOW-UP
Treatment Options
If the dog has moderate to severe left heart failure, it may be hospitalized for stabilization with injectable diuretics (such as furosemide), vasodilator drugs (such as nitroglycerin ointment, hydralazine, or sodium nitroprusside), and oxygen therapy. If the dog has mild heart failure, it may be managed on an outpatient basis. Dogs with left heart failure are very fragile and need aggressive treatment, with as little stress as possible. Once the dog is stable and breathing is improved, long-term oral medications are started, such as the following:
In addition to drug therapy, dogs with heart failure should not be fed salty foods, and low-salt diets may be used to limit salt intake. Although strenuous exercise should be avoided, mild exercise may be done based on guidelines from your veterinarian.
Follow-up Care
Intensive monitoring is often needed during hospitalization. Laboratory tests, chest x-rays, and other tests are often repeated until the dog is stable. Follow-up visits are usually scheduled within 7-14 days after discharge. Recheck visits may include chest x-rays and laboratory tests. The interval between visits and further testing depends on the underlying disease and how your dog responds to medications. Periodic monitoring is needed for the life of your dog. Notify your veterinarian if any signs of heart failure return while the dog is on therapy.
Congestive Heart Failure in Dogs, Right-Sided
Rebecca E. Gompf, DVM, MS, DACVIM (Cardiology)
BASIC INFORMATION
Description
Right heart failure occurs when the right side of the heart is no longer working properly and cannot pump blood effectively to the lungs and left heart. Fluid accumulates in the abdomen and the chest. Eventually, if right heart failure is not treated, breathing is affected and death may occur.
Causes
A number of diseases can cause right heart failure in dogs (see also the handouts on each of these conditions):
A disease that can mimic right heart failure is pericardial effusion. If a large amount of fluid builds up in the pericardial sac around the heart, the right heart does not fill properly, and fluid may accumulate in the abdomen.
Clinical Signs
Dogs with right heart failure cannot exercise. They develop abdominal distention and loss of muscle mass, which can be so severe that the back bones and ribs become prominent. When the abdomen is full of fluid, the dog may not be comfortable lying down and may breathe faster (more than 50 times per minute), with increased effort.
Diagnostic TestsTREATMENT AND FOLLOW-UP
Treatment Options
If there is a significant amount of fluid in the chest, it is usually removed so that the dog can breathe easier. Fluid may also be removed from the abdomen and from the pericardial sac to make the dog more comfortable.
Dogs with moderate to severe right heart failure may be hospitalized for stabilization with injectable diuretics (such as furosemide) and oxygen therapy. Once the dog is stable, oral medications are started. Which medications are chosen depends on the disease causing the right heart failure. Choices include the following:
In addition to drug therapy, dogs with heart failure should not be fed salty foods, and low-salt diets may be used to limit salt intake. Although strenuous exercise should be avoided, mild exercise may be done based on guidelines from your veterinarian. If heartworm disease is present, it will be treated once the right heart failure is stable.
Follow-up Care
Intensive monitoring is often needed during hospitalization. Follow-up visits are usually scheduled within 7-14 days after discharge. Recheck visits may include chest x-rays, laboratory tests, and ECGs. The interval between visits and further testing depends on the underlying disease and how your dog responds to medications. Periodic monitoring is needed for the life of your dog. Notify your veterinarian if any signs of heart failure return while the dog is on therapy.
Dilated Cardiomyopathy in Cats
Rebecca E. Gompf, DVM, MS, DACVIM (Cardiology)
BASIC INFORMATION
Description
Dilated cardiomyopathy (DCM) is a disease in which the heart muscle becomes flabby and weak and the heart chambers dilate. The heart cannot effectively pump blood to the body, so the cat lacks energy and fluid may accumulate in the lungs, chest cavity, or both. As the heart dilates, the valvular openings between the chambers of the heart enlarge and the valves begin to leak, which adds an additional burden on the heart. Abnormal heart rhythms (arrhythmias) are also common, especially atrial fibrillation and ventricular arrhythmias.
Causes
Taurine deficiency can cause a reversible type of DCM in cats. Taurine is an essential amino acid that must be supplied in the food of cats. Commercial cat foods are supplemented with taurine, so taurine-deficient DCM is uncommon unless the cat is on a vegetarian diet, is fed exclusively dog food or a single kind of canned cat food, or has a medical problem that interferes with absorption of taurine from the intestinal tract.
Idiopathic DCM occasionally occurs in cats, which means the cause is unknown.
Clinical Signs
Signs often develop suddenly in cats with DCM. Some of the early signs may be exercise intolerance, weakness, decreased appetite, and cold feet. Increased rate and effort of breathing (faster than 50 times per minute) may be the first sign noted by the owner. If a blood clot becomes lodged in one of the front legs or in both rear legs, those legs will be paralyzed and cold, with blue foot pads. Your cat also may also be in pain if the clot happened recently.
Diagnostic TestsTREATMENT AND FOLLOW-UP
Treatment Options
If moderate to severe heart failure is present, the cat is often hospitalized for stabilization with injectable diuretics (such as furosemide), oxygen therapy, removal of fluid from the chest, and other measures. After the cat is stable, oral medications are started and may include the following:
Cats with heart failure should not be fed salty foods, and low-salt diets may be used to limit their salt intake. Some cats do not like to eat low-salt diets, however. All cats with DCM are started on taurine supplementation, because some cats with normal taurine blood levels respond to taurine supplementation. If the left atrium is enlarged, medications may be started to prevent blood clots from forming. Baby aspirin has been used for many years for this purpose, and clopidogrel (Plavix) may also be beneficial.
Follow-up CareDilated Cardiomyopathy in Dogs
Rebecca E. Gompf, DVM, MS, DACVIM (Cardiology)
BASIC INFORMATION
Description
Dilated cardiomyopathy (DCM) is a disease in which the heart muscle becomes flabby and weak and the heart chambers dilate. The heart cannot effectively pump blood to the body, so the animal lacks energy and fluid accumulates in the lungs, abdomen, or both.
As the heart dilates, the valvular openings between the chambers of the heart enlarge, and the valves begin to leak, which adds an additional burden on the heart. Abnormal heart rhythms (arrhythmias) are also common, especially atrial fibrillation and ventricular arrhythmias.
Causes
DCM is more common in large and giant breeds of dogs and in the American cocker spaniel. In most cases, no exact cause is found (idiopathic), but the disease is inherited as an autosomal dominant characteristic in certain families of boxers and Doberman pinschers.
Nutritional deficiencies of taurine and L-carnitine may cause DCM in American cocker spaniels. Taurine deficiency may also cause DCM in the golden retriever and Newfoundland. Less common causes of secondary cardiomyopathy include myocarditis (an inflammation of heart muscle), hormonal problems (hypothyroidism, hypoadrenocorticism, hyperthyroidism), and high doses of the chemotherapeutic drug doxorubicin.
Clinical Signs
Signs often develop suddenly in dogs with DCM. Some of the first signs are exercise intolerance, weakness, and cold feet. Coughing, loss of appetite, and increased rate and effort of breathing may occur. Abdominal distention with fluid and loss of muscle mass may be noted.
Diagnostic Tests
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