Glendale Animal Hospital - The Family Veterinarian

CARDIOVASCULAR DISEASE

The heart is a muscular organ located in the thorax of the dog. It, along with the arteries which carry blood away from the heart and the veins which carry blood back to the heart, comprise the cardiovascular system. The heart itself serves as the pump to move blood to and from as described above. In general, this system carries oxygen and nutrients to the tissues of the body and carbon dioxide and wastes so that they can be excreted from the body. This system also transports hormones in the body and maintains body temperature.

The heart pumps blood to the lungs each time it beats. There, carbon dioxide is released and the blood absorbs oxygen. Once oxygenated, the blood returns to the heart where it is ready to be pumped to the tissues of the body. To supply itself with blood, the heart has its own circulation system called the coronary arteries and veins.

Diseases of the heart are common in the dog. While dogs infrequently suffer from heart attacks like humans, valvular insufficiencies and congestive heart disease is common in older canines. As mentioned, the heart is a muscle, but it has a unique system of nerves to control its contractions and valves to direct blood flow. Interruption of any of these components can lead to cardiac disease.

 

ARRHYTHMIA (DYSRHYTHMIAS)

When nerve conduction is altered in the heart, the rate and rhythm of the heart can vary from normal and an arrhythmia occurs. Some arrhythmias may be mild and go undetected while others can lead to heart failure and death if not properly treated. Nodes within the heart act like electrical pacemakers, directing and regulating how the heart beats. Stimuli produced by these nodes are carried to the muscular tissue by their own small nerves, but it is important to understand that the central nervous system, chemicals in the blood and hormones can alter this process.

Arrhythmias may be caused by infections of the heart, congenital heart defects, diseases of the heart muscle, trauma, neoplasia of the cardiovascular system, neurologic disorders, endocrine disease, infections elsewhere in the body, digestive system disease, electrolyte disturbances, drugs, toxins and other external insults. With so many possible causes, cardiac arrhythmias are a challenge for your veterinarian to diagnose and to treat. Clinical signs of arrhythmia may be nonexistent or so mild as to be easily overlooked. Dogs with symptoms will exhibit weakness which may seem to come and go, inability to perform routine levels of exercise, collapse or fainting spells (syncope), troubled breathing or a cough and possibly a swelling of the abdomen. Some dogs may die without warning or any hints of illness!

Other types of cardiovascular disease may mimic the signs of arrhythmia and as other diseases may produce heart dysfunction, a thorough diagnosis is very important. A thorough history, the clinical signs, chest X-ray, EKG analysis, blood, serum, urine testing and cardiac ultrasound are often all needed to properly diagnose the cause of the arrhythmia.

There are many different types of arrhythmia, a description of which is far beyond the scope of this program, although several simplified groupings are available. Bradyarrhythmias occur when some part of the heart rate becomes slower than normal. Tachyarrhythmias occur when some part of the heart rate is faster than it should be, and Conduction Disturbances include a variety of irregularities consistent with grossly altered conduction of nerve impulses within the heart. It is important to note that all these disturbances can lead to cardiac arrest and death unless CPR and other appropriate measures are taken to save the dog. 

TREATMENT OF ARRHYTHMIA

Treatment of this problem is no simple task. A most exacting diagnosis is critically important so that the cause can be addressed directly and not by trial and error. If secondary conditions are present, these should be addressed first as often the arrhythmia will disappear as this other problem becomes resolved or controlled.

There is no one exact medication to treat each and every arrhythmia as each is unique in nature and similar dysfunction will often produce variable degrees of clinical illness. Your veterinarian will best be able to select appropriate medications, but there are a wide variety of possible drugs that can be utilized. Some of these include the following: digitalis, furosemide, captopril, hydralazine, lidocaine, propranolol, atropine and theophylline. The appropriate combinations will have to be carefully individualized for each dog and regular follow-up care will be important to keep the condition under control.

 

VALVULAR DISEASES

ENDOCARDIOSIS

Endocardiosis involves thickening and degeneration of the heart valves, often the mitral valve, due to aging/normal wear and tear on the valve; the exact cause of this condition remains unknown. Related structures may also become thickened and nodular as well. When this occurs, blood will leak "backwards" during each heart cycle creating a sound called a murmur. How loud the murmurs is and where it is located will often reflect how much degeneration has occurred. Clinical signs will include heart murmur and possible signs of congestive heart failure. Diagnosis can be made with X-rays and ultrasonography. ((Endocardiosis))

TREATMENT OF ENDOCARDIOSIS

There is no treatment for endocardiosis, nor is any treatment indicated unless congestive heart failure occurs.

 

BACTERIAL ENDOCARDITIS
Inflammation and infection of the lining of the heart, usually involving the heart valves. Infectious agents, usually bacteria, often staph or strep; occasionally Rickettsia or Bartonella in dogs.  On rare occasion fungi and brucellosis may cause this type of infection.

Most often seen in medium to larger dogs; rarely cats.  Most affected dogs are 4 to 6 years of age but infection can occur at any age 
Males are more likely to be affected than females—may be as great as a 2:1 ratio of males-to-females 

CLINICAL SIGNS
The presence of gram-negative bacteria in the blood (known as “gram-negative bacteremia”) results in very sudden (known as “peracute”) or sudden (known as “acute”) clinical signs; the presence of gram-positive bacteria in the blood (known as “gram-positive bacteremia”) results in signs over a moderate amount of time (known as “subacute”) or long-term (known as “chronic”) 
Generalized (systemic) signs are secondary to sudden lack of blood supply that leads to death of tissues (known as “infarction”), infection, or damage due to the body's immune response; usually override heart signs (such as congestive heart failure [CHF] and/or irregular heart beats [arrhythmias]); congestive heart failure is a condition in which the heart cannot pump an adequate volume of blood to meet the body's needs—CHF signs include cough; difficulty breathing (known as “dyspnea”); bluish discoloration of the skin and moist tissues (mucous membranes) of the body caused by inadequate oxygen levels in the red-blood cells (known as “cyanosis”) 
May have had signs of infectious disease involving the mouth, gastrointestinal tract, and/or genital tract (such as inflammation/infection of the prostate [prostatitis]) within the past few weeks to several months in some patients 
Animal may have signs of other diseases and/or history of factors that increase the likelihood of infection of the lining of the heart, such as being on medications to decrease the immune response (known as “immunosuppressive drug therapy”), narrowing of the aortic valve, the heart valve from the left ventricle to the aorta (the main artery of the body; condition known as “aortic stenosis”), recent surgery, infected wounds, abscesses, or skin infection characterized by the presence of pus (known as “pyoderma”) 
Sluggishness (lethargy) 
Weakness and/or lameness 
Fever 
Lack of appetite (known as “anorexia”) 
Stomach and/or intestinal disturbances 
General signs of discomfort and “not feeling well” (known as “malaise”) 
Difficulty breathing (dyspnea) caused by congestive heart failure (CHF); congestive heart failure is a condition in which the heart cannot pump an adequate volume of blood to meet the body's needs 
Irregular heart beats (arrhythmias) 
Single or shifting-leg lameness; “shifting-leg” lameness is characterized by lameness in one leg, then that leg appears to be normal and another leg is involved 
Heart murmur 
CAUSES
Bacterial infection associated with the mouth, bone, prostate, skin, and other sites 
Diagnostic or surgical procedures that may lead to introduction of bacteria into the bloodstream 
RISK FACTORS
Congenital (present at birth) heart defect involving narrowing just below the aortic valve, the heart valve from the left ventricle to the aorta (the main artery of the body; condition is “subaortic stenosis”) 
Decreased ability to produce a normal immune response (known as “immunosuppression”) from treatment with long-term or high-dose steroids or secondary to cancer or administration of chemotherapy 
Treatment
HEALTH CARE
Virtually all animals with suspected inflammation/infection of the lining of the heart, usually involving the heart valves (infective endocarditis) should be hospitalized 
Good hydration for patients with generalized bacterial infection (known as “septic patients”), particularly those receiving a particular class of antibiotics (known as an “aminoglycoside”) 
Aggressive fluid therapy—for patients with kidney failure 
Actual or impending (that is, about to occur) congestive heart failure (CHF) limits fluid volumes that can be administered; this problem is virtually insurmountable in patients with coexistent kidney failure 
Impending (that is, about to occur) congestive heart failure (CHF)—cautious use of fluid therapy 
ACTIVITY
Variable—depends on whether or not congestive heart failure (CHF) is present or impending (that is, about to occur)
DIET
Moderate sodium restriction if congestive heart failure (CHF) is present or impending (that is, about to occur)
SURGERY
Inflammation/infection of the aortic valve (aortic valve endocarditis)—almost always results in left-sided congestive heart failure (CHF) that is difficult to control medically; congestive heart failure is a condition in which the heart cannot pump an adequate volume of blood to meet the body's needs; surgery to replace the aortic valve is indicated—this surgical procedure routinely is performed in human medicine, but rarely attempted in veterinary medicine because of lack of expertise, lack of facilities, and high cost
Medications
Medications presented in this section are intended to provide general information about possible treatment. The treatment for a particular condition may evolve as medical advances are made; therefore, the medications should not be considered as all inclusive.
Treatment is variable—depends on severity of generalized bacterial infection (sepsis) and presence or absence of congestive heart failure (CHF); congestive heart failure is a condition in which the heart cannot pump an adequate volume of blood to meet the body's needs 
ANTIBIOTICS
Backbone of treatment, but usually don't eradicate infection before irreversible heart-valve damage occurs; more than minimal damage to the aortic valve is life-threatening 
High-dose, intravenous (IV) administration of antibiotics designed to kill bacteria (known as “bactericidal antibiotics”) is imperative and recommended for as long as feasible, followed by subcutaneous (SC or under the skin) administration 
Antibiotics administered by mouth—recommended only after at least 4 weeks of injectable therapy and at least 1 week after blood work changes and clinical signs of inflammation and infection have disappeared; long-term (greater than 4 months) treatment required to eradicate the infection from abnormal or damaged heart valves 
Antibiotic selection determined by both the urgency of complications of the generalized bacterial infection (sepsis) and results of bacterial culture; coagulase-positive staphylococci and streptococci are incriminated most often as causing the disease, so choices of antibiotics can be made logically before bacterial culture results are obtained 
Coagulase-positive staphylococci—usually resistant to penicillin and ampicillin 
Streptococci—often resistant to aminoglycosides and fluoroquinolones 
Gram-negative bacteria—often sensitive to third-generation cephalosporins, fluoroquinolones, and aminoglycosides 
Bartonella—only aminoglycosides appear bactericidal; can try doxycycline, fluoroquinolone, rifampin, or azithromycin 
First-generation cephalosporins—reasonable choice for stable patients until bacterial culture results are obtained 
Treat life-threatening, generalized bacterial infection (sepsis) immediately with drug combinations; pending bacterial culture results, one of three regimens is recommended: (1) penicillin, ampicillin, ticarcillin, or a first-generation cephalosporin combined with an aminoglycoside—high doses of aminoglycosides cannot be administered, and fluid support with monitoring for kidney toxicity (side effect of aminoglycosides) is required; thus aminoglycosides are not good choices for animals with overt or impending (that is, about to occur) congestive heart failure (CHF) or those with kidney failure; (2) clindamycin plus enrofloxacin; (3) advanced-generation cephalosporins or ticarcillin-clavulanic acid (Timentin®)—high dosages, but only normal dosages if patient has kidney failure 
TREATMENT OF CONGESTIVE HEART FAILURE (CHF)
Various heart medications (such as pimobendan, angiotensin-converting enzyme [ACE] inhibitors, and amlodipine) and medications to remove excess fluid from the body (known as “diuretics,” such as furosemide) are indicated for patients with long-term (chronic) congestive heart failure (CHF); congestive heart failure is a condition in which the heart cannot pump an adequate volume of blood to meet the body's needs 
Oxygen, nitroglycerin, high-dose furosemide, and hydralazine for patients with sudden (acute), severe fluid build-up in the lungs (known as “pulmonary edema”) 
“Blood thinners” or medications to prevent the development of blood clots (known as “anticoagulant therapy”) may be used 
Aspirin and/or dalteparin may reduce the spread of the bacteria and prevent the development of blood clots 
Heparin can be used in the hospital setting to decrease the likelihood of blood-clot formation 
Follow-Up Care
PATIENT MONITORING
Emergence of antibiotic resistance—relapsing fever and changes in the white-blood cell count indicating inflammation; imperative to adjust treatment on the basis of bacterial culture results 
Weekly physical examination and complete blood count (CBC) after discharge 
Repeat blood cultures 1 week after antibiotics are discontinued or if fever recurs 
PREVENTIONS AND AVOIDANCE
Indwelling catheters—restrict to appropriate usage; place intravenous (IV) catheter into vein using sterile technique (known as “aseptic placement”); replace IV catheter within 3 to 5 days 
Administer antibiotics to animals undergoing dentistry—controversial, except in animals with congenital (present at birth) heart defects and infections of the mouth 
Avoid careless use of steroids 
POSSIBLE COMPLICATIONS
Congestive heart failure (CHF), condition in which the heart cannot pump an adequate volume of blood to meet the body's needs 
Kidney failure 
Presence of infected blood clots in many tissues and organs 
Persistent or dormant diseases of several joints caused by an immune response (known as “immune-mediated polyarthropathy”) 
EXPECTED COURSE AND PROGNOSIS
Best prognosis associated with short history of bacteria in the blood (bacteremia), rapid diagnosis, and aggressive treatment 
Death rate relatively higher in animals recently given steroids 
Grave prognosis for most patients with inflammation/infection of the aortic valve (aortic valve endocarditis); the aortic valve is the valve from the left ventricle to the aorta (the main artery of the body) 
Dormant congestive heart failure (CHF) may develop months to years later with inflammation/infection of the mitral valve (mitral valve endocarditis); the mitral valve is the heart valve between the left atrium and the left ventricle 
Key Points
Inflammation and infection of the lining of the heart, usually involving the heart valves 
Grave prognosis if the aortic valve is involved; the aortic valve is the valve from the left ventricle to the aorta (the main artery of the body) 
Guarded prognosis if only the mitral valve is involved; the mitral valve is the heart valve between the left atrium and the left ventricle 

Infections in other parts of the body easily enter the blood stream and as all blood eventually passes through the heart, these bacteria may become deposited on the valves and lining tissues of the heart and begin an infection there. Valves become damaged and begin to leak blood and ultimately congestive heart failure will result.

Infections of the uterus and prostate, dental infections, skin infections, pneumonia and infections after medical or surgical care can all lead to this condition. The clinical signs can mimic other conditions and include fever, weakness, heart murmur, vomiting, poor appetite, lameness and congestive heart failure signs. Some animals may become ill and die of heart failure in a short period of time. Diagnosis is based on history or suspicion of infection, clinical signs, blood cultures, X-rays, blood counts and serum chemical analysis. EKG and ultrasound analysis may also be helpful in establishing the diagnosis. ((Endocarditis))

TREATMENT OF BACTERIAL ENDOCARDITIS

If proper diagnosis and culture of the attacking organisms is made, then general antibiotic therapy specific for the organism should be effective. The after effects of the infection such as arrhythmia or congestive heart failure may, however, require therapy specific for these conditions.

 

CONGESTIVE HEART FAILURE

Heart failure occurs when or as the heart is unable to properly circulate blood throughout the body and the heart becomes unable to meet increased demand placed upon it during exercise. The causes of congestive heart disease are numerous as most any condition that damages the heart or part of the heart in some way will ultimately produce this condition. These include valvular diseases, cardiomyopathy, congenital diseases/defects, arrhythmia, heartworm disease, pericardial diseases and cardiac neoplasia. Diseases of the respiratory system can also produce failure of the heart.

The heart is divided into two sides. The right side is responsible for receiving blood from the body and pumping it to the lungs; the left side is responsible for receiving blood from the lungs and pumping it back through the tissues of the body. The clinical symptoms of heart disease will vary depending on which side (both sides can be affected) of the heart is dysfunctional.

Right-sided heart failure will generally produce clinical signs that include weakness, fainting, inability to exercise, enlargement of abdominal organs and possibly the collection of fluid within the abdomen (ascites), distention of the veins and swelling to the feet and lower legs. These symptoms occur as venous blood cannot flow back to the heart readily and "pools" in the extremities and abdominal cavity.

Left-sided heart failure with often produce signs of weakness, fainting, decreased urination, coughing, difficulty breathing, sometimes rapid breathing and possibly a blue or purple discoloration to the gums and tongue (cyanosis). Some dogs may find it difficult to get comfortable and lie still. These symptoms occur as fluid builds up in the lung tissues causing pulmonary edema.

Dogs with Generalized heart failure (both sides) will then often exhibit some combination of the symptoms noted above. Generalized and non-specific signs of these conditions may also manifest including weight loss, poor appetite and loss of muscle mass and condition. Diagnosis is based on physical exam, history of the symptoms, X-rays, ultrasonography, blood counts and serum chemistries, EKG analysis and blood pressure measurements. 

TREATMENT OF CONGESTIVE HEART FAILURE

While it should be understood that most all cases of heart failure result in death of the dog (not many heart transplants are given to canines each year), many patients can live for years and have a high quality of life with proper treatment and monitoring. Unless treating a specific underlying condition such as a bacterial endocarditis, most therapy centers on controlling the symptoms or problems produced as the heart fails.

Many patients are given a diuretic such as furosemide to help remove fluid from the lungs and organs. Drugs such as nitroglycerin or hydralazine are used to dilate blood vessels and decrease the pressure against which the heart must pump. Drugs such as Captopril or Enalapril also are used to dilate blood vessels and remove fluids and are sometimes used in combination with the aforementioned agents.

Digitalis is often employed in more chronic cases of heart failure or as the overall condition of the dog worsens. This drug improves the strength with which the heart pumps and tends to slow the heart to a more regular beat. It can be used with other medications, but it must be carefully administered to avoid toxic side effects. Oxygen therapy may be given to some dogs and low sodium diets are available to further limit fluid accumulation.

Overall, the best combination and dosage of drugs used for every dog will vary with the chronically and severity of the disease AND the response of the dog to the therapy. Most dogs with advanced heart failure will also be unable to exercise at a normal level. Even if mentally they desire the long walk or play session, the stress which exercise places on the heart should be clearly understood and thusly limited by the owner.

The long-term prognosis for each patient, irrespective of those with rapidly progressive disease, can be enhanced by regular follow-up care with the veterinarian. Blood tests to monitor serum electrolytes and detect early evidence of drug toxicities or organ failure, repeated X-rays or EKG's to access heart function and general physical examinations all greatly help dogs with this disease live longer and happier lives. Again, it must be understood that at some point, the degree of heart failure may become too advanced, or general organ failure may ultimately overtake even the best of patients.

 

DISEASES OF THE HEART MUSCLE

CARDIOMYOPATHY

In short, cardiomyopathy is a serious and often fatal dysfunction of the heart muscle that produces abnormal contractility of the heart muscle, thus altered pumping of the heart. Two forms of cardiomyopathy are commonly recognized: Dilated Cardiomyopathy, where the heart becomes grossly distended and congestive heart failure ensues; Hypertrophic Cardiomyopathy which describes an abnormal thickening of the muscle of the left ventricle of the heart. The exact causes of these conditions are unknown, but German Shepherd Dogs, Great Danes and Doberman Pinschers are more commonly affected suggesting a genetic relationship.

Clinical signs may be similar to other cardiac conditions and include weakness, poor appetite, weight loss, a rapid, labored breathing, coughing, swelling to the abdomen or extremities, fainting episodes and sudden death. Some dogs may display no symptoms before a sudden and often severe onset of the disease. This condition, again, often appears similar to many other diseases of the heart. Diagnosis is based on history, physical examination, EKG testing, X-rays, Echocardiograms and complete blood and urine testing.

TREATMENT OF CARDIOMYOPATHY

Treatment for most dogs is partially similar to that of congestive heart failure and the extent of treatment will depend on the severity of the disease and the associated clinical signs. Most dogs will need rest and avoidance of any stressful activity. A low sodium diet is also important. Digitalis, diuretics such as furosemide and other drugs are all employed. Careful monitoring of the patient and organ function tests and EKG analysis are all needed to monitor the health of the dog as time goes by. Dogs with dilated cardiomyopathy may have a slightly better survival rate than dogs with the hypertrophic form. Overall, however, long-term survival is not likely.

 

MYOCARDITIS

Myocarditis denotes inflammation of the heart muscle, vessels and lining tissues. It can be caused directly by infectious organisms such as bacteria, parvovirus, canine distemper virus, toxoplasmosis and aspergillosis, or secondary to other diseases such as endocrine disease, kidney disease, electrolyte disturbances, toxins and chemicals including drugs. As every drop of blood must pass through the heart, the organ is highly susceptible to attack from most anything.

Attack of the heart muscle can lead to arrhythmia and congestive heart failure. If infection of the heart is occurring, the condition will most often come on suddenly, accompanied by fever, lethargy, weakness, coughing and trouble breathing and other symptoms related to the disease or condition that lead to the inflammation of the heart. When the condition is secondary to other diseases, the cardiac disruption needs to be viewed in relation to that disease process and correction thereof will often lead to improvement in heart function.

Diagnosis is based on all the clinical signs, X-rays, EKG testing, blood counts, serum chemical analysis, urinalysis and any testing specific to other diseases which may effect the heart. Diagnosis is difficult and cooperation with your veterinarian will provide the best opportunity to spot the primary cause and render treatment that will allow the heart muscle and related tissues to heal. Treatment is, therefore, specific for the condition that actually damaged the heart and for the complications left afterwards.

 

PERICARDIAL DISEASE

The pericardium is a thin sac that surrounds the heart as it sits inside the chest. The most common conditions of this tissue relate to some type of fluid building up inside the sac and restricting the normal movement (beating) of the heart muscle. On occasion scar tissue may form on the tissue and also limit heart motion. The build-up of fluid is called Pericardial Effusion; when that restricts heart activity, the term Tamponade is used; and when fibrous tissue causes the restriction it is termed Constrictive Pericarditis.

These conditions are all rare and can be caused by various types of infection, foreign objects that get into the chest, tumors of the heart, or most commonly, for no certain reason at all. Clinical symptoms include lethargy and weakness, troubled breathing, cough, fluid collecting in the abdomen (ascites), fainting and even sudden death. Diagnosis is accomplished through physical examination, EKG analysis, X-rays and echocardiography. Blood counts, serum chemistry and other specialized tests may be needed to diagnose the primary cause of the disease.

TREATMENT OF PERICARDIAL DISEASE

As with other cardiac conditions, careful identification and treatment of any primary condition is essential. Placing a needle in between the pericardium and the heart to drain off any fluid is always indicated. Many cases can be cured after 1 or 2 treatments. In some cases, surgical removal of part of the pericardium will be required. This involves opening the chest and doing surgery around the heart and lungs. This treatment is also effective for restrictive pericarditis.

 

HEARTWORM DISEASE

Canine heartworm disease is a heart and circulatory disorder caused by the worm parasite Dirofilaria immitis. This parasite is recognized worldwide and can infest domestic and wild dogs and a few other species (not man). These worms exist in the heart and large blood vessels of the dog and reproduce by releasing tiny immature larvae into the blood. These larvae are called microfliaria and may remain in the blood for years.

When a mosquito bites one of these infected dogs and ingests blood, some of these microfilaria are also ingested. Once inside the mosquito, the larvae further develop into infective larvae and after this, when the mosquito bites another dog, some of these larvae will pass into and under the skin of that dog. Once inside the dog, these larvae further develop and migrate towards the circulatory system through body tissues. Finally, after about 6 months, they reach the heart and pulmonary blood vessels where they "settle in" and as adults, repeat the life cycle, with some adult worms living for up to 8 years inside the heart. It is these adult worms that cause the damage associated with actually having heartworm disease. ((Heartworms)) ((Heartworm Lifecycle)) ((Map of Heartworm Disease))

The presence of the worms can damage the blood vessels which lead from the heart to the lungs (pulmonary circulation), the heart muscle and internal heart valves. Blood flow is then restricted and the heart must work harder to pump, leading to heart disease including congestive heart failure. It is also not uncommon for pieces of worms or blood clots to damage lung tissues as well. Also, in some cases, the number of worms may become so great as to block blood flow from the liver and leading to liver failure. Other complications of this disease include glomerulonephritis and hemolytic anemia.

Clinical signs, it should be noted, often occur YEARS after infestation, so regular testing and prevention is more important than waiting for trouble to begin. Clinical signs include coughing, fatigue, weakness, fainting, weight loss, spitting up blood and pale gums. If liver failure syndrome occurs, clinical signs would then reflect that condition as well. Diagnosis is based on physical examination, chest and abdominal X-ray, echocardiography, EKG testing, blood counts and direct and "indirect" heartworm tests which can detect the disease from/in blood.

Prevention of heartworm disease is important in most areas. Dogs should all have an annual blood test to detect the presence of any worms and if not infected, a monthly pill can prevent the disease from ever becoming established in your dog.

TREATMENT OF HEARTWORM DISEASE.

Treatment is of concern, as killing the worms too quickly can produce massive thromboembolism (clots) in the lungs and kill the dog. After a thorough evaluation, most dogs are hospitalized and placed on intravenous fluids; then 4 injections of an arsenic-containing drug are given over a 2-day period. Other medications may be used to minimize side effects of killing the worms. If the patient does well, a few weeks later treatment is also given to eradicate any microfilaria, which still inhabit the bloodstream. A new treatment, using the drug melarsomine is now on the market, which promises to increase the level of safety of treatment and still effectively kill the heartworms. This drug often has fewer side effects and requires a lessor level of care for the dog.

 

THROMBOEMBOLISM

Thromboembolism involves clots that break free from where they form in the heart, aorta or other great vessels and then lodge in smaller vessels causing circulatory restriction. Most commonly, this is secondary to congestive heart failure or valvular heart disease in which larger clots can easily form. Occasionally after trauma or other injury clots may form while the patient is trying to heal.

Symptoms include a very sudden onset of pain to a limb or in the abdomen, weakness, fainting, difficulty breathing and possibly neurologic signs if the clot affects some area of the brain or nervous system. Sudden death in some cases can occur. Diagnosis is quite difficult and can be based on clinical signs, physical examination, history of trauma or heart disease, blood counts and serum chemistries, X-rays, ultrasound testing and a neurological evaluation if needed. Unfortunately, sophisticated testing needed to accurately diagnose this problem is often unavailable.

TREATMENT OF THROMBOEMBOLISM

Caught and diagnosed early, thromboembolism can be treated with blood-thinning drugs, drugs to dilate the blood vessels, IV fluids to maintain circulation and medications to control pain. New fibrinolytic drugs can be used in some cases to dissolve clots. Long term care in dogs deemed susceptible to having embolism problems include the use of aspirin, coumadin or heparin to deter blood clotting. Careful and regular monitoring of these patients will also be required.

 

PATENT DUCTUS ARTERIOSUS

In the unborn animal, there is an interconnection between the pulmonary artery and the aorta near the heart. This allows blood to bypass the normal flow through the lungs, as the lungs are not needed nor used by the fetus. After the dog is born, this connection will, in most cases, close down in a few days or weeks, with all blood pumping through the lungs to be oxygenated. On occasion, this does not happen and a patent ductus arteriosus is then said to be present.

This is the most common congenital heart defect. It is considered to be hereditary, so dogs with the condition should not be bred. It is more common in females; Poodles, German Shepherd Dogs, Collies, Yorkies and Pomeranians seem most commonly affected. When the defect is present after birth, blood to be pumped to the body flows backward into the pulmonary circulation and blood to be pumped to the lungs (unoxygenated) can flow towards the body circulation.

Clinical signs include a very loud and machine-like murmur heard on auscultation of the chest by the veterinarian, cough, blue gums and tongue (cyanosis), rear leg weakness and ultimately death. Many dogs can live a few years with the defect as long as stress and the amount of exercise is kept to a minimum. Diagnosis is based on these physical findings, EKG analysis, X-rays and on occasion special X-rays where dye is run through the heart while taking the X-rays. ((PDA))

TREATMENT OF PATENT DUCTUS ARTERIOSUS

If caught early and no decompensation of heart function has/is occurred, then surgical ligation (meaning to simply tie off) of the patent ductus will produce a complete cure and the dog can have a normal lifespan. Without treatment, most dogs die before the age of 4. This does, however, mean that the pet will undergo open-heart surgery.

 

PERSISTENT RIGHT AORTIC ARCH

Right aortic arch is a rare abnormality where the aorta forms on the side opposite where it normally forms; the ductus arteriosum (as in patent ductus arteriosus) acting like a rubber band, traps the esophagus between the aorta and the pulmonary artery thus blocking the flow of food from the mouth to the stomach. ((PRAA))

Most common in the Great Dane, Doberman Pinscher, German Shepherd Dog and the Irish Setter, pups usually do well until they begin to eat solid foods at which time the main symptom includes regurgitation of food almost as soon as it is swallowed. Most dogs have a great appetite and want to eat, but are thin, as they are unable to ingest any food. Some dogs may aspirate (breathe in) vomit and suffer from aspiration pneumonia which certainly complicates this situation. Diagnosis is based on the history, clinical signs and having the dog eat food laced with barium and taking X-rays to elucidate the blockage.

TREATMENT OF PERSISTENT RIGHT AORTIC ARCH

Properly diagnosed early in select patients, this problem is correctable with surgical ligation and separation of the remnant of the ductus arteriosus, thus freeing the esophagus from its constriction. These patients will generally not survive without this type of surgery. This would require opening the chest and performing surgery around the heart.

 

HEART DEFECTS

Various types of heart defects may be diagnosed, in young puppies primarily. Valvular defects include Aortic Stenosis, Pulmonary Stenosis and Tricuspid Stenosis; all involve a narrowing of the specific valve, a restriction of blood flow and backwards pressure within the heart. Septal defects involve a hole or opening between chambers of the heart where no such opening should exist. These include Atrial Septal Defect and Ventricular Septal Defect. Patent ductus arteriosus is another common heart defect.

In early cases, no clinical signs may exist, with an unusual murmur being noted by the doctor upon physical examination. Allowed to persist, most result in congestive heart failure with the clinical signs matching the side of the heart that is failing. Diagnosis is based on ultrasonography and clinical signs, or necropsy is the animal does not survive. Usually no treatment is undertaken as open-heart surgery, rarely done in dogs, would be needed.

 

SHOCK

Shock is mentioned many times throughout this program, as there are many conditions that can lead to shock. By definition, shock is a failure of the general circulation; that is, the flow of blood becomes decreased far below what is optimal for life. It is not one disease or simple process, but rather, a complex, multifaceted and dynamic process. A discussion of shock could cover many pages. For most people, it is simply important to understand that the circulation is not occurring as designed or that blood is not flowing properly through the body in a "shocky" dog.

Several different sub-classifications of shock will help further understand the problem.

Hemorrhagic shock occurs when blood, for some reason, is lost from the system. There then is less blood available to pump through the body. Hypovolemic shock is said to occur from any disease that leads to dehydration, which is a lack of water in the system. Cardiogenic shock occurs when the heart, for any reason, fails to pump the blood through the body properly.

Septic shock or blood poisoning occurs when massive infection enters the blood. Dilation of blood vessels then occurs causing blood to pool in the tissues and not return to the heart for pumping. Anaphylactic shock occurs when an allergic reaction dilates all the blood vessels and again, blood pools away from the heart. Several other forms of shock are also recognized.

All forms of shock will generally lead to signs of profound weakness, cool skin temperature, pale gums and other mucus membranes, a rapid heart rate, rapid, shallow respiration, decreased mental responsiveness and a decrease in core body temperature. Dogs with septic shock may have a fever. Left untreated, shock leads to heart failure and death. Diagnosis is based on history, physical examination, blood counts and blood pressure measurements.

TREATMENT OF SHOCK

The basic aim in treatment of all forms of shock is to restore normal circulation. Generally, IV fluids and electrolytes, bicarbonate injections, injections of cortisone-like drugs, antibiotics for sepsis and oxygen therapy will work towards that end. Warming the patient and the mechanical support of respiration may also be needed. It should be remembered that any initiating factor must be addressed in addition to general treatment and that if organ damage has occurred due to circulatory failure, further complications will be expected.