Endocarditis in Dogs

Overview of Canine Endocarditis

Endocarditis is a serious infection involving the valves of the heart that can occur in dogs. It is usually a bacterial infection, although on rare occasions fungal infections can occur.

This condition is uncommon in dogs, and very rare in cats, and the incidence of disease increases as dogs get older. Male dogs are at slightly greater risk than females, and any breed may be affected. Previous procedures that could introduce bacteria into the blood stream, such as dentistry or intravenous catheterization, or that suppress the immune system, such as administration of glucocorticoids, may predispose dogs to the development of bacterial endocarditis. Pre-existing heart disease also increases the risk of developing endocarditis.

Because it is so uncommon, it is often overlooked and misdiagnosed with dire consequences, as the disease is often fatal.

What to Watch For

• Fever
• Anorexia
• Malaise
• Coughing
• Shortness of breath
• Weakness
• Collapse

Diagnosis of Endocarditis in Dogs

• Thorough history and physical exam on your dog
• Cardiac ultrasound
• Electrocardiography (EKG)
• Chest X-rays
• Blood cultures

Treatment of Endocarditis in Dogs

Treatment of endocarditis may include the following;

• Antibiotics
• Anti-arrhythmics (drugs that control abnormal heart rhythms)
• Drugs that treat congestive heart failure, such as diuretics, cardiac glycosides, vasodilators, and angiotensin converting enzyme inhibitors
• Drugs that treat shock like glucocorticoids

Home Care and Prevention

Administer all antibiotics as prescribed. If congestive heart failure has developed, administer all cardiac medications and/or prescription diets as recommended by your veterinarian.

Antibiotics are recommended if a dog with a previously diagnosed heart condition is going to undergo a procedure that might introduce bacteria into the bloodstream. This is a controversial preventative measure, however.

In-depth Information on Endocarditis in Dogs

Endocarditis is an often fatal disease caused by an infection of the heart valves. The infection is usually caused by bacteria, although fungal endocarditis can occur as well on rare occasions. Endocarditis occurs infrequently in dogs, and is very rare in cats and is a difficult disease to diagnose. Dogs are more likely to get be affected by endocarditis as they get older, and male dogs are slightly more susceptible than female dogs. Pre-existing heart disease increases the risk of dogs developing bacterial endocarditis.

Endocarditis most commonly affects two of the four major valves in the heart: the mitral valve and the aortic valve. Endocarditis causes little growths called “vegetations,” which affect the ability of the valves to function properly.

In order for the valves to become infected, there has to be a period of time when bacteremia, which is the presence of bacteria in the bloodstream, is occurring. In most cases, the cause of the bacteremia that leads to the endocarditis is never identified. Known causes of bacteremia include surgical procedures involving the oral, gastrointestinal, and urinary tract; dentistry procedures; intravenous catheterization; implantation of pacemakers; administration of drugs that suppress the immune system; and previous heart valve infections. Once introduced into the bloodstream, the bacteria, somehow manage to overcome the dog’s immune defenses, and an infection on the valve in established. Vegetations grow at the site of infection and cause the valve to malfunction. This usually leads to heart failure.

Making a certain diagnosis of endocarditis can be very difficult. Usually there is a vague history of lethargy and poor appetite. Eventually, most dogs develop heart failure and demonstrate the common signs of coughing, shortness of breath, weakness, or collapse. Many clinicians refer to the disease as “the great imitator” because of the variety of clinical signs in patients with the disorder.

Bacterial endocarditis often leads to a condition called septic embolization, in which microscopic pieces of the vegetations (emboli) from the infected valves break off and enter the bloodstream. These emboli travel through the bloodstream and affect other organs in the body. The most commonly affected organs are the kidney and spleen, although the brain, intestine, and the heart may also be affected.

The immune system’s response to embolization sometimes does more damage than good, often leading to arthritis and glomerulonephritis, a type of kidney inflammation. Embolization of the kidneys or the heart is a very serious consequence of endocarditis and can trigger a series of complications that may lead to a fatal outcome.

Sometimes, bacteremia can progress to a more serious condition called sepsis in which overwhelming infection in the bloodstream affects the blood flow to the vital organs. Sepsis often progresses further, and the patient succumbs to septic shock, in which blood pressure drops and many organs begin to fail. If this happens, the outcome is almost invariably fatal.

Diagnosis In-depth

• Thorough history and physical exam. Although the great diversity of clinical signs in dogs with endocarditis makes it “the great imitator,” on occasion, an owner will reveal a history of an event that might have predisposed the dog to endocarditis, such as a recent dental procedure or recent placement of an intravenous catheter. Usually, however, the history is vague and non-specific, such as lethargy and poor appetite. Most dogs have a fever on physical examination. If the dog is already in heart failure, presence of a cough, weakness, and shortness of breath may be present as well. Fever and a heart murmur, especially one that had not been detected on previous examinations, is suggestive of endocarditis.
• Cardiac ultrasound. This is an important tool in the diagnosis, as the visualization of vegetations on the mitral and/or aortic valve is highly supportive of a diagnosis. If heart failure is present, ultrasound also helps assess the degree to which the heart is compromised.
• Electrocardiography (EKG). EKG analysis detects abnormal heart rhythms in 50 to 75 percent of dogs with endocarditis. Seriously abnormal rhythms carry a poorer prognosis for survival.
• Thoracic radiograms. X-rays of the chest help diagnose the heart failure that often develops as a consequence of the malfunctioning, infected valves.
• Blood cultures. Isolation and identification of bacteria in the bloodstream strongly support a diagnosis of endocarditis, in conjunction with other diagnostic findings. Positive blood cultures have been reported in about 75 percent of dogs with bacterial endocarditis.

Therapy In-depth

The goals of therapy for bacterial endocarditis are to sterilize the vegetations on the valves, to treat any heart failure or other heart abnormalities such as abnormal rhythms, and to manage any abnormalities that might be affecting other organ systems as a result of the heart valve infection.

• Antibiotics. Antibiotics are the mainstay of therapy for endocarditis. Therapy usually lasts for two to six weeks to ensure complete killing of the infecting organism. Initially, they should be given intravenously so that effective blood levels are achieved rapidly. Dogs that respond well are sent home with oral antibiotics.
• Anti-arrhythmics. Drugs that control abnormal heart rhythms are used to treat severe or life-threatening abnormal rhythms.
• Drugs that treat congestive heart failure (diuretics, cardiac glycosides, vasodilators, angiotensin converting enzyme inhibitors). Heart failure is the most common cause of death in dogs with bacterial endocarditis. Palliation of the clinical signs of heart failure may be achieved using a variety of drugs. The specific drug regimen is tailored to the individual patient.
• Treatment for shock. Septic shock is a serious complication that is difficult to treat and carries a poor prognosis for survival. Intravenous fluids, antibiotics, and perhaps a dose of glucocorticoids (this is very controversial) may be given in an attempt to reverse this condition.

Follow-up Care for Dogs with Endocarditis

Optimal treatment for your dog requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your dog does not rapidly improve.

Administer all prescribed medication as directed. Alert your veterinarian if you are experiencing problems treating your dog.

Feed any prescription diets for the management of heart failure (low sodium diets) or kidney failure (low protein diets), as recommended.

Consult with your veterinarian concerning the administration of antibiotics as a preventive measure in instances where your pet may need a procedure that is known to induce bacteremia, such as a dental cleaning or tooth extraction.