What is Heart Valve Infection (Infective Endocarditis)?
Infections that take root in the heart can cause severe illness in dogs. This is called infective endocarditis (IE). As the name suggest, the infection begins in the endocardium, the thin membrane lining on the outer edge of the heart, but it typically moves to one of the heart valves. The mitral and aortic valves on the left side of the heart are the most common sites for infection, but occasionally the tricuspid valve on the right side may also be affected. If the infection isn’t treated immediately, it will damage the valves permanently and your dog may have lifelong heart problems. Most instances of IE occur because bacteria migrates from another infection in the body. Dogs with bacterial infections in the mouth from dental problems are particularly at risk. Infected wounds or injuries during surgery can also be a contributing factor. Humans often develop a heart infection because of a prior heart condition, but this is less common in dogs. Dogs with subaortic stenosis, an inherited heart condition that creates very fast blood flow through the aortic valve, do have a higher risk of IE, but otherwise one study found that out of 61 dogs with IE only four had a congenital heart problem prior to the infection. Dogs with a weakened or suppressed immune system are more at risk. Most IE is bacterial, but fungal infections also rarely cause a similar problem. Symptoms may be heart related if your dog has congestive heart failure, or they may affect other parts of the body as bacteria from the heart are carried in the blood stream. Early on IE can be treated with antibiotics, but once the valves are affected veterinarians can only treat congestive heart failure symptomatically.
Heart infections begin in the lining of the heart but quickly move to interior valves where they can cause permanent damage. This is called infective endocarditis. It is a rare condition in dogs, but it is difficult to treat and can often end up being fatal.
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Symptoms of Heart Valve Infection (Infective Endocarditis) in Dogs
These are some of the signs you might see if your dog has IE. Symptoms often develop over several weeks, but seeking veterinary treatment immediately will give your dog a better chance of survival.
- Difficulty breathing
- Exercise intolerance
- Weight loss
- High systolic blood pressure
- General malaise
- Painful or swollen joints
- Urinary or vaginal infection
- Blood or pus in the urine
- Unstable gait or seizures
- Behavioral changes
These are some of the most common organisms that cause IE
- Bacteria (Streptococcus, Staphylococcus, Klebsiella, Escherichia coli)
- Tick and insect borne parasites (Rickettsia, Bartonella)
- Fungal infection
Causes of Heart Valve Infection (Infective Endocarditis) in Dogs
Veterinarians aren’t sure why some dogs develop IE while others with a similar infection do not. These are some of the factors that could cause or contribute to the disease.
- Bacteremia (bacteria in the blood)
- Bacterial infection in another part of the body (mouth, bones, prostate, uterus, kidneys, intestines)
- Abscess or bite wound
- Surgical procedure
- Weak immune system
- Immunosuppressant medications (such as a steroid or chemotherapy treatment for cancer)
- Aortic stenosis
- More common in large breed dogs
- More common in middle-aged dogs
Diagnosis of Heart Valve Infection (Infective Endocarditis) in Dogs
Since IE can affect many different parts of the body, symptoms are often nonspecific and hard to identify. The veterinarian will physically examine your dog and take blood and urine samples. Bacteria can often be found in the blood with IE, but not always, so this isn’t a definitive test. The veterinarian will also probably hear a heart murmur over the affected valve, which can be another good indication of IE rather than another infective illness. If IE is suspected, the veterinarian will order chest x-rays. These will often show chamber enlargement, and sometimes fluid in the abdomen or lungs, especially if the right side of the heart is affected. Electrocardiography may also be ordered to record abnormal heart rhythms. An echocardiogram, an ultrasound of the heart, is usually the best diagnostic test for identifying dysfunctional valves. The veterinarian may be able to tell you which valve or valves are deffective, as well as ascertain the extent of the damage. The veterinarian will want to know about prior infections, wounds, and dental or surgical procedures as these will make IE more likely. Any immune-suppressant medication or another condition that weakens your dog’s immune system can also be relevant.
Treatment of Heart Valve Infection (Infective Endocarditis) in Dogs
Initial treatment will be aimed at eliminating the bacteria or other organisms that are causing the infection. An oral antibiotic will be prescribed based on the strain of bacteria that is causing your dog’s illness. An antifungal medication may also be prescribed if the infection is not bacterial. Unfortunately, eliminating the bacteria won’t reverse damage to the valves. Further treatment will be focused on reducing symptoms of congestive heart failure in your dog. ACE inhibitors can help increase blood flow. Diuretics may be prescribed to reduce fluid retention. Digoxin may be given in extreme cases. Conditions that affect the mitral or tricuspid valves will respond better and symptoms may be treatable over an extended period of time. If the aortic valve is damaged, heart failure usually happens quickly.
Recovery of Heart Valve Infection (Infective Endocarditis) in Dogs
Your dog will only make a complete recovery if he is treated very early. Once the heart valves are damaged, your dog’s heart will be permanently weakened. Some conditions may still be manageable symptomatically for a number of years, but the heart will have to work harder and will likely fail at a young age. Proactive antibiotic treatment is recommended if you know your dog is at risk. Dogs with aortal stenosis or a weakened immune system should be given antibiotics before surgery or dental procedures to reduce the chance of bacteria traveling to the heart. This won’t eliminate all instances, but it can help to prevent some cases with an obvious cause.
Heart Valve Infection (Infective Endocarditis) Questions and Advice from Veterinary Professionals
Our 10yr old dog died suddenly this week, vet said heart failure. It was onset by extreme vomiting including blood. He showed NO signs of illness whatsoever. Rushed him the vet in the am and he died by 2pm that same day. Later same day, our 2 years old dwarf rabbit also suddenly died. lethargic, spasms followed by a seizure and instant death. Can they be related?
We ruled out any poisoning in the home.
Condolences on the loss of two of your pets so close together. In these types of cases, poisoning is the usual cause of death if two pets of different species die so close together; infectious causes are possible, but for a definitive answer a necropsy of both animals would give the underlying cause of their death. Regards Dr Callum Turner DVM
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Recently scheduled a full dental cleaning and root canal for a slab fracture on a left upper molar on my 7 year old Aussie. Started Clavamox 375mg, BID 2 days prior to procedure. Of note, he also has a MDR1 gene mutation and can't receive certain medications. After administering the pre-anesthesitic meds (versed and butorphanol- which he shouldn't have gotten with his MDR1 mutation) he developed multiple runs of SVT, PVC's and an atrial arrhythmia, requiring IV lidocaine. Procedure was cancelled, meds reversed and now awaiting and echocardiogram to evaluate structure and function or his heart. My question to you is Clavamox an appropriate/typical antibiotic to use if he does indeed have IE? I was instructed to continue the antibiotic until the fracture tooth is taken care of.
Herding breeds with MDR1 gene mutation should avoid certain drugs (like the link below); many people just stay fixated on ivermectin, but many other drug categories are included too. As for treatment for infective endocarditis, broad spectrum antibiotics should be given until the results of culture and sensitivity come back for a more appropriate antibiotic since there are various different bacteria which may cause infective endocarditis. Antibiotic choice is down to the Veterinarian which I cannot criticise. Regards Dr Callum Turner DVM
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