Endocarditis is inflammation (usually due to infection), of the lining of heart valves and heart chambers. It is different from myocarditis (inflammation of the heart muscles) and pericarditis (inflammation of the pericardial sac around the heart). Endocarditis usually affects those with existing heart disease, like valve disorders, but may also occur is those with artificial heart valves. Because endocarditis is nearly always due to infection, it is commonly known as infective endocarditis (IE).
Causes and associated risk facotrs
Two essential factors lead to the development of IE
- An anatomical abnormality: this may be a natural valve damaged by age or previous rheumatic fever, a natural but abnormal valve (like a bicuspid aortic valve), an artificial valve, or even a congenital defects such as a ASD (hole in the heart). Those with artificial valves have 1-4 percent risk of IE in the first year after surgery, and 1 percent yearly thereafter.
- Infecting organisms in the blood. These may be bacterial or even fungal, but the more common offenders are:
- Strep. viridans - often from the mouth, often released into the bloodstream during dental procedures such as cleaning or extraction
- Staph. aureus - this organism lives on body surfaces, and can infect even normal heart valves. It is commonly seen in intravenous drug users, where it affects the tricuspid valve mainly.
- Enterococci - these bacteria may enter the blood from a diseased or infected bowel (colon) or urinary tract. Strep. bovis and Cl. septicum are associated with colon malignancies.
- HACEK organisms - a group of bacteria living on the gums, often carried into the blood by saliva contaminating the needles used in IV drug abusers.
- Candida albicans - a yeast found in the blood of immune compromised patient
- Pseudomonas - not very common.
In some cases, the organism is not identified before treatment must be started, and these are called culture-negative IE. Eventually, some organisms are found, and these include aspergillus, brucella, coxiella, mycobacteria and chlamydia.
Intravenous drug use, recent invasive procedures (angiograms, or dental work) history of previous IE, and congenital or acquired heart lesions are all risk factors for IE.
The common symptoms suggesting IE are:
- Fever - more than 38°C, persistent, often with chills and night sweats,
- Extreme fatigue and weakness,
- Muscle and (often) joint pains,
- Shortness of breath during mild activity,
- Swelling of the legs, feet and abdomen in severe cases - this, together with breathing difficulty, may indicate heart failure,
- Painful lumps in the fingers and toes (Osler's nodes),
- Bleeding spots under the nails (splinter haemorrhages), and
- Dark urine - blood due to kidney involvement.
A suggestive history in a patient with a known heart problem should alert any doctor. On examination there is often a heart murmur in a patient with no previous heart problem. This, and any splinter haemorrhages or other signs of emboli, warrant a search for IE.
A list called Duke's criteria specifies major and minor criteria which must be met for the diagnosis of IE. However, this is an old list, and has been modified to include more objective evidence of infection (culture results), and of endocardial problems (for instance, by TEE).
This test is to identify the organism likely to be causing the problem, and to determine which antibiotic will eradicate it. At least two positive cultures, taken before treatment is begun, are required.
Other blood tests
Full blood count and CRP tests will confirm infection, and can be used to monitor progress on treatment.
Chest X-ray and ECG
These are routinely done, but are often non-contributory.
The most reliable images are provided by transoesophageal echocardiograms (TEE), which can show heart and valve structure (abnormalities) and function (like leaking), and any vegetations on the valve (vegetations are lumps of abnormal tissue adhering to the valve, containing colonies of the organism in the blood. Pieces may break off and lodge elsewhere in the body, like under the nails, or even in the brain). TEE will also show if there is an abscess in the ring of tissue around the base of the valve: this is a life-threatening complication requiring urgent treatment.
If untreated, IE can cause severe problems, or death. Septic emboli can produce abscesses, which may be very difficult to treat, especially if they are in the brain, where they cause a stroke.
Standard treatment is to give symptomatic treatment, plus aggressive antibiotic therapy, as determined by the blood culture results. If improvement is not rapid, or if the patient deteriorates, urgent surgery is considered. Whilst dangerous in such a sick patient, surgery may be life-saving.
Replacing the diseased valve with an artificial valve is most often done, except for tricuspid valves, where artificial valves are too risky, as they clot and cause added problems. A diseased Tricuspid valve may be removed, leaving the right heart chamber without an inlet valve.
Infection beyond the valve, into the ring, happens in 20 percent of cases, and these nearly always need surgery. This has a high mortality rate, between 19 and 43 percent. Surgery here is complex.
After surgery, antibiotic treatment must be continued for many days, to prevent infection settling on the new artificial valve.
Swift diagnosis, appropriate antibiotic treatment and well-timed surgery have meant a successful outcome in the vast majority of patients. The 5-year survival rate for aortic and/or mitral valve replacement done for IE is around 79 percent.
If totally artificial valves are used, they last indefinitely, but the patient must be on anti-coagulation treatment (Warfarin) for life, and this has its own problems. Tissue valves don't need Warfarin, but have a limited life-span of about 10 to 15 years, after which they need replacing - meaning another operation.
All patients with valve replacement require prophylactic antibiotics before any procedures, even minor ones like dental work. Specific protocols for this are provided to patients.
(Dr A G Hall)