Infective Endocarditis

Author(s): John B. Chambers and John L. Klein

Infective endocarditis is uncommon but not rare, and is still under-recognized. It has an average hospital mortality of 20%. Mortality is reduced by early detection, prompt initiation of appropriate antibiotics and timely surgery when indicated. About 40% of patients require surgery as an inpatient and a further 10% in the first two years after discharge.

Patients with prosthetic valves have a 0.3–1.2% incidence per year. Previous infective endocarditis and corrected congenital heart disease also increase susceptibility (Table 52.1). IV drug use greatly increases the risk of left as well as right-sided endocarditis.

Infection of the intra-cardiac leads of implanted cardiac devices (Chapter 58) causes a similar presentation as infection of heart valves. Removal of an infected device is almost always required to achieve cure of infection.

Priorities ⬆ ⬇

Think of the diagnosis
Consider if there is fever or raised inflammatory markers and any of:
- High or moderate risk cardiac structural disease (Table 52.1) especially prosthetic heart valve
- Previous episodes of infective endocarditis
- Stroke in a young patient
- Arterial embolism
- IV drug use (‘pneumonia’ can be caused by septic pulmonary emboli from tricuspid valve endocarditis)
- Tunnelled central venous catheter, including Hickman line or haemodialysis catheter
- Multisystem illness
- Chronic malaise, sweating and weight loss, often for several weeks
- Acute aortic or mitral regurgitation (may present with acute pulmonary oedema)
Send blood cultures
- If you suspect endocarditis it is essential to send blood cultures before starting antibiotic therapy since prior antibiotic therapy is the most common cause of blood culture-negative endocarditis.
- If the patient is stable, send three cultures taken at 2–4 h intervals.
- If the patient is unstable because of sepsis or severe valve regurgitation take two cultures 30–60 min apart and then start antibiotics.
- Infective endocarditis is often first suspected when a typical organism is grown from the first blood culture (Table 52.2).
The clinical assessment is given in Table 52.3 and urgent investigation in Tables 52.4 and 52.5. The diagnosis is aided by the modified Duke criteria (Table 52.6).
Emergency surgery may be indicated for heart failure caused by acute mitral or aortic regurgitation, and within 48h if there are severe valve lesions associated with a stroke or with large residual vegetations. Seek an immediate cardiac opinion.

Further Management ⬆ ⬇

Discuss antibiotic therapy with an infection specialist (clinical microbiologist or infectious diseases physician). Current recommendations are given in Table 52.7.
Discuss management with the endocarditis team at your surgical centre. Indications for early transfer are given in Table 52.8.
Remove infected intravenous cannulae.
Consider the appropriate route for antimicrobial delivery (e.g. PICC line).
Monitoring is given in Table 52.9.
Cardiac surgery is usually needed:
- As an emergency for critical valve destruction causing haemodynamic collapse.
- Within 48h for severe valve disease in the presence of a stroke or large residual vegetation.
- At a time determined by the endocarditis team, usually at 1–2 weeks for: failure to control sepsis; severe valve destruction; emboli despite treatment with the correct antibiotic at the correct dose.
Correct anaemia with transfusion if haemoglobin is <80g/L.
If the creatinine rises:
- Consider the possible causes: pre-renal failure; glomerulonephritis related to IE; renal infarct/abscess; vancomycin or gentamicin-nephrotoxicity; interstitial nephritis related to antibiotic; other causes, for example bladder outflow obstruction.
- Check urinalysis and urine microscopy, and arrange ultrasound of the urinary tract.
- Reduce antibiotic doses as necessary.
- Discuss management with a cardiac surgeon if renal failure is due to severe valve regurgitation, uncontrolled sepsis or glomerulonephritis.
- Seek advice from a nephrologist if you suspect glomerulonephritis or interstitial nephritis (casts in urine, large kidneys on ultrasound scan).
Seek further opinions from a:
- Maxillofacial surgeon if endocarditis is due to viridans group streptococci or other oral commensal.
- Gastroenterologist if endocarditis is due to the Streptococcus bovis group (up to 40% are associated with colorectal tumours including carcinoma).
- Spinal surgeon if there is back pain (and order MRI of spine).

Problems

Missed infective endocarditis

Some scenarios recur:

Possible lymphoma in a patient with a prosthetic heart valve.
Search for source of gastro-intestinal blood or malignancy in a patient with normochromic normocytic anaemia, weight loss and fever/sweats (often subtle and easily missed).
IV drug use with a chest infection (lung cavitations).

Blood culture-negative endocarditis

Prior antibiotic therapy is the most common cause. Other causes to consider are given in Table 52.10. Ask advice from an infection specialist about:

Stopping antibiotics and repeating blood cultures if the diagnosis is not secure.
Sending blood for serology (especially for Bartonella and Coxiella burnetii).

IV drug use with cavitating lung lesions but normal tricuspid valve

Consider septic thrombophlebitis of the femoral veins and arrange an ultrasound scan of the leg veins.

Should echocardiography be done in all patients with Staphylococcus aureus bacteraemia?

All patients with community-acquired S. aureus bacteraemia should have echocardiography since the risk of endocarditis is high.

The need in patients with hospital-acquired line-related bacteraemia is less certain and you should be guided by local hospital protocols. Echocardiography is unequivocally indicated if:

There are suggestive features, for example new regurgitant murmur or splinter haemorrhages.
The fever fails to settle in 72h.
Persistent bacteraemia despite intravenous line removal and antibiotic therapy.

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Information ⬇

Priorities ⬆ ⬇

Further Management ⬆ ⬇

Further Reading ⬆