Major criteria
Three positive blood cultures (taken 12 h apart) showing typical organisms, such as Streptococcus viridans, Staphylococcus aureus, or Enterococci
Evidence of endocardial infection, such as demonstration of a vegetation, abscess, prosthetic valve dehiscence or new regurgitation on echocardiography
Minor criteria
Predisposing factors (such as intravenous drug abuser, underlying valvular lesion or septal defect)
Fever >38°C
Embolic or vascular phenomena (such as splinter hemorrhages or vasculitis)
Immunological phenomena (such as Osler’s nodes or Roth spots)
Serology consistent with infective endocarditis
Blood cultures compatible with, but not typical for, endocarditis
Echocardiographic findings consistent with infective endocarditis and not covered by major criteria
Streptococcus or Streptococcus (45%), Staphylococcus or Staphylococcus (35%) and Enterococcus faecalis (10%) are the commonest organisms causing native or late (>2 months) prosthetic valve endocarditis. S. aureus and S. epidermidis (50%), Gram-negative bacilli and fungi are the commonest organisms causing early (<2 months) prosthetic valve endocarditis. If the organism is unknown, broad-spectrum antibiotics are prescribed using benzylpenicillin and gentamicin (which covers Streptococcus) or vancomycin and gentamicin (if Staphylococcus is suspected). Once the blood cultures results are available, appropriate antibiotic therapy can then be prescribed, tailored to the causative organism.
The majority of patients presenting with infective endocarditis are managed medically without the need for operative intervention. Surgery is usually reserved for patients with heart failure; infective endocarditis caused by highly resistant or virulent organisms, such as fungi or S. aureus; local invasion (producing heart block, periannular abscesses, fistula or leaflet perforation); prosthetic valve dehiscence; recurrent emboli despite appropriate antibiotic therapy; or the presence of vegetations >10 mm.
Discussion
The main principles of surgery for patients with infective endocarditis include debridement of infected tissues, closure of cardiac defects and valve repair or replacement. In patients with aortic valve endocarditis extending into an aortic root abscess, reconstruction with a bovine pericardial patch may be possible; otherwise aortic root replacement with an aortic homograft is required. In patients with mitral and tricuspid valve endocarditis, valve repair is the preferred option, especially if <50% of the valve is affected. In intravenous drug abuser patients with tricuspid valve endocarditis, it may be necessary to excise the valve leaflets without valve replacement in order to reduce the risk of recurrence but this can only be done in the absence of any significant pulmonary hypertension. Operative mortality is approximately 5–10% for patients with native valve endocarditis and 10–20% for patients with prosthetic valve endocarditis. Similarly, 5-year survival is better for patients with native valve endocarditis (80%) compared to those with prosthetic valve endocarditis (60%).
Key Points
1.
Infective endocarditis has an incidence of 2–4 cases per 100,000 persons per year with native valves and 0.5–1% per year following valve replacement surgery.
2.
Patients with infective endocarditis can present with clinical features of the cardiac lesion, infection, immune complex deposition or systemic embolization.
3.
Echocardiography is the mainstay in the diagnosis of infective endocarditis, allowing identification of any vegetation present and the spread of infection into the surrounding structures.
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
