Infective endocarditis (IE)

Overview:

• IE is an infection of the endocardium or vascular endothelium
• The disease may occasionally occur as a fulminating or acute infection, but more commonly runs an insidious course and is known as subacute (bacterial) endocarditis (SBE)
• Annual incidence is 6-7 per 100,000 in the UK
• Occurs most commonly on rheumatic or congenitally abnormal valves (as well as in mitral valve prolapse and calcified aortic valve disease)
• It also occurs in association with congenital lesions (e.g. VSD)

Aetiology:

Many organisms cause IE. Currently, the 3 most common organisms are:

• Streptococcus viridans (50% of cases)
• Enterococcus faecalis
• Staphlococcus aureus (50% of acute cases)

Clinical features of IE:

Malaise 95%

Murmurs 90%

Pyrexia 90%

Haematuria 70%

Cardiac failure 50%

Petechiae 50%

Splenomegaly 40%

Arthralgia 25%

Cerebral emboli 20%

Osler’s nodes 15%

Splinter haemorrhages 10%

Mycotic aneurysm 10%

Clubbing 10%

Janeway lesions 5%

Roth spots 5%

Presentations:

Subacute endocarditis:

• Fever
• Night sweats
• Weight loss
• Weakness
• Symptoms due to cardiac failure or embolism
• Another important presentation is a combination of renal failure and a heart murmur

Acute endocarditis:

• In IVDUs or following an acute suppurative illness (e.g. meningitis or pneumonia) the development of acute IE is suggested by the:
• Persistence of fever
• Development of heart murmurs
• Vasculitis (with petechial haemorrhage)
• Embolism

Investigations:

Blood:

• Normochromic normocytic anaemia is usual
• Raised ESR and CRP
• Raised WCC

LFTs:

• Mild disturbances
• Raised ALP

Immunoglobulins and complement:

• Serum Igs are increased
• Total complement and C3 complement are decreased (owing to immune complex formation)

Urine:

• Microscopic haematuria is nearly always present
• Proteinuria may occur

Blood cultures:

• Are positive in ~75% of cases

Echocardiography:

• Useful for identifying vegetations
• Useful for documenting valvular dysfunction and to identify patients in need of urgent surgery

CXR:

• May show evidence of HF
• Evidence of emboli in right-sided endocarditis

Drug treatment:

• Treat any underlying infection (e.g. drainage of a dental abscess)
• Treatment is with an appropriate antibiotic to which the bacteria is susceptible to for 4-6 weeks
• The first 2 weeks will be IV therapy, followed by 2-4 weeks of oral therapy

Surgical treatment:

There are several situations in which surgery is necessary:

• Extensive damage to a valve
• Early infection of prosthetic material
• Worsening renal failure
• Persistent infection but failure to culture an organism
• Embolization
• Large vegetations
• Progressive cardiac failure

The timing of surgery is important. On the one hand, the infection should, if possible, be eradicated before surgery is undertaken, but on the other hand the heart should not be left in a badly compromised haemodynamic state. In general, early surgery is preferable.

Prognosis:

• The prognosis is worse when:
• The organism cannot be isolated
• Cardiac failure is present
• Infection occurs on a prosthetic valve
• The micro-organisms found are resistant to therapy
• In general, 70% of those affected are treated effectively