Infective Endocarditis

This refers to inflammation of the endocardium that lines the surface of heart valves.

It can lead to vegetations on the valve surface that can destroy the valve.

In addition, it can lead to septic emboli formation leading to other complications.

Causes

Staphylococcus aureus

This is the most common cause of IE which is usually seen in IV drug abusers

It is a high virulence organism that destroys valves, most commonly the tricuspid valve

Risk factors for this bacterium include skin breaches (dermatitis, IV lines), kidney failure and diabetes

Viridans Streptococci

This is a group of low-virulence bacteria that affects previously damaged valves.

It is associated with poor dentition with sequelae of dental procedures

It causes small vegetations that do not completely destroy the valve and so causes a subacute endocarditis

The damaged endocardium develops small thrombotic vegetations of platelets and bacteria

Staphylococcus epidermidis

This is associated with endocarditis of prosthetic valves

Streptococcus bovis

This is associated with endocarditis in patients with colorectal carcinoma

HACEK organisms

These are Gram negative bacteria which give negative blood cultures

Fungi

Candida and Aspergillus, seen in IV drug users and immunocompromised patients

Non – bacterial thrombotic endocarditis

This is due to sterile vegetations that arise in association with a hypercoagulable state or an underlying adenocarcinoma

Vegetations usually occur on the  mitral valve and lead to mitral regurgitation

Libman-Sacks endocarditis

This is when you get vegetations associated with SLE.

Vegetations occur on both sides of the mitral valve and lead to mitral regurgitation.

Symptoms

Septic symptoms – fever, anaemia, clubbing, weight loss

Cardiac symptoms – heart murmur (due to valve disease), heart failure, chest pain

Immune complex deposition – Roth spots (retinal haemorrhage with pale centers), splinter haemorrhages and Osler nodes (tender lesions on fingers and toes)

Septic emboli – these can cause abscesses in organs, e.g., in skin they are called Janeway lesions (on palms), ischaemic strokes

Diagnosis

The is done using the modified Duke criteria, which use major and minor criteria:

Major Criteria

2 Positive blood cultures – 3 cultures are taken from different sites when the patient is febrile, looking for typical microorganisms which cause infective endocarditis

Involvement of the endocardium, which is shown by an echocardiogram. A transthoracic echocardiogram cannot rule out IE – perform TOE if high suspicion

Minor Criteria

Predisposition (e.g., valve prolapse)

IV drug use

Fever > 38 degrees celcius

Microbiologic evidence (e.g., blood cultures not meeting major criterion)

Immunologic phenomena, e.g., Osler nodes/Roth spots

Vascular signs e.g., splinter haemorrhages, Janeway lesions

Management

Antibiotic therapy according to cultures and sensitivity 

Initial empirical therapy may involve amoxicillin and low dose gentamicin

Some severe cases may require valve replacement surgery, e.g., if there is acute heart failure, severe valve incompetence or recurrent embolic events