Infective endocarditis

Infective endocarditis (IE) is an infection of the endocardium of the heart

It produces both intra-cardiac effects as well as a whole range of systemic effects, both emboli (sterile or infected) and a variety of immunological mechanisms


Epidemiology

• 1.7-6.2 cases per 100000 patients / year
• Higher in at-risk groups such as IV drug users
• More common in men (3x)
• More common in elderly
• Other diseases such as diabetes, cancer, and alcoholism

Risk factors

• Previous IE with valvular damage
• Invasive vascular procedures
• Recreational drug abuse
• Rheumatic heart disease (fewer than 20% of cases of IE)
• Elderly patients with calcific aortic stenosis
• Congenital heart disease (accounts for 15%) with bicuspid aortic valve being the most common
• Prosthetic valve implants

Pathogenesis

Thrombus acting as a prerequisite for invasion and adhesion

• Acute IE
• Direct infection of the thrombus
• Subacute IE
• Infection not enough for invading thrombus
• Nonbacterial thrombotic endocarditis
• Renal failure, SLE, neoplasia, malnutrition

Common organisms responsible

• Staphylococcus aureus (the one with IV drug abuse and prosthetic valves 30%)
• Streptococcus
• Pseudomonas aeruginosa
• HACEK
• Haemophilus aphrophilus
• Actinobacillus actinomycetemcomitans
• Cardiobacterium hominis
• Eikenella corrodens
• Kingella kingae
• Fungi
• Enterococci

Presentation

• FEVER + MURMUR
• Subtle and non-specific
• Back pain
• Weight loss
• Polymyalgia-like symptoms
• Look for history of invasive procedures
• Look for history of infarcts in other organs such as kidneys and spleens

Examination

• Fever
• Murmurs
• Petechiae
• Splinter or subungual haemorrhages
• Osler's nodes
• Clubbing
• Roth's spots
• Janeway lesions
• Arthritis
• Splenomegaly
• Meningitis

Differential diagnosis

• SLE
• Atrial myxoma
• Lyme disease
• Antiphospholipid syndrome
• Polymyalgia rheumatica
• Reactive arthritis

Investigations

• Blood cultures
• Serological tests
• Imaging studies
• Transthoracic echocardiography (TTE)
• Transoesophageal echocardiography (TEE)

Diagnostic criteria

• The Duke criteria

Management

• Hospitalisation
• Blood cultures
• Temperature records
• Basic haematology and biochemistry investigations
• ECG and CXR
• Comprehensive TTE
• Blood cultures
• Take 3 to 6 cultures at short intervals
• Referral
• When positive to cardiologist
• At outset to microbiologist
• TTE or TEE
• In all patients with prosthetic heart valves
• Serological testing
• Only if still suspected by cultures negative after 7 days

Medical

• Antibiotic therapy 2-6 weeks

Surgical

• Needed in about 50% of patients
• Stable patients - after antibiotic therapy
• Unstable patients - earlier opportunity

Complications

• Valve dysfunction
• Myocardial abscess
• Embolic phenomena
• Heart failure
• Metastatic infection
• Immunological disease and organ dysfunction
• Complications even after bacteriological care
• Conduction defects (patients with IE should have daily ECGs)

Prognosis

• Cure rates 60 to 98%
• Lower by 10% in PVE for all categories

Prevention

• ANTIBIOTIC PROPHYLAXIS