Infective Endocarditis

Question 1

Definition

Answer 1

Infection of intracardiac endocardial structures (mainly heart valves)

Question 2

Aetiology

Answer 2

· Most common organisms causing infective endocarditis:

o Streptococci (40%) - mainly a-haemolytic S. viridans and S. bovis

o Staphylococci (35%) - S. aureus and S. epidermidis

o Enterococci (20%) - usually E. faecalis

o Other organisms:
· Haemophilus
· Actinobacillus
· Cardiobacterium
· Coxiella burnetii
· Histoplasma (fungal)

Question 3

Pathophysiology

Answer 3

o Vegetations form when organisms deposit on the heart valves during a period of bacteraemia

o The vegetations are made up of platelets, fibrin and infective organisms

o They destroy valve leaflets, invade the myocardium or aortic wall leading to abscess cavities

o Activation of the immune system can lead to the formation of immune complexes –> vasculitis, glomerulonephritis, arthritis

Question 4

Risk factors

Answer 4

o Abnormal valves (e.g. congenital, calcification, rheumatic heart disease)

o Prosthetic heart valves

o Turbulent blood flow (e.g. patent ductus arteriosus)

o Recent dental work/poor dental hygiene (source of S. viridans)

Question 5

Epidemiology

Answer 5

UK Incidence: 16-22/1 million per year

Question 6

Presenting symptoms

Answer 6

· Fever with sweats/chills/rigors
o NOTE: this might be relapsing and remitting

· Malaise

· Arthralgia

· Myalgia

· Confusion

· Skin lesions

· Ask about recent dental surgery or IV drug use

Question 7

Signs on physical examination

Answer 7

· Pyrexia

· Tachycardia

· Signs of anaemia

· Clubbing

· New regurgitant murmur or muffled heart sounds

· Frequency of heart murmurs:
o Mitral > Aortic > Tricuspid > Pulmonary

· Splenomegaly

· Vasculitic Lesions
o Roth spots on retina
o Petechiae on pharyngeal and conjunctival mucosa
o Janeway lesions (painless macules on the palms which blanch on pressure)
o Osler’s nodes (tender nodules on finger/toe pads)
o Splinter haemorrhages

Question 8

Investigations (bloods)

Answer 8

· Bloods
o FBC - high neutrophils, normocytic anaemia
o High ESR/CRP
o U&Es
o NOTE: a lot of patients with infective endocarditis tend to be rheumatoid factor positive

Question 9

Investigations (other)

Answer 9

· Urinalysis
o Microscopic haematuria
o Proteinuria

· Blood Culture
o Do microscopy and sensitivities as well

· Echocardiography
o Transthoracic or transoesophageal (produces better image)

· Duke’s Classification - a method of diagnosing infective endocarditis based on the findings of the investigations and the symptoms/signs

Question 10

Management plan

Answer 10

· Antibiotics for 4-6 weeks

· On clinical suspicion = EMPIRICAL TREATMENT
o Benzylpenicillin
o Gentamicin

· Streptococci - continue the same as above

· Staphylococci
o Flucloxacillin/vancomycin
o Gentamicin

· Enterococci
o Ampicillin
o Gentamicin

· Culture Negative
o Vancomycin
o Gentamicin

· SURGERY - urgent valve replacement may be needed if there is a poor response to antibiotics

Question 11

Possible complications

Answer 11

· Valve incompetence

· Intracardiac fistulae or abscesses

· Aneurysm

· Heart failure

· Renal failure

· Glomerulonephritis

· Arterial emboli from the vegetations shooting to the brain, kidneys, lungs and spleen

Question 12

Prognosis

Answer 12

· FATAL if untreated

· 15-30% mortality even WITH treatment