Infective endocarditis

Question 1

What is infective endocarditis?

Answer 1

Infection of intracardiac endocardial structures, mainly heart valves.

Question 2

What is the aetiology of infective endocarditis? (x6)

Answer 2

• Streptococci (40%): mainly alpha-haemolytic Streptococcus viridans or Streptococcus bovis
• Staphylococci (35%): S. aureus and occasionally S. epidermis in IV drug users
• Enterococci (20%): E. faecalis
• HACEK: (Gram -ve) Haemophilus, Actinobacillus, Cardiobacterium, Eikenella, Kingella
• Coxiella burnetti
• Histoplasma fungus

Question 3

What is bacteraemia and what differentiates it from septicaemia?

Answer 3

It is bacterial infection that has spread into the blood. Bacteriaemia that has spreads and harms other parts of the body i.e., multiplied in the blood, is called septicaemia.

Question 4

!!! What is the pathophysiology of infective endocarditis? (x2 and x3 consequences)

Answer 4

Vegetations form as a result of lodging of organism on the heart valves during a period of bacteraemia. These usually occur at sites of previous endothelial damage from turbulent blood flow. These vegetations are made up of platelets, fibrin and infective organisms (a PROTHROMBOTIC milieu) and are poorly penetrated by the cellular or humoral immune system. Vegetations destroy valve leaflets and invade the myocardium/aortic wall leading to abscess cavities. Activation of the immune system also causes formation of immune complexes leading to cutaneous vasculitis, glomerulonephritis or arthritis.

Question 5

What are the types of infective endocarditis? (x2)

Answer 5

Acute (associated with spiking fevers and develops over days/weeks) and sub-acute (associated with vague symptoms and develops over weeks/months).

Question 6

What are the risk factors of infective endocarditis? (x5)

Answer 6

Abnormal valves (congenital, post-rheumatic, calcification/degeneration), prosthetic heart valves, turbulent flow, recent dental work, IV drug use.

Question 7

What is the epidemiology of infective endocarditis: Incidence?

Answer 7

16-22 per million per year in the UK.

Question 8

What are the symptoms of infective endocarditis? (x6)

Answer 8

• Fever
• Malaise
• Arthralgia and myalgia
• Confusion esp. in elderly
• Meningitis symptoms such as skin lesions secondary to septic emboli
• Headache – may be a constitutional symptom or secondary to septic emboli

Question 9

What are the signs of infective endocarditis? (x6 (x4))

Answer 9

• Pyrexia, tachycardia
• Signs of anaemia (from haemolysis)
• Auscultation: new regurgitant murmur or muffled heart sounds
• Clubbing
• Splenomegaly
• Vasculitic lesions: petechiae particularly on retinae (Roth’s spots), Janeway lesions, Osler’s nodes, splinter haemorrhages (from septic emboli)

Question 10

What valves are affected most commonly in infective endocarditis

Answer 10

Mitral, then aortic, then tricuspid, then pulmonary.

Question 11

What are the investigations for infective endocarditis?

Answer 11

• BLOOD: FBC (increased neutrophils and normocytic anaemia), high ESR and CRP, rheumatoid factor positive (if this is the aetiology)
• URINALYSIS: microscopic haematuria and proteinuria from septic emboli
• BLOOD CULTURE: at least 3 sets prior to antibiotic therapy – bacteraemia or fungaemia. Around 5% will come back negative.
• ECHOCARDIOGRAPHY: to identify to vegetations and valve abscess
• ECG: abscess can lead to conduction changes, manifesting as prolonged PR intervals, T wave abnormalities, and AV block
• CXR: septic pulmonary emboli: focal lung infiltrates +/- central cavitation (particularly occurs if tricuspid valve affected by endocarditis)

Question 12

What is a cavitation?

Answer 12

Lucent area (white/giving off light) contained within a consolidation, mass, or nodule

Question 13

What are the diagnostic criteria for infective endocarditis? (x2)

Answer 13

DUKE DIAGNOSTIC CRITERIA: TWO MAJOR CRITERIONS: for example, positive blood culture in two separate samples, positive echocardiogram of vegetation, abscess, prosthetic valve dehiscence or new valve regurgitation. OR ONE MAJOR CRITERION PLUS AT LEAST THREE MINOR CRITERIONS: minor criterions include high grade pyrexia, risk factors, one positive blood culture, echocardiogram shows other changes, and vascular signs.

Question 14

What is high-grade pyrexia?

Answer 14

At least 38 degrees.

Question 15

How is infective endocarditis managed medically?

Answer 15

Antibiotics for 4-6 weeks (at least 6 weeks for prosthetic valve endocarditis)

Question 16

What antibiotics should be given on (i) clinical suspicion, (ii) streptococci, (iii) staphylococci, (iv) enterococci, (v) HACEK, (vi) culture negative?

Answer 16

• CLINICAL SUSPICION: empirical (directly against likely cause) benzylpenicillin and gentamicin
• STREPTOCOCCI: continue as above
• STAPHYLOCOCCI: flucloxacillin/vancomycin and gentamicin
• ENTEROCOCCI: ampicillin and gentamicin
• HACEK: ampicillin/ceftriaxone and gentamicin
• NEGATIVE CULTURE: vancomycin and gentamicin

Question 17

How is infective endocarditis surgically managed?

Answer 17

Valve replacement.

Question 18

When is surgical management indicated in infective endocarditis?

Answer 18

If poor response to antibiotics and deterioration.

Question 19

What are the complications of infective endocarditis?

Answer 19

Valve incompetence, intracardiac fistulae, abscesses, aneurysm formation, heart failure, renal failure, glomerulonephritis, arterial emboli from the vegetations to brain, kidneys, lungs, spleen.

Question 20

What is the prognosis of infective endocarditis?

Answer 20

15-30% mortality if treated.