Infective endocarditis — branching viva

Stage 1 — The febrile child with congenital heart disease

Examiner: A nine-year-old girl with repaired tetralogy of Fallot presents with two weeks of low-grade fever, fatigue and anorexia. She has a new harsh diastolic murmur. Take me through your diagnostic approach. [1]

Expected thread: Recognise the risk substrate (congenital heart disease) and the cardinal sign (a new murmur). State that infective endocarditis is the leading diagnosis. Draw three sets of blood cultures from separate sites before any antibiotic, then request echocardiography, and apply the Modified Duke criteria. State the two major criteria (typical organism in two separate cultures; echocardiographic vegetation, abscess or new prosthetic dehiscence) and how the case becomes definite endocarditis. [3]

Stage 2 — The new atrioventricular block

Examiner: It is now day four of appropriate targeted therapy. The cardiac monitor shows a new first-degree atrioventricular block progressing to complete heart block. What has happened, and what do you do? [1]

Expected thread: A new atrioventricular block or higher-degree block in endocarditis means an aortic-root abscess has eroded into the conduction tissue. This carries a high mortality. Escalate immediately: urgent echocardiography, discussion with a cardiac surgery centre, and preparation for surgical debridement. State that no antibiotic regimen rescues an abscess, because the problem is now mechanical. [1]

Stage 3 — The neonate with staphylococcal bacteraemia

Examiner: A different scenario. A neonate in intensive care with a long-standing central line has Staphylococcus aureus bacteraemia that persists despite seventy-two hours of appropriate flucloxacillin. The murmur is unremarkable. What is going on? [5]

Expected thread: Persistent Staphylococcus aureus bacteraemia in a neonate with a central line is right-sided infective endocarditis until excluded. The murmur is often absent in right-sided disease, so the clue is the organism and the line rather than the murmur. Perform echocardiography and remove the infected line, because leaving the line in place converts a treatable bacteraemia into a destructive endocarditis. Adjust the antibiotic regimen to cover staphylococci and consider the addition of agents that reach prosthetic material. [1]

Examiner probes (held in reserve)

• State the commonest indication for surgery in infective endocarditis. (Heart failure from acute valve regurgitation.) [1]
• Which cardiac conditions still require prophylaxis before dental procedures? (Prosthetic valve, previous endocarditis, unrepaired cyanotic congenital heart disease, repaired congenital heart disease with a residual defect within six months, cardiac transplantation with valvulopathy.)
• Why must therapy run for four to six weeks rather than ten days? (The biofilm within the vegetation shields the organism from a short course.)