Infective endocarditis

Question 1

Define infective endocarditis

What are the two broads groups of cases?

Most common bacteria?

Answer 1

Infective endocarditis is an infection of the endocardial surface of the heart

A fever and new murmer is infective endocarditis until proven otherwise

There are 2 broad groups of cases:

• Patients with a structural abnormality of the heart e.g. valve disease, valve replacements or congenital cardiac defects
  
  • Insidious (gradual) onset, caused by normal GI/skin commensals that enter the blood in trivial episodes of bacteraemia, then become emeshed in platelet aggregates on abnormal endcardium and proliferate
• Patients with strucurally normal heart valves
  
  • Acute, fulminating presentation with pathogenic organisms that directly invade the valve, seen in IV drug addicts, after open heart surgery or following septicaemia

Most common bacteria is streptoccus viridans, with staph aureus and strep epidermis also seen

Question 2

Describe the classical presentation of a patient with infective endocarditis

Answer 2

Acute febrile plus a new murmer

May present with insidiou illnes (malaise, lethargy, anorexia, arthralgia)

Other presentations may be with distal infarctions or AKI due to immune complex deposition

Question 3

What clinical features would there be on examination of a patient with infective endocarditis?

Answer 3

• Fever + changing/new heart murmer
• Microscopic haematuria (70%)
• Splenomegaly (40%)
• Osler’s nodes (15%)
  
  • Tender red nodules in the finger due to immune complex deposition
• Clubbing (10%)
• Splinter haemorrhages (10%)
• Roth spots (5%)
  
  • pale areas with surrounding haemorrhage on the retina
• Janeway lesions
  
  • Painless plamar/plantar macules
• Petechial rash
• Digital infarcts

Question 4

What are the common infecting organisms for infective endocarditis?

Answer 4

• Streptococcus viridans (most common)
• Staph aureus
• Strep epidermis

Question 5

What morphological changes would be seen on an affected heart valve with infective endocarditis?

What complications may there be?

Describe for acute infective endocarditis and subacute infective endocarditis

Answer 5

Acute infective endocarditis:

• Bacterial proliferation in the valve leads to necrosis of the valve tissue, with rapid perforation of the valves, leading to acute cardiac failure

Subacute infective endocarditis:

• As the infective organisms are poorly virulent, there is very gradual onset destruction of the valves
• Stimulation of thrombus formation leads to systemic and the persistant low grade inflammation leads to immunological phenomena

Complications:

• Systemic emboli (or pulmonary abscesses in right sided disease)
• Valvular incompetence and congestive cardiac failure
• Glomerulonephritis

Question 6

What investigations need to be done for a patient with suspected infective endocarditis?

Why?

Answer 6

• Bloods:
  
  • FBC (may show a mild normochromic normocytic anaemia and polymorphonuclear luecocytes)
  • U&Es (commonly show renal dysfunction, urine frequently shows protein and blood content)
  • CRP/ESR (raised in any infection, but may be useful to show reponse to therapy)
• Cultures:
  
  • key diagnostic investigation in infective endocarditis​
  • take 3 sets at different times and sites
• Urinalysis:
  
  • Look for proteinuria and microscopic haematuria
• ECG:
  
  • at regular intervals, may be MI due to emboli or conduction defects
• Transthoracic echocardiography:
  
  • can elicit vegetations and abscesses​
  • In all patients, but negative echo does not rule out endocarditis

Question 7

How is the diagnosis infective endocarditis made?

Answer 7

Duke major criteria:

• Positive culture (typical organism in two cultures)
• Endocardial involvement on echo (vegetations, abscess, new regurgitation)

Duke minor criteria

• Predisposition
• Fever >38
• Vascular immunological signs
• Culture/echo positivity not sufficient for ‘major’ criteria

Diagnosis can be made if there are two major, or one major and three minor criteria

Question 8

Outline the antibiotic regimen used to treat endocarditis

Answer 8

• The location of infection means long courses of antibiotics (4-6weeks) are required.
• Empirical therapy is with benzypenicillin, gentamicin and flucoxacillin if acute, IV for 4 weeks
• Most patients should respond within 48 hours of appropriate antibiotic therapy, signalled by a reduction in fever and decreases in inflammatory markers CRP and ESR.
• If relief does not occur, certain prospects need to be considered: PE, Abscess/extensive infection, drug reaction, other nosocomial infection.

Question 9

Describe the indications for surgery

Answer 9

Factors balancing the scales against and for surgery include:

• age
• co-morbidities
• presence of prosthetic material
• cardiac failure
• organism
• vegetation size
• valvular obstruction
• perivalvular infection
• worsening disease
• systemic embolization