Infective Endocarditis

Question 1

On what side of the heart does IE usually occur?

Answer 1

Usually on the left side

Right side more common in IV drug users

Question 2

What does IE occur in?

Answer 2

Valves with a congenital or acquired defect
On normal valves with strep pneumoniae or staph aureus
On prosthetic valves, early or late
In association with a ventricular septal defect or persistent ductus arteriosus

Question 3

What are causes of culture negative endocarditis?

Answer 3

Coxiella burnetii
Chlamydia spp
Bartonella spp
Legionella

Question 4

What is the pathology of IE?

Answer 4

Mass of fibrin, platelets and infectious organisms form vegetations along the edges of the valve
Virulent organisms destroy the valve, producing regurgitation and worsening heart failure

Question 5

How is IE diagnosed using the Duke’s criteria?

Answer 5

Direct evidence of IE by histology to culture of organism from vegetation
2 major criteria
1 major and 3 minor criteria
5 minor criteria

Question 6

What is Duke’s major criteria for IE?

Answer 6

Positive blood cultures
Typical organism from 2 cultures
Coxiella burnetii or IgG titre 1:800
Evidence for endocardial involvement 
Oscillating intracardiac mass on a valve ro supporting structures
Abscess
New partial dehiscence of prosthetic valve
New valvular regurgitation

Question 7

What is Duke’s minor criteria for IE?

Answer 7

Predisposition (IV drug user, prosthetic valve)
Fever 38c
Vascular phenomena (emboli, septic pulmonary infarcts)
Immunological phenomena (Osler’s nodes, glomerulonephritis)
Microbiological evidence- positive blood culture

Question 8

What are the clinical features of IE?

Answer 8

Malaise, fever, night sweats, weight loss, anaemia , splenomegaly. Clubbing is rare occurs late
Valve destruction- heart failure or new or changing murmurs
Embolization of vegetations and metastatic abscess formation in the brain, spleen, kidney. From high sided causes pulmonary infarction and pneumonia
Immune complex deposition in blood vessels producing a vasculitis and petechial haemorrhages in the skin, under the nails (splinter haemorrhages) and in the retinae (Roth’s spots). Osler’s nodes and Janeway lesions. Artgralgia and glomerulonephritis. Haematuria is common

Question 9

What investigations are required for IE?

Answer 9

Blood cultures taken before antibiotics given- 3 sets (6 bottles) over 24 hours
Transthoracic echocardiography (TTE) identifies vegetations and underlying valvular dysfunction
Serological tests for unusual organisms
Chest X-ray may show heart failure or evidence of septic emboli in right- sided endocarditis.
ECG may show MI (emboli to the coronary circulation) or conduction defects (due to extension of the infection to the valve annulus and adjacent septum).
Blood count shows a normochromic, normocytic anaemia with a raised ESR and often a leucocytosis.
Urine dip shows haematuria