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Infective Endocarditis

Pathophysiology

  • Transient Bacteraemia – Can occur from poor dentition, dental infections, prosthetic valve, IVDU etc.

  • Damage to valve

  • Formation of vegetations – Endothelium is exposed, leading to thrombus formation around the central cluster of the pathogen = Vegetation


N.B. Immune complexes can be formed and deposited in organs like the kidneys, skin and eyes (Type 3 hypersensitivity reaction)

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Gross pathology of subacute bacterial endocarditis involving mitral valve. Left ventricle of heart has been opened to show mitral valve fibrin vegetations due to infection with Haemophilus parainfluenzae. - Centers for Disease Control and Prevention (https://commons.wikimedia.org/wiki/File:Haemophilus_parainfluenzae_Endocarditis_PHIL_851_lores.jpg)

Risk factors:

  • Age

  • Male

  • Poor dentition and dental infections

  • IVDU

  • Co-morbid conditions - Prosthetic valves, Valvular HD, IV devices e.g. central lines, shunts,  Haemodialysis, HIV


Causes:

  • Staph aureus (most common)

  • Strep viridans

  • Enterococci


Presentation

Main features that should make you immediately suspect IE are a Fever + New/changing heart murmur.


O/E - Tachycardia, Splinter haemorrhages, Osler nodes/Janeway lesions (very rarely seen)

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“Osler's nodes on left hand from a 43 year old male with subacute bacterial endocarditis” © Roberto J. Galindo CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/) “Janeway lesion on palm of a 36 year old male with staphylococcus endocarditis” © Warfieldian CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/3.0/)

N.B. Presentation is diverse and variable – Can present acutely and progress rapidly w/symptoms of HF (typically on normal valves), or it can present subacutely/chronically w/non-specific symptoms (typically on abnormal/prosthetic valves).


Investigations and Management

An ECG should be done straight away to rule out 1st degree heart block (Prolonged PR). If found, it's indicative of an Aortic root abscess, which is a rare, but severe, complication of IE. Managed with surgical repair.


Other investigations to do include:

  • Blood culture – 3 sets taken 30 mins apart from 3 separate peripheral sites

  • Bloods – FBC, CRP, U&E, LFT

  • Echo - 1st line imaging

  • Urine dip – Check for renal involvement

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“Vegetation on tricuspid valve by echocardiography. Arrow denotes the vegetation.” © Daisuke Koya, Kazuyuki Shibuya, Ryuichi Kikkawa and Masakazu Haneda. CC BY 2.0 (https://creativecommons.org/licenses/by/2.0/)

Other indications for surgical intervention include:

  • Extensive valve damage

  • Prosthetic valve endocarditis

  • Persistent infection despite medical therapy

  • Large vegetations

  • Serious embolisation

  • Fungal endocarditis

  • Progressive cardiac failure


Management is with long-term IV Abx.


Complications

  • Aortic root abscess (1st degree HB/Prolonged PR)

  • Acute valvular insufficiency → HF

  • Embolism e.g. stroke

  • Infection e.g. osteomyelitis, septic arthritis



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