Infective endocarditis

Today at morning report, we discussed a case of tricuspid valve  endocarditis in IVDU. Here are some points to keep in mind about endocarditis:

Subacute bacterial endocarditis – often due to strep species of low virulence (mainly viridans strep); clinical course is slowly progressive, indolent over weeks to months, has low propensity to embolize

Acute bacterial endocarditis –  fulminant disease over days to weeks, more likely staph aureus, and frequently causes metastatic infection

 

Microbiology: based on a large cohort 2700+ patients with infective endocarditis:

  • ​Staph aureus – 31%
  • Viridans group strep (oral flora) – 17%
  • CoNS – 11%
  • Strep bovis – 7%
  • Other strep – 5%
  • Enterococcus – 11%
  • Then, atypical organisms: HACEK – 2% / Fungi – 2% / non-HACEK gram negative organisms – 2%; 8% are culture-negative
In IVDU, staph aureus is still the most common – especially MRSA – followed by strep species and enterococcus; though we classically think of gram negative endocarditis (pseudomonas, E coli) in association with IVDU, these are rarer.
Indications for surgery: The class I indications (ACC / AHA guidelines) can be categorized as such:
  • ​heart failure – valvular dysfunction causing refractory pulmonary edema or cardiogenic shock
  • Prevention of embolization – vegetation > 10 mm with prior embolization (class I) or isolated vegetation > 15 mm and feasible valve repair (class IIb); recurrent emboli despite appropriate antibiotic therapy (class II)
  • uncontrolled infection – resistant organism – S. aureus (in many cases), fungi (candida, aspergillus) – (class I), persistent cultures after 7-10 days appropriate therapy (class I); enlarging vegetation despite 7-10 days appropriate therapy (class I), other evidence of uncontrolled infection defined as abscess / fistula / pseudoaneurysm (class I)
  • prosthetic valve endocarditis
  • neurologic complications – TIA / ischemic stroke without hemorrhagic conversion, cerebral abscess, silent microembolism
The indications for surgery in endocarditis associated with IVDU are generally the same though in general, surgery is not advised unless the patient agrees to enter drug rehabilitation program post-operatively. In IVDU, there is a risk of co-infection with HIV/Hepatitis B/C, but the presence of HIV infection is not a contraindication though it is considered higher-risk by CT surgery in advanced AIDS. Unfortunately, outcomes after surgery for patients with IE and IVDU are often poor: though they have similar short-term mortality, they have a substantially higher long-term mortality (noted at 60% in 13 months in 1 study; 45% at 20 months in another study) though these outcomes are related to risk of reinfection rather than operative mortality. Larger vegetations (> 2 cm) are a/w worse mortality.
Timing of surgery: no strict consensus on optimal timing but emergent = within 24 hours / urgent = within a few days / elective = after 1-2 weeks of antibiotic therapy. In general, early surgery is warranted for indications above and there is no advantage to delaying surgery