Infective Endocarditis Flashcards
(40 cards)
Vegetations on the mitral valve caused by endocarditis
Mesh of platelets, fibrin, microorganisms, and inflammatory cells
Acute endocarditis
Hectically febrile illness that rapidly damages cardiac structures, seeds extracardiac sites, and, if untreated, progresses to death within weeks
Subacute endocarditis
Follows an indolent course; causes structural cardiac damage only slowly, if at all; rarely metastasizes; and is gradually progressive unless complicated by a major embolic event or a ruptured mycotic aneurysm
Risk factors for endocarditis
- Congenital heart disease
- Intracardiac devices
- Rheumatic heart disease
- IV drug use
- Degenerative valve disease
- Advanced age
- Hemodialysis
Risk of infective endocarditis following valve replacement
The risk of PVE is greatest during the first 6–12 months after valve replacement; gradually declines to a low, stable rate thereafter; and is similar for mechanical and bioprosthetic devices.
Common bacteria involved in infective endocarditis
Note that many bacteria can cause IE, but these are the most prevalent:
- Staphylococcus aureus
- Coagulase-negative Staphylococci
- Enterococci
Primary entry for streptococci
Oral tract
Primary entry for staphylococci
Skin
Primary entry for HACEK organisms
Upper respiratory tract
Haemophilus species, Aggregatibacter species, Cardiobacterium hominis, Eikenella corrodens, and Kingella kingae
Streptococcus gallolyticus subspecies gallolyticus (formerly S. bovis biotype 1)
Originates from the gastrointestinal tract, where it is associated with polyps and colonic tumors, and enterococci enter the bloodstream primarily from the genitourinary tract.
Nosocomial
(of a disease) originating in a hospital.
68–85% of CoNS strains that cause PVE are resistant to ___.
68–85% of CoNS strains that cause PVE are resistant to methicillin.
___ is contraindicated for most cases of infective endocarditis
Methicillin is contraindicated for most cases of infective endocarditis
How species of pathogen differs in IV drug use-induced IE
In addition to more frequent causes, Pseudomonas aeruginosa and Candida species often affect these individuals.
Marantic endocarditis
Uninfected vegetations seen in patients with malignancy and chronic diseases, specifically those resulting in a hypercoagulable state.
Nonbacterial thrombotic endocarditis
Undamaged endothelium is quite resistant to infection in most individuals. However, if the endothelium is damaged, a platelet-fibrin clott may develop, and this site is susceptible to infection. During transient bacteremia, these thrombi may serve as a nucleation site.
Often in these individuals there is pre-existing structural heart disease predisposing to endothelial injury, such as mitral regurgitation, aortic stenosis, aortic regurgitation, ventricular septal defects.
The organisms that commonly cause endocarditis have . . .
The organisms that commonly cause endocarditis have surface adhesin molecules, collectively called microbial surface components recognizing adhesin matrix molecules (MSCRAMMs), that mediate adherence to NBTE sites or injured endothelium.
Clinical manifestations of endocarditis
- Fever
- Chills
- Night sweat
- Weight loss
- Embolization of vegetation fragments and downstream effects (infection or infarction or remote tissues)
- Type III hypersensitivity reactions
The diagnosis of infective endocarditis is established with certainty only when . . .
The diagnosis of infective endocarditis is established with certainty only when vegetations are examined histologically and microbiologically.
Modified Duke criteria
- Designed to provide a good guess of whether or not someone has IE
- 2 major, 1 major + 3 minor, or 5 minor establish presumptive diagnosis if no other explanation is available
- Major: 1) positive blood culture + confirmation, 2) evidence of endocardial involvement
- Minor: 1) Predisposing heart condition OR IV drug use, 2) Fever, 3) Vascular phenomena (evidence of embolism), 4) Evidence of type III hypersensitivity, 5) Microbiologic evidence other than positive blood culture
Pending culture results, empirical antimicrobial therapy should . . .
Pending culture results, empirical antimicrobial therapy should be withheld initially from hemodynamically stable patients with suspected subacute endocarditis, especially those who have received antibiotics within the preceding 2 weeks
The delay allows blood for additional cultures to be obtained without the confounding effect of empirical treatment.
Patients with acute endocarditis or with deteriorating hemodynamics who may require urgent surgery should receive. . .
Patients with acute endocarditis or with deteriorating hemodynamics who may require urgent surgery should receive empirical treatment immediately after three sets of blood cultures are obtained over several hours.
Utility of serological testing in infective endocarditis
Serologic tests can be used to implicate organisms that are difficult to recover by blood culture: Brucella, Bartonella, Legionella, Chlamydia psittaci, and C. burnetii.
Transthoracic echocardiography in infective endocarditis
Noninvasive and exceptionally specific; however, it cannot image vegetations <2 mm in diameter, and in 20% of patients the images are inadequate. TTE detects vegetations in 65–80% of patients with definite clinical endocarditis but is not optimal for evaluating prosthetic valves or detecting intracardiac complications.
Safe and detects vegetations in >90% of patients with definite endocarditis, but still a ~10% false negative rate.
