INFECTIVE ENDOCARDITIS Flashcards
What is the characteristic lesion of infective endocarditis (IE)?
A) Myocardial abscess
B) Vegetation
C) Endothelial plaque
D) Granuloma
Answer: B) Vegetation
Rationale: The prototypic lesion of IE is a vegetation, which consists of platelets, fibrin, microorganisms, and scant inflammatory cells.
Which of the following is the MOST common cause of infective endocarditis?
A) Viridans streptococci
B) Staphylococcus aureus
C) Enterococci
D) HACEK organisms
Answer: B) Staphylococcus aureus
Rationale: S. aureus is the most common bacterial species causing IE, particularly in patients with prosthetic valves, intravenous drug use, and nosocomial infections.
What is the most common portal of entry for viridans streptococci in IE?
A) Skin
B) Oral cavity
C) Gastrointestinal tract
D) Urinary tract
Answer: B) Oral cavity
Rationale: Viridans streptococci enter the bloodstream through dental procedures, gingival disease, or poor oral hygiene, making the oral cavity the primary portal.
Which cardiac condition is associated with the highest risk of developing infective endocarditis?
A) Atrial septal defect
B) Patent ductus arteriosus
C) Hypertrophic cardiomyopathy
D) Prosthetic heart valves
Answer: D) Prosthetic heart valves
Rationale: Prosthetic valve endocarditis (PVE) has the highest risk, especially within the first year after surgery. Bioprosthetic valves carry a higher risk than mechanical valves.
What term describes a similar infective process occurring in arteriovenous shunts or patent ductus arteriosus?
A) Infective vasculitis
B) Infective pericarditis
C) Infective endarteritis
D) Nonbacterial thrombotic endocarditis
Answer: C) Infective endarteritis
Rationale: Infective endarteritis is the analogous process of IE but occurs in arteriovenous and arterio-arterial shunts (e.g., patent ductus arteriosus, coarctation of the aorta).
Which of the following statements about acute infective endocarditis (IE) is TRUE?
A) It has an indolent course
B) It rarely metastasizes
C) It can cause rapid cardiac damage and death within weeks if untreated
D) It is commonly caused by viridans streptococci
Answer: C) It can cause rapid cardiac damage and death within weeks if untreated
Rationale: Acute IE is characterized by a hectically febrile illness, rapid cardiac destruction, extracardiac seeding, and a high mortality risk if untreated.
When is the risk of prosthetic valve endocarditis (PVE) the highest?
A) Immediately after surgery
B) During the first year after valve replacement
C) Two years after surgery
D) The risk remains constant over time
Answer: B) During the first year after valve replacement
Rationale: The risk of PVE is highest during the first year after valve replacement, then declines to a low, stable rate.
What is the most common cause of infective endocarditis in people who inject drugs (PWID)?
A) Streptococcus pyogenes
B) Viridans streptococci
C) Staphylococcus aureus
D) Enterococcus faecalis
Answer: C) Staphylococcus aureus
Rationale: S. aureus is the most common pathogen in PWID-related IE, particularly involving the tricuspid valve.
What is the primary source of infection in community-acquired native valve endocarditis (NVE)?
A) Skin
B) Urinary tract
C) Oral cavity
D) Gastrointestinal tract
Answer: C) Oral cavity
Rationale: The oral cavity is the primary portal of entry for viridans streptococci, a major cause of community-acquired NVE.
Cardiac implantable electronic device (CIED)-associated infective endocarditis is most commonly caused by which organism?
A) Pseudomonas aeruginosa
B) Coagulase-negative staphylococci (CoNS) and Staphylococcus aureus
C) Streptococcus pneumoniae
D) Candida species
Answer: B) Coagulase-negative staphylococci (CoNS) and Staphylococcus aureus
Rationale: CIED-IE occurs at device contact sites and is most commonly caused by CoNS and S. aureus.
Which type of endocarditis is associated with malignancy and chronic disease?
A) Marantic endocarditis
B) Libman-Sacks endocarditis
C) Culture-negative endocarditis
D) Nonbacterial thrombotic endocarditis (NBTE)
Answer: A) Marantic endocarditis
Rationale: Marantic (noninfectious) endocarditis occurs due to hypercoagulable states, particularly in cancer and chronic illness, leading to sterile vegetations.
Which blood culture protocol is recommended for diagnosing infective endocarditis?
A) A single blood culture set
B) Three sets of blood cultures from different venipuncture sites over 1–2 hours
C) A single blood culture obtained from a central line
D) Blood cultures should only be drawn if fever >39°C
Answer: B) Three sets of blood cultures from different venipuncture sites over 1–2 hours
Rationale: IE is characterized by continuous bacteremia, so at least three blood culture sets from different venipuncture sites are recommended.
Which of the following is a classic peripheral manifestation of subacute infective endocarditis?
A) Janeway lesions
B) Septic arthritis
C) Meningitis
D) Splenic rupture
Answer: A) Janeway lesions
Rationale: Janeway lesions are non-tender hemorrhagic macules on the palms and soles, commonly seen in subacute IE.
Which of the following is considered a major criterion for diagnosing infective endocarditis?
A) Fever ≥ 38.0°C (100.4°F)
B) Presence of Osler’s nodes
C) Positive blood culture for Staphylococcus aureus from two separate cultures
D) Injection drug use
✅ Correct Answer: C) Positive blood culture for Staphylococcus aureus from two separate cultures
Rationale: The Modified Duke Criteria classify positive blood cultures for typical microorganisms (e.g., Staphylococcus aureus, Streptococcus viridans, HACEK group, etc.) from two separate cultures as a major criterion. Fever (A), Osler’s nodes (B), and injection drug use (D) are minor criteria.
Which of the following is a minor criterion for infective endocarditis?
A) Evidence of endocardial involvement via echocardiogram
B) New valvular regurgitation
C) Presence of glomerulonephritis or Osler’s nodes
D) Persistently positive blood cultures from two different draws taken 12 hours apart
✅ Correct Answer: C) Presence of glomerulonephritis or Osler’s nodes
Rationale: Glomerulonephritis, Osler’s nodes, Roth spots, and other immunologic phenomena are considered minor criteria in the Modified Duke Criteria.
Choice A & B are major criteria (evidence of endocardial involvement).
Choice D is also a major criterion (persistently positive blood cultures).
Which of the following vascular phenomena is considered a minor criterion for infective endocarditis?
A) Oscillating intracardiac mass seen on echocardiogram
B) Positive blood culture for Coxiella burnetii
C) Septic pulmonary emboli
D) New partial dehiscence of a prosthetic valve
✅ Correct Answer: C) Septic pulmonary emboli
Rationale: Vascular phenomena (such as major arterial emboli, septic pulmonary emboli, Janeway lesions, and mycotic aneurysms) are considered minor criteria.
Choice A (oscillating intracardiac mass) and Choice D (prosthetic valve dehiscence) are major criteria under echocardiographic findings.
Choice B (positive Coxiella burnetii culture) is also a major criterion.
Which of the following best defines definitive infective endocarditis according to the Modified Duke Criteria?
A) One major and one minor criterion
B) Two minor criteria only
C) Two major, or one major plus three minor, or five minor criteria
D) Positive echocardiogram alone
✅ Correct Answer: C) Two major, or one major plus three minor, or five minor criteria
Rationale: The Duke Criteria define definitive infective endocarditis as meeting:
Two major criteria, OR
One major + three minor criteria, OR
Five minor criteria
Which of the following cardiac conditions requires antibiotic prophylaxis before a dental procedure?
A) Mitral valve prolapse with regurgitation
B) Unrepaired cyanotic congenital heart disease
C) Hypertension with left ventricular hypertrophy
D) Atrial septal defect repaired 2 years ago without complications
✅ Correct Answer: B) Unrepaired cyanotic congenital heart disease
Rationale: According to Table 128-9, patients with unrepaired cyanotic congenital heart disease (including palliative shunts or conduits) require antibiotic prophylaxis.
Choice A (Mitral valve prolapse) does not require prophylaxis.
Choice C (Hypertension with LVH) is not an indication.
Choice D (Atrial septal defect repaired without complications) does not need prophylaxis unless residual defects remain near prosthetic material.
Which of the following is the preferred oral antibiotic regimen for endocarditis prophylaxis before a dental procedure?
A) Ceftriaxone 1 g IV 30 minutes before the procedure
B) Azithromycin 500 mg PO 1 hour before the procedure
C) Amoxicillin 2 g PO 1 hour before the procedure
D) Doxycycline 100 mg PO 1 hour before the procedure
✅ Correct Answer: C) Amoxicillin 2 g PO 1 hour before the procedure
Rationale: Amoxicillin 2 g PO 1 hour before a procedure is the first-line oral antibiotic for endocarditis prophylaxis (Table 128-8).
Choice A (Ceftriaxone IV) is used for penicillin-allergic patients who cannot take oral medication.
Choice B (Azithromycin) is an alternative for penicillin allergy.
Choice D (Doxycycline) is not a recommended regimen in this guideline.
A patient with a prosthetic heart valve and penicillin allergy (hives and anaphylaxis) requires dental prophylaxis. What is the best alternative antibiotic regimen?
A) Cefazolin 1 g IV 30 minutes before the procedure
B) Amoxicillin 2 g PO 1 hour before the procedure
C) Azithromycin 500 mg PO 1 hour before the procedure
D) Ampicillin 2 g IV 30 minutes before the procedure
✅ Correct Answer: C) Azithromycin 500 mg PO 1 hour before the procedure
Rationale: For patients with a penicillin allergy (including anaphylaxis, angioedema, or urticaria), cephalosporins should be avoided.
Macrolides (Azithromycin 500 mg PO or Clarithromycin 500 mg PO) or Clindamycin 600 mg PO are preferred alternatives.
Choice A (Cefazolin IV) is not recommended for patients with severe penicillin allergy.
Choice B (Amoxicillin) and Choice D (Ampicillin IV) should be avoided due to penicillin allergy.
- S. aureus IE, mobile vegetations >10 mm in diameter, and infection involving the mitral valve anterior leaflet are independently associated with an increased risk of embolization
- IE is rejected if an alternative diagnosis is established, if symptoms resolve and do not recur with ≤4 days of antibiotic therapy, or if surgery or autopsy after ≤4 days of antimicrobial therapy yields no histologic evidence of IE
- In at-risk patients, maintaining good dental hygiene is recommended and antibiotic prophylaxis is recommended only when there is manipulation of gingival tissue or the periapical region of the teeth or perforation of the oral mucosa
