A 37-year-old woman with a history of mitral valve prolapse and mitral regurgitation presents for evaluation. She reports no symptoms of shortness of breath or exercise intolerance. She plans to undergo health-screening procedures, including dental exams for routine cleaning and filling of several caries, pelvic examination with removal of an intrauterine device (IUD), and colonoscopy in the next year.
Question 8.5.1 According to the American Heart Association (AHA) 2007 guidelines on prevention of infective endocarditis, what should she receive prior to these procedures?
A) Amoxicillin 2 g orally
B) Azithromycin 500 mg orally
C) Clindamycin 600 mg orally
Answer 8.5.1 The correct answer is "D." Even now it seems the news has not made it to every corner of the world. But in 2007 there were major changes to the AHA guidelines on infective endocarditis prevention. The one change that would seem to affect the greatest number of patients in primary care practices is the "downgrading" of mitral valve prolapse with regurgitation, which is no longer considered a high-risk condition. If the patient had a condition for which prophylaxis was warranted, all of the other regimens ("A," "B," "C") are options depending on the patient's allergies and other medications, conditions, etc.
Question 8.5.2 According to the AHA 2007 guidelines on the prevention of infective endocarditis, which of the following conditions is NOT a high-risk condition for the adverse outcome of infective endocarditis?
A) Bioprosthetic aortic valve
B) Mechanical aortic valve
C) Congenital heart disease completely repaired with prosthetic material
E) Previous history of infective endocarditis
Answer 8.5.2 The correct answer is "D." The guidelines recommend antibiotic prophylaxis for conditions considered to be high risk for adverse outcomes of infective endocarditis. High-risk conditions include prosthetic valves (bioprosthetic homograft and allograft valves and mechanical valves), previous infective endocarditis, and complex cyanotic congenital heart disease.
Moderate-risk conditions, for which prophylaxis is not indicated, include acquired valvular dysfunction, such as rheumatic heart disease, hypertrophic cardiomyopathy, bicuspid aortic valve, and mitral valve prolapse with auscultatory evidence of valvular regurgitation and/or thickened leaflets. Hip replacement is also not a reason for routine dental prophylaxis.
Infective endocarditis is much more likely to result from transient bacteremia that occurs with routine dental care at home, like brushing and flossing, than from dental, GI, and GU procedures. Accordingly, good oral hygiene to lower the risk of bacteremia is more important than prophylactic antibiotics.
Question 8.5.3 If your patient had a mechanical aortic valve, appropriate endocarditis prophylaxis might include:
A) Ampicillin IV 2 hours prior to colonoscopy if biopsy of lesions is anticipated
B) Ampicillin IV 2 hours prior to pelvic examination and IUD removal
C) Amoxicillin PO 2 hours prior to routine dental cleaning
D) Amoxicillin PO 2 hours prior to any injection of local anesthesia and filling of caries
Answer 8.5.3 The correct answer is "C." For high-risk conditions (e.g., mechanical aortic valve), antibiotic prophylaxis is recommended by the AHA prior to cleaning of teeth and removal of plaque. The risk of endocarditis is highest for dental procedures that might traumatize the oral mucosa, such as tooth extractions, periodontal procedures, and cleaning of teeth with removal of adherent plaque. "A," "B," and "D" are incorrect. Prophylaxis is not recommended prior to these procedures. The risk of endocarditis is low for procedures such as lower GI endoscopy and pelvic examination with IUD removal, because the microorganisms likely to cause transient bacteremia following these interventions are not capable of adhering to cardiac valve tissues. Antibiotic prophylaxis is not recommended for restorative dental procedures (e.g., fillings).
All of the evaluations, including the dental examination, seem to go well. However, 1 month later, she returns to see you for gradually (perhaps even subacutely?) worsening fever, malaise, and night sweats. You are concerned that she may have developed infective endocarditis.
Question 8.5.4 The evaluation of a patient suspected of having subacute bacterial endocarditis (SBE) should include all of the following EXCEPT:
A) Three sets of blood cultures obtained at 1-hour intervals within the first 24 hours of assessment
B) Auscultation of chest for evidence of new or changing murmur
C) Transthoracic or transesophageal echocardiogram
Answer 8.5.4 The correct answer is "D." Spiral chest CT is not indicated in the diagnosis of SBE. History is important: onset of infection can sometimes be related to a recent dental extraction, IV drug abuse, or invasive medical procedure. Symptoms generally begin insidiously and may include weakness, fatigue, fever, night sweats, arthralgias/myalgias, and hematuria. "C," echocardiography, is indicated. The yield for visualization of vegetations for transthoracic echocardiography is 60% to 77% and increases to 96% with transesophageal echocardiography. A prolongation of the PR interval on an electrocardiogram may suggest involvement of the cardiac conduction system.
You carefully examine the patient and find that she is febrile and slightly tachycardic.
Question 8.5.5 You look for signs of infective endocarditis, paying particular attention to all of the following EXCEPT:
B) Painless erythematous macules on the palms and soles
D) Painless nodules over bony prominences
Answer 8.5.5 The correct answer is "D." Classical physical examination findings of SBE include intermittent fever; petechiae; conjunctival hemorrhage; splinter hemorrhages under the nails; erythematous painful nodules on the fingers, palms, and soles (Osler nodes); fundic hemorrhages (Roth spots); painless erythematous macules on the palms and soles (Janeway lesions); and a new diastolic murmur. "D" is not a physical examination finding in SBE. Painless nodules over bony prominences are observed in rheumatic fever and are one of the Jones criteria. Remember that in a modern medical practice, most patients with SBE will not present with these findings, and you must maintain a high degree of suspicion for SBE in the appropriate clinical scenario.
Laboratory evaluation in endocarditis may be remarkable for anemia, leukocytosis, elevated erythrocyte sedimentation rate (ESR), and microscopic hematuria.
Question 8.5.6 Which of the following is/are included in the major criteria of the modified Duke criteria for endocarditis?
A) Positive blood cultures
B) Janeway lesions (painless macules on palms and soles)
C) Echocardiographic evidence of valvular vegetation
Answer 8.5.6 The correct answer is "E." The modified Duke criteria were developed to provide clinicians with standardized criteria for the diagnosis of endocarditis. They have been validated by pathologic examination and are more sensitive than other endocarditis criteria systems. See Table 8-2.
TABLE 8-2DUKE CRITERIA FOR BACTERIAL ENDOCARDITIS ||Download (.pdf) TABLE 8-2 DUKE CRITERIA FOR BACTERIAL ENDOCARDITIS
|Definite endocarditis is established by the presence of 2 major criteria and at least 1 minor criterion. Probable endocarditis is established by the presence of 1 major and 1 minor criterion, or 3 minor criteria. |
|Major Duke criteria || |
New valvular regurgitation
Echocardiographic evidence of vegetations
Two positive blood cultures of an organism known to cause endocarditis
Single blood culture or antibody evidence of Coxiella burnetii (Q fever)
|Minor Duke criteria (not an exhaustive list but these are the most common manifestations) || |
Vascular phenomena (e.g., Janeway lesions, splinter or conjunctival hemorrhages, and septic emboli)
History of predisposing illness (e.g., IV drug abuse, heart lesion, and artificial valve)
Immunologic phenomena (e.g., glomerulonephritis and Osler nodes)
Three words about blood cultures—more is better. The sensitivity of blood cultures for endocarditis and bacteremia is directly related to the amount of blood taken for culture and the number of cultures drawn. Three sets of blood cultures are recommended for suspected endocarditis, and at least 20 mL should be drawn for each culture. Timing of blood cultures is less important, but sick patients should have the cultures drawn in rapid succession (e.g., over an hour or 2).
You draw a CBC, which shows leukocytosis with a "left shift" (e.g., a high percentage of bands and other immature neutrophils). Chest x-ray and urinalysis are unrevealing. You draw blood cultures and admit her to the hospital and start antibiotics. The next morning two blood cultures are reported to grow Gram-positive cocci in clusters. You start IV vancomycin and order a transesophageal echocardiogram. Indeed, the echocardiogram shows a small vegetation on her mitral valve. Blood cultures return showing methicillin-sensitive S. aureus.
Question 8.5.7 What is the most appropriate treatment of this patient now?
A) Nafcillin 2 g IV q 4 hours for 4 to 6 weeks
B) Penicillin G 2 million units IV q 2 hours for 4 to 6 weeks
C) Vancomycin 1 g IV q 12 hours for 4 to 6 weeks
D) Ceftriaxone 1 g IV q 24 hours for 2 weeks
E) Levofloxacin 500 mg IV q 24 hours for 4 to 6 weeks
Answer 8.5.7 The correct answer is "A." Nafcillin is the drug of choice for the treatment of methicillin-sensitive S. aureus endocarditis. Vancomycin should be reserved for patients with penicillin allergy or patients with methicillin-resistant S. aureus (MRSA). Neither ceftriaxone nor levofloxacin would be considered appropriate therapy for staphylococcal endocarditis.
HELPFUL (AND IMPORTANT) TIP:
Patients who have a sensitive organism (MSSA) actually have better outcomes (fewer deaths, etc.) with nafcillin than with vancomycin. So, save vancomycin for MRSA or other resistant organisms. Other options for hospital-acquired MRSA include linezolid and tigecycline.
While hospitalized, the patient develops symptoms of heart failure and worsening mitral regurgitation by echocardiogram. The heart failure is managed medically, but the regurgitation is now categorized as "severe." She has had 3 days of antibiotics and is currently hemodynamically stable.
Question 8.5.8 Which of the following is the most appropriate course of action?
A) Complete 6 weeks of antibiotics and manage her heart failure medically for the foreseeable future.
B) Complete 6 weeks of antibiotics and manage her heart failure medically, if possible; plan for valve replacement after 6 weeks of antibiotics.
C) Refer her for emergent valve replacement surgery, then complete the course of antibiotics.
D) Refer her for immediate coronary catheterization, and continue antibiotics.
E) Refer her for heart transplant.
Answer 8.5.8 The correct answer is "C." Progressive heart failure due to moderate-to-severe valvular dysfunction is an indication for surgery. There is evidence that early surgery reduces mortality and embolic complications especially in patients who have left-sided endocarditis associated with large vegetations and severe valvular dysfunction. This is true even in the absence of congestive heart failure and in the presence of less virulent pathogens. Thus, "B" is incorrect. Also, "A" is incorrect, as the patient should have surgery. "D" and "E" are incorrect, as there is no indication for coronary catheterization or heart transplant.
Other indications for surgery in cases of endocarditis include multiple embolic events, infections that are difficult or impossible to treat adequately with medications (e.g., fungal infections), cardiac conduction abnormalities due to infection, persistent bacteremia, partially dehisced prosthetic valve, and perivalvular infection (e.g., cardiac abscess and fistula).
Question 8.5.9 Which of the following organisms is most often responsible for causing infective endocarditis?
B) Streptococcus viridans
Answer 8.5.9 The correct answer is "B." S. viridans is the most likely organism to cause endocarditis. Gram-negative organisms, such as E. coli and P. mirabilis, are infrequent causes of infective endocarditis. Other organisms that cause endocarditis include the HACEK organisms (Haemophilus species, Actinobacillus actinomyces comitantes, Cardiobacterium hominis, Eikenella species, and Kingella kingae). In summary, organisms typically found causing endocarditis are S. aureus, S. viridans, enterococci (aerobic, Gram-positive organisms in chains that are GI or vaginal flora), Streptococcus bovis, and HACEK organisms.
Objectives: Did you learn to…
Determine who is an appropriate candidate for infective endocarditis prophylaxis?
Recognize signs and symptoms of infective endocarditis?
Diagnose infective endocarditis?
Prescribe appropriate treatment for infective endocarditis?