Infective Endocarditis (IE)
Definition: Infection of the endothelium of the heart, usually but not limited to the valves. Can be divided according to either subacute onset (often due to Strep viridians) or acute onset (less common, often due to Staph aureus).
Pathophysiology: Infection of the valves with bacteria (or rarely fungi) cases injury to the valve and valvular regurgitation. The bacteria continues to grow on the valve and can form a large mass or vegetation. Parts of this vegetation can embolize to other parts of the body. The immune response to these organisms leads to the production of immune complexes. Essentially, infection of the endothelium causes 1) persistent bacteremia, 2) valvular disfigurement (with vegetations/regurgitation), 3) septic emboli and 4) immune complex phenomenon.
Predisposing conditions:
1. Abnormal valve*: prior endocarditis, h/o rheumatic heart disease, valvular heart disease, congenital heart disease, prosthetic valves
2. Abnormal risk of bacteremia: poor dentition, tooth extraction (or other GI/GU procedures breaking mucosal barriers like endoscopy), IV drug use, hemodialysis
Symptoms:
1. Persistent bacteremia can cause fevers, weight loss, night sweats, fatigue. These symptoms are nonspecific.
2. Valvular disfigurement can cause symptoms of CCF.
3. Septic emboli thrown from the bacterial vegetation can travel anywhere and can cause stroke, renal infarcts, splenic infarcts, infected joints, pulmonary embolism.
4. Immune complex phenomenon can cause arthritis or glomeruonephritis.
Remember: Fever + regurgitant murmur = IE until proven otherwise
Signs:
1. New regurgitant murmurs due to valvular disfigurement
2. Septic Emboli causing
a. Janeway lesions - nontender, hyperpigmented macules on palms or soles
b. splinter hemorrhages in nailbed
c. subconjunctival hemorrhage
3. Immune complexes causing
a. Roth spots (retinal hemorrhage + pale center)
b. Osler’s Nodes (tender nodules on tips of fingers and toes)
Diagnostic studies
· 3 sets of blood cultures from different sites, ideally >1 hour apart, should be drawn before starting antibiotics!
· Echocardiogram
· FBP with differential, ESR, rheumatoid factor, creatinine, urinalysis
· EKG (to assess for conduction abnormalities)
Modified Duke Criteria:
Major 1. Sustained bacteremia by organism known to cause endocarditis (at least 2 cultures positive) 2. Endocardial involvement documented by either vegetation or new valvular regurgitation seen on echocardiogram Definite if 2 major OR 1 major & 3 minor OR 5 minor criteria Possible if 1 major & 1 minor OR 3 minor | Minor 1. Fever > 38 2. Predisposition [like RHD, see above] 3. Embolic phenomena -arterial emboli -septic pulmonary infarct -mycotic aneurysm -intracranial hemorrhage -conjunctival hemorrhage -Janeway lesion 4. Immunologic phenomena - glomerulonephritis - Osler's nodes, Roth spots - +Rheumatoid factor 5. Blood cultures that don't meet criteria (only 1 positive) |
Microbiology:
1. In native valve endocarditis, Strep viridans, Staph aureus and Enterococcus are the most common organisims
2. The organisms that cause endoarditis are different in:
· IV drug abusers – Staph aureus most common
· prosthetic valve endocarditis - Staph epidermidis most common <6mo after surgery
· immunosuppression – fungi more common
Treatment:
· Start empiric antibiotics, adjust according to organism and sensitivities, continue for at least 4 weeks after last positive blood culture
a. Start with penicillin 1.2mu IV Q4hrly + gentamicin 60mg BD
b. Add anti-staph agent (like cloxacillin) if acute onset
· Surgery may (rarely) be necessary if refractory CCF, persistant/refractory bacteremia, invasive infection, prosthetic valve, fugal infection
Endocarditis Prophylaxis:
· Indicated for patients with h/o rheumatic heart disease, previous endocarditis, congenital heart disease, valve replacement
· prescribe when pt to undergo invasive dental procedures (like tooth extraction).
· Use amoxicillin 2g or penicillin 250 mg PO 30-60 min prior to procedure OR erythromycin if PCN allergy
Clinical Case
A 35 yo F with a history of rheumatic heart disease presents to H2 complaining of fever and fatigue for 3 weeks and shortness of breath that has been present for the last 1 week. The fever is high-grade and occurs during the day and night. The shortness of breath started one week ago and has slowly been getting worse. Over the last day the patient has been unable to lie flat and sleeps with 3 pillows under her head.
PMHx: Diagnosed with rheumatic heart disease as a child but not on any medications. No recent hospitalizations. The patient also reports a tooth extraction that was performed one month ago. No other surgeries
Social/Family History: Unremarkable
Exam: The patient is febrile to 38.2 but BP/HR are normal. She is not pale but has no edema and the JVP is not raised. On CV exam you that the apex beat is displaced to the 6th IC space at the anterior axillary line. On auscultation you note a S3 gallop + 2 different murmurs: a 4/6 high-pitched holosystolic murmur is heard at the apex and radiates to the axilla and a 2/6 low-pitched mid-diastolic murmur heard best at the apex. On pulmonary exam you note crackles that are heard in both lung bases. On extremity examination you appreciate non-tender, hyperpigmented macules along the outside of the soles of the feet and flesh coloured, tender nodules at the tips of the finger.
1. What is your diagnosis/impression?
Infectious endocarditis (review definition and pathophysiology)
In CCF (note that the patient has left sided heart failure)
2. What are this patient’s risk factors for bacterial endocarditis?
rheumatic heart disease, dental procedure (review classes of risk factors)
3. What are the symptoms of infectious endocarditis in this patient?
Fevers/malaise (from bacteremia) and shortness of breath (from CCF with pulmonary edema due to valvular regurgitation)
4. What signs of infectious endocarditis do you note in this patient?
Regurgitant murmur, Janeway lesions (embolic phenomenon) and Osler’s nodes (immune complex phenomenon). Review other signs of embolic and immune complex phenomena.
5. What are the murmurs that you hear in this case and what types of valvular lesions and what are they caused by?
MS due to RHD, MR due to either RHD or infectious endocarditis. Note that stenosis is not caused by IE but that IE generally causes MR, AR or TR.
6. What investigations would you order?
Note that blood cultures and echo are most important for diagnosis. Would also get ECG, FBP, ESR, creatinine, rheumatoid factor, urinalysis, urine culture
7. What are the 3 most likely organisms that would cause IE in this patient?
Strep viridans, Staph aureaus, Enterococcus! Briefly note other possible causes and in what circumstances.
8. What treatment do you want to begin?
IV penicillin and IV gentamicin. Note that antibiotics may be changed according to blood culture sensitivities (for example if Staph Aureus resistant to penicillin).
His labs and EKG are normal. Both blood cultures (you sent 2) grow gram positive cocci in chains and are eventually identified as Strep viridans. You are still waiting for the echocardiogram.
9. Have you confirmed the diagnosis of IE?
Yes. Pt has 1 Major and 4 Minor Dukes criteria. Review modified Dukes criteria.
The echocardiogram reveals MS/MR and large vegetation on the mitral valve. His repeat blood cultures drawn 2 days after beginning antibiotics are still positive for GPC and he remains febrile. On his 3rd day of antibiotic treatment the patient defervesces and his blood cultures are now negative.
10. How long do you want to continue antibiotic treatment for?
6 weeks (after last positive blood culture)
11. What are the potential complications of endocarditis?
Septic emboli to brain, spleen, kidneys. CCF, abscess formation around the valve leading to conduction defects.
The patient completes a 6 week course of IV antibiotics. His surveillance blood cultures have remained negative.
12. How can you prevent the patient from getting IE again?
Endocarditis prophylaxis.
13. When would you give endocarditis prophylaxis?
Before invasive dental procedures.
14. What antibiotic regimen would you give him? When should he take the antibiotics?
penicillin 250 mg PO 30-60 min prior to procedure OR amoxicillin OR erythromycin if PCN allergy
