Endocarditis: Pathology review

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Endocarditis: Pathology review




Endocarditis: Pathology review

USMLE® Step 1 questions

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A 36-year-old man presents to the emergency department with fever, chills, and cough of three days duration. The patient uses intravenous heroin regularly and reports he last used heroin earlier today. He is currently living in a homeless shelter. Temperature of 38.7 °C (101.6 °F), pulse is 105/min, respirations are 22/min, blood pressure is 100/63 mmHg, and oxygen saturation is 91% on room air. On physical examination, the patient appears disheveled. Erythematous lesions are noted on the chest and arms bilaterally. Rales are appreciated in the lungs bilaterally, and a holosystolic murmur is appreciated at the left lower sternal border. Laboratory values are demonstrated below:  
 Laboratory value  Result 
Complete Blood Count, Serum 
 Hemoglobin  12.5 g/dL 
 Hematocrit  40.5% 
 Leukocyte count  18,100 /mm3 
 Platelet count  250,000/mm3 
Inflammatory Markers, Serum 
ESR                 44 mm/hr 
 CRP  18 mg/L 
Electrolytes, Serum 
                  Sodium                131 mEq/L 
               Potassium                 3.6 mEq/L 
                 Chloride                 94 mEq/L  
              Bicarbonate                 20 mEq/L 
                 Calcium                8.4 mg/dL 
Blood is drawn and sent for culture, and the patient is started on empiric antibiotics. Three days later, 3 of 4 blood cultures obtained on admission grow Gram-positive, coagulase-positive bacteria. Which of the following is the most common initial site of infection in this patient?   

Memory Anchors and Partner Content


Two people came into the cardiology ward.

One of them was 25 year old Darren, who came in with a fever, chills and fatigue.

On the clinical examination, his fingernails had splinter hemorrhages and the palm of his hands had some erythematous flat lesions.

There were also some track marks on his forearm.

The other one is 75 year old Anna, who also had a fever and the same splinter hemorrhages and erythematous flat lesions that we previously saw.

On auscultation, a heart murmur was heard.

On her history, she said she was at the dentist 2 weeks ago.

Okay, so both people likely have endocarditis, or inflammation of the inner layer of the heart.

Remember that the heart’s wall is made up of three layers, the epicardium being the outermost layer, then the myocardium, and the endocardium, which is the layer that gets inflamed.

The inflammation can affect the heart valves, the mural endocardium or even prosthetic valves!

The most common cases of endocarditis are due to a microbial infection, and this is called infective endocarditis but in some cases, endocarditis can also be non-infective.

For non-infective endocarditis, the first step is usually damage to the endocardium.

Damage exposes the underlying collagen and tissue factor, which causes platelets and fibrin to adhere, which forms tiny blood clots.

This is called Nonbacterial Thrombotic Endocarditis or NBTE.

Tiny clots and fibrin can develop into vegetation, especially on the heart valves which damages them and makes it harder for them to open or close.

Although the exact cause of NBTE is unknown, it’s thought that a proinflammatory state where cytokines levels are elevated can increase clot formation.

This can happen with hypercoagulable states, like when there’s a malignancy, especially pancreatic adenocarcinoma.


  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Management Considerations in Infective Endocarditis" JAMA (2018)
  4. "Infective Endocarditis in Adults: Diagnosis, Antimicrobial Therapy, and Management of Complications" Circulation (2015)
  5. "2015 ESC Guidelines for the management of infective endocarditis" European Heart Journal (2015)
  6. "Poor oral hygiene as a risk factor for infective endocarditis–related bacteremia" The Journal of the American Dental Association (2009)
  7. "Clinical Presentation, Etiology, and Outcome of Infective Endocarditis in the 21st Century" Archives of Internal Medicine (2009)
  8. "2017 AHA/ACC Focused Update of the 2014 AHA/ACC Guideline for the Management of Patients With Valvular Heart Disease" Journal of the American College of Cardiology (2017)
  9. "Antibiotic prophylaxis for infective endocarditis: a systematic review and meta-analysis" Heart (2017)

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