INFECTIOUS SYNDROMES

Infective Endocarditis

Classification: Microbial infection of the endocardial surface, usually a cardiac valve or intracardiac prosthetic/device surface (Fiske & Bloch, 2019).

Key diagnostic discriminator: Persistent bacteremia plus compatible echocardiographic endocardial involvement. Embolic, immune-complex, and valvular findings can make this a multisystem disease (European Society of Cardiology, 2023; Fiske & Bloch, 2019).

Clinical priority: Acute neurologic deficit may be septic embolic stroke or hemorrhage. New conduction delay can indicate periannular abscess. Pulmonary edema or shock may indicate acute valve failure (European Society of Cardiology, 2023; Fiske & Bloch, 2019).

Etiology and risk factors

  • Major risks include prior endocarditis, prosthetic valve or repair material, selected congenital heart disease, intracardiac device, injection drug use, hemodialysis/vascular access, and sustained bacteremia (Fiske & Bloch, 2019).
  • Staphylococcus aureus can infect normal valves and cause acute destructive disease. Viridans streptococci, enterococci, coagulase-negative staphylococci, HACEK organisms, fungi, and other pathogens occur in specific contexts (Fiske & Bloch, 2019).

Pathophysiology

  • Endothelial/valvular injury permits platelet-fibrin deposition. Transient or sustained bacteremia seeds this surface; organisms adhere and become embedded in a vegetation protected from immune clearance (Fiske & Bloch, 2019; Norris, 2020).
  • Vegetations destroy valves, extend into periannular tissue, and continuously shed organisms or emboli. Circulating immune complexes contribute to glomerulonephritis and peripheral findings (Fiske & Bloch, 2019; Norris, 2020).
  • Left-sided disease embolizes systemically; right-sided disease, common with injection exposure or right-sided devices, produces septic pulmonary emboli (Fiske & Bloch, 2019; Norris, 2020).

Clinical manifestations

  • Fever, chills, malaise, anorexia, weight loss, new/changing murmur, heart failure, persistent bacteremia, or embolic symptoms. Older or immunocompromised patients may have muted fever (Fiske & Bloch, 2019).
  • Possible findings include petechiae, splinter hemorrhages, painless Janeway lesions, painful Osler nodes, retinal Roth spots, splenomegaly, hematuria, stroke, vertebral pain, or pulmonary nodules/infarcts in right-sided disease (Fiske & Bloch, 2019).

Findings that argue against or redirect

  • A single contaminated culture without compatible clinical or imaging evidence is insufficient. Negative cultures after prior antibiotics do not exclude endocarditis (Fiske & Bloch, 2019).
  • A normal initial transthoracic echocardiogram does not exclude disease when pretest probability is moderate/high, prosthetic material is present, or the organism/risk is high. Proceed to transesophageal imaging or repeat imaging as indicated (Fiske & Bloch, 2019).
  • A simple flow murmur with rapidly resolving bacteremia and an alternative source lowers probability but requires clinical judgment (Fiske & Bloch, 2019).

Diagnostic evaluation

  • Obtain three sets of blood cultures from separate peripheral venipunctures at approximately 30-minute intervals before antibiotics when the patient is stable enough. Do not delay therapy in shock or another immediately life-threatening presentation (European Society of Cardiology, 2023; Fiske & Bloch, 2019).
  • Perform transthoracic echocardiography promptly. Use transesophageal echocardiography when suspicion remains high, the transthoracic study is negative or inconclusive, or prosthetic-valve, intracardiac-device, or perivalvular disease is possible (European Society of Cardiology, 2023; Fiske & Bloch, 2019).
  • Integrate microbiology, echocardiography and other cardiac imaging, predisposing cardiac conditions, fever, and vascular and immunologic phenomena using validated diagnostic criteria. Evaluate suspected embolic, neurologic, renal, conduction-system, or heart-failure complications with targeted testing (European Society of Cardiology, 2023; Fiske & Bloch, 2019).

Expected diagnostic and laboratory findings

  • Major evidence includes typical organisms from appropriately collected cultures or persistent bacteremia and imaging evidence of vegetation, abscess, new prosthetic dehiscence, or other endocardial involvement (European Society of Cardiology, 2023; Fiske & Bloch, 2019).
  • Supportive abnormalities include normocytic anemia, elevated ESR/CRP, leukocytosis, microscopic hematuria/proteinuria, low complement with immune-complex disease, and embolic infarcts. These are nonspecific (European Society of Cardiology, 2023; Fiske & Bloch, 2019).

Differential diagnosis

  • Nonbacterial thrombotic endocarditis: sterile vegetations in malignancy/hypercoagulability; repeated cultures negative and another systemic cause present (Fiske & Bloch, 2019).
  • Atrial myxoma: constitutional/embolic picture with an intracardiac mass but no microbiologic evidence (Fiske & Bloch, 2019).
  • Vasculitis or autoimmune disease: immune/vascular manifestations with negative cultures and disease-specific serology/biopsy (Fiske & Bloch, 2019).
  • Occult bacteremia, osteomyelitis, infected device, or other deep infection: alternative source explains cultures and imaging (Fiske & Bloch, 2019).

Treatment and management

  • After cultures are collected, begin prompt empiric therapy when indicated and transition to prolonged pathogen-directed bactericidal antimicrobial therapy based on susceptibility, valve type, and complications (European Society of Cardiology, 2023; Fiske & Bloch, 2019).
  • Involve an endocarditis team early, including infectious disease, cardiology, cardiac surgery, microbiology, and other specialists required by complications (European Society of Cardiology, 2023; Fiske & Bloch, 2019).
  • Urgent or early surgery is considered for heart failure from valve dysfunction, uncontrolled infection or abscess, and prevention of septic embolization in selected high-risk disease. Remove infected intracardiac hardware when indicated and address the source of bacteremia (European Society of Cardiology, 2023; Fiske & Bloch, 2019).

Additional complications and red flags

  • Obtain urgent specialist input before anticoagulation changes or invasive procedures when intracranial embolic/hemorrhagic complication is possible (European Society of Cardiology, 2023; Fiske & Bloch, 2019).

Clinical Reasoning Priorities

  • Recognize first: Suspect infective endocarditis when persistent fever or bacteremia occurs with a prosthetic valve, prior endocarditis, intracardiac device, structural valve disease, injection exposure, embolic findings, a new murmur, or otherwise unexplained heart failure (European Society of Cardiology, 2023; Fiske & Bloch, 2019).
  • Reassess probability: Multiple blood cultures growing a typical organism, a vegetation or perivalvular lesion, and compatible vascular or immunologic phenomena substantially increase probability. Prior antimicrobial exposure can produce culture-negative disease, so negative cultures alone do not exclude endocarditis (European Society of Cardiology, 2023).
  • Do not miss: Acute valve failure, periannular abscess, new conduction abnormality, persistent sepsis, stroke, systemic embolization, and septic pulmonary emboli are immediately consequential complications (European Society of Cardiology, 2023; Norris, 2020).
  • Use decisive testing: Obtain three sets of peripheral blood cultures before antibiotics when clinically feasible and perform prompt echocardiography. Transesophageal echocardiography is required when transthoracic imaging is nondiagnostic despite high suspicion or when prosthetic-valve, device-associated, or perivalvular infection is possible (European Society of Cardiology, 2023).
  • Act on time-sensitive decisions: Do not delay empiric antimicrobial therapy in shock or another unstable presentation. Engage infectious disease, cardiology, cardiac surgery, and microbiology early when heart failure, uncontrolled infection, abscess, prosthetic material, or high embolic risk may require procedural management (European Society of Cardiology, 2023).

For the systemic consequences of infection, review Sepsis and Septic Shock. For antimicrobial selection principles, see Antimicrobial Selection and Stewardship.

Content last reviewed:

References

European Society of Cardiology. (2023, August 25). 2023 ESC guidelines for the management of endocarditis. https://www.escardio.org/guidelines/clinical-practice-guidelines/all-esc-practice-guidelines/endocarditis/

Fiske, C. T., & Bloch, K. C. (2019). Infectious diseases. In G. D. Hammer & S. J. McPhee (Eds.), Pathophysiology of disease: An introduction to clinical medicine (8th ed.). McGraw-Hill Education.

Norris, T. L. (2020). Porth’s essentials of pathophysiology (5th ed.). Wolters Kluwer.