Infective endocarditis

Infective endocarditis (IE) is an infection of the endocardium that typically affects one or more heart valves. The condition is usually a result of bacteremia, which is most commonly caused by dental procedures, surgery, distant primary infections, and nonsterile injections. IE may be acute (developing over hours or days) or subacute (progressive over weeks to months). Acute bacterial endocarditis is usually caused by Staphylococcus aureus and leads to rapid destruction of endocardial tissue, while subacute bacterial endocarditis is most commonly caused by viridans streptococci and generally affects individuals with preexisting damage to the heart valves, structural heart defects, or prosthetic valves. Clinical features include constitutional symptoms (fatigue, fever/chills, malaise), signs of pathological cardiac changes (e.g., new or changed heart murmur, heart failure signs), and, in some cases, manifestations of subsequent damage to other organs (e.g., glomerulonephritis, septic embolic stroke). Management is complex and infectious disease specialists should be involved early. Diagnosis is made based on the Duke criteria, the main features of which are positive blood cultures and evidence of endocardial involvement on echocardiography. Initial treatment of IE consists of empiric IV antibiotics, which are then adapted according to blood culture results and continued for several weeks. Categorization into native valve endocarditis or prosthetic valve endocarditis helps to further tailor regimens. Surgery may be necessary in complex cases (e.g., valve perforation). IE prophylaxis is administered in specific circumstances, e.g., in patients with congenital heart disease having certain dental procedures. IE is typically fatal if left untreated.

Pathogens

Risk factors for infective endocarditis ^[1][4][10]

• Demographics
  • Male sex
  • Age > 60 years
• Cardiac conditions
  • Acquired valvular disease (e.g., rheumatic heart disease, aortic stenosis, degenerative valvular disease)
  • Prosthetic heart valves
  • Congenital heart defects (e.g., VSD, bicuspid aortic valve)
  • Previous IE
  • Cardiac implantable electronic device (CIED) ^[4]
• Noncardiac risk factors
  • Poor dental status
  • Dental procedures
  • Nonsterile venous injections (e.g., in IV drug use)
  • Intravascular devices
  • Surgery
  • Chronic hemodialysis
  • Immunocompromise (e.g., HIV infection, diabetes)
  • Other bacterial infections (e.g., UTIs, spondylodiscitis, periodontal infection)

• Pathogenesis ^[1]
  1. Damaged valvular endothelium → exposure of the subendothelial layer → adherence of platelets and fibrin → sterile vegetation (microthrombus)
  2. Localized infection or contamination → bacteremia → bacterial colonization of vegetation → formation of fibrin clots encasing the vegetation → valve destruction with loss of function (valve regurgitation) ^[11]
• Valve involvement ^[10]
  • Frequency of valve involvement: mitral valve > aortic valve > tricuspid valve > pulmonary valve
  • The tricuspid valve is the most commonly affected valve in persons who inject drugs (associated with Pseudomonas, S. aureus, and Candida).
• Clinical consequences ^[1][11]
  • Bacterial vegetation → bacterial thromboemboli → vessel occlusion → infarctions
  • Emboli can lead to metastatic infections of other organs.
  • Formation of immune complexes and antibodies against tissue antigens → glomerulonephritis, Osler nodes

“Don't tri drugs for the sake of your tricuspid valves.”

Constitutional symptoms ^[1][12]

• Fever and chills (seen in ∼ 90% of patients) ^[1]
• Tachycardia
• General malaise, weakness, weight loss, night sweats
• Dyspnea, cough, pleuritic chest pain
• Arthralgias, myalgias

Patients with subacute IE often present with nonspecific flu-like symptoms, while patients with acute IE often present with signs of acute sepsis.

A high index of suspicion is required in patients with risk factors for IE, as classic extracardiac manifestations (e.g., splinter hemorrhages, Janeway lesions) are absent in the majority of patients. ^[6][13]

Cardiac manifestations ^[1][12]

• Development of a new heart murmur or change in a preexisting murmur (seen in ∼ 75% of patients) ^[1];
  • Tricuspid valve regurgitation
    • Holosystolic murmur that is loudest at the left sternal border
    • Seen in persons who inject drugs, immunocompromised individuals, patients with congenital heart disease, and patients with instrumentation in the right heart (e.g., central venous catheters) ^[2]
  • Aortic valve regurgitation: early diastolic murmur that is loudest at the; left 3^rd and 4^thintercostal spaces and along the left sternal border ^[4]
  • Mitral valve regurgitation: holosystolic murmur that is loudest at the heart's apex and radiates to the left axilla
• Heart failure (e.g., dyspnea, lower limb edema) due to valve insufficiency
• Arrhythmias: Suspect a perivalvular abscess in patients with IE who develop a new conduction abnormality (e.g., heart block). ^[14]

Extracardiac manifestations of IE ^[1][12]

Extracardiac manifestations are typically caused by septic microemboli and/or immune complex precipitation and are more commonly seen in left-sided IE, with the exception of pulmonary embolic manifestations, which are more common in right-sided IE. ^[1][15]

• Peripheral embolic and immunologic phenomena: seen in only 5–10% of patients. ^[1][15]
  • Petechiae, especially splinter hemorrhages (hemorrhages underneath fingernails)
  • Janeway lesions
    • Small, nontender, erythematous macules on palms and soles
    • Microabscesses with neutrophilic capillary infiltration and areas of hemorrhage caused by septic microemboli from valve vegetations
  • Osler nodes: painful nodules on pads of the fingers and toes caused by immune complex deposition
  • Roth spots: round retinal hemorrhages with pale centers
• Emboli to intraabominal organs
  • Acute renal injury
    • Including hematuria and anuria
    • Due to renal artery occlusion or glomerulonephritis
  • Splenomegaly and possible LUQ pain
    • Due to splenic artery occlusion or splenic abscess
    • May lead to splenic rupture ^[16]
• Neurological manifestations: (e.g., seizures, paresis): due to septic embolic stroke, hemorrhage, meningitis, encephalitis, and/or abscess ^[17][18]
• Pulmonary manifestations: caused by septic emboli resulting from tricuspid valve involvement
  • Signs of pulmonary embolism (e.g., dyspnea)
  • Signs of pulmonary infection, e.g., multifocal pneumonia, lung abscess, and/or empyema. ^[19]
• Others: Arthritis

Up to one-third of patients with left-sided IE present with symptoms of stroke. ^[18]

IE should always be considered as a cause of fever of unknown origin (FUO), especially in the presence of a new heart murmur.

“FROM JANE:” Features of IE include Fever, Roth spots, Osler nodes, Murmur, Janeway lesions, Anemia, Nail bed hemorrhage, and Emboli.

• IE can be classified by:
  • Type of affected valve (native vs. prosthetic)
  • Acuity of the infection
  • Location of the infection (left- vs. right-sided).
• Although this is not a definitive classification system, it can help in the approach to management and selection of empiric antibiotic regimens.

Classification by valve type and duration of infection

Classification by location

Approach ^[15][21]

• Suspect IE based on clinical findings (e.g., fever without focus combined with a new murmur) and predisposing conditions.
• The modified Duke criteria help categorize the diagnostic likelihood of IE: definite vs. possible vs. rejected. ^[6]
  • Used as a diagnostic guide; not a substitute for clinical judgment
  • Incorporate clinical, microbiological, pathological, and imaging criteria.
• All patients should receive multiple blood cultures and echocardiography.
• Obtain ECG and additional imaging to investigate any complications or new focal symptoms or signs of metastatic infection.
• Consider serology to evaluate blood culture-negative endocarditis.
• Consult infectious disease (ID) if the diagnosis is uncertain.

Draw three sets of blood cultures, each from a different venipuncture site, as soon as IE is suspected, preferably before antibiotic treatment is initiated.

Laboratory studies ^[15]

Routine studies

• CBC: : leukocytosis with left shift
• Inflammatory markers: ↑ CRP, ↑ ESR ^[21]
• BMP: to assess renal function for antibiotic dosing
• Urinalysis: to assess for hematuria and nephritic sediment ^[13][24]

Blood cultures ^[25]

See also “Intravascular catheter-related bloodstream infections” and “Bacteremia.”

• Sampling protocol
  • Prior to treatment: three sets from different venipuncture sites ^[15][25]
  • Monitoring: two sets every 24–48 hours until clearance
• Interpretation
  • Positive bacterial cultures: Assess according to the modified Duke criteria.
  • Negative bacterial cultures do not rule out endocarditis; patients with endocarditis may have a negative result due to: ^[6][25][26]
    • Antibiotic therapy prior to blood culture sampling
    • Fastidious bacteria (most commonly Coxiella burnetii and Bartonella spp.)
    • Fungal infection
    • Noninfective endocarditis

Negative blood cultures do not rule out IE. A significant proportion of patients with IE have sterile cultures.

Echocardiography ^[15]

Transthoracic echocardiography (TTE) is the initial test of choice for all patients with suspected IE. It should ideally be performed within 12 hours of presentation and repeated after completing treatment. Transesophageal echocardiography (TEE) is more invasive and is added in select cases. ^[15]

• Indications for TEE include:
  • Presence of high-risk features
  • TTE findings inconclusive or suggestive of IE
  • Preoperative planning
  • Concern for intracardiac complications (e.g., abscess)
• Echocardiographic findings fulfilling Duke criteria for IE: similar in TTE and TEE ^[6][27][28]
  • Valvular vegetations: Hyperechoic mobile masses located on the valve, mural endocardium, or prosthetic material ^[29]
  • Abscess (e.g., perivalvular abscess)
  • New valvular regurgitation (especially with valve prolapse, perforation, or destruction)
  • Prosthetic valve dehiscence
• Other high-risk findings include:
  • Valve aneurysm
  • Fistula or pseudoaneurysm
  • Heart failure

TEE is more sensitive (∼ 90%) than TTE (∼ 75%) and is more reliable in ruling out IE in patients with moderate-to-high pretest probability.

Additional investigations ^[15][25]

• Serology: to assess blood-culture negative endocarditis (in consultation with the infectious disease service)
  • Most commonly for Coxiella burnetii and Bartonella spp.
  • A C. burnetii anti-phase I IgG titer of ≥ 1:800 is part of the modified Duke criteria.
  • Limitations: cross-reactivity between different pathogens, confounding from prior infections
• Tissue sampling (after surgery)
  • Histopathology of resected valves (gold standard) ^[25][30]
  • Gram stain and culture: to plan duration of postoperative antimicrobial therapy ^[25]
  • Molecular testing (e.g., T. whipplei PCR) ^[30]
• ECG: indicated in every patient to assess for complications (e.g., AV block/branch blocks in paravalvular extension) ^[6][21]
• Additional imaging: performed in selected cases to assess for complications (e.g., emboli)
  • CXR: The presence of multiple pulmonary infiltrates may suggest right-sided IE. ^[13]
  • Abdominal ultrasound: if splenic abscess or infarction is suspected
  • Cardiac CTA: to assess perivalvular disease or coronary artery anatomy prior to cardiac surgery ^[28]
  • MRI head: Consider for the assessment of intracranial septic emboli.
• Dental assessment: in all patients with confirmed IE regardless of the initial source of bacteremia
• Colonoscopy: in patients with bacteremia involving S. gallolyticus to rule out colon cancer and mucosal lesions

Obtain an ECG in all patients with suspected IE to assess for new conduction abnormalities (e.g., AV block, bundle branch block) that suggest the development of a perivalvular or myocardial abscess. Consider urgent cardiac imaging (e.g., TEE, cardiac MRI) if these abnormalities are present. ^[6][21]

• Acute disease (leading to valve insufficiency, septic embolic infarcts, tendinous cord rupture) ^[31]
  • Erosion → fibrin deposits on valves
  • Ulceration
  • Perforation
• Chronic disease (leading to valve insufficiency and valve stenosis) ^[31]
  • Erosion → reorganization of fibrin layer
  • Granulation tissue → valve scarring/fibrosis
  • Calcification → thickened and/or shortened tendinous cords

Noninfective endocarditis (nonbacterial thrombotic endocarditis) ^[32][33]

• Description
  • Rare, noninfective form of endocarditis due to sterile platelet thrombus formation on the heart valves (usually mitral and aortic valves)
  • Libman-Sacks endocarditis: a type of noninfective endocarditis with verrucous vegetations in individuals with systemic lupus erythematosus or antiphospholipid syndrome ^[32]
• Etiology
  • Malignancy (e.g., pancreatic adenocarcinoma)
  • Hypercoagulable states
  • Underlying trauma (e.g., from indwelling vascular catheters)
  • Previous rheumatic fever
  • Autoimmune conditions (e.g., systemic lupus erythematosus, rheumatoid arthritis, antiphospholipid syndrome) ^[34]
  • Chronic infections (e.g., TB, pneumonia, osteomyelitis)
• Clinical features
  • Valves and cardiac function are rarely impaired.
  • Compared to IE, vegetations are easily dislodged and embolization is common, leading to hemorrhages under the nails, skin, and retina
  • Most affected individuals are asymptomatic until embolization occurs.
• Diagnostics
  • Negative blood cultures
  • Echocardiography: valve vegetations
  • Biopsy (definitive diagnosis)
    • Sterile vegetations on either surface of the valve composed of immune complexes, mononuclear cells, and thrombi interwoven with fibrin strands
    • Not always feasible, therefore diagnosis is mostly made based on clinical findings, negative blood cultures, echocardiography findings, and no response to antibiotic treatment
• Treatment
  • Anticoagulation with heparin
  • Treatment of the underlying condition

Prosthetic valve thrombosis ^[35]

• Overview
  • Usually affects mechanic valves
  • Rare if anticoagulation is adequate
• Etiology: insufficient anticoagulatory therapy after valve replacement
• Clinical features
  • Signs of acute heart failure
    • Left heart failure: dyspnea and cough
    • Right heart failure: edema and jugular venous distention
  • Deterioration of general condition, cardiac arrhythmias, cerebral emboli (stroke)
• Diagnostics: transesophageal echocardiography
• Treatment
  • Anticoagulation and fibrinolysis
  • Surgical valve replacement

The differential diagnoses listed here are not exhaustive.

Initial management ^{[6][15][36][37]}

• Unstable patients: Use the ABCDE approach and initiate management of sepsis as needed.
• Consults ^[38]
  • Consult infectious disease early to plan treatment and evaluate the need for empiric therapy.
  • Identify patients with indications for surgery consult in IE.
• Antibiotic therapy
  • Start early empiric antibiotic therapy for IE once samples for blood cultures have been obtained. ^[6][37]
  • Switch to targeted antibiotic therapy for IE once blood culture results are available. ^[6][37]
• Supportive care: Treat urgent complications (e.g., acute heart failure, heart block) and initiate management of the underlying cause (e.g., removal of infected central lines).

If IE is suspected, first obtain blood cultures, then consult infectious disease to plan empiric antibiotic therapy. When culture results are available, adapt the therapy accordingly.

Supportive care

• Management of antithrombotic agents ^[15][36]
  • Existing anticoagulation is commonly stopped for ≥ 2 weeks if CNS emboli are present.
  • Antiplatelet agents should not be initiated, but long-term therapy may be continued if there are no bleeding complications.
  • Initiation of anticoagulation is not routinely recommended.
• Management of cardiovascular complications: See “Acute heart failure management” and “Management of heart block.” ^[39]
• Others
  • Removal of infected central lines and CIEDs ^[40][41]
  • Management of opioid use disorder if IE is related to IV drug use. ^[42][43]
  • Inpatient dental evaluation

Antibiotics

Empiric antibiotic therapy ^[15]

The goal is to provide broad-spectrum coverage for potential bacterial causes of IE (including multidrug-resistant organisms) until blood culture results are available.

• Choice of empiric agent: Consult infectious diseases and take into account patient and disease factors as well as local and individual flora and resistance patterns (see “Risk factors for IE" and “Classification”).
• Common empiric antibiotic regimens
  • Native valve endocarditis: vancomycin PLUS a beta-lactam (e.g., ceftriaxone, cefepime)
  • Prosthetic valve endocarditis: Add gentamicin PLUS rifampin to vancomycin PLUS a beta-lactam (if ≤ 1 year after placement).

Targeted antibiotic therapy ^[15]

Targeted antibiotic therapy based on culture and sensitivity results is recommended for all patients with IE.

• Common targeted antibiotic regimens
  • Staphylococci
    • Methicillin-susceptible staphylococci (MSSA): antistaphylococcal beta-lactam (e.g., nafcillin, oxacillin)
    • Methicillin-resistant staphylococci (MRSA): vancomycin
    • Prosthetic valve endocarditis; (≤ 1 year after placement): Add gentamicin PLUS rifampin to the regimen described for native valve IE.
  • Viridans group streptococci; : beta-lactam (e.g., penicillin G, ampicillin)
  • Enterococci: combination therapy (e.g., ampicillin PLUS gentamicin)
  • HACEK: ceftriaxone (first-line)
• Duration of therapy: variable depending on many factors, e.g., drug regimen, affected valve; can be 2–6 weeks or longer after the first sterile blood culture
• Blood culture-negative endocarditis: empiric therapy until additional investigations (e.g., serology) yield results

Surgery ^[15][36][38]

These procedures typically follow a multidisciplinary decision made by cardiology, cardiothoracic surgery, and infectious disease services.

• Indications for surgery consult in IE include:
  • Prosthetic valve endocarditis
  • Valve dysfunction leading to heart failure
  • Uncontrolled infection: e.g., enlarging vegetation, persistent bacteremia
  • Perivalvular extension or complications: e.g., abscess, pseudoaneurysm, fistula, heart block
  • Fungal endocarditis
  • High embolic risk: e.g., mobile vegetation > 10 mm, recurrent embolism
• Surgical options: valve replacement or valve repair (see “Treatment” in “Valvular heart diseases”)
• Complications
  • Acute surgical complications: e.g., rebleeding from surgical sites, coagulopathy, acute renal failure, pneumonia
  • Cardiac complications: e.g., CHF, myocarditis, pericarditis, new AV block
  • Systemic emboli: e.g., stroke

Surgical intervention is required in 50–60% of patients with IE. ^[38]

Unstable patients

• Perform ABCDE survey.
• Begin treatment of complications causing hemodynamic instability, e.g.:
  • Sepsis management
  • Management of acute heart failure
  • Management of bradycardia (e.g., due to heart block)

All patients

• Perform a clinical evaluation, including cardiac surgical history (e.g., date and type of valvular repair or replacement) and screening for extracardiac manifestations of IE.
• Establish IV access, draw three sets of blood cultures from different venipuncture sites, and obtain routine laboratory studies (e.g., CBC, BMP).
• Order echocardiogram.
• Use the modified Duke criteria to categorize the diagnostic likelihood of IE.
• Obtain ECG and screen for new conduction abnormalities.
• Consult infectious diseases.
• Start empiric antibiotics for IE after blood samples are obtained.
• Screen for clinical features of metastatic infections and consider imaging to confirm their presence (e.g., CXR, CT abdomen and pelvis, CT head).
• Identify patients with indications for surgery consult surgery in IE.
• Switch to targeted antibiotic therapy for IE once blood culture results are available.
• Begin treatment of underlying conditions (e.g., removal of infected central lines and CIEDs, treat opioid use disorder)
• Admit to hospital.
• Screen and monitor for complications (e.g., valvulopathy, acute heart failure, perivalvular abscess, AV block, stroke, pulmonary embolism).

• Cardiac complications
  • New or worsened valvular regurgitation
  • Partial dehiscence of a prosthetic valve ^[15]
  • Congestive heart failure
  • Perivalvular abscess and fistula
  • Myocarditis
  • Conduction abnormalities: e.g., AV blocks
• Embolic complications
  • Systemic embolism in left-sided endocarditis: e.g., stroke, renal infarct, splenic infarct
  • Pulmonary embolism in right-sided endocarditis
  • Septic emboli and mycotic aneurysms
• Metastatic infections: due to septic emboli or bacteremia
  • Multifocal pneumonia, lung abscess
  • Spondylodiscitis
  • Splenic abscess
  • Meningitis, brain abscess
• Acute kidney injury: Often multifactorial ^[4]

We list the most important complications. The selection is not exhaustive.

Endocarditis prophylaxis ^{[36][44][45][46]}

Prophylaxis is indicated prior to certain procedures with a high risk of bacteremia in patients with high-risk cardiac features. ^[44]

• Cardiac risk factors requiring IE prophylaxis (for procedures that may cause bacteremia)
  • Presence of prosthetic cardiac valve or material
  • History of endocarditis
  • Certain types of congenital heart disease (CHD), e.g., unrepaired cyanotic CHD, repaired CHD (within 6 months of repair), repaired CHD with residual post-operative shunt or regurgitation
  • Valvulopathy in cardiac transplant recipients ^[36][46]
• Procedures requiring IE prophylaxis in patients at risk for IE
  • Some dental procedures
  • Any invasive procedure involving infected tissue (e.g., abscess drainage)
  • Placement of a CIED ^[41][47]
  • Surgical placement of prosthetic cardiac or intravascular material (e.g., heart valve, intravascular graft) ^[47]
• Common regimens (usually administered 30–60 minutes prior to the procedure) ^[36]
  • Prior to dental procedures ^[44]
    • No penicillin allergy: amoxicillin OR ampicillin OR cefazolin
    • Penicillin allergy: a macrolide (e.g., azithromycin; ) OR doxycycline
  • Prior to CIED placement: cefazolin
  • Pathogen-specific agents may be indicated depending on the site of the procedure. ^[36]

IE prophylaxis is not routinely recommended prior to nondental procedures (including respiratory, skin, musculoskeletal, gastrointestinal, and genitourinary procedures) unless infected tissue is present. ^[36]