Endocarditis is an infection of the endocardium that is usually associated with infection of the cardiac valve leaflets. Blood cultures are generally used for diagnosis, and are very sensitive for most organisms.


Indications for Testing

Risk factors and appropriate clinical presentation

Criteria for Diagnosis

To establish final diagnosis, use the modified Duke Criteria for Infective Endocarditis (2009).

Laboratory Testing

  • CBC – frequently shows leukocytosis and left shift toward immature cell forms
  • Blood cultures – three sets from separate venipuncture sites; first and last set at least 1 hour apart
    • Perform prior to antibiotic administration
    • Very sensitive for most organisms
  • C- reactive protein (CRP)
  • For blood culture-negative disease, consider
    • Coxiella – antibody testing
    • Bartonella – polymerase chain reaction (PCR)
    • Brucellaculture, antibody testing
    • HACEK organisms (Haemophilus spp, Aggregatibacter spp [A. aphrophilusA. actinomycetemcomitans], Cardiobacterium hominisEikenella corrodens, Kingella kingae)
      • Cardiobacterium hominis
      • Eikenella corrodens
      • Kingella kingae
    • Antinuclear antibodies (ANA)/rheumatoid arthritis (RA) testing
    • Unusual causes – Tropheryma whipplei, fungi (yeastsmolds)
  • Urine analysis – may demonstrate hematuria, proteinuria, pyuria, red cell casts

Imaging Studies

  • Transthoracic echocardiogram (TTE) or transesophageal echocardiogram (TEE) is the gold standard for visualization of vegetations, but negative study does not rule out endocarditis
    • TTE
      • Recommended first test
      • Sensitivity dependent on vegetation size – if >10 mm, test is 100% sensitive
      • Prosthetic values may be better visualized with TTE
    • TEE
      •  Use in patients with negative TTE and high clinical suggestion of endocarditis
      •  Very sensitive – negative study has negative predictive value of 90%

Differential Diagnosis



  • Incidence – 3-10/100,000; incidence increases with age (up to 20/100,000)
  • Age – mean 30-60 years, depending on population
  • Sex – M>F, 3:1 to 9:1


  • Variety of organisms – Staphylococcus and Streptococcus spp account for most cases
  • Specific medical condition associations
    • Intravenous (IV) drug use – Staphylococcus spp, Streptococcus anginosus group
    • Rheumatic heart disease – Streptococcus anginosus group
    • Gastrointestinal neoplasm in elderly – Streptococcus bovis
    • Healthcare-associated infection – Enterococcus spp, Staphylococcus spp
    • Prosthetic valves – Staphylococcus spp
    • Culture-negative disease – CoxiellaBartonella, BrucellaHACEK organisms
    • Fungi – yeastsmolds
      • Usually 2-3 months after left ventricular assist device (LVAD) implantation
      • Immunocompromised patients

Risk Factors

  • IV drug use
  • Structural heart disease – rheumatic carditis, valvular stenosis, congenital heart disease
  • Hemodialysis
  • Cardiovascular prostheses, intravascular devices
  • Poor dentition
  • HIV
  • Prior episode of infective endocarditis (IE)
  • ​Age >60 years


  • Classification
    • Native valve endocarditis, prosthetic valve endocarditis, and nonvalvular device endocarditis (eg, pacemaker, LVAD)
    • Right- versus left-sided valves
    • Community versus healthcare acquired
  • Turbulent blood flow produced by abnormalities on valvular leaflets
    • In patients with rheumatic heart disease, mitral valve most commonly involved; aortic valve second most commonly involved
    • Right-sided endocarditis more common with IV drug use
  • Transient bacteremia occurs
    • Bacteria naturally adhere to abnormal tissue and form vegetations on the valve
    • Bacteria proliferate within the vegetations

Clinical Presentation

  • Constitutional – fever, anorexia, night sweats, weight loss
  • Cardiovascular – new-onset murmur, congestive heart failure, dysfunctional prosthetic valve
  • Renal – glomerulonephritis
  • Embolic phenomena
  • Osler nodes – painful blue or purple nodules on the fingers, toes, palms, and soles (rare)
  • Roth spots – retinal hemorrhages with central white spots (rare)
  • Janeway lesions – nontender nodules on hands and feet (rare)
  • Splinter hemorrhages – subungual linear hemorrhages on the long axis of the distal third of nail
  • Complications
    • Valvular collapse with heart failure
    • Periannular extension of the infection into the adjacent myocardium
    • Rupture of the myocardium from extension
    • Embolization (highest with left-sided lesions); stroke
    • Mycotic aneurysm
    • Splenic/hepatic abscesses
    • Intracardiac abscesses



Incidence – lower than in adult population

Risk Factors

  • Congenital heart disease
    • Highest risk in cyanotic heart disease, endocardial cushion defects, high-velocity jets
  • Indwelling catheters
  • Rarely – malignancy, osteomyelitis


  • Streptococcus anginosus group – rheumatic heart disease
  • Staphylococcus epidermidis – nosocomial infection

Clinical Presentation

  • Constitutional – lethargy, fever, malaise
  • Cardiovascular – new-onset murmur
  • Adult manifestations such as Osler nodes and Janeway lesions uncommon
  • Complications

ARUP Laboratory Tests

Aid in diagnosis of bacterial process

Detect presence of bacteria in blood

Testing is limited to the University of Utah Health Sciences Center only

Low volume will result in decreased recovery of pathogens

Preferred test to detect acute phase inflammation (eg, autoimmune diseases, connective tissue disease, RA, infection, or sepsis)

Related Tests

Nonspecific test used to detect inflammation associated with infections, cancers, and autoimmune diseases

Confirm infectious agent as C. burnetii (Q-fever) in symptomatic patients

Detect Bartonella species in blood, cerebrospinal fluid (CSF), or tissue

Identify Brucella in blood, CSF, body fluids, and abscesses

Recommended serology test to detect recent infection from Brucella in the context of a clinically compatible illness and exposure history

Reference method for identification of most bacterial species

Aid in initial diagnosis of connective tissue disease

Preferred panel for the workup of suspected RA or undifferentiated inflammatory arthritides

Panel includes cyclic citrullinated peptide (CCP) antibody, IgG; rheumatoid factor

Medical Experts



Mark A. Fisher, PhD, D(ABMM)
Associate Professor of Clinical Pathology, University of Utah
Medical Director, Bacteriology, Special Microbiology, and Antimicrobial Susceptibility Testing, ARUP Laboratories


Jonathan R. Genzen, MD, PhD
Associate Professor of Clinical Pathology, University of Utah
Chief Operations Officer, Medical Director of Automated Core Laboratory, ARUP Laboratories


Additional Resources
Resources from the ARUP Institute for Clinical and Experimental Pathology®