The diagnosis of IE is still a challenge today. The most important techniques in diagnosis are blood cultures and echocardiography (Holland 2016).
For diagnosis, one should
- Obtain a history of any risk factors, such as vitiation, i.v. drug use, etc.
- Obtain clinical symptoms, e.g., fever, heart murmur
- Obtain laboratory findings
- Draw blood cultures repeatedly (minimum is 3 aerobic and 3 anaerobic) (Herold 2022).
Itis obligatory to take blood cultures repeatedly both before starting antibiosis and during the course for targeted antibiosis (Renz- Polster 2008).
According to the ESC guideline, the diagnosis of infective endocarditis is made according to the simplified and modified Duke criteria. These criteria are based on clinical, laboratory chemistry, imaging findings, and major or minor criteria (Knirsch 2022). Sensitivity and specificity are around 80%. Subsequent modifications have resulted in a sensitivity for pediatric patients of nearly 90% (Knirsch 2022). For prosthetic valve endocarditis, the sensitivity is also 90% (Saha 2022).
Duke- Criteria:
Main criteria are:
1. blood culture positive for IE:
- 1. a. Typical pathogens in at least 2 separate blood cultures such as.
- Streptococcus bovis, Staphylococcus viridans, or HACEK- group.
or
- Staphylococcus aureus "community-acquired".
or
- Enterococci without primary focus (Knirsch 2022)
or
- 1. b. pathogens compatible with IE in multiple positive blood cultures:
- at an interval of > 12 hours in at least 2 blood cultures
- or
- regardless of spacing in 3 or the majority of ≥ 4 blood cultures
- or
- 1. c. a single culture positive for Coxiella burnetii or an increase in the phase I IgG antibody titer to > 1: 800 (Knirsch 2022).
2. positive imaging for IE:
- 2. a. Echocardiographic evidence of:
- Valve perforation or aneurysm.
- vegetation
- New onset dehiscence on a prosthetic valve.
- Pseudoaneurysm, intracardiac fistula, abscess (Knirsch 2022)
Or
- 2. b. F- FDG PET / CT or SPECT / CT:
- abnormal activity in the position of a prosthetic valve after implantation > 3 months (Knirsch 2022)
or
- 2. c. Cardiac computed tomography:
- Evidence of a paravalvular lesion (Knirsch 2022).
Ancillary criteria are:
- 3. a. predispositions such as Z. n. IE, history of known cardiac defect, i. v. drug abuse, etc. (Knirsch 2022)
- 3. b. > 38 degrees C fever (Knirsch 2022)
- 3. c. Vascular phenomena (including those detected on imaging) such as:
- septic pulmonary infarcts
- arterial embolism
- intracranial hemorrhage
- mycotic aneurysms
- Janeway lesions
- conjunctival hemorrhage (Knirsch 2022)
- 3. d. Occurrence of immunologic changes such as:
- Osler nodules
- glomerulonephritis
- rheumatoid factors
- Roth spots (Knirsch 2022)
- 3. e. Microbiological evidence by:
- Positive blood cultures, but not meeting the major criteria.
or
- Serological evidence of active infection by pathogens compatible with IE (Knirsch 2022).
The diagnosis is considered confirmed in the presence of:
- 2 main criteria
- or
- 1 major criterion and 3 minor criteria
- or
- 5 secondary criteria (Knirsch 2022)
or
- Pathologic criteria for the definite presence of an IE are met such as:
- histological evidence of IE
or
- microbiological evidence of IE
or
- histological preparation with evidence of active endocarditis (Knirsch 2022).
There is a suspected diagnosis of:
- 1 major criterion and 1 minor criterion.
- or
- 3 minor criteria (Knirsch 2022)
If the Duke criteria are not met, IE cannot be ruled out. This is only the case if (Girndt 2022):
- Resolution of symptoms after ≤ 4 days of antibiotic therapy.
or
- Existence of a clear alternative diagnosis
or
- the criteria of a possible IE are not fulfilled
or
- Lack of pathological evidence at surgery or autopsy after ≤ 4 days of antibiotic therapy (Knirsch 2022).