From the Guidelines
The diagnosis of endocarditis should be based on the modified Duke criteria, as updated by the 2015 ESC guidelines 1, which combines major and minor clinical findings to prioritize morbidity, mortality, and quality of life. The major criteria include positive blood cultures for typical organisms (such as Streptococcus viridans, Staphylococcus aureus, or HACEK organisms) and evidence of endocardial involvement on echocardiography (vegetation, abscess, or new valvular regurgitation) as defined by the European Society of Cardiology 2015 modified criteria for the diagnosis of infective endocarditis 1. Some key points to consider in the diagnosis of endocarditis include:
- Major criteria:
- Blood cultures positive for IE, including typical microorganisms consistent with IE from 2 separate blood cultures, or microorganisms consistent with IE from persistently positive blood cultures 1
- Imaging positive for IE, including echocardiogram positive for IE, or abnormal activity around the site of prosthetic valve implantation detected by 18 F-FDG PET/CT or radiolabelled leukocytes SPECT/CT 1
- Minor criteria:
- Predisposition, such as predisposing heart condition, or injection drug use 1
- Fever 1
- Vascular phenomena, including major arterial emboli, septic pulmonary infarcts, infectious (mycotic) aneurysm, intracranial haemorrhage, conjunctival haemorrhages, and Janeway’s lesions 1
- Immunological phenomena, including glomerulonephritis, Osler’s nodes, Roth’s spots, and rheumatoid factor 1
- Microbiological evidence, including positive blood culture but does not meet a major criterion as noted above or serological evidence of active infection with organism consistent with IE 1 Definite endocarditis is diagnosed with either 2 major criteria, 1 major plus 3 minor criteria, or 5 minor criteria, as per the 2015 ESC guidelines 1. It is essential to obtain blood cultures before starting antibiotics, with at least three sets from different venipuncture sites, and to use both transthoracic and transesophageal echocardiography, as the latter has higher sensitivity for detecting vegetations 1. Early diagnosis is crucial as delayed treatment can lead to severe complications, including heart failure, embolic events, and death, emphasizing the need to prioritize morbidity, mortality, and quality of life in the diagnosis and management of endocarditis.
From the Research
Diagnostic Criteria for Endocarditis
The diagnostic criteria for endocarditis have been studied and refined over the years. According to 2, the Duke criteria were developed to improve the diagnosis of infective endocarditis. These criteria include two major criteria (typical blood culture and positive echocardiogram) and six minor criteria (predisposition, fever, vascular phenomena, immunologic phenomena, suggestive echocardiogram, and suggestive microbiologic findings).
Major and Minor Criteria
The study by 3 evaluated the presence and individual value of each criterion of the modified Duke criteria in patients with infective endocarditis. The results showed that the echocardiography major criterion was the most important, and its absence would lead to 43% of cases being classified as possible instead of definite. The minor criteria, such as fever and predisposition, contributed to the diagnosis in only 10% of cases.
Updates to Diagnostic Criteria
A more recent study by 4 suggested that the microbiological diagnostic criteria should be updated to regard Enterococcus faecalis as a "typical" endocarditis bacterium, similar to viridans group streptococci and Staphylococcus aureus. This update improved the sensitivity of the diagnostic criteria to correctly identify definite endocarditis from 70% to 96%.
Echocardiography in Diagnosis
The study by 5 found that healthcare-associated Staphylococcus aureus bacteremia had a low rate of endocarditis, especially in the absence of high-risk features. The authors suggested that echocardiography might not always be required in these cases, and that careful clinical follow-up is warranted instead.
Key Points
- The Duke criteria are used to diagnose infective endocarditis and include major and minor criteria.
- The echocardiography major criterion is the most important for diagnosis.
- Updates to the diagnostic criteria, such as regarding Enterococcus faecalis as a "typical" endocarditis bacterium, can improve sensitivity.
- Echocardiography may not always be required in cases of healthcare-associated Staphylococcus aureus bacteremia with low risk of endocarditis.
- The diagnostic criteria for endocarditis continue to evolve, with studies such as 6 providing insights into the epidemiology and clinical manifestations of the disease.