Infective endocarditis (IE) is a microbial infection of the endocardial structures produced by blood dissemination of the causal microorganism. The characteristic lesion is endocarditis vegetation, which can be evidenced by echocardiography.
Diagnosis of infectious endocarditis is put both on history and clinical examination (fever, recent valvular murmurs, neurological and mucocutaneous signs), as well as laboratory tests (biological inflammatory syndrome – elevated ESR, increased C-reactive protein, leukocytosis, the presence of rheumatoid factor and circulating immune complexes, decreased serum complement, cryoglobulinemia, positive blood cultures, nitrogen retention, hematuria, proteinuria) and imaging (ECG, echocardiography – transthoracic or transesophageal).
Infective endocarditis is a severe disease and can cause complications such as peripheral arterial embolism, stroke, brain abscess, valve ring abscess, mycotic aneurysm, glomerulonephritis, heart failure, or conduction abnormalities.
Infective endocarditis – Duke Diagnostic Criteria
For diagnosis, they were originally used Durack criteria and then Reyn criteria. Currently, the diagnosis of infectious endocarditis is made by Duke criteria, which involves echocardiographic evaluation of the patient.
Thus, for a definite diagnosis of endocarditis are needed either 2 major criteria (2M) or one major and three minor criteria (1M +3 m) or five minor criteria (5m). For possible endocarditis are needed less criteria than for accurate diagnosis. Endocarditis may be invalidated when an alternative diagnosis is established or when symptoms resolved in less than 4 days after initiation of antibiotic therapy.
- Two separate blood cultures positive with typical microorganisms (Streptococcus viridans, Streptococcus bovis group HACEK – Haemophilus parainfluenzae, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, Kinella kingae, Staphylococcus aureus, enterococci, in the absence of a primary outbreak).
- persistently positive blood cultures for specific infective endocarditis microorganisms: two positive blood cultures from blood samples collected every 12 hours, or 3 or 4 positive blood cultures, collected separately.
- unique blood culture positive for Coxiella burnetii or specific IgG antibody specific to Coxiella
- evidence of endocardial involvement: echocardiographic presence of oscillating intracardiac mass (located in the heart valves or supporting structures, or in the path of regurgitant jet or prosthetic material in the absence of anatomical explanations), ring abscess, prosthetic valve dehiscence or new valvular regurgitation (worsening or changing of preexisting murmur is insufficient).
- Cardiac diseases predisposing to E. I. or intravenous drug use (drug addicts);
- fever over 38 degrees Celsius;
- vascular phenomena – peripheral arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial hemorrhage, Janeway lesions;
- immunological phenomena: glomerulonephritis, Osler nodes, Roth spots, the presence of rheumatoid factor;
- Microbiological evidence: positive blood cultures not meeting major criterion or serological evidence of active infection with a microorganism that can produce infective endocarditis;
- echocardiographic evidence consistent with EI, but not a major criterion requirements;
Suspicion of endocarditis arises when is present a biological inflammatory syndrome, thrombocytopenia, normocytic normochromic anemia, signs of kidney damage,positive immunoassay and new cardiac murmurs. Blood cultures (at least 3 positive for the same organism) and transthoracic echocardiography (sensitivity 70%) or transesophageal (sensitivity 90%) confirm the diagnosis. Vegetation favorite location is on the atrial face of mitral valve and ventricular face of aortic valves (areas of maximum turbulence). Guidance criteria for diagnosis is the patient classification in a category of risk: patients with valvular diseases, congenital heart disease, prosthetic valves, those on immunosuppressive therapy, dialysis or under drugs. In case of suspected endocarditis and transthoracic echocardiogram is inconclusive, transesophageal echocardiography will be done, which has a negative predictive power of 90% (even 95% if there are two negative results within a few days – a week).