Diagnosis of infective endocarditis

Since the symptoms of infective endocarditis are nonspecific, they change greatly and can develop unnoticeably, a high degree of alertness is required in diagnosis. Endocarditis should be suspected in patients with fever without obvious sources of infection, especially if there is noise in the heart. Suspected endocarditis should be very high if the bacteriological examination of the blood is positive in a patient who has a history of heart valve damage, recently undergoing invasive procedures or injecting drugs intravenously. Patients with reported bacteraemia are shown a multiple complete examination to identify new valve sounds and symptoms of embolism.

[1], [2], [3], [4], [5]

Bacteriological diagnosis of infective endocarditis

If suspicion of endocarditis is carried out a 3-fold bacteriological study of the blood (20 ml - for each study) for 24 hours (assuming RSE, two cultures are obtained within the first 1-2 hours). If the study was not preceded by antibiotic therapy, with endocarditis, all three bacteriological blood tests are usually positive, because bacteremia is continuous; at least one culture is positive in 99%. If the study was preceded by antimicrobial therapy, a bacteriological study of the blood can be both positive and negative.

In addition to positive blood cultures, there are no specific laboratory tests. The infectious process often causes normocytic normochromic anemia, an increase in the number of leukocytes and ESR, an increase in the content of immunoglobulins, circulating immune complexes and rheumatoid factor, but these data have no diagnostic value. Urinalysis often demonstrates microhematuria, sometimes erythrocyte cylinders, pyuria, or bacteriuria.

Identifying the microorganism and determining its sensitivity to antimicrobial therapy are vital for proper treatment. To detect certain microorganisms, bacteriological examination of blood can take 3-4 weeks. Some microorganisms (for example, aspergillus) may not give a positive culture. Part of the pathogens (for example, Coxiella burnetii, Bartonellosis sp., Chlamydia psittaci, Brucella) are identified by serodiagnosis, to identify other (eg Legionella pneumophila), special culture media are needed. Negative results of bacteriological examination of blood may indicate a weakening of the biological properties of microorganisms due to antimicrobial therapy, infection with microorganisms that do not grow on standard culture media or other diagnosis (eg, noninfectious endocarditis, atrial myxoma with embolism, vasculitis).

Infective endocarditis is reliably diagnosed when microorganisms are detected histologically (or cultured) in endocardial vegetation obtained during cardiac surgery, embobectomy or autopsy. Since vegetation is rarely available for research, clinical criteria for establishing a diagnosis have been developed (with sensitivity and specificity> 90%).

[6], [7], [8], [9], [10], [11],

Instrumental diagnosis of infective endocarditis

Perform echocardiography, usually transthoracic (TTE), and not transesophageal (TEE). Although TSE is somewhat more accurate, it is invasive and more expensive. TSE is used in the following cases:

• suspicion of endocarditis in a patient with prosthetic valves;
• situation where TTE has no diagnostic value;
• The diagnosis of infective endocarditis has been established clinically.

Revised clinical diagnostic criteria for Duke infectious endocarditis

Large criteria of infective endocarditis

• Two positive blood cultures on microorganisms typical of endocarditis.
• Three positive blood cultures on microorganisms compatible with endocarditis.
• Serological detection of Coxiella burnetii.
• Echocardiographic signs of involvement in the endocardium process: fluctuating volumetric formation on the cardiac valve, supporting structures, in the flow path of regurgitation or on the implanted material without other anatomical prerequisites.
• Cardiac abscess.
• For the first time the arisen / revealed splitting of the prosthetic valve.
• New valve regurgitation

Small criteria of infective endocarditis

• Preceded diseases of the heart.
• Intravenous injection of drugs.
• Fever is 38 ° C or higher.
• Vascular symptoms: arterial embolism, septic pulmonary embolism, mycotic aneurysm, intracranial hemorrhage, conjunctival petechiae, or Janeway's symptom.
• Immunological changes: glomerulonephritis, Osler's nodules, Rota spots, rheumatoid factor.
• Microbiological signs of infection, compatible with endocarditis, but not included in large criteria.
• Serological signs of infection with a microorganism compatible with endocarditis

For setting a specific clinical diagnosis, there are two large criteria, or one large and three small, or five small criteria.

For the statement of a possible clinical diagnosis, one large and one small or three small criteria are necessary. The diagnosis of "infective endocarditis" is excluded in the following cases:

• a reliable alternative diagnosis has been put forward, explaining the results of studies similar to infective endocarditis;
• resolution of symptoms and manifestations after antimicrobial therapy for 4 days or less; absence of pathological signs of infective endocarditis according to the study of material obtained during surgery or autopsy; lack of clinical criteria for possible endocarditis.