Management of active infective endocarditis

Abstract

The pathology of infective endocarditis varies but is classifi ed into infection, cardiac, cerebrovascular, and embolism symptoms. Fever as a symptom of infection is the typical remittent fever observed in bacteremia; however, fever is often mild in patients who have already received antibiotics. Once treatment is initiated, the fever abates and the sense of serious illness disappears; therefore, endocardial lesions may not be examined for some weeks. In such a situation, endocardial or cerebrovascular infection lesions have not always been controlled despite the mild fever. When poor results of treatment for infection lead to a terminal condition of bacteremia, septic shock develops. In septic shock, the peripheral blood vessels are abnormally dilated; the heart develops a high-output hyperdynamic state as if a large arteriovenous shunt had formed while blood fl ow in major organs decreases, and renal and respiratory failure rapidly progresses. Cerebrovascular as well as cardiac lesions observed in infective endocarditis are serious and often fatal. A study involving 2523 patients who underwent surgery for valvular disease of the heart associated with infective endocarditis showed an incidence of cerebral lesions of 9.7%. Such cerebral lesions are caused by infective cerebral vasculitis (including infective cerebral aneurysms) and bacteria-associated embolism. As a result, cerebral hemorrhage (subarachnoid, intracranial), cerebral infarction, and hemorrhagic infarction occur. Cerebral abscess or meningitis also sometimes develops. The statistics cited above revealed the following make-up of cerebral lesions: cerebral infarction, 65%; cerebral hemorrhage, 32%; cerebral abscess, 3%; and meningitis, 1%. Bacteria-associated cerebral aneurysms develop in 4%– 15% of cases of infective endocarditis. However, the cause of intracranial hemorrhage is hemorrhagic infarction in 75% of cases and bacteria-associated cerebral aneurysms in only 19%. Some studies have also suggested that pyrogenic arteritis that does not induce arterial wall dilation is the source of hemorrhage. As a result of infective embolism of small vessels, infl ammation develops fi rst in the adventitia. The presence of cerebral lesions markedly limits the indications for cardiac surgery by cardiopulmonary bypass.