Cardiac infections in the immunocompromised host

Bacterial infections of the heart in compromised patients are uncommon but may be increasing in relative frequency. They are associated with near-equal frequencies in patients who have pre-existing or simultaneous infections at other sites, patients with neoplasms (usually solid tumors), those who have undergone cardiac surgery, and intravenous drug or ethanol abusers. Staphylococcus aureus is the bacteria most often identified, in contrast to a preponderance of Streptococcus isolated in the pre- and early antibiotic era. Gram-negative bacilli are the causative organisms in a significant number of cases. The endocardium remains the most common site of infection, and left-sided valves are most commonly involved, especially the mitral valve, often in the absence of pre-existing valvular damage. The majority of cases are associated with involvement at other sites, and premortem blood cultures are positive in approximately two thirds of patients who undergo autopsy. Fungal infections involving the heart do not occur as often as bacterial infections. The frequency, however, is increasing. Fungal infections usually occur in patients who have received treatment with antineoplastic agents, antibiotics, or corticosteroids, alone or in combination, or who have had abdominal or cardiac surgery. Candida is the organism found most frequently and usually causes myocarditis or endocarditis, whereas Aspergillus involves the myocardium but may be invasive to the endocardium or pericardium. Other fungi that occasionally infect the heart include Phycomycetes and Cryptococcus. Dissemination is usually present and involves the lungs, kidneys, brain, or gastrointestinal tract. The diagnosis may be difficult prior to death, because blood cultures are positive in only one third of patients who come to autopsy. Precipitin tests and antibody titers for specific organisms may be helpful in providing early diagnosis. Survival rates can be improved by early diagnosis and the institution of aggressive antifungal treatment.