Opportunistic infections in the cardiac transplant patient.

The risk of opportunistic infection in the cardiac transplant patient is determined by the interaction between the epidemiologic exposures that the patient encounters and the patient's net state of immunosuppression. The epidemiologic exposures include those encountered in both the community and the hospital, with the latter being more important as they usually occur at a point in time when the patient's net state of immunosuppression is at its highest. The net state of immunosuppression is a complex function whose major determinants are the immunosuppressive program and the presence or absence of infection with a group of immunomodulating viruses, particularly cytomegalovirus. Strategies for preventing opportunistic infection in this patient population are based on the following factors: technically impeccable surgery, precisely managed immunosuppression, environmental protection (particularly in the hospital), and the use of preventative antimicrobial strategies. These last are of two types, prophylactic and preemptive. The key point in both these approaches is to link the preventative strategy to the intensity of the immunosuppressive program and to target the antimicrobial program to the time period and patient group at greatest risk. For most opportunistic infections this is the time period 1 to 6 months after transplantation (when viral infections are prevalent), and the small group of patients more than 6 months after transplantation who are chronically overimmunosuppressed because of rejection.