[Acute rejection: the diagnostic and therapeutic problems].

Acute allograft rejection is still a leading cause of both early and late mortality and morbidity after cardiac transplantation. Besides cell-mediated acute rejection, a "humoral" form exists which is more frequent in younger patients in the early postoperative period, and less likely to respond to the usual therapy. Cyclosporine therapy has deeply affected the clinical, laboratory and histological aspects of acute rejection. Though endomyocardial biopsy remains the most reliable diagnostic tool, other noninvasive procedures are of great value for a final diagnosis; among these are electrocardiography and two-dimensional echocardiography, which are the two elective techniques for post-transplantation follow-up in children. The laboratory and immunological assays, on the contrary, share a very low specificity. In conclusion, the diagnosis of acute rejection is still a clinical one, though supported by laboratory and histological evidence. In our experience, the natural evolution of many mild and mild-moderate rejection episodes toward regression does not support an excessive prophylaxis or an early treatment of symptom-free acute rejection. In addition, treatment of rejection must be personal and specific to each patient.