Dilemma of Variety of Histopathologic Grading Systems for Acute Cardiac Allograft Rejection by Endomyocardial Biopsy

From the International Society for Heart Transplantation Registry, it can be seen that more than 2000 hearts are now being transplanted per year and that this number is likely to continue to rise. Because the leading causes of death in the first year after heart transplantation are infection and acute rejection, it is clear that the problem of managing heart recipients becomes that of correctly diagnosing acute rejection. For many years the endomyocardial biopsy has provided a safe, reliable, morphologic index of acute rejection. Notwithstanding the drawback of an invasive technique and sampling error, the endomyocardial biopsy has prevailed as the single most reliable method for diagnosing acute rejection. In 1974 a grading system for the diagnosis of acute rejection from biopsy material was first described. Since then, the grading system has been updated, and over the years many different grading systems have evolved to accommodate better the style of managing heart recipients in different centers worldwide. Although this is satisfactory for individual centers, it has become clear that there is difficulty in comparison of different treatment regimens from transplant centers using different grades. For continued improvement of survival in heart recipients, multicenter trials using different treatment and management protocols must be tried. To accomplish this, direct comparisons between one regimen and another must be made. For this purpose, a universal grading system has been suggested. This article makes an initial attempt to point out the weaknesses and strengths of the current grading systems and an initial attempt to define the criteria that would be accepted in a universal, or standard, grading system.