Somatostatin receptor scintigraphy predicts impending cardiac allograft rejection before endomyocardial biopsy

The invasive nature of endomyocardial biopsy has led to a search for altern ative diagnostic modalities for the detection of cardiac allograft rejectio n. To date, no non-invasive test meets all the requirements for the detecti on of acute and chronic rejection. The rejection process usually presents w ith lymphocyte infiltration with or without myocyte necrosis, which indicat es the severity of cardiac allograft rejection and the necessity of treatme nt. Activated lymphocytes express somatostatin receptors: thus somatostatin receptor imaging could be used to target them. The aim of this study was t o assess the feasibility of using somatostatin receptor imaging to target a ctivated lymphocytes in the process of cardiac allograft rejection. Thirtee n somatostatin receptor imaging studies were performed on ten cardiac allog raft recipients 12-4745 days after transplantation, simultaneously with end omyocardial biopsy, to assess the imaging of activated lymphocytes in compa rison with histological findings. Somatostatin receptor imaging was perform ed 4 h after the injection of 110 MBq of the somatostatin analogue indium-1 11 pentetreotide. In-111-pentetreotide uptake was visually scored and semi- quantitatively estimated by the calculation of a heart-to-lung ratio (HLR). The visual score correlated with the HLR, Intense/moderate uptake on visua l assessment and an HLR >1.6 was observed in eight studies. Zn three of the se studies there was significant rejection in the simultaneous endomyocardi al biopsy [International Society of Heart and Lung Transplantation (ISHLT) rejection grade 3A/4]. Intense/moderate uptake was associated with mild or no rejection in the remaining five patients, and in four of them the next e ndomyocardial biopsy performed 1 week later demonstrated significant reject ion requiring treatment. Two patients with low uptake and an HLR <1.6 had n o evidence of rejection either in the simultaneous endomyocardial biopsy or in the endomyocardial biopsy performed the following week. These prelimina ry results indicate the Feasibility of targeting activated lymphocytes with somatostatin receptor imaging in the detection of cardiac allograft reject ion. Somatostatin receptor imaging may predict impending rejection at least 1 week before the endomyocardial biopsy becomes positive. The late appeara nce of diagnostic endomyocardial biopsy probably reflects a lag-time betwee n lymphocytic activation and induction of myocyte damage. Furthermore, soma tostatin receptor imaging at 4 h may in any case allow earlier intervention in the event of rejection, given the time required for histological proces sing of endomyocardial biopsy.