809 Intraplaque Haemorrhage as a Trigger of Lesion Progression in Cardiac Allograft Vasculopathy

Purpose: Diagnosis of antibody-mediated rejection (AMR) is still a matter of controversial discussion. We suggested that immunoglobulin staining might improve the diagnostic spectrum of AMR because of seasonal effects in complement deposition. Methods and Materials: We studied prospectively all endomyocardial biopsies harvested since 01/2011 (n 205) for acute cellular rejection (ISHLT), endothelial swelling and microvascular deposition of C4d, C3d and IgA/M/G in paraffin sections (immunohistochemistry). Pathologic and immunopathologic AMR findings were classified according to the ISHLT and studied for seasonal effects in an ordinal (Jan-Mar vs. Apr-Jun vs. Jul-Sept vs. Oct-Dec) and nominal model (Oct-Mar vs. Apr-Sept). Results: Overall, 16% of biopsies showed signs of acute cellular rejection of any grade and 46% of samples showed evidence of endothelial swelling. In the ordinal model (Jan-Mar vs. Apr-Jun vs. Jul-Sep vs. Oct-Dec), seasonal effects were found for endothelial swelling (83% vs. 14% vs. 49% vs. 40%; p 0.001), IgA deposition (62% vs. 71% vs. 86% vs. 92%; p 0.046), C4d deposition (36% vs. 9% vs. 20% vs. 15%; p 0.003) and C4d deposition in combination with endothelial swelling (35% vs. 5% vs. 9% vs. 4%; p 0.001). In the nominal model (Oct-Mar vs. Apr-Sep) we found similar results showing seasonal effects for endothelial swelling (70% vs. 30%; p 0.001), C4d deposition (29% vs. 14%; p 0.012) and C4d deposition in combination with endothelial swelling (25% vs. 7%; p 0.001). No other combinations of histopathology or immunopathology or acute cellular rejection showed seasonal behavior. AMR according to the ISHLT was not associated with impaired graft function in echocardiography. Conclusions: Complement deposition seems to be more pronounced in autumn and winter. IgA deposition might add important information about coincident alloimmune responses derived from mucosal surfaces and might be considered to complement current diagnostic parameters.