757 In vivo characterization of plaque composition in late Cardiac Allograft Vasculopathy

Purpose: Allograft vasculopathy is the leading cause of late mortality after cardiac transplantation. Late cardiac allograft vasculopathy, as seen at necropsy, manifests as a diffuse obliterative process characterized by concentric intimal proliferation. Investigation of coronary plaque composition in vivo has become possible with the introduction of virtual histology (VH) intravascular ultrasound (IVUS). In this study we evaluated the feasibility of in vivo plaque characterization in late allograft vasculopathy using VH-IVUS. Methods and Materials: 15 patients (median age 61years; 3273years) 8 years (4-14years) after heart transplantation were included into this study. In all patients at least one coronary artery was investigated using VH-IVUS. VH-IVUS data were obtained using a continuous pullback (0.5mm/s) and a commercially available mechanical sector scanner (Eagle Eye GoldTM, Volcano Therapeutics). A region of interest (11-15mm) was selected and analyses were done offline with pcVH-review software (Volcano Therapeutics). Four histological plaque components (fibrous, fibrolipidic, necrotic and calcified) were correlated with a specific spectrum of the radiofrequency signal. Results: Median plaque length was 14mm (11-15mm), vessel segment volume 209mm3 (125-314mm3), and plaque-plus-media-volume 95mm3 (46-156mm3), resulting in a volume stenosis of 44% (34-56%). The remodeling index was 1.01 (0.88-1.21). VH demonstrated that 67% (47-77%) of plaque volumen was composed of fibrous, 10% (5-19%) of fibrolipidic, 14% (8-26%) of necrotic and 7% (2-12%) of calcified tissue. Conclusions: In vivo analysis of plaque composition in cardiac allograft vasculopathy is feasible using VH-IVUS. The high proportion of fibrous tissue identified by VH is well in line with post mortem data. It can be speculated that the addition of VH to standard IVUS will be helpful for the differentiation between early allograft vasculopathy from donor-transmitted atherosclerosis, and for investigating the effects of new therapy on disease progression.