Human-like atherosclerosis in minipigs: a new model for detection and treatment of vulnerable plaques.

Advanced atherosclerosis, through thrombosis, leads to ischemic heart disease and ischemic stroke, the leading causes of death and disability worldwide. Advanced atherosclerosis and imaging of atherosclerosis are the focus of this dissertation with particular emphasis on the vulnerable plaque and vulnerable plaque detection. Aspects of advanced atherosclerosis and the vulnerable plaque in humans are described along with the basis for the selected minipig models and methods for atherosclerosis acceleration used. The overall aims of the studies were to develop an animal model of advanced atherosclerosis with human like vulnerable plaque morphology and use this animal model to test an imaging modality aimed at vulnerable plaque detection. The first aim is addressed in 3 papers, where accelerated plaque development in the coronary and carotid arteries is investigated in down sized Rapacz pigs. Down-sized Rapacz pigs are minipigs with familial hypercholesterolemia caused by a mutation in the low density lipoprotein receptor. Paper 1 describes the lipid profile in the down-sized Rapacz on chow and atherogenic diets and spontaneously developed and balloon accelerated coronary plaque with a morphology that resembles the morphology of human vulnerable plaque. Paper 2 describes vein graft disease in internal jugular vein grafts inserted into the common carotid artery. Plaques with necrotic cores were found in oversized vein grafts only indicating an effect of flow and shear stress on plaque development. Paper 3 describes the effects of wall shear stress on local plaque development in surgically stenosed common carotid arteries in the down-sized Rapacz pigs. This study indicated that the combination of low and oscillatory wall shear stress was needed for development of advanced plaque. In paper 4, we interrogated coronary lesions in the down-sized Rapacz with a commercially available diagnostic tool VH IVUS. It is claimed that VH IVUS can characterize the tissue components that constitute plaque reliably. However, we found that VH IVUS does not reliably assess the most important plaque component of all, i.e. the necrotic core. In conclusion, we developed an animal model of advanced atherosclerosis with human like vulnerable plaque morphology. The usefulness of this animal model was demonstrated in a study testing an imaging modality aimed at vulnerable plaque detection in humans.