A n a l y s is o f t h e I n c i d e n c e , R i s k F a c t o r s , a n d I m p a c t o n G r a f t S u r v iv a l M a r g r e t B. An d r e s d o t t i r , 1,2 K a r e l J .M . A s s m a n n , A n d r ie s J. H o it s m a , R o b e r t A ,P. K o e n e , a n d J a c k F .M . W