In this open, prospective, non-randomised, parallel group, unicentric pilot-study will be compared the progress of valvular and coronary calcification with regard to the therapy with either acetyl-salicylic acid or phenprocoumon. The progress of calcification is documented by comparison of cardial stratified computed tomography. It is supposed that treatment with phenprocumon leads to increased coronary and valvular calcification as well to decreased blood levels of carboxylated matrix-GLA-protein