Improvement of Myocardial Blood Flow by PhosphoDiesterase 5 Inhibition in Coronary Artery Disease

The aim of this study is to prospectively investigate if intermittent Phosphodiesterase 5 inhibition for 15 weeks improves myocardial perfusion by angiogenesis in patients with therapy refractory myocardial ischemia due to coronary artery disease judged to be unsuitable for surgical or percutaneous revascularisation. For proof of efficacy the following tests will be performed at baseline and one day and 4 weeks after discontinuation of therapy: Exercise tolerance will be evaluated by bicycle exercise testing. Blood tests will be performed to evaluate markers of angiogenesis (endothelial progenitor cells, vascular endothelial growth factor, basic fibroblast growth factor). The improvement of myocardial perfusion will be tested functionally as increase of coronary flow reserve by positron emission tomography. Moreover, changes in ventricular function, symptoms and quality of life will be assessed.