Heparin responsiveness in vitro as a prognostic tool for vascular graft stenosis: a tale of two cell types?

Vascular graft stenosis after infrainguinal vein grafting or coronary artery bypass graft surgery is a significant cause of morbidity and suboptimal long-term clinical outcome of patients with vascular disease. Numerous animal and clinical studies have been undertaken to reveal the pathophysiological mechanisms accounting for this detrimental process. Stenotic lesions are dominated by neointima formation with migration and proliferation of SMCs and deposition of extracellular matrix. This appears to be a conserved response in the vasculature not only after vein grafting but also after various injurious stimuli such as angioplasty, endarterectomy, embolectomy, and arterial catheterization. However, the mechanisms of the process of stenosis are still not fully understood, and there is neither an effective treatment for prevention nor a diagnostic test for reliable prediction of patients at risk for developing graft stenosis. Most clinical and experimental studies have focused on the control of SMC proliferation with the intention of developing strategies for the prophylaxis of restenosis, whereas relatively little has been achieved in the area of early tests to define the prognosis and need for clinical monitoring of particular patients.