Stainless steel stents and magnetic resonance imaging looking into a black hole

Imaging of thoracic aortic disease

Aortic pathology can be more complex to understand on imaging than is initially appreciated. There are a number of imaging modalities that provide excellent assessment of aortic pathology and enable the accurate monitoring of disease. This review discusses the imaging of the most common disease processes that affect the aorta in adults, with the primary focus being on CT and MRI.

Percutaneous pulmonary valve implantation in the native right ventricular outflow tract

Percutaneous pulmonary valve implantation into dysfunctional right ventricular (RV) to pulmonary artery conduits is being increasingly performed in many European and North American centers with satisfactory results and low-complication rates. We report the first application of this elaborate technique in the native RV outflow tract of a young patient who developed severe supravalvular pulmonary stenosis following an arterial switch operation for transposition of the great arteries. The procedure may be used as an alternative to surgical repair for the treatment of selected patients with supravalvular pulmonary stenosis complicating congenital heart surgery.

Hemocompatibility of silicon-based substrates for biomedical implant applications

Silicon membranes with highly uniform nanopore sizes fabricated using microelectromechanical systems (MEMS) technology allow for the development of miniaturized implants such as those needed for renal replacement therapies. However, the blood compatibility of silicon has thus far been an unresolved issue in the use of these substrates in implantable biomedical devices. We report the results of hemocompatibility studies using bare silicon, polysilicon, and modified silicon substrates. The surface modifications tested have been shown to reduce protein and/or platelet adhesion, thus potentially improving biocompatibility of silicon. Hemocompatibility was evaluated under four categories—coagulation (thrombin–antithrombin complex, TAT generation), complement activation (complement protein, C3a production), platelet activation (P-selectin, CD62P expression), and platelet adhesion. Our tests revealed that all silicon substrates display low coagulation and complement activation, comparable to that of Teflon and stainless steel, two materials commonly used in medical implants, and significantly lower than that of diethylaminoethyl (DEAE) cellulose, a polymer used in dialysis membranes. Unmodified silicon and polysilicon showed significant platelet attachment; however, the surface modifications on silicon reduced platelet adhesion and activation to levels comparable to that on Teflon. These results suggest that surface-modified silicon substrates are viable for the development of miniaturized renal replacement systems.