In vitro study of unimplanted and explanted specimens from Biomer blood sacs of ventricular assist devices

Biomer, a smooth segmented polyurethane elastomer, is currently chosen for its durability and hemocompatibility to manufacture the blood sacs of temporary ventricular assist devices (VADs). In order to study the effects of implantation time on Biomer, specimens obtained from both unimplanted and explanted blood sacs were subjected to comparative static tensile tests on a computerised mechanical testing machine, equipped with air-actuated grips and an infra-red extensometer. The material showed a high elongation at break. When observed under a scanning electron microscope (SEM), the inner surface of the specimens from removed blood sacs showed no thrombotic deposits, calcifications, microbial contamination or structural changes. Both the unimplanted and explanted specimens tested mechanically presented distinctive fracture patterns.