Evaluation of surface-bound heparin and platelet inhibition in a centrifugal pump left ventricular assist system

Cannula selection and cannulation techniques for nonpulsatile mechanical ventricular assistance

The successful use of mechanical ventricular assistance is, in large part, dependent upon easy insertion of well designed inflow and outflow cannulas. This manuscript describes a family of cannulas specifically designed for use in a nonpulsatile ventricular assist device (VAD) circuit. Although a variety of commercially available cannulas can be employed in a nonpulsatile VAD circuit, the cannulas described in this manuscript possess a number of unique design features. The reinforced thin-walled design and end hole construction optimize fluid flow characteristics in both the inflow and outflow cannula. The extended length allows the cannulas to transverse the skin at a point far distant from the mediastinum, reducing the potential for ascending cannula site infection. The purpose of this manuscript is not to review all cannulas available for nonpulsatile VAD circuits, but rather to describe in detail a family of cannulas that are ideal VAD cannulas based on their design characteristics. In addition individual cardiac surgeons implant very few of these devices annually. Thus the advantages and disadvantages of common cannulation sites and a proven technique for cannula insertion will also be presented.

Preliminary results of left heart bypass in pigs using a heparin-coated centrifugal pump

To assess the feasibility of left ventricular assist without systemic heparinization, we used a commercially available (Sarns 3M) centrifugal pump with tubing set and cannulas, all internally precoated for the purpose of this study with heparin, to bypass the left ventricle in 12 pigs for periods of either 1 or 3 hours. There was no significant activation of clotting and there was no sign of generalized embolization. However, on postmortem studies, 5 kidneys out of 22 examined showed signs of minimal thromboembolism. This experiment shows that artificial left ventricular assist, free of systemic heparinization but using heparin precoating, is feasible and safe, at least for a short period of time.