U.S. Pat. No. 4,625,712 and copending application Ser. No. 129,7l4 filed 12/07/87 disclose miniature high-speed blood pumps which can be threaded through a blood vessel to provide heart assist in emergency situations without major surgery. Typically, such pumps are inserted through, e.g., the femoral artery. An inflow cannula is positioned ahead of the pump during insertion, and this cannula must typically be pushed through the aortic valve in a retrograde direction.
In the past, such retrograde insertion was usually done by means of a wire guide over which the inflow cannula was slipped, and which was subsequently withdrawn. This method was unsatisfactory not only because it was awkward and carried a risk of injury to the vascular system and to the aortic valve, but also because it required the continuing observation of the wire during insertion by x-ray or other procedures. In an emergency, appropriate x-ray equipment may not be immediately available, and heart assist may have to be provided so quickly that the slow wire guide method may not be suitable.
A requirement therefore exists for an inflow cannula which can be attached to the intake of an intravascular blood pump and can be pushed ahead of the pump for blind retrograde insertion into the left ventricle through the aortic valve without any additional apparatus and without danger of injury to the patient.