Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
1998-10-05
2001-01-23
Polutta, Mark O. (Department: 3762)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C623S003100, C600S016000, C600S017000
Reexamination Certificate
active
06176848
ABSTRACT:
The invention relates to an intravascular blood pump comprising a drive unit and a pump unit, said blood pump being sized to be introduced through the vascular system of a human body to perform a pumping action, e.g., in the heart.
An intravascular blood pump is introduced through puncture of a blood vessel into the vascular system of the body and is advanced to the heart or to a different site where blood is to be pumped. Those parts which are inserted into the body must have a diameter small enough to allow them to fit through the externally accessible large vessels. The largest diameter permitted is about 7 mm.
From EP 0 157 871 B1 and EP 0 397 668 B1, intravascular blood pumps are known wherein the pump unit comprises a tubular housing having an impeller arranged for rotation therein. The impeller is connected to an extracorporeal drive unit via a flexible shaft guided through a catheter. The drive unit is arranged to drive the flexible shaft which in turn drives the pump unit. The drive unit, being operated at an extracorporeal site, can have any desired size. The desired reduction of the friction between the shaft and the catheter requires continuous lubrication by liquid. A part of this liquid containing abrasive particles will leak through the sliding bearing and the sealing of the pump unit and thus enter the blood stream. The remaining part will be collected extracorporeally after passing through the catheter along the shaft. Further, the flexible shaft restricts the range of applications of the blood pump because the latter can be advanced only to those sites in the body which do not require too extensive flexure of the catheter and the shaft accommodated therein.
A blood pump known from WO94/09835 is provided as a temporary supportive device for the heart. This blood pump, which is used on the surgically exposed heart, comprises a rod-shaped housing which contains the motor and the pump and can be inserted into the aorta by its pump portion whereas the motor portion remains external of the aorta.
Further, from EP 0 157 859 B1, there is known a blood pump wherein the motor unit and the pump unit are combined in one integral design. This pump is suited for implantation but is not useful as an intravascular blood pump to be introduced into the body by a minimum-invasion surgical intervention.
It is an object of the invention to provide an intravascular blood pump, i.e. a blood pump adapted to be advanced through blood vessels, which, while offering the required high pumping performance, is of small size and is sealed in a simple and safe manner.
It is a further object of the invention to provide an intravascular blood pump wherein the danger of hemotoxic damage due to shear stresses on the blood is largely reduced.
The blood pump according to the invention is defined by claim
1
.
In the blood pump of the invention, the drive unit and the pump unit are directly connected to each other, and the blood pump is provided as a rod-shaped thin member, with the motor housing and the pump housing having the substantially the same outer diameter. The diameter of a blood pump to be positioned through a minimum-invasion intervention is restricted to about 5 to 7 mm since the width of vessels in the outer regions of the body is at maximum slightly above 7 mm. A blood pump of the instant type is suited to achieve a pumping performance of substantially 4 liters per minute at a counterpressure of about 100 mm Hg.
According to the invention, in an intravascular blood pump, the impeller is axially supported on a step bearing arranged external of the motor housing and is coupled to the motor shaft via a magnetic coupling through one end wall of the motor housing. Said end wall is an integral part of the motor housing and is provided to seal the same. This obviates the need to guide a rotating shaft through the motor housing. Thus, no sealings with a resultant danger of leakage or of blood depositing thereon will be required on this site. The end wall of the motor housing is made from a non-magnetic material, particularly of a synthetic material or ceramic. It is possible to support the impeller on a rod which is non-rotating and arranged to extend through the end wall of the motor housing. The sealing between the rod and the end wall poses no problems because both parts are stationary.
Further, according to the invention, orientation means are provided to hold the impeller in a coaxial orientation with the axis of the motor. First, the impeller is axially supported and radially centered relative to the housing by means of a step bearing. Still, such a step bearing which is arranged along the axis of the impeller cannot keep the impeller from performing oscillating movements around the step bearing. To restrict or preclude such oscillating movements, corresponding orientation means are provided which can be of a mechanical, magnetic or hydromechanical type and will cause the impeller to exactly maintain its axial orientation. The centered arrangement of the impeller relative to the pump housing is obtained by the step bearing. The radial orientation relative to the longitudinal axis is accomplished by the orientation means which are provided separately and at a distance from the step bearing.
Preferably, the rod supporting the impeller extends into the motor housing and thus obtains good guidance and constancy with regard to its axial orientation. This is of importance for a true, centrically precise guidance of the impeller. A guidance with such a high accuracy is necessary since, for minimizing hemotoxic damage and for avoiding hydraulic losses in efficiency, the gap between the blades of the impeller and the pump housing should not exceed a tenth of a millimeter. A faulty concentric running of the impeller would also increase the danger of hemolysis.
A further advantage of the blood pump resides in that the impeller can easily be dismounted and replaced. The motor housing and the pump housing form a unit onto which the impeller, provided as a separate and exchangeable part, is slipped until abutting on the step bearing. The unit comprising the drive unit and the pump housing is easily cleaned and disinfected since it does not include shaft passages or moving parts and is free of interspaces susceptible to contaminants depositing thereon.
Upon rotation of the impeller, the impeller conveys blood in the predetermined flow direction. In this situation, the impeller is subjected to a force which tends to pull the impeller away from the drive unit. The magnetic coupling by which the impeller is coupled to the motor shaft pulls the impeller against the step bearing, thus preventing that the impeller is pulled off from the step bearing during operation.
Because of its good mobility in the vascular system, the intravascular blood pump of the invention can be used in various applications, for instance
a) as a left heart support pump with the option (cf. b)) to generate a pulsating flow,
b) as a right heart support pump with the option of pulsatile operation by modulation of the pump speed,
c) as a uni- or biventricular support system during thoracic/transthoracic surgical interventions on the beating or non-beating heart without using a heart-lung machine,
d) as a blood pump provided for local perfusion of an organ and having a corresponding sealing device.
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Rau Guenter
Reul Helmut
Siess Thorsten
Fulwider Patton Lee & Utecht LLP
Impella Cardiotechnik GmbH
Polutta Mark O.
Serke Catherine
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