Note: Descriptions are shown in the official language in which they were submitted.
CA 022~0993 1998-10-02
Sg/Dt
Intravascular blood Pump
The invention relates to an intravascular blood pump
comprising a drive unit including a motor, and a
pump unit tightly connected to the drive unit, with
the pump unit comprising a tubular housing and an
impeller arranged for rotation therein. A pump of
the above type is known from the publication "The
International Journal of Artificial Organs", Vol.
18, No. 5 (1995), pages 273 to 285. The pump is in-
troduced 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.
U.S.-4,969,865, EP 0 157 871 B1 and EP 0 397 668 B1
describe further known intravascular blood pumps
wherein, however, only the pump unit is advanced in
the blood stream while the drive unit is arranged
extracorporeally and is connected to the pump unit
via a flexible shaft.
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In a blood pump known from EP O 157 859 B1, the
drive unit and the pump unit are combined integrally
with each other. This pump is suited for implanta-
tion but is not useful as an intravascular blood
pump to be introduced into the body by a minimum-
invasion surgical intervention.
Intravascular blood pump must have an outer diameter
small enough to avoid clogging of a blood vessel.
The largest allowable outer diameter is in the range
of about 7 mm. If the drive unit is arranged close
to the pump unit, the performance of the drive unit
is limited due to the restrictions imposed by the
constructional design. Thus, it is imperative to
make full use of the pump performance and to mini-
mize losses of performance and flow.
According to DE 37 05 637 A1, it is possible to
block flow paths along a catheter by use of annular
balloons.
It is an object of the invention to provide an in-
travascular blood pump adapted to be used with high
efficiency within a blood vessel, particularly also
externally of the aorta.
The above object is solved by the subject matter of
claim 1.
In the instant intravascular blood pump, the drive
unit is combined with the pump unit to form an inte-
gral constructional unit. This means that both units
are inserted together into the blood vessel. At a
,
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site upstream of the respective organ, the blood
pump is inserted into a supply vessel for this organ
such that the pump unit with its central suction
orifice is located before the drive unit when viewed
in the flow direction. The pump unit is provided
with a blocking device for preventing a short cir-
cuit of the flow along the external side of the pump
housing. Thereby, it is prevented that fluid/ blood
from the discharge side of the pump can pass by the
pump housing and thus reach the intake side. All of
the sucked blood is directed to flow past the drive
unit in the flow direction. Thus, applicability of
the claimed pump is not restricted to insertion into
the aorta where the aortic valve can act as a block-
ing device.
The danger that the pump becomes adhered to the ves-
sel by the suction force is minimized because of the
central position of the suction orifice in the ves-
sel. Since the complete blood flow streams past the
drive unit, it is safeguarded that the pressure
built up by the pump will keep the elastic vessel
open even if the diameter of the vessel nearly cor-
responds to that of the pump unit or the drive unit.
Further, the flow-off stream between the motor and
the vessel reliably provides for dissipation of the
heat generated in the drive unit, precluding the
occurrence of hemotoxic damage due to excessive sur-
face temperatures (above 41~C). Advantageously, a
centering device is arranged to project from the
periphery of the drive unit. The centering device is
provided, on the one hand, for keeping the flow-off
passage open and, on the other hand, for centering
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the drive unit in the blood vessel. Further, the
centering device together with the blocking device
prevents rotation and axial dislocation of the whole
pump in the blood vessel.
Embodiments of the invention will be explained in
greater detail hereunder with reference to the draw-
ings.
Fig. 1 is a systematic view of the intravascular
blood pump arranged within a blood vessel,
and
Fig. 2 is a view of a second embodiment of the
blood pump arranged within a blood vessel.
In Fig. 1, the blood pump is shown as positioned
within a blood vessel 10, e.g., in an artery. The
blood pump comprises a motor unit 11 and a pump unit
12 tightly attached to each other while arranged at
a mutual distance. Drive unit 11 accommodates a
drive motor. The rear end of drive unit 11 is con-
nected to a catheter 13 having the power supply and
control lines for the motor 14 passing therethrough.
Pump unit 12 is provided with a tubular pump housing
15 arranged coaxially with the rotor and having a
suction opening 16 formed on one end. An impeller
17, arranged for rotation within pump housing 15,
comprises a hub 18 flared in the flow direction and
blades extending radially from hub 18. Hub 18 is
seated either on the output shaft of motor 14 or is
-
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supported for free rotation and coupled to the out-
put shaft of the motor through a magnetic coupling.
Motor 14 and pump housing 15 are substantially of
the same diameter. This diameter is in the range of
5 to 8 mm so that the blood pump will not obstruct
the blood vessel. The blood stream leaving pump
housing 15 will then flow along on the outer surface
of motor 14.
An expandable blocking device 20, comprising a flex-
ible sealing screen shaped substantially as a trun-
cated cone, is attached externally around pump hous-
ing 15. The smaller end of the sealing screen is
attached to the pump housing while the larger end is
adapted to fold outwards and thus abut the wall of
blood vessel 10, or to collapse and thus externally
abut the pump housing 15. The flexible sealing scre-
en forming the blocking device 20 acts in the manner
of a check valve. When the pressure in the region 21
upstream of suction opening 16 is lower than the
pressure at the pump discharge opening, the sealing
screen will expand and block the annular space be-
tween the pump housing and the vascular wall. In
this manner, it is precluded that blood flows back
from the outlet side 22 of the pump to the intake
side 21. The complete blood stream will thus be
forced to flow along motor 14.
For stabilizing the central position of the drive
unit 11 within blood vessel 10, drive unit 11 is
provided with a centering device 23 extending from
the periphery of drive unit 11 and provided in the
~ _,
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manner of projecting spring-like ribs tapering to-
wards the outside.
In the embodiment according to Fig. 2, pump housing
15 is connected to a suction hose 25 projecting in
the forward direction, centrally reaching into the
blood vessel and having its end provided with open-
ings for blood intake. Suction hose 25 is sealingly
attached to the cylindrical pump housing 15 and ex-
tends the same in the forwards direction.
The blocking device 2Oa according to Fig. 2 compris-
es an annular balloon attached to pump housing 15 or
suction hose 25. This balloon is connected to a lu-
men of catheter 13 and thus can be inflated extra-
corporeally by gas or liquid. The balloon prevents a
backflow of blood and provides for the centering of
pump unit 12 and suction hose 25 in the blood ves-
sel.
