Blood pumping catheter.

The invention relates to a catheter for pumping blood through the vascular system of a living being.

US-A-4,753,221, the entire disclosure of which is to be incorporated whereby this reference discloses apparatus comprising an elongated catheter having a distal end portion which is of sufficiently small diameter and sufficient flexibility to enable it to be passed through a portion of the being's vascular system so that the distal end portion of the catheter is located within or closely adjacent the being's heart. The catheter includes an expandable pump member located at the distal end portion and drive means for effecting the operation of the pump. The distal end portion of the catheter includes an inlet for blood to flow therein and an outlet for blood to flow thereout. The instrument can be used for either left side heart applications or right side heart applications. When used for left side heart applications, the catheter is constructed so that the inlet is in fluid communication with the left ventricle while the outlet is in fluid communication with the aorta. When used for right side heart applications, the catheter is constructed so that the inlet is in fluid communication with the right ventricle while the outlet is in fluid communication with the pulmonary artery. In one embodiment the distal end portion of the instrument is arranged to extend through the aortic valve. In another embodiment the distal end portion is located over the aortic valve and includes a cover to contact valve while enabling blood to flow therethrough. In all cases the blood can be pumped through the heart and into the vascular system without requiring any pumping action of the heart itself.

The placing of the known catheter through or immediately adjacent the aortic valve is a skilled job which is normally only done by highly trained medical personnel. It is one object of the invention to provide a blood pumping catheter which is safe and easy to use and which may be used by less skilled medical personnel.

Accordingly the invention provides in one aspect apparatus to be located within the aorta of a living being to pump blood through the vascular system of the being in the absence of contact with the aortic valve, the apparatus comprising an elongate catheter having an end portion to be located distally of the operator and dimensioned to be received within the aorta so that the end portion is in proximity to the aortic valve, comprising pump means located at the end portion and drive means operatively connected to the pump means, the end portion including an inlet located distally of the pump means and an outlet located proximately of the pump means, the inlet and outlet being in fluid communication with the aorta, barrier means being present to direct substantially all of the blood flowing through the aorta into the inlet, through the pump means and out through the outlet <u style="single">characterised in that</u> the barrier means is located about the end portion and is adapted to contact the wall of the aorta in blood flow sealing engagement at a location longitudinally spaced from and upstream of the aortic valve. In this way apparatus according to the invention need not contact the aortic valve, which means that the apparatus may be safely used by less skilled medical personnel.

The distal end portion preferably comprises a flexible tubular portion extending about the pump means and the barrier means comprises a flexible skirt extending about the periphery of the tubular portion. The distal end portion and the pump means, in the form of an impeller or the like, are preferably arranged to be expandable between a retracted configuration during insertion of the catheter, and an expanded configuration when the distal end portion is in the operative position spaced apart from the aortic valve.

In another aspect the invention provides a catheter to be located within the aorta of a person for pumping blood through the vascular system of the person, the catheter comprising rotary pump means disposed at the end of the catheter distal from the operator, rotary drive means operatively connected to the pump means extending within the catheter, a tube extending about the pump means and defining an inlet for the flow of blood to the pump means at one end and an outlet at the other <u style="single">characterised by</u> a flexible skirt extending about the periphery of the tube, the skirt being hingedly connected to the tube and arranged in use to extend generally parallel to the axis of the tube to sealingly engage the side walls of the aorta to hold the end at a position longitudinally spaced from and upstream of the aortic valve.

In yet another aspect the invention provides a catheter to be placed within the body of a person <u style="single">characterised in that</u> the catheter comprises an outer sleeve having a flexible tube-like end portion to be located distally of the operator, the end portion being expandable between a retracted condition during insertion of the catheter and an expanded condition when the end portion is at the desired location within the body, a plurality of fingers disposed about the periphery of the end portion and arranged to be movable to expand the end portion between the retracted and expanded conditions.

In order that the invention may be better understood it will now be described by way of example with reference to the accompanying diagrammatic drawings, in which: <ul id="ul0001" list-style="none"><li>Figure 1 is a perspective view of the distal end of apparatus according to the invention;</li><li>Figure 2 is an enlarged sectional view taken along line 2-2 of Figure 1 and showing the device of Figure 1 in its operative state to pump blood to the being's vascular system; and</li><li>Figure 3 is an enlarged sectional view taken along line 3-3 of Figure 2.</li></ul>

As shown in Figure 1 apparatus (20) according to the invention is arranged to be disposed within the vascular system, and in particular, the aorta (22, Figure 2) to effect the pumping of blood through the vascular system. The apparatus comprises a catheter having pumping means (24) located at its distal end portion (26), i.e that end remote from the operator. The catheter comprises an elongated outer tube or sleeve (20A) of small diameter, e.g 5 to 10 French (1.7-3.3 mm), with various components located therein and with the pumping means (24) and barrier means, to be described later, at its distal end portion (26). The catheter is sufficiently flexible to enable it to be passed through the vascular system to its desired position within the aorta remote (i.e downstream) from the aortic valve (28) (Figure 2). The positioning of the catheter (20) is carried out through the use of a conventional tubular guide catheter (not shown), which is first introduced and threaded through the vascular system in a conventional manner. For example, the catheter (20) is inserted percutaneously into the femoral artery (not shown), up through the descending aorta (not shown) until its distal end portion (26) is located at a desired position within the aorta (22) downstream of the aortic valve (28) and downstream of the junction of the coronary arteries (30) to the aorta. Thus, the distal end portion (26) may be located within the ascending aorta, the aortic arch or the descending aorta, as desired.

As shown best in Figure 2, the distal end portion (26) of the catheter (20) includes the pump means (24). That means can take various forms such as those disclosed in US-A-4,753,221. Thus, the pump means (24) is preferably a centrifugal pump which is arranged to be operated, e.g rotated, by drive means (32) shown. The drive means (32) can take various forms, but preferably comprises the high speed rotary drive system described and claimed in US-A-4,606,902 entitled Spiral Wire Bearing for Rotating Wire Drive Catheter, the disclosure of which is incorporated by reference herein. That drive system comprises an elongated drive wire or cable (32A) supported in the centre of the catheter tube (20A) along its central longitudinal axis (34), by means of a spiral bearing (32B). That bearing comprises a helical or spiral coil of wire extending substantially the entire length of the catheter tube from a proximately located point outside the body to the distal end portion of the catheter. The outer diameter of the helical bearing is sufficiently great so that its loops just clear the interior surface of the catheter tube (20A) to hold the bearing securely in place therein. The inside diameter of the central passage extending down the length of the helical bearing is just slightly greater than the outside diameter of the drive cable so the drive cable can rotate freely therein.

In the interests of reducing the size of any wear debris created by the rotation of the drive cable within the spiral bearing, the drive cable may be swaged or drawn to increase the engaging surface area thereof, while the cross-sectional shape of the spiral bearing can be rectangular to also increase the engaging surface area.

The drive cable is arranged to be connected at the proximal end thereof to an electric motor (not shown) or some other drive means for rotating the cable at high speed, e.g from 10,000 to 200,000 rpm, to effect the operation of the pump (24).

The distal end portion of the catheter is of a generally tubular construction which is arranged to be expanded from a retracted orientation (not shown) to an expanded orientation (as shown in Figures 1 to 3), and vice versa. When the distal end portion is in the compact orientation its outside diameter is sufficiently small to enable the catheter to be readily inserted longitudinally into the aorta, via a percutaneous insertion at a desired location, e.g into the femoral artery. Once the catheter is within the aorta, and in particular at the desired position at which it is to be operated, the distal end portion is expanded to the expanded orientation shown in the drawings.

The pump (24) is an expandable/contractible member so that when the distal end portion of the catheter is expanded, automatically expands from a closed or compact position to the open, operative position.

In the embodiment shown herein the pump (24) is an axial type pump basically comprising a central hub (24A) from which four blades or impellers (24B) extend. The blades are biased to naturally project outward radially. However, the blades are formed of flexible material so that when the distal end portion of the catheter (20) is compacted (unexpanded) the blades are flexed into the closed or compressed position extending beside one another. When released or freed they extend radially outward from the hub (24A). Moreover each of the blades (24B) is angled so that when the pump is rotated about the central axis (34) of the catheter the blades (24B) draw blood from the heart into an inlet (to be described later) in the distal end portion of the catheter to the blades and from there the blades force the blood out of an outlet into the direction of arrows (to be described later) into the aorta (22).

The proximal end of the hub (24A) is connected to the distal end of the drive cable (32A) so that the rotation of cable causes the concomitant rotation of pump's blades (24B).

The edges of each of the blades (24B) are preferably rounded so as not to present any sharp edges which could adversely affect the blood cells pumped thereby.

The pump (24) is held in position centered within the distal end portion by a bearing support (36).

As can be seen the distal end portion of the catheter (20) is in the form of a cup-shaped member (38). The member (38) is formed of a flexible and/or resilient material, e.g an elastomeric material. The member (38) is tubular in shape, e.g it constitutes a truncated cone, including an enlarged diameter open ree end (40) located at the distal end thereof and a smaller diameter open end (42) located at the proximal end thereof. The cup-shaped member (38) is mounted on the sleeve (20A) forming the outer wall of the catheter at the distal end thereof via a plurality of resilient fingers (44). The fingers extend at equally spaced locations about the periphery of the catheter's sleeve (20A). Each finger (44) is formed of a resilient material and is slightly arcuate in shape. The distal end (46) of each of the fingers (44) is secured to the outer periphery of the cup-shaped member immediately adjacent the opening (42) while the proximal end (48) of each of the fingers (44) is fixed to the catheter sleeve (20A). Each of the fingers (44) is biased radially outward so that when unconstrained, they move to the expanded position shown in the drawings, thereby expanding the cup-shaped member (38) from a retracted or compacted orientation (not shown), in which it is somewhat like a folded umbrella, to the expanded orientation shown. The fingers (44) and the cup-shaped member (38) are arranged to be compressed or contracted radially inward by being disposed within the tubular guide and/or introducing catheter (not shown) during placement of the device (20) in the patient.

In particular, the device is arranged to be inserted through a conventional tubular guide/introducing catheter into the body to the desired position within the aorta and the guide/introducing catheter is then retracted to expose the distal end portion of the device (20). This action enables the resilient fingers (44) to move radially outward to the position shown, thereby causing the cup-shaped member (38) to also assume the expanded orientation shown.

In normal operation the flared open end (40) of the cup-shaped member (38) serves as the inlet to the pump (24), while the smaller diameter opening (42) and the open spaces (50) between the fingers (44) contiguous with the opening (42) serves as the outlet from the pump. Thus the pump is located so that its blades are disposed within the cup shaped member (38) between the inlet and the outlet.

In order to ensure that substantially all, if not all, of the blood which will flow through the aorta flows into the pump's inlet (and not around the outside of the catheter), the distal end portion of the catheter includes the heretofore mentioned barrier means. That means is in the form of a barrier wall of a flexible skirt (62) which extends about the periphery of cup­shaped member (38) contiguous with the opening (inlet) (40). The skirt is very flexible so that it engages and conforms to the periphery of the inner surface of the aorta as shown clearly in Figures 2 and 3. This action has the effect of isolating the portion of the aorta (22) upstream (distally) of the pump from the portion of the aorta downstream (proximally) of the pump, except for the passageway through the pump itself, i.e through the cup-shaped member (38) from the inlet to the outlet.

Accordingly, when the pump is operated at a relatively high speed, e.g 10,000 to 100,000 rpm, higher pressure is produced in the aorta downstream of the barrier wall than upstream. This action causes blood to be drawn in the direction of arrows (54) from the heart (56) through the aortic valve (28) into the pump's inlet (40) from whence it flows to the pump's outlet (42, 50) and from there into the aorta (22) for passage to the remainder of the person's vascular system.

In some applications, e.g to ensure that sufficient blood flows into the coronary arteries (30), the operation of the catheter's pump will be co-ordinated with the pumping action of the heart. Thus, for such applications the speed of the pump is cycled, i.e slowed down or stopped, in synchronism with the pumping action of the heart so that there will be repetitive periods when the higher pressure downstream of the pump pushes the blood upstream of the pump into the coronary arteries. The pump speed/time cycle can be established and/or adjusted to anything desired.

Not only does the barrier wall (52) provide the isolation function described above, it also serves to hold the distal end of the catheter at the desired operative position within the aorta.

As will be appreciated from the foregoing since the catheter is arranged to be located at a position remote from the heart and the aortic valve, it can be used by less skilled personnel than would otherwise be required if the catheter had to be located into the heart through the aortic valve or immediately over the aortic valve. Moreover, some medical situations, e.g a patient having a calcified aortic valve or whose heart has stopped beating, may not be conducive to the disposition of a catheter through or immediately over the aortic valve. It is for such applications that the subject catheter is particularly suited. Furthermore, the location of the distal end of the catheter remote from the aortic valve ensures that the entrance to the coronary arteries is not blocked by any portion of the catheter.