Surgery – Cardiac augmentation
Reexamination Certificate
1999-01-28
2001-06-12
Layno, Carl H. (Department: 3762)
Surgery
Cardiac augmentation
C600S018000
Reexamination Certificate
active
06245007
ABSTRACT:
TECHNICAL FIELD
This invention relates to an intravascular blood pump, and in particular to pump adapted to be inserted into the apex of the heart, and alternatively to a pump adapted to be inserted via the aorta into the heart.
BACKGROUND OF THE INVENTION
In recent years great advancements have been made in the field of cardiac surgery. Surgical procedures to repair the heart or the heart's own blood supply are now frequently performed. One of the best known is the procedure called coronary artery bypass grafting, in which blood vessels taken from other parts of the patient's body are used to replace those portions of the coronary artery that have been damaged by disease. During such surgery it is necessary to take over the heart's function temporarily, either through a total bypass where the blood is pumped and oxygenated externally, or by the use of an intravascular blood pump.
Intravascular blood pumps are known that have a drive section integral to them, such as the one disclosed in U.S. Pat. Nos. 5,147,388 and 5,275,580. Others are intended to by powered by a remote power source via e.g. a drive shaft or cable, such as the ones disclosed in U.S. Pat. Nos. 4,625,712; 4,846,152; 4,964,864 and 5,112,349.
It is known to insert intravascular pumps into the heart through the vascular tree, via e.g. the femoral artery and the aorta. See, e.g., U.S. Pat. Nos. 4,625,712; 4,846,152 and 4,944,722. This placement suffers from the disadvantage that the aortic valve of the heart must be entered “backwards”, i.e. against its natural flow direction. Great care must therefore be taken to avoid damage to the thin flaps of tissue that form the valve.
It is also known to insert intravascular blood pumps directly into the heart, piercing the heart wall at the heart's apex. See, e.g., U.S. Pat. Nos. 5,147,388; 5,275,580; 5,376,114; 5,755,784 and 5,776,190. Two problems arise with respect to the use of intravascular blood pumps that are inserted at the apex. First, such devices tend to be long and stiff, and it is difficult to maneuver the pump into position relative to the heart's internal structures. Second, the heart normally has some pressure within it, and blood tends to be forced backwards through the pump to spurt out into the open at some time during the insertion when the pump's outlet is within the heart and the pump's inlet is still outside the heart.
There has also been interest in a left atrial approach. This approach involves cutting a slit into the top of the heart into the left atrium, and threading the pump through the mitral valve into position on both sides of the aortic valve. Alternatively, this approach might involve threading the pump into the left atrium via a pulmonary vein.
SUMMARY OF THE INVENTION
The invention provides a blood pump having inlet and outlet ports, at least one of which can be opened or closed to fluid flow so that the blood pump can be inserted into the heart with the port closed, and the port can be opened to allow pumping blood. If the pump is being inserted via the apex of the heart, for example, the closed port restricts or prevents loss of blood or spurting of blood through the inlet port as the blood pump is inserted into position.
In one aspect of the invention, the intravascular blood pump generally comprises a driver, and a pump mechanism. The pump mechanism comprises inner and outer sleeves in sliding interengagement, and an impeller mounted within at least one of the inner and outer sleeves. One of the inner and outer sleeves includes a port, and the other of the inner and outer sleeves is movable relative to the port between a first position sealing the port and a second position wherein the port is open. The impeller is operatively connected to the driver to rotate the impeller to pump fluid through the port.
Preferably, the pump mechanism of the blood pump includes two portions that move axially with respect to each other after the pump mechanism has been inserted through the apex of the heart. Therefore, the blood pump can be moved into position while it is short or more readily maneuvered, for example, the blood pump can be positioned adjacent the aortic valve while it is short. Then once positioned, as one portion slides forward with respect to the other, the pump mechanism's outlet extends forward and opens, and its inlet, which had been sealed during the insertion, opens as well.
Alternatively, the inlet and/or outlet ports can be opened or closed via rotation, for example, by rotating one portion relative to another.
The invention may be considered as an intravascular blood pump having a cable assembly and a pump mechanism attached to that cable assembly. The cable assembly includes an outer sheath, an inner sheath partially enclosed within the outer sheath, and a drive cable partially enclosed within the inner sheath. The pump mechanism an outer sleeve, an inner sleeve, and an impeller. The inner sleeve has a vent for admitting the patient's blood into the pump mechanism, and is attached to the outer sheath of the cable assembly. The inner sleeve is in sliding engagement with the outer sleeve, and is attached to the inner sheath of the cable assembly. The impeller is mounted within the inner sleeve, and is attached to the drive cable. Assembled in such a manner, the pump mechanism is movable between a retracted position wherein the port is sealed by the inner sleeve, and an extended position wherein the port is open to admit blood to the impeller.
In preferred embodiments there is a locking mechanism attached to the inner sheath and adapted to engage the outer sheath so that the pump mechanism can be locked in the extended position while the intravascular blood pump is residing within the patient after insertion by the surgeon. Conveniently, the attachment between the inner sheath and the inner sleeve will be accomplished by a support member. Also conveniently, a distal member will be attached to the inner sleeve in a position adjacent and distal of the impeller for the purposes of providing a protective tip and improving the flow characteristics of the blood in that area.
While the intravascular blood pump of the present invention is particularly adapted for apical insertion, it will be clear that if the impeller is reversed, the invention can be used for insertion into the heart via the aortic valve. Many of the pump's desirable characteristics will still be available to the practitioner in such a mode.
In another aspect of the invention, the intravascular blood pump generally comprises a sheath having a flange and an internal lumen, and a drive cable partially enclosed within the internal lumen of the sheath. The sheath comprises a bearing portion generally adjacent the flange. The bearing has an end, at least one slot extending substantially between the flange and the end, and a channel along the end of the bearing portion providing fluid communication between the internal lumen and the slot. An impeller is mounted on the drive cable so that the impeller is rotated when the drive cable rotates. The impeller has a cap receiving the bearing portion of the sheath. The cap slideably engages the end of the bearing portion for rotation relative to the bearing portion. The cap has a flange disposed adjacent but not contacting the flange of the sheath to form a gap permitting the escape of fluid from the layer of fluid between the cap and bearing portion. Means, such as a reservoir of fluid, is provided for introducing a flow of fluid into the lumen of the sheath so that the flow of fluid passes through the slot to provide a layer of fluid between the cap and the bearing portion.
Most preferably, the bearing includes a plurality of longitudinally extending slots substantially equally spaced apart along the bearing portion, and a plurality of channels are provided along the end of the bearing portion to allowing fluid communication between the internal lumen and plurality of slots.
In yet another aspect of the invention, the intravascular blood pump generally comprises a pump housing h
Bedingham William
Castro Gustavo H.
Gonzalez Bernard A.
Burns Doane , Swecker, Mathis LLP
Layno Carl H.
Terumo Cardiovascular Systems Corporation
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