Guidable intravascular blood pump and related methods

An improved intravascular blood pump system (10) and related methods involving the broad inventive concept of equipping the intravascular blood pump (12) with guiding features such that the intravascular blood pump can be selectively positioned at a predetermined location within the circulatory system of a patient.

FIELD OF THE INVENTION

The present invention relates generally to blood pumps and, more particularly, to an improved intra-vascular blood pump having a guide mechanism which provides the ability to selectively guide the intravascular pump to a desired location within a patient's circulatory system.

DESCRIPTION OF RELATED ART

Over the years, various types of blood pumps have been developed for the purpose of augmenting or replacing the blood pumping action of damaged or diseased hearts. Blood pumps are commonly used in three situations: (1) for acute support during cardio-pulmonary operations; (2) for short-term support while awaiting recovery of the heart from surgery; or (3) as a bridge to keep a patient alive while awaiting heart transplantation. The pumps may be designed to provide right and/or left ventricular assist, although left ventricle assist is the most common application in that it is far more common for the left ventricle to become diseased or damaged than it is for the right ventricle.

Blood pumps must provide leak-free operation and must avoid contamination of the fluid by the pump components and the external environment. Such pumps must also pump the fluid at a suitable rate without applying excessive Reynolds shear stress to the fluid. It is well known to those skilled in the art that lysis or cell destruction may result from application of shear stress to cell membranes. Red blood cells are particularly susceptible to shear stress damage as their cell membranes do not include a reinforcing cytoskeleton to maintain cell shape. Lysis of white blood cells and platelets also occurs upon application of high shear stress. Lysis of red blood cells can result in release of cell contents which trigger subsequent platelet aggregation. Sublytic shear stress leads to cellular alterations and direct activation and aggregation of platelets and white blood cells.

Intravascular blood pumps comprise miniaturized blood pumps capable of being percutaneously or surgically introduced into the vascular system of a patient, typically to provide left and/or right heart support. One type of intravascular pump is an axial flow blood pump comprising a cable-mounted rotor surrounded by a protective shroud. The pump, along with the rotor and shroud, are mounted at the end of an elongated flexible catheter. The catheter is inserted into the aorta from a remote entry point, such as an incision below the groin that provides access into a femoral artery. The catheter then passes through the descending aorta until it reaches the ascending aorta, near the heart. The catheter device encloses a rotating drive cable which is coupled to the impeller blade at one end, and which emerges from the exposed end of the catheter, near the patient's groin, at the other end. When the exposed end of the drive cable is mechanically rotated, using a device located outside the patient's body, it conveys the rotational force through the length of the catheter, causing the impeller to spin at high speed near the heart. This type of blood pump finds particular application in providing ventricular assist during surgery or providing temporary bridging support to help a patient survive a crisis.

While generally effective in providing ventricular assisting functions, prior art intravascular blood pumps nonetheless suffer various drawbacks. A significant drawback is that prior art intravascular blood pumps are difficult to guide into the appropriate position within the circulatory system of a patient. This is due largely to the fact that the elongated catheter is incapable of providing the degree of control necessary to easily negotiate the pump through the tortuous pathways leading up to and into the heart. When attempting to place the blood pump in a trans-valvular configuration (with the inlet in the left ventricle and the pump outlet in the ascending aorta), the natural tendency of the catheter to stay straight may cause the pump to be inadvertently placed in the carotid ostia, which can be dangerous if the pump is operated to withdraw blood from the brain.

To overcome these difficulties, certain guide mechanisms may be employed to assist the physician placing the pump in the appropriate position within the circulatory system. One type of supplemental guide mechanism is a guide catheter. Guide catheters are designed with certain guidability characteristics such that physicians can selectively position them within the vasculature or heart with relative ease. A central lumen is provided within the guide catheter such that the intravascular pump may be introduced therein and guided while it is advanced towards the predetermined circulatory site. While generally effective at providing a guiding feature for such intravascular blood pumps, employing such supplemental guide mechanisms is nonetheless disadvantageous in that they consume valuable space within the vessels. A guide catheter, for example, would necessarily be larger in diameter than the diameter of the pump and protective shroud in order to provide adequate passage of those components. As will be appreciated, this restricts the amount of space available for blood to flow within the particular vessel, and increases the size of the required puncture wound for accessing the vessel.

The present invention is directed at eliminating and/or reducing the effects of the foregoing drawbacks of prior art intravascular blood pumps.

SUMMARY OF THE INVENTION

The present invention overcomes the drawbacks of the prior art by providing an improved intravascular blood pump equipped with integrated features for selectively guiding the intravascular blood pump to a predetermined location in the patient's circulatory system, i.e. heart and/or vasculature. In so doing, the intravascular blood pump of the present invention eliminates the need for supplemental guiding mechanisms, such as a separate, large diameter guide catheter as used in the prior art.

In a first broad aspect of the present invention, an intravascular blood pump system is provided comprising an intravascular blood pump having a cannula coupled thereto and an “over-the-wire” type guide mechanism for selectively positioning the intravascular blood pump and cannula at a predetermined location within the circulatory system of a patient. To accomplish this, a central lumen is formed through at least a portion of the intravascular blood pump system such that a guide element, such as a guide wire, may be progressed therethrough and advanced to the predetermined location in the circulatory system of the patient. After the guide element is advanced to this desired location, the intravascular blood pump and cannula may thereafter be advanced along the guide element to the desired location.

In a second broad aspect of the present invention, an intravascular blood pump system is provided comprising an intravascular blood pump having a cannula coupled thereto and a “side-rigger” or “rapid exchange” type guide mechanism for selectively positioning the intravascular blood pump and cannula at a predetermined location within the circulatory system of a patient. To accomplish this, a side lumen is formed along a length of at least one of the intravascular blood pump and the cannula. A guide element, such as a guide wire, may be advanced to the predetermined location in the circulatory system of the patient. After the guide element is advanced to this desired location, the intravascular blood pump and cannula may thereafter be advanced along the guide element to the desired location.

In a third broad aspect of the present invention, an intravascular blood pump system is provided comprising an intravascular blood pump having a cannula coupled thereto and a “guide catheter” type guide mechanism for selectively positioning the intravascular blood pump and cannula at a predetermined location within the circulatory system of a patient. The pump system of this broad aspect includes a conduit assembly and a separate pump assembly. The conduit assembly includes a guide catheter, a rotor shroud, and a cannula, with the cannula and guide catheter disposed on either side of the rotor shroud. The pump assembly includes a rotor, a drive member coupled to the rotor, and a pump disposed between the rotor and the drive member. The guide catheter is dimensioned to receive and guide the pump assembly to the point where the rotor docks within the rotor shroud so as to form an operational blood pump. This configuration allows the conduit assembly to be precisely and efficiently guided into a desired position within the body through the use of conventional guiding techniques well known in interventional cardiology. The pump assembly may thereafter be introduced into and guided within the conduit until the pump assembly is docked within the rotor shroud. This dual construction arrangement provides improved placement of the pump assembly by using the conduit as a guiding mechanism.

The foregoing broad aspects of the present invention may be manifested according to the following recitations:

According to a first broad recitation of the present invention, an intravascular blood pump system is provided comprising an intravascular blood pump having a cannula coupled thereto, and a guide mechanism adapted to guide the intravascular blood pump and cannula to a predetermined location within the circulatory system of a patient.

In a further embodiment, the intravascular blood pump includes a rotor, a shroud for receiving the rotor, and a drive cable coupled to the rotor for driving the rotor within the shroud.

In a further embodiment, the cannula is coupled to the shroud of the intravascular blood pump.

In a further embodiment, the guide mechanism comprises a guide catheter coupled to the shroud.

In a further embodiment, the guide catheter may be used to guide the shroud and cannula to the predetermined location within the circulatory system of the patient, after which point the rotor and drive cable of the intravascular blood pump may be docked within the shroud for pump operation.

In a further embodiment, the drive cable sheath is provided having a central lumen for receiving the drive cable, and wherein a purge fluid delivery system is coupled to the drive cable sheath to deliver purge fluid to the rotor.

In a further embodiment, the drive cable sheath includes at least one side lumen for delivering the purge fluid towards the rotor.

In a further embodiment, a portion of the purge fluid is delivered through the at least one side lumen and past the rotor, and a portion of purge fluid is rerouted back from the rotor through the central lumen of the drive cable.

In a further embodiment, a perfusion assembly is provided communicatively coupled to the guide catheter for selectively rerouting blood from within the guide catheter to a point downstream from the introduction site of the guide catheter into the vasculature of the patient.

In a further embodiment, the perfusion assembly includes a first conduit communicatively coupled to the guide catheter, a second conduit dimensioned to be introduced into the vasculature of the patient, and a selectively operable valve disposed in between the first conduit and the second conduit.

In a further embodiment, a blood pressure detection mechanism is provided to detect the pressure of the blood proximate at least one of the intravascular blood pump and cannula.

In a further embodiment, the blood pressure detection mechanism comprises at least one of fluid filled column disposed within at least a portion of the cannula, a piezoelectric element coupled to at least one of the intravascular blood pump and cannula, and a strain gauge coupled to at least one of the intravascular blood pump and cannula.

In a further embodiment, the blood pressure detection mechanism involves calculating blood pressure based on the relationship between the torque and motor current of a motor used to drive the rotor.

In a further embodiment, the guide mechanism comprises a guide element disposed at least partially within the cannula.

In a further embodiment, the guide element comprises a guide wire for passage through a side lumen formed in the cannula.

In a further embodiment, the guide element comprises a selectively deformable element disposed at least partially within the cannula.

In a further embodiment, the intravascular blood pump and cannula may be selectively advanced to the predetermined location within the vasculature of the patient by first passing the guide wire to the predetermined location and thereafter sliding the intravascular blood pump and cannula along the guide wire to the predetermined location.

In a further embodiment, the guide element comprises a guide wire for passage through a lumen extending through the drive cable and rotor.

In a further embodiment, the intravascular blood pump and cannula may be selectively advanced to the predetermined location within the vasculature of the patient by first passing the guide wire to the predetermined location and thereafter sliding the intravascular blood pump and cannula along the guide wire to the predetermine location.

In a further embodiment, the guide mechanism further includes guide element for passage through the guide catheter to facilitate placement of the shroud and the cannula at the predetermined location within the vasculature of the patient.

In a further embodiment, the guide mechanism further includes a guide element for passage through a side lumen formed along at least a portion of the guide catheter.

In a further embodiment, the guide element comprises at least one of a guide wire and a balloon catheter.

DETAILED DESCRIPTION OF THE INVENTION

The present invention involves an intravascular pump system for use in a number of broad ranging applications involving the augmentation of blood flow within the circulatory system of a patient. As will be described below, the intravascular blood pump system of the present invention overcomes the drawbacks of the prior art by providing a guide mechanism as part of the intravascular blood pump. This advantageously allows the intravascular blood pump to be selectively guided to a predetermined location within the circulatory system of a patient without the need for bulky supplemental guide mechanisms, such as a separate guide catheter.

The intravascular pump assembly of the present invention is particularly suited for trans-valvular use, such as for left and/or right ventricular assist procedures. By way of example only, such ventricular assist procedures may be employed in cardiac operations including, but not limited to, coronary bypass graft (CABG), cardiopulmonary bypass (CPB), open chest and closed chest (minimally invasive) surgery, bridge-to-transplant and/or failure-to-wean-from-bypass situations. It is to be readily understood, however, that the intravascular blood pump assembly and methods of the present invention are not to be limited to such applications. Moreover, while illustrated and described largely with reference to left-heart assist applications, it is to be readily understood that the principles of the present invention apply equally with regard to right-heart assist application, which are contemplated as within the scope of the present invention. These and other variations and additional features will be described throughout.

Referring toFIG. 1, shown is a guidable intra-vascular blood pump system10according to a first broad aspect of the present invention shown, by way of example only, in a left-heart assist configuration within a human heart. The system10includes an intravascular blood pump12, a cannula14, and an “over-the-wire” type guide mechanism16. A drive cable assembly18and a motor assembly20are provided to drive the intravascular blood pump12. The “over-the-wire” guide mechanism16comprises a suitable guide element dimensioned to pass slideably through a central lumen extending through the drive cable18, blood pump12, and cannula14. Suitable guide elements may include any number of conventional guiding devices, including but limited to those employed in cardiology. By way of example only, the guide element is shown as a guide wire22. According to the present invention, the “over-the-wire” guide mechanism16provides the ability to selectively guide the blood pump12and cannula14to a predetermined position in the circulatory system of a patient, such as the trans-valvular position shown.

To accomplish this, the guide wire22is first introduced into the vascular system of a patient through any suitable access point, such as through the use of the well known Seldinger technique. The guide wire22can then be advanced within the patient to a desired location within the circulatory system of the patient. This may be done-using the control features of the guide wire22itself, or may be facilitated through the use of any number of supplemental guidance mechanisms or techniques to ensure the proper and efficient placement of the guide wire22. Such supplemental guidance techniques may include, but are not necessarily limited to, guide catheters and/or techniques involving ultra-sound or flouroscopy. Once the guide wire22is positioned at the desired location (such as in left ventricle as shown), the blood pump12and cannula14may thereafter be advanced along the guide wire22and positioned in the trans-valvular configuration shown. Under the operation of the motor assembly20, the blood pump12may be used for left-heart assist by selectively withdrawing blood from the left ventricle (through the interior of the cannula14) for delivery outward through outflow apertures formed in the blood pump12. This outflow from the blood pump12flows along the exterior of the drive cable assembly18in a substantially axial fashion for arterial distribution throughout the body.

Referring toFIGS. 2–5, an exemplary embodiment of the intravascular blood pump system10ofFIG. 1will now be described. As shown inFIG. 2, the intravascular blood pump system10includes a motor coupler24and, as will be described in greater detail below, a purge fluid delivery system26for providing a two-way fluid flow within the drive cable assembly18during pump operation. The purge fluid delivery system26includes a fluid inlet conduit28for introducing pressurized purge fluid from a fluid source (not shown) for delivery into the blood pump12, and a fluid outlet conduit30to withdraw a return flow of purge fluid from the blood pump12. The motor coupler24establishes a mechanical connection between a motor (not shown) and a drive cable (not shown) for providing motive force to the blood pump12for pump operation. The drive cable assembly18includes a drive cable sheath32which, in addition to serving a purge fluid delivery function, also serves as a protective housing for the drive cable (not shown). Although shown in broken form for clarity, it will be appreciated that the drive cable assembly18(and all components thereof) may be provided in any suitable length sufficient for intravascular applications. That is to say, the length of the drive cable assembly18must be enough to reach between the motor coupler24and purge fluid delivery system26, located outside the patient, and the desired location within the patient's circulatory system where the blood pump12is to be positioned.

The intravascular blood pump12is shown (by way of example only) as an axial flow intravascular blood pump. The blood pump12includes pump body34, a rotor shroud36having flow ports38, and an internally disposed rotor (not shown) having a shaft rotatably disposed within the pump body34and an impeller rotatably disposed within the rotor shroud36. The cannula14is fixedly attached to the rotor shroud36and may extend any suitable length therefrom depending upon the particular intravascular application. The cannula14preferably includes a plurality of ports or fenestrations40about its distal region, as well as an end port42, which allow for the ingress or egress of blood into or from the cannula14depending upon the operation of the blood pump12. That is to say, if the pump12is configured for left-heart assist as shown inFIG. 1, then the ports40,42will allow the ingress of blood into the cannula14from the left ventricle. If, on the other hand, the blood pump12is configured for right-heart assist (i.e. with the pump12in the right atrium and the distal end of the cannula14located within the pulmonary artery), then the ports40,42will allow the egress of blood from the cannula14into the pulmonary artery. (Details on right-heart assist applications will be discussed in greater detail below.) The pump12and cannula14may be dimensioned to any suitable diameter for intravascular applications. For example, the range of sizes may include, —but is not necessarily limited to, 9 French to 30 French, although the range is more preferably from 14 French to 24 French, and most preferably from 18 French to 20 French.

The “over-the-wire” type guide mechanism16includes the guide wire22and, as will be explained in greater detail below, a central lumen extending through the cannula14, blood pump12, drive cable assembly18, purge fluid delivery system26, and motor coupler24. As noted above, the central lumen is dimensioned to slideably receive the guide wire22such that the blood pump12and cannula14may be slideably advanced along the guide wire22to a desired location within the circulatory system of a patient after the guide wire22has been so positioned using conventional guidance techniques. It is to be readily understood that, while shown as a conventional guide wire22, the guide element forming part of the guide mechanism16of the present invention may include any number of well known guidance mechanisms depending upon the application, including but not limited to balloon catheters, imaging wires, and guide catheters dimensioned to be slideably received through the central lumen. For example, although not appropriate for retrograde progression (such as the left-heart application shown inFIG. 1), a balloon catheter may be a suitable guidance mechanism for a right-heart assist application. In such a case, the balloon may be inflated and used as a “sail” to direct the catheter to a desired location (such as the pulmonary artery), after which point the blood pump12and cannula14can be advanced over the catheter to a trans-valvular configuration with the blood pump12in the right atrium and the ports38,40of the cannula14in the pulmonary artery.

FIGS. 3 and 4further detail the construction of the blood pump12, cannula14, drive cable assembly18, and “over-the-wire” guide mechanism16. The blood pump12includes a rotor44having a shaft46and an impeller48. The shaft46is rotatably disposed within the pump body34via a bearing pack comprising, by way of example, ball bearing assemblies50,52and spring54. Ball bearings assemblies50,52are well known in the art, each comprising an inner race which rotates along with the rotor shaft46, an outer race which remains in a static and fixed position against the inner surface of the pump body34, and a plurality of ball bearings disposed between the inner and outer races. The spring54biases each bearing assembly50,52axially away from one another to reduce axial play during pump operation. The shaft46is generally hollow and dimensioned to receive a cable adapter60therein for the purpose of coupling the rotor44to a drive cable62forming part of the drive cable assembly18. The drive cable62may be secured to the cable adapter60in any number of suitable fashions, including but not limited to the use of adhesives, crimping, and laser welding. These same techniques may be used to secure the cable adapter60within the shaft46of the rotor44. A radial seal64is provided in between the wall of the pump body34and a distal stepped region66on the rotor shaft46, the function of which will be described below.

The impeller48includes a hub56and a plurality of blades58extending therefrom. The hub56is generally conical and, according to the first broad aspect of the present invention, is hollow throughout to form part of the central lumen of the guide mechanism16. In this regard, the hub56is preferably provided with a gasket or seal member68at its distal tip. The seal member68may be made of any suitable sealing material (including but not limited to silicone) such that the pump12and cannula14may be easily progressed along the guide wire22for delivery to a desired circulatory site. The seal member68should also be robust enough to prevent the ingress of blood into the interior of the rotor hub56during pump operation, whether the guide wire22remains in place or is fully withdrawn. The blades58are dimensioned to reside in close tolerance with the interior surface of the shroud36. In operation, the blades58impart both an axial and radial vector on the blood which causes it to flow outward through the flow ports38formed in the shroud36. As used herein, the term “axial flow” is deemed to include flow characteristics like that shown inFIG. 3, which include both an axial and slight radial component. It is to be readily appreciated that, although shown as an axial flow type, blood pump12may comprise any number of suitable types of intravascular blood pumps, including but not limited to so-called “mixed flow” intravascular blood pumps without departing from the scope of the present invention.

The cannula14is coupled at its proximal end to the rotor shroud36. This may be accomplished in any number of fashions, including but not limited to the use of adhesives. This may also be facilitated by dimensioning the shroud36to include a narrow inlet region70capable of being received flushly within the proximal end of the cannula14. The inlet region70of the shroud36should preferably have a tapered interior surface for establishing a smooth flow transition between the cannula14and the region containing the impeller blades58. Although shown as a single integral element, it is to be understood that the pump body34and shroud36may comprise two separate (and sometimes separable) components, the significance of which will become apparent below. The pump body34and shroud36may be constructed from any number of suitable materials, including but not limited to stainless steel or other medical grade compositions or alloys. The cannula14may also be constructed from any number of suitable materials, including but not limited to medical grade plastics. As shown, the cannula14may also be fortified with spiral-wound reinforcement wire72within the walls of the cannula14.

The drive cable assembly18includes the drive cable62and the drive cable sheath32. The drive cable62is coupled to the rotor44via the cable adapter60. The drive cable sheath32includes a central lumen74and a plurality of side lumens76. The central lumen74serves as a protective covering for the drive cable62. The central lumen74, along with the side lumens76, also forms part of the purge fluid delivery system26shown above inFIG. 2, which will be described in greater detail below. The side lumens76are provided in fluid communication with the fluid inlet conduit28, while the central lumen74is provided in fluid communication with the fluid outlet conduit30. The side lumens76are thus configured to deliver purge fluid into the pump12, while the central lumen74is configured to transport purge fluid away from the pump12along the length of the drive cable62.

The pressurized purge fluid within the side lumens76may take one of two flow paths upon entry into the pump12. One flow path passes through the interior of the pump12and onward past the radial seal64to prevent the ingress of blood into the pump body34during pump operation. More specifically, the purge fluid flows distally around the cable adapter60, through the ball bearing assemblies50,52, and onward past the radial seal64. This egress of purge fluid past the radial seal64can be controlled to effectively thwart the ingress of blood past the radial seal64, which might otherwise cause clotting and/or pump damage. The other flow path is directed back out the central lumen74for delivery to the fluid outlet conduit30. In so doing, this flow path bathes the components of the pump12and/or drive cable62and thereby reduces frictional heating within the pump12and/or the central lumen74of the sheath32during pump operation.

The “over-the-wire” guide mechanism16includes a central lumen through which the guide wire22may extend for the purpose of slideably advancing the blood pump12and cannula14into a desired position within the circulatory system of a patient. In the embodiment shown, this central lumen is established by forming and co-aligning the individual central lumens within each of the drive cable62, the cable adapter60, the shaft46and hub56of the rotor44, and the cannula14. In this regard, the drive cable62is preferably of wound-wire construction having a central lumen formed therein. The central lumens within the cable adapter60, rotor44, and gasket68may be formed via machining or molding processes. These central lumens should preferably be sized such that they permit the slideable passage of the pump12and cannula14therealong, but do not interfere with or constrain the guide wire22to cause inadvertent rotation of the guide wire22during pump operation. As noted above, it is also contemplated to remove the guide wire22after the pump12and cannula14are properly positioned in the patient. In this case, the gasket or seal68on the hub56should be robust enough to reseal after the guide wire22is withdrawn and prevent the ingress of blood into the interior of the rotor44.

Referring toFIG. 5, the motor coupler24includes a housing78, a drive shaft adapter80, and a bearing assembly82. The drive shaft adapter80includes a drive shaft coupler84dimensioned to receive a drive shaft of a motor (not shown), and a drive cable coupler86dimensioned to receive the drive cable62. Any of a variety of attachment techniques may be employed to securely fasten the drive cable62to the drive cable coupler86, including but not limited to adhesives, crimping, and laser welding. The drive shaft adapter80is rotatably disposed within the housing78by the bearing assembly82. The bearing assembly82includes a sleeve88(which may alternatively be formed as an integral part of the housing78) for retaining a pair of ball bearing assemblies90,92and a spring94of the type described above. That is, each bearing assembly90,92generally comprises an inner race which rotates along with the drive shaft adapter80, an outer race which remains in a static and fixed position against the inner surface of the retaining sleeve88, and a plurality of ball bearings disposed between the inner and outer races. The spring0.94is provided to bias each bearing assembly90,92axially away from one another to reduce axial play during operation.

The purge fluid delivery system26includes a housing96having a central lumen98, an inflow port100, and an outflow port102. The housing96is also dimensioned to matingly receive a portion of the motor coupler24. In this regard, a seal element104is provided sandwiched in between the housing96and housing78and including an aperture which extends about the drive shaft adapter80as it exits the housing78to prevent the ingress of purge fluid into the motor coupler24. A fluid guide structure106is also provided within the central lumen98for the purpose of separating the inflow and outflow ports100,102. The fluid guide structure106includes a central lumen108through which the drive cable62extends, and an elevated portion110that retains an O-ring112against the inner surface of the central lumen98of the housing96. The drive cable sheath32is secured to the housing96such that the inflow port100is communicatively coupled to the side lumens76, and the outflow port102is communicatively coupled to the central lumen74. In this fashion, pressurized purge fluid may be introduced through the inflow port100via inflow conduit28, and removed through the outflow port102via outflow conduit30. By way of example, the inflow conduit28and outflow conduit30may be coupled to their respective ports100,102via barbed connectors114. Similarly, the inflow and outflow conduits28,30may be equipped with any number of suitable connectors (such as those illustrated by way of example inFIG. 2) for establishing fluid communication with a source of pressurized fluid (not shown). The pressurized fluid source (not shown) may include, but is not necessarily limited to, the use of a syringe, an indeflator, a fluid delivery pump, or an accumulator arrangement to provide the requisite delivery of pressurized fluid. The purge fluid delivery system26thus provides a two-way transmission of purge fluid within the drive cable sheath32for the purposes of cooling the blood pump12and preventing the ingress of blood past the radial seal64and into blood pump12.

Referring toFIG. 6, shown is a guidable intra-vascular blood pump system120according to a second broad aspect of the present invention. As will be described hereinafter, the intravascular blood pump system120differs from the intravascular blood pump system10described above only as to the type of guide mechanism employed. In the interest of clarity and consistency, then, like reference numerals will be used to denote like elements and distinctions pointed out where necessary. Moreover, due to the commonality of principles employed in both intravascular blood pump systems10,120, a discussion to the level of detail set forth above is not deemed necessary with regard to the intravascular blood pump system120. Instead, those aspects in common with the intravascular blood pump10are hereby incorporated into the discussion of the intravascular blood pump system120.

In its most general form, the intravascular blood pump system120of this second broad aspect of the present invention comprises the blood pump12and cannula14arrangement, wherein the cannula14is equipped with a “side-rigger” or “rapid exchange” guide mechanism122. In an important aspect of the present invention, the “rapid20exchange” or “side-rigger” guide mechanism122includes a guide carriage124formed along at least a portion of the cannula14, and a suitable guide element (such as guide wire22) dimensioned to pass slidably through a lumen (not shown) extending through the guide carriage124. The “rapid exchange” guide mechanism122thereby provides the ability to selectively guide the blood pump12and cannula14to a predetermined position in the circulatory system of a patient in the manner described above. Namely, the guide wire22may be first introduced into the vascular system of a patient through any suitable access point and guided to a desired location within the circulatory system of the patient, i.e. the left ventricle as shown. The blood pump12and cannula14may thereafter be advanced along the guide wire22and positioned in the trans-valvular configuration shown for providing left-heart assist.

FIGS. 7–9further illustrate the “side-rigger” or “rapid-exchange” guide mechanism122of this second broad aspect of the present invention. In a preferred embodiment, the “side-rigger” guide mechanism122includes a lumen126formed within the guide carriage124. The guide carriage124is preferably formed as an integral extension of the wall of the cannula14.FIGS. 7 and 8comport with the embodiment shown inFIG. 6, namely illustrating the guide carriage124formed along the exterior surface of the cannula14.FIG. 9illustrates an alternate embodiment wherein the guide carriage124may be formed along the interior surface of the cannula14. In either case, the guide wire22is advanced to a desired location in the vasculature of the patient, after which point the blood pump12and cannula14can be slidably advanced therealong for delivery to the desired location according to the present invention. The guide wire22may thereafter be withdrawn from the patient. If the guide carriage124is formed along the exterior surface of the cannula14(as shown inFIGS. 7–8), then the cannula14should preferably be positioned so that the guide carriage124does not extend in a trans-valvular fashion. For example, with reference toFIG. 6, the guide carriage124should be positioned wholly within the left ventricle such that the pulsatile blood flow during beating heart procedures will not inadvertently pass through the side lumen126and pass through the aortic valve.

The intravascular blood pump system120is constructed in virtually the same manner as the intravascular blood pump system10shown and described above, with the exception of the location of the respective guide mechanisms16,122. More specifically, because the guide mechanism122is disposed along the side of the cannula14, there is no need to form a central lumen extending through the blood pump12, drive cable assembly18, purge fluid delivery system26, and motor coupler24as detailed above with regard to the intravascular blood pump system10. As such, these components need not be specially machined or molded to include such central lumens as was required with the intravascular blood pump system10set forth above.

Referring toFIG. 10, shown is a guidable intravascular blood pump system130according to a third broad aspect of the present invention. Again, due to the commonality between many of the same components and features of the intravascular blood pump systems described above and the intravascular blood pump system130, like reference numerals will be used to denote like elements and distinctions pointed out where necessary. As will be explained in greater detail below, the intravascular blood pump system130employs yet another unique and useful guide mechanism according to the present invention. However, because many of the same components are employed, a discussion to the level of detail set forth above is not deemed necessary with regard to the intravascular blood pump system130. Instead, those aspects in common with the intravascular blood pumps described above are hereby incorporated into the discussion of the intravascular blood pump system130.

In its most general form, the intravascular blood pump system130of this third broad aspect of the present invention comprises the blood pump12and cannula14arrangement, wherein a “guide catheter”132is provided as the guide mechanism for positioning the pump12and cannula14at a desired location within the circulatory system of the patient. More specifically, with brief reference toFIG. 12, the intravascular blood pump system130is formed in two separate assemblies according to the present invention: a conduit assembly134and pump assembly136. In its most basic form, the conduit assembly134comprises the guide catheter132and cannula14coupled to the rotor shroud36. The pump assembly136is constructed such that the pump body34and rotor44can be disengaged from the rotor shroud36and removed entirely from the conduit assembly134. Referring again toFIG. 10, this dual construction forms a significant feature of the present invention because it provides the ability to form the blood pump12at a desired location in a patient using two separate and distinct steps. The first step involves positioning the conduit assembly134(with the pump assembly136removed) within a patient such that the shroud36and cannula14are each disposed in a desired location, such as a trans-valvular configuration for cardiac assist procedures. In an important aspect, the task of positioning the conduit assembly134within the patient may be advantageously facilitated through the use of any number of well known guidance mechanisms, including but not limited to guide wires, balloon catheters, imaging wires, guide catheters, and/or techniques involving ultra-sound or flouroscopy. The second step in providing the intravascular blood pump system130of the present invention involves advancing the pump assembly136through the conduit assembly134such that the rotor44docks within the shroud36to form the pump12at the desired location.

By way of clarification, the term “cannula” is used to denote cannula14because it serves a primary purpose of transporting fluid into the blood pump12, whereas the term “catheter” is used to denote the catheter132because it serves a primary purpose of guiding or directing devices or components (i.e. the pump assembly136) to a desired location within the body. It is to be readily understood, however, that these terms are only used for convenience and in a general fashion such that the cannula14may serve certain guiding functions and the catheter132may serve certain fluid transportation functions without departing from the scope of the present invention. For example, the cannula14may be equipped with dedicated lumens to receive various guide mechanisms (such as guide wires, balloon catheters, selectively deformable elements such as Nitonol, etc). In similar fashion, the guide catheter132may be used to transport fluid to and/or from the patient, such as by providing apertures138along predetermined regions of the catheter132.

FIG. 11demonstrates a significant feature of the present invention involving the use of the guide catheter132to transport fluid to and/or from the patient. An optional perfusion assembly140is provided as part of the intravascular blood pump system130of the present invention. The perfusion assembly140includes a conduit142in fluid communication with the apertures138, which in this case are formed near the distal region of the guide catheter132a short distance downstream from the blood pump12. In use, blood will pass along the exterior of the guide catheter132for distribution throughout the body, as well as within the interior of the guide catheter132after passing into the apertures138. The perfusion assembly140may then be employed to selectively reroute blood from within the guide catheter132to a point within the patient's vasculature downstream from the point where the guide catheter132enters the body. A hemostasis valve assembly146of the perfusion assembly140permits the drive cable assembly18to pass through to the purge fluid delivery system26while preventing blood flow other than into the perfusion assembly140. A seal assembly150of the purge fluid delivery system26permits the drive cable62to pass through to the motor20while preventing the flow of purge fluid other than into and from the purge fluid delivery system26. The perfusion assembly140includes a control mechanism148for selectively controlling the distribution of perfusion blood flow from the perfusion assembly140into the patient. This control mechanism148may be automatic based on certain feedback criteria or manually operated.

FIGS. 12–17illustrate an exemplary construction of the intravascular blood pump system130according to the third broad aspect of the present invention. As shown inFIG. 12, the conduit assembly134may be selectively disengaged so as to remove the pump assembly136therefrom. According to the present invention, the conduit assembly134may be introduced (without the pump assembly136) into the circulatory system of a patient and selectively guided such that the rotor shroud36and cannula14are positioned at a desired location. The pump assembly136can thereafter be selectively introduced into the conduit assembly134. A challenge in such a “back-loading” arrangement is ensuring that the pump assembly136docks appropriately within the rotor shroud36and is maintained in proper engagement during operation of the resulting pump12.

An exemplary docking arrangement will now be described with reference toFIG. 14. In a preferred embodiment, the rotor44may be properly and accurately docked within the shroud36by forming angled mating surfaces on corresponding portions of the shroud36and pump body34. More specifically, an angled mating surface may be formed on the interior surface of the rotor shroud36along that portion extending proximally from the flow aperture38. A corresponding angled mating surface may be provided along the exterior surface of the pump body34along a distal portion thereof. The mating surfaces shown inFIG. 14may preferably be formed in the range from about 2 degrees to 10 degrees, and more preferably formed in the range from about 3 degrees to 6 degrees. Mating angles within these ranges are adequate to guide the distal end of the pump body34to a point generally flush with the proximal edge of the flow aperture38as shown inFIG. 14. In this fashion, the pump assembly136and the rotor shroud36combine to form the blood pump12. More importantly, this docking is carried out such that the rotor44and rotor blades58are maintained in proper position for efficient and safe pump operation.

An exemplary biasing scheme for maintaining the pump assembly136in this docked relationship will now be described with reference toFIGS. 12–13and16–17. The conduit assembly134is preferably equipped with a male quick-connect coupling152capable of engaging with a female quick-connect coupling154forming part of the perfusion assembly140of the present invention. A bias spring156is provided in between the perfusion assembly140and the housing96of the purge fluid delivery system26. The bias spring156is preferably dimensioned so as to be in tension when the male quick-connect152is engaged within the female quick-connect154as part of the docking process of the present invention. As such, the bias spring156serves to maintain the pump assembly136in the docked position within the rotor shroud36. The bias spring156may be coupled to the housing96of the purge fluid delivery system26in any number of suitable fashions. One such coupling arrangement may comprise a female quick-connect coupling158attached to the housing96and a male quick-connect coupling160attached to the bias spring156.

An exemplary embodiment of the perfusion assembly140is shown with reference toFIGS. 12–13and17. The perfusion assembly140shown includes the hemostasis valve146coupled to the female quick-connect coupling154. A length of tubing162extends between the opposing barb connectors of the hemostasis valve146and the female quick-connect coupling154. A continuous lumen is formed extending through the interior of the male quick-connect coupling152, the female-quick-connect coupling154, the tubing162, and the hemostasis valve146. The drive cable assembly18extends through this continuous lumen and exits through a Touehy-Borst hemostasis seal164which prevents the migration of blood out of the proximal end of the perfusion assembly140. A side-port166is disposed in fluid communication with the central lumen of the perfusion assembly140. In one embodiment, this side-port166may be equipped with a conduit168having a stop-cock170to selectively control the distribution of blood through a perfusion conduit (i.e. conduit142ofFIG. 11) coupled to the stop-cock170. It will be appreciated that this type of manual control system for selectively perfusing the patient may be replaced with control circuitry for automatically controlling the rate of perfusion. Such automatic perfusion may be based on control algorithms based on contemporaneous feedback or pre-programmed thresholds.

The foregoing discussion details a host of inventive aspects forming part of the present invention. It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concepts thereof. The following evidences, by way of example only, various additional aspects forming part of the present invention.

FIG. 18illustrates an alternate configuration of the intravascular blood pump system130of the third broad aspect of the present invention having an alternate bearing assembly, purge fluid delivery, and docking scheme. The bearing assembly includes a seal spring182and a bearing assembly180. The bearing assembly180includes an inner race184, an outer race186, and a plurality of balls188which enable the inner race184to rotate along with the rotor shaft46while the outer race186remains in a static and fixed position relative to an inner surface of the pump body34. An O-ring190is disposed within a groove formed in the rotor shaft46so as to maintain the bearing assembly180against the seal spring182. The O-ring190is further secured within the groove in the rotor shaft46via a contoured lip portion extending from the distal end of the cable adapter60. The proximal end of the cable adapter60flushly engages the drive cable62.

The purge fluid delivery system of the embodiment shown inFIG. 18provides for a one way delivery of purge fluid to the blood pump12. That is, pressurized fluid (namely, fluid pressurized to some level elevated above the blood pressure in the surrounding vessel) is injected in between the drive cable62and the interior of the protective sheath32during operation. This serves to reduce any frictional heating that exists between the drive cable62and sheath32. The pressurized fluid also flows through the interior of the pump12such that, if the seal at192is broken, the pressurized fluid will flow past the open seal192and onward through the blood flow ports38formed in the shroud36. This serves to keep blood from entering the pump12in an effort to avoid clotting and/or damaging the pump12.

The pump assembly136may be docked within the conduit assembly134in any number of different fashions without departing from the scope of the present invention. That is to say, the docking scheme shown inFIG. 18is set forth by way of example only and is not to be deemed limiting or restrictive as to numerous ways to temporarily engage or “dock” the pump assembly136within the conduit assembly134. The only requirement is that the pump assembly136and conduit assembly134dock such that the rotor44is disposed within the shroud36to provide the desired axial flow through the cannula14and out the shroud36. The exemplary docking scheme involves forming an annular engagement groove194along the interior of the shroud36, and forming a complementary annular ridge196along the exterior surface of the pump body34. During insertion, the pump assembly136will be advanced into the conduit assembly134until the annular ridge196on the pump body34engages within the groove194formed in the shroud36. This docking scheme is generally advantageous in that the engagement action between the annular ridge196and groove194will provide tactile feedback to the physician during the process of inserting the pump assembly136into the conduit assembly134such that the physician will be able to determine when the docking has been completed.

As will be appreciated by those skilled in the art, the location of the annular ridge196and engagement groove194may be varied such that they are disposed closer or farther away from the flow apertures38. It may be advantageous to form these docking structures close to the flow apertures38in an effort to thwart the ingress of blood into the junction extending between the interior of the shroud36and the exterior surface of the pump body34. It is also contemplated to employ selectively inflatable structures, such as balloons, in an effort to temporarily engage or dock the pump assembly136within the conduit assembly134. In this regard, one or more lumens may be formed within the pump body34extending from the interior of the pump body34in fluid communication with a balloon disposed along the exterior surface of the pump body34. The pressurized fluid flowing within the interior of the pump body34may then be used to inflate the balloon, which will then engage within an annular groove in the shroud36, such as at194. Of course, the engagement structures may also be reversed without departing from the scope of the present invention. For example, the shroud36may be equipped with a fluid delivery lumen therein for inflating a balloon disposed on the interior surface of the shroud36, which may in turn be disposed within an annular engagement groove formed along the exterior surface of the pump body34.

While this invention has been shown in use largely in during left-heart applications, it is to be readily appreciated that this does not limit the applications of this invention for use in left heart support only. Rather, the guidable intravascular blood pump of the present invention can be utilized in right-heart support applications and a wide variety of other applications apparent to those skilled in the art. For example, with reference toFIG. 19, shown is an intravascular blood pump200(of the type shown and described above with reference toFIGS. 2–5) configured for use in a right-heart support application. In this embodiment, the intravascular blood pump system200is equipped, by way of example, with an “over-the-wire” guide mechanism16comprising a balloon catheter202. It is to be readily appreciated that, although shown and described below in terms of an embodiment of the type shown inFIGS. 2–5, the intravascular blood pump systems120,130disclosed herein may also be configured for use in right-heart applications. Such right-heart configurations, and others apparent to those skilled in the art based on the broad principles enumerated in this application, are contemplated as being within the scope of the present invention.

The intravascular blood pump system200is shown positioned within the heart, such as may be advantageous to provide right heart support during beating heart surgery. To position the guidable intravascular blood pump system200in the right heart according to the present invention, a suitable guide element (such as balloon catheter202) is first advanced to a desired location within the heart via the “sail” action of an inflated balloon. After the balloon catheter202is located in the desired position (such as in the pulmonary artery as shown), the intravascular blood pump system200according to the present invention may be advanced over the balloon catheter202and guided into a desired arrangement. For right heart support, this would involve advanced into the pump12and cannula14overt the balloon catheter202until the fluid inlet204is disposed within the vena cava (or right atrium) and the fluid outlet206is positioned within the pulmonary artery. The pump12may then be selectively (i.e. automatically or on-demand) controlled to transport blood from the vena cava (or right atrium) in a trans-valvular fashion through the tricuspid valve, the right ventricle, and the pulmonary valve for deposit within the pulmonary artery. Providing right-heart support during beating heart surgery advantageously overcomes conditions where cardiac output may become compromised during beating heart surgery, such as when the heart is lifted to gain access to posterior vessels, thereby avoiding the need for cardiopulmonary bypass.

It is also contemplated as part of the present invention that the guidable intravascular blood pump systems can be introduced into the patient's vasculature to achieve the intravascular access into the right or left heart through any number of access points, including but not limited to the internal jugular vein, the brachiocephalic vein, carotid artery, axillary artery, femoral vein, femoral artery, and subclavian artery. The intravascular blood pump systems of the present invention may also be introduced via direct introduction, such as into the aorta, the atria, and the ventricles. As is well known in the art, such intravascular access may be achieved percutaneously through the use of the Seldinger technique or directly through the use of minimally invasive access techniques.

Those skilled in the art will also appreciate that, although shown and described above in terms of “axial flow,” the present invention is not limited to the axial flow type intravascular blood pumps. Rather, the intravascular blood pumps12may comprise any number of suitable types of intravascular blood pumps, including but not limited to so-called “mixed flow” intravascular blood pumps, without departing from the scope of the present invention.

With regard to the embodiments shown inFIGS. 10–17, it is furthermore contemplated that the guide catheter132may be separable from the conduit assembly134after the pump assembly136is docked within the shroud36to form the pump12at the desired location within the circulatory system of the patient. This may be accomplished by providing the guide catheter132in a detachable fashion via any number of suitable arrangements. By removing the guide catheter132after the pump12assembled, wound management of the access point into the patient's vasculature may be improved. This is due, in part, to the substantial reduction in size of the device extending into the patient (i.e. the drive cable assembly18as opposed to the larger diameter guide catheter132).

It is also contemplated to incorporate various pressure sensing and/or guidability features into at least one of the cannula14and pump12. Such features may include, but are not necessarily limited to, those shown and described in commonly-owned and co-pending U.S. patent application Ser. No. 09/280,988 (filed Mar. 30, 1999) entitled “Steerable Cannula,” and U.S. patent application Ser. No. 09/280,970 (filed Mar. 30, 1999) entitled “Pressure Sensing Cannula,” the disclosures of which are hereby expressly incorporated by reference as if set forth herein in their entirety. These pressure sensing features may include, but are not necessarily limited to, the use of fluid-filled lumens, piezo-electric pressure sensing elements, strain gauges, and analysis of the torque/current relationship (based on the dynamic pressure differential between the inlet and outlet of the pump). The guidability features may include, but are not necessarily limited to, the use of side lumens and deformable materials (i.e. Nitonol).

Various pump and cannula arrangements have been described and shown above for providing right and/or left heart support wherein blood is deliberately re-routed through and past the right and/or left ventricle in an effort to reduce the volume of blood to be pumped by the particular ventricle. While “unloading” the ventricles in this fashion is preferred in certain instances, it is to be readily understood that the pump and cannula arrangements described herein may also be employed to “preload” the ventricles. Ventricular preloading may be accomplished by positioning the outflow cannula from the pump into a given ventricle such that the pump may be employed to fill or preload the ventricle with blood. This may be particularly useful with the right ventricle. On occasion, the right ventricle is not supplied with sufficient levels of blood from the right atrium such that, upon contraction, the right ventricle delivers an insufficient quantity of blood to the pulmonary artery. This may result when the right ventricle and/or right atrium are in a stressed or distorted condition during surgery. Preloading overcomes this problem by actively supplying blood into the right ventricle, thereby facilitating the delivery of blood into the pulmonary artery. The same technique can be used to preload the left ventricle and thus facilitate the delivery of blood from the left ventricle into the aorta.