WO2001083021A1

WO2001083021A1 - Cannulation system and related methods

Info

Publication number: WO2001083021A1
Application number: PCT/US2001/013523
Authority: WO
Inventors: Walid N. Aboul-Hosn; William Kanz; Bruce Baker; Michael Guidera; Desmond O'connell; Kim L. Kosalek; Sedig Noor
Original assignee: A-Med Systems, Inc.
Priority date: 2000-04-28
Filing date: 2001-04-27
Publication date: 2001-11-08
Also published as: AU2001255718A1

Abstract

The present disclosure involves a cannulation system and related methods for augmenting the cardiac output of the heart during cardiac surgery.

Description

CANNULATION SYSTEM AND RELATED METHODS Cross-Reference to Related Applications

This application claims the benefit under Title 35, United States Code, §119 (e) of United States Provisional Patent Application Serial No. 60/200,812, filed April 28, 2000, entitled "Cannulation System and Related Methods," the contents of which are hereby expressly incorporated by reference as if set forth fully herein. Background Of The Invention I . Field of the Invention

The present invention relates generally to a cannulation system for transporting bodily fluids. More particularly, the present invention is directed to a cannulation system and related methods for augmenting the cardiac output of the heart during cardiac surgery. II. Discussion of the Prior Art

Major heart surgery is oftentimes accomplished by procedures that require full cardiopulmonary bypass (CPB) through the use of artificial heart-lung machines and complete cessation of cardiopulmonary activity. While the average mortality rate with this type of procedure is low, it is nonetheless associated with a complication rate that is often much higher compared to when cessation of the heart and CPB are not required. The use of CPB continues to represent a major assault on a host of body systems. For example, there is noticeable degradation of mental faculties following such surgeries in a significant percentage of patients who undergo coronary artery bypass grafting (CABG) procedures. The CABG procedure generally involves open chest surgical techniques to treat diseased vessels. During this procedure, the sternum of the patient is cut in order to spread the chest apart and provide access to the heart. During surgery the heart is stopped, and by the use of CPB blood is diverted from the lungs to an artificial oxygenator. In general CABG procedures, a source of arterial blood is then connected to a coronary artery downstream from the occlusion. The source of blood is often an internal mammary artery, and the target coronary artery is typically among the anterior or posterior arteries which may be narrowed or occluded. The degradation of mental faculties resulting from CABG procedures is commonly attributed to cerebral arterial blockage and emboli from debris in the blood generated by the use of CPB. At the same time, the dramatic increase in the life expectancy of the general population has resulted in patients that are more likely to be older and in poor health, with less cardiovascular, systemic, and neurologic reserve needed to recover from the trauma caused by the use of CPB. As a consequence, inflammatory, hemostatic, endocrinologic, and neurologic stresses are tolerated to a much lesser degree by a significant number of patients today, and play a more significant role in CPB-induced morbidity.

The combined statistics of postoperative morbidity and mortality continue to illustrate the shortcomings of CPB. The extracorporeal shunting and artificially induced oxygenation of blood activates a system wide roster of plasma proteins and blood components in the body including those that were designed to act locally in response to infection or injury. When these potent actors are disseminated throughout the body without normal regulatory controls, the entire body becomes a virtual battleground. The adverse hemostatic consequences of CPB also include prolonged and potentially excessive bleeding. CPB-induced platelet activation, adhesion, and aggregation also contribute to a depletion in platelet number, and is further compounded by the reversibly depressed functioning of platelets remaining in circulation. The coagulation and fibrinolytic systems both contribute to hemostatic disturbances during and following CPB. However, the leading cause of morbidity and disability following cardiac surgery is cerebral complications. Gaseous and solid micro and macro emboli, and less often perioperative cerebral hypoperfusion, produce neurologic effects ranging from subtle neuropsychologic deficits to fatal stroke. Advances in computed tomography, magnetic resonance imaging, ultrasound, and other imaging and diagnostic techniques have added to the understanding of these complications. But with the possible exception of perioperative electroencephalography, these technologies do not yet permit real time surgical adjustments that are capable of preventing emboli or strokes in the making. Doppler and ultrasound evaluation of the carotid artery and ascending aorta, and other diagnostic measures, can help identify surgical patients at elevated risk for stroke and are among the growing list of pharmacologic and procedural measures for reducing that risk.

CPB also affects various endocrine systems, including the thyroid gland, adrenal medulla and cortex, pituitary gland, pancreas, and parathyroid gland. These systems are markedly affected not only by inflammatory processes, but also by physical and biochemical stresses imposed by extracorporeal perfusion. Most notably, CPB is now clearly understood to induce euthyroid-sick syndrome which is marked by profoundly depressed triiodothyronine levels persisting for days following cardiothoracic surgery. The efficacy of hormone replacement regimens to counteract this effect are currently undergoing clinical investigation. By contrast, levels of the stress hormones epinephrine, norepinephrine, and cortisol are markedly elevated during and following CPB, and hyperglycemia is also possible.

Beating heart bypass surgery has been recognized as desirable because it has the possibility of avoiding the necessity of placing the patient on a full CPB system. However, attempts at beating heart bypass surgery have met with limited success and have essentially been limited to surgery on the anterior heart vessels due to problems which develop when the beating heart is lifted or displaced from its normal position in order to perform the beating heart surgery. Typically when the beating heart is lifted or manipulated in order to provide surgical access to posterior heart vessels, a number of difficulties are encountered. When the beating heart is lifted and manipulated, the right side of the heart tends to collapse, particularly the right auricle or atrium and frequently the right ventricle and/or pulmonary artery. When the right side of the heart collapses, pulmonary blood flow either ceases or becomes inadequate, thus forcing the use of CPB.

Another difficulty encountered is that, even if the right side of the heart does not collapse, the pulmonary artery and/or the pulmonary vein frequently become crimped or kinked thus also impeding the pulmonary blood flow. Similarly, during the lifting and manipulation of the beating heart for lateral or posterior access, the left side of the heart, particularly the left auricle or left atrium can also collapse or partially collapse, thus impeding aortic circulatory blood flow. Further, when the beating heart is lifted or manipulated for beating heart surgery access or during catheterization or cannulation procedures, the heart may lapse into arrhythmia or disrhythmia or may arrest at least a portion of the time or most of the time that the surgery is being performed thus likewise impeding pulmonary blood flow and arterial circulatory blood flow. As a result, patients undergoing beating heart surgery are at risk of having to be placed on CPB on an emergency basis in the event that the pulmonary and/or circulatory blood flow is compromised during the surgery, which presents the CPB- induced side effects previously described. The medical community is currently performing more beating heart bypass surgery in an effort to avoid the use of full CPB. The need is increasing for apparatus systems, methods and associated equipment to enhance the capability and versatility of beating heart surgery and to avoid CPB procedures in any heart surgery. The present invention is directed at addressing this need. Summary Of The Invention

The present invention involves a cannulation system suitable for use in augmenting the cardiac output of the heart during beating heart surgery. The cannulation system of the present invention includes a dual cannula assembly communicatively coupled to a centrifugal blood pumping system. The centrifugal blood pumping system includes a miniature centrifugal blood pump, a motor, a magnetic drive cable assembly coupling the centrifugal blood pump to the motor, and a microcomputer-based control console communicatively coupled to the motor for controlling the operation of the motor and hence the centrifugal blood pump. The dual cannula assembly includes a first vascular cannula and a second vascular cannula. In a preferred embodiment, the first and second vascular cannulas are coupled to the centrifugal blood pump to provide right-heart support during beating heart surgery.

The first vascular cannula is communicatively coupled to the inlet to the blood pump, the second vascular cannula is communicatively coupled to the outlet of the centrifugal blood pump, and the first and second vascular cannulas are introduced into the heart such that fluid inlet apertures in the first vascular cannula are disposed in the right atrium and such that fluid outlet apertures in the second vascular cannula are disposed in the pulmonary artery. Under the direction of the control console, the miniature centrifugal blood pump may be selectively operated to withdraw blood from the right atrium and to reroute this blood for delivery into the pulmonary artery. Providing right heart support in this fashion advantageously eliminates the need for cardiopulmonary bypass (CPB) during beating heart surgery. Each vascular cannula and the centrifugal blood pump are provided with quick-connect couplings to facilitate the process of setting up and breaking down the system in the surgical setting. This overcomes deficiencies in the prior art wherein blood pumps and cannulas are coupled using traditional "barb-type" connectors, which are inconvenient and time-consuming to assemble and disassemble.

Brief Description Of The Drawings

FIG. 1 is a perspective view of a cannulation system according to one embodiment of the present invention, including a pump and cannula assembly communicatively coupled to a control console and motor assembly;

FIG. 2 is a perspective view of the pump and cannula assembly according to one embodiment of the present invention, including first and second vascular cannulas dimensioned to be quick-connect coupled to a miniature centrifugal blood pump assembly;

FIG. 3 is a side view of the first vascular cannula provided in accordance with one embodiment of the present invention; FIG. 4 is a side view of the second vascular cannula provided in accordance with one embodiment of the present invention, illustrating the curved distal portion;

FIG. 5 is a side view of the second vascular cannula provided in accordance with one embodiment of the present invention;

FIG. 6 is a partial sectional view illustrating the first and second vascular cannulas of the present invention disposed in a first exemplary fashion within the heart for use in providing right heart support during beating heart surgery;

FIG. 7 is a partial sectional view illustrating the first and second vascular cannulas of the present invention disposed in a second exemplary fashion within the heart for use in providing right heart support during beating heart surgery;

FIG. 8 is a partial sectional view illustrating the first and second vascular cannulas of the present invention disposed in a third exemplary fashion within the heart for use in providing right heart support during beating heart surgery;

FIG. 9 is a partial sectional perspective view of the miniature centrifugal pump of the present invention, detailing the female quick-connect fluid outflow port, the priming port, and the magnetic drive cable assembly coupled to a rotor;

FIG. 10 is a side view of the centrifugal pump assembly of the present invention, including miniature centrifugal blood pump, the inflow tubing, and magnetic drive cable assembly; FIG. 11 is a cross-sectional view of the centrifugal pump assembly of the present invention taken along lines 11 - 11 in FIG. 10;

FIG. 12 is an upper perspective view of a first pump housing member forming part of the pump housing of the miniature centrifugal pump of the present invention; FIG. 13 is a lower perspective view of the first pump housing member of the miniature centrifugal pump of the present invention;

FIG. 14 is an upper perspective view of a second pump housing member forming part of the pump housing of the miniature centrifugal pump of the present invention;

FIG. 15 is a lower perspective drawing of the second pump housing member of the miniature centrifugal pump of the present invention; FIG. 16 is a top view of the second pump housing member of the miniature centrifugal pump of the present invention shown in FIGS. 14 and 15;

FIG. 17 is a cross-sectional view of the second pump housing member of the present invention taken along lines 17 - 17 in FIG. 16;

FIG. 18 is a cross-sectional view of the second pump housing member of the present invention taken along lines 18 - 18 in FIG. 16;

FIG. 19 is a side view of the magnetic drive cable assembly according to an exemplary embodiment of the present invention;

FIG. 20 is a cross-sectional view of the magnetic drive cable assembly of the present invention taken along lines 20 - 20 in FIG. 19; FIG. 21 is an exploded perspective view of an impeller assembly for use within the miniature centrifugal pump according to an exemplary embodiment of the present invention;

FIG. 22 is a side view of the impeller assembly of the present invention as shown in FIG. 21;

FIG. 23 is a top view of the impeller assembly of the present invention as shown in FIGS. 21 and 22;

FIG. 24 is a cross-sectional view of the impeller assembly of the present invention taken along lines 24 - 24 in FIG. 23; FIG. 25 is a graph setting forth, by way of example only, the flow versus pressure characterization of the centrifugal pump of the present invention dimensioned for use as a blood pump according to an exemplary of the present invention;

FIG. 26 is a view of the front of the control console according to one embodiment of the present invention; and

FIG. 27 is a view of the back of the control console according to one embodiment of the present invention. Description Of The Preferred Embodiment

Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. It is furthermore to be readily understood that, although discussed below primarily within the context of providing right heart support during beating heart surgery, the cannulation system of the present invention may be employed in any number of cardiac procedures wherein the natural pumping ability of the heart needs to be augmented or replaced. The cannulation system disclosed herein boasts a variety of inventive features and components that warrant patent protection, both individually and in combination. Referring initially to FIG. 1, shown in perspective is a cannulation system 10 according to a preferred embodiment of the present invention. Generally speaking, the cannulation system 10 includes a pump and cannula assembly 12 and a pump controller assembly 14. The pump and cannula assembly 12 comprises a miniaturized centrifugal blood pump 24 having a first vascular cannula 16 and second vascular cannula 18 respectively coupled to the fluid inlet and fluid outlet of the pump 16. The pump controller assembly 14 includes a control console 22, a motor 20, and a flow probe 48. The control console 22 is communicatively coupled to the motor 20 via a control line 40 and to the flow probe 48 via a control line 50. The flow probe 48 is preferably coupled to inflow tubing for the purpose of determining the flow rate of the centrifugal pump 16. Under the direction of the control console 22, the motor 20 may be operated such that the centrifugal pump 16 selectively withdraws fluid (i.e. blood) through inflow apertures 46 formed in the first vascular cannula 16 and delivers it through the outflow apertures 44 formed in the second vascular cannula 18. By selectively positioning the vascular cannulas 16, 18 in the heart, blood can be selectively removed from one area and returned into another area to augment or replace the heart's own beating function. This is advantageous in that allows the surgeon to maintain the hemodynamic stability of a patient during beating heart surgery. Moreover, the first and second vascular cannulas 16, 18 establish a protected blood flow path within portions of the heart such that at least partial blood flow is maintained at all times, even during compromise conditions that may occur when the heart is manipulated or rotated during surgery to access lateral or posterior vessels on the heart.

FIG. 2 illustrates the elements of the pump and cannula assembly 12. The miniature centrifugal blood pump 24 includes a fluid inflow port 32 (having an inflow tubing member 28 coupled thereto) , a fluid outflow port 34, and an internally disposed rotor (not shown) coupled to a magnetic drive cable assembly 30. A priming port 78 is provided which, as will be described in greater detail below, is capable of being coupled to a syringe (not shown) for the purpose of evacuating air from within the pumping circuit to prime the pump 16 in preparation for use. With combined reference to FIGS. 1 and 2, the magnetic drive cable assembly 30 couples to the motor 20 which, in turn, is communicatively linked to the control console 22 via an electrical control line 40. Both the motor 20 and magnetic drive cable assembly 30 will be explained in detail below.

Suffice it to say for now that the magnetic drive cable assembly 30 advantageously provides the ability to position the miniature centrifugal pump 16 within the sterile field adjacent the operation site of the patient (not shown) . In contrast to typical CPB circuits, this minimizes the distance the blood must travel before being reintroduced into the heart, thereby reducing the likelihood of hemolysis by decreasing the amount of foreign material that the blood is exposed to during operation. The motor 20 is preferably maintained adjacent yet outside the sterile field, such as through the use of a positioning assembly 44. The control console 22 may be disposed on any suitable structure disposed outside the sterile field, such as a table or cart 46.

In an important aspect of the present invention, the pump and cannula assembly 12 is equipped with quick- connect elements for communicatively coupling the vascular cannulas 16, 18 to the blood pump 24. More specifically (and by way of example only) , the blood pump 24 is provided with a female quick-connect fitting 84 on the fluid outflow port 34 and a male quick-connect fitting 96 on the distal end of the inflow tubing member 28, the first vascular cannula 16 is provided with a female quick-connect fitting 19, and the second vascular cannula 18 is provided with a male quick-connect fitting 29. This provides several significant advantages over prior art blood pump and cannula arrangements, which traditionally involve coupling the open end of a cannula directly on a barb-type fitting on the pump. One advantage of employing quick-connectors involves ease-of-use. More specifically, the first vascular cannula 16 and second vascular cannula 18 may be quickly and easily coupled to and de-coupled from the blood pump 24 by simply engaging and disengaging the mating pairs of quick-connect fittings 96, 19 and 84, 29, respectively. This is far superior to the above- identified prior art technique for coupling a cannula to a blood pump, which is oftentimes time consuming and difficult due to the "press fit" engagement between the tubing and barb-type fitting on the pump. The importance of this distinction is particularly evident in a surgical setting, wherein the cannulas 16, 18 and/or pump 16 may be quickly and easily changed out (if need be) without disrupting the surgery. The prior art technique, on the other hand, would be time consuming and thus possibly place the patient at risk during component change out . While certain substances (such as alcohol) can be used to facilitate the "press fit" engagement between tubing and barb-type connectors, the use of such substances in the surgical setting is disadvantageous in that they may be harmful if introduced into the blood stream. The quick-connectors of the present invention obviate the need for any such substances during surgery. Another advantage of providing quick-connectors is that the cannulas 16, 18 can only be connected to the pump 16 in the correct manner. That is to say, the female quick-connect fitting 19 of the first vascular cannula 16 can only be coupled to the male quick-connect fitting 96 on the inlet side of the pump 16, while the male quick-connect fitting 29 of the second vascular cannula 18 can only be coupled to the female quick-connect fitting 84 on the outlet side of the pump 16. As such, the first vascular cannula 16 can only be employed on the inlet side of the pump 16 and that the second vascular cannula 18 can only be employed on the outlet side of the pump 16. Traditional coupling techniques, on the contrary, could easily be configured in an incorrect manner because there would be nothing to prevent a user from press-fitting the wrong cannula over a particular barb-type fitting. This creates a risk that a cannula specifically dimensioned to access one area of the heart may be erroneously introduced into an area within the heart that is not suited to receive that particular cannula geometry. The present invention eliminates that risk by equipping the pump 16 and cannulas 16, 18 such that they can only couple together in one fashion.

With reference to FIG. 3, the first vascular cannula 16 includes a wire-reinforced main tubular portion 60, a non-reinforced clamping portion 62, and a non- reinforced inflow portion 64. The walls of the first vascular cannula 16 may be constructed from any number of suitable materials, including but not limited to polyurethane . By way of example only, the first vascular cannula 16 may be dimensioned to be introduced into the heart such that fluid inlet apertures 46 are disposed within at least one of the right atrium, right ventricle, and inferior vena cava . In one embodiment, the main tubular portion 60 and inflow portion 64 are approximately 22 French in size and approximately 12 inches in combined length, although these dimensions may vary without departing from the scope of the invention. The fluid inflow portion 64 may be equipped with any number of fluid inlet apertures 46. In the embodiment shown, however, there are approximately 32 such fluid inlet apertures 46. The female quick-connect fitting 19 may be rigidly coupled to the clamping portion 62 via any number of attachment mechanisms or techniques, including but not limited to the use of adhesives and/or ultrasonic welding. The female quick-connect fitting 19 and corresponding male quick- connect fitting 96 of the inlet of the blood pump 24 may comprise any number of quick-connect arrangements, including but not limited to those shown and described in U.S. Patent No. 5,052,725, the contents of which are hereby expressed incorporated by reference. The first vascular cannula 16 may be equipped with a variety of optional features. For example, a sealing assembly 65 may be provided for selectively sealing off the aperture formed in the female quick-connect fitting 19. In the embodiment shown, the sealing assembly 65 includes a plug member 21 for placement within the aperture formed in the female quick-connect fitting 19, a ring member 67 coupled to the first vascular cannula 16, and a flexible tether member 69 extending therebetween. The sealing assembly 65 may be comprised of any number of suitable materials, including but not limited to vinyl. The first vascular cannula 16 may be equipped with various features to facilitate visualizing portions of the cannula during and after insertion into the heart, including but not limited to disposing a pair of barium stripes on the fluid inflow portion 64 capable of being visualized through the use of well known external visualization devices or techniques. A suture ring 66 may be provided along the main tubular portion 60. The suture ring 66 is preferably a low durometer silicone rubber structure around which the purse string suture for the cannula is tightened. The suture ring 66 is designed to resist slippage on the main tubular portion 60 such that the first vascular cannula 16 is maintained in a fixed position once the fluid inflow portion 64 is disposed in the selected location within the heart. Hash marks 70 (formed, by way of example, from non- toxic ink) may be provided along the main tubular portion 60 to indicate the general location that the suture ring 66 should likely be located to ensure proper placement of the fluid inflow portion 64 within the heart.' With reference to FIGS. 4 and 5, the second vascular cannula 18 includes a wire-reinforced main tubular portion 80, a non-reinforced clamping portion 82, and a non-reinforced outflow portion 84. The walls of the second vascular cannula 18 may be constructed from any number of suitable materials, including but not limited to polyurethane . By way of example only, the second vascular cannula 18 may be dimensioned to be introduced into the heart such that the fluid outlet aperture 24 is disposed within the pulmonary artery. To facilitate this, the outflow portion 84 may be curved such that its distal tip is positioned in the range of approximately 80 and 100 degrees from the plane containing the main tubular portion 80. The fluid outflow portion 84 may be equipped with any number of fluid outlet apertures 44. For example, FIGS. 1 and 2 illustrate a plurality of fluid outlet apertures 44 formed in a blunt distal tip, while FIG. 4 illustrates a single fluid outlet aperture 24 formed in an angle distal tip. In one embodiment, the main tubular portion 80 and outflow portion 84 are approximately 18 French in size and approximately 15 inches in combined length, although these dimensions may vary without departing from the scope of the invention. The male quick-connect fitting 29 may be rigidly coupled to the clamping portion 82 via any number of attachment mechanisms or techniques, including but not limited to the use of adhesives and/or ultrasonic welding.

The male quick-connect fitting 29 and corresponding female quick-connect fitting 84 of the outlet of the blood pump 24 may comprise any number of quick-connect arrangements, including but not limited to those shown and described in U.S. Patent No. 5,052,725, the contents of which are hereby expressed incorporated by reference.

The second vascular cannula 18 may be equipped with a variety of optional features. For example, a sealing assembly 85 may be provided for selectively sealing off the aperture formed in the male quick-connect fitting 29. In the embodiment shown, the sealing assembly 85 includes a cap member 88 for placement over the aperture formed in the male quick-connect fitting 29, a ring member 87 coupled to the second vascular cannula 18, and a flexible tether member 89 extending therebetween. The sealing assembly 85 may be comprised of any number of suitable materials, including but not limited to vinyl. The second vascular cannula 18 may be equipped with various features to facilitate visualizing portions of the cannula during and after insertion into the heart, including but not limited to disposing a pair of barium stripes on the fluid outflow portion 84 capable of being visualized through the use of well known external visualization devices or techniques. A suture ring 86 may be provided along the main tubular portion 80. The suture ring 86 is preferably a low durometer silicone rubber structure around which the purse string suture for the cannula is tightened.

The suture ring 86 is designed to resist slippage on the main tubular portion 80 such that the second vascular cannula 18 is maintained in a fixed position once the fluid outflow portion 84 is disposed in the selected location within the heart.

Referring to FIGS. 6-8, the first and second vascular cannulas 16, 18 of the present invention are particularly suited for use in providing right heart support during beating heart surgery. For clarity, the first and second vascular cannulas 16, 18 are shown in position within the heart without the remaining elements of the cannulation system 10 of the present invention (i.e. centrifugal pump assembly 16, control console 22, suture rings 66, 86) . The first vascular cannula 16 is introduced into the heart such that the fluid inlet apertures 46 in the distal portion 64 are disposed within at least one of the right atrium, the inferior vena cava, and/or right ventricle. In the embodiment shown, the first vascular cannula 16 is introduced into the heart through an incision formed in the atrial appendage and the fluid inlet apertures 46 are disposed in both the right atrium and the inferior vena cava. The second vascular cannula 18 is introduced into the heart such that the fluid inlet apertures 44 in the distal portion 84 are disposed within the pulmonary artery. This can be accomplished by introducing the second vascular cannula 18 into the heart through an incision formed in the wall of the pulmonary artery (FIG. 6) , the wall of the right atrium (FIG. 7) , or the wall of the right ventricle (FIG. 8) . After positioning the first and second vascular cannulas 16, 18 in the above- identified fashions, the first vascular cannula 16 is communicatively coupled to the inlet to the blood pump 24 (via the cooperative engagement of the female quick-connect fitting 19 and the male quick-connect fitting 96 on the inflow tubing 28 of the blood pump 24) and the second vascular cannula 18 is communicatively coupled to the outlet of the blood pump 24 (via the cooperative engagement of the male quick-connect fitting 29 and the female quick-connect fitting 84 on the outflow 36 of the blood pump 24) . Under the direction of the control console, the blood pump 24 may be selectively operated to withdraw blood from the right atrium, right ventricle, and/or inferior vena cava and to reroute this blood for delivery into the pulmonary artery. Providing right heart support in this fashion advantageously eliminates the need for cardiopulmonary bypass (CPB) during beating heart surgery. The centrifugal pump assembly 24 will now be described in detail with reference to FIGS. 9-11. The centrifugal pump assembly 24 includes the miniature centrifugal blood pump 26, inflow tubing 28, and magnetic drive cable assembly 30. The miniature centrifugal blood pump 26 comprises first and second pump housing members 72, 74 (which collectively form a pump housing assembly) , an impeller assembly 76, a priming port 78, a fluid inlet port 80 forming part of the first pump housing member 72, and a fluid outlet port 82 equipped with a female quick-connect fitting 84. As will be explained in greater detail below, the impeller assembly 76 comprises an impeller 86 coupled to a shaft 90. The impeller 86 includes a plurality of blades 88 extending generally radially therefrom. The shaft 90 extends generally perpendicularly from the impeller 86 for connection to the magnetic drive cable assembly 30. The priming port 78 provides the ability to communicatively couple a de-airing device, such as the syringe referenced above, with the interior of the pump housing assembly for the purpose of priming the centrifugal blood pump 26 before use. In the embodiment shown, the priming port 78 comprises a luer-type fitting commonly known in the art for coupling with syringes. It is to be readily understood that any number of alternate coupling arrangements may be provided for coupling de-airing devices to the pump 26 without departing from the scope of the present invention. The female quick-connect fitting 84 and the luer-type priming port 78 are rigidly bonded to the pump housing, such as through the combined use of adhesives and ultraviolet welding techniques. Providing the priming port 78 in this manner is advantageous in that it provides a quick, easy, and convenient fashion to couple and decouple priming devices to and from the pump 26. Providing the female quick-connect fitting 84 in this manner is advantageous in that it provides a quick, easy and convenient fashion to couple and de-couple the fluid outlet 34 of the pump 26 to and from the male quick-connect fitting 29 on the second vascular cannula 18.

The inflow tubing 28 comprises a generally flexible length of plastic conduit having a first end 92 bonded to the fluid inlet port 80 of the first pump housing member 72 and a second end 94 bonded to a male quick- connect fitting 96. As above, these bonds may be achieved through the combined use of adhesives and ultraviolet welding techniques. The male quick-connect fitting 96 is dimensioned to cooperatively couple with a female quick- connect fitting provided as part of the first vascular cannula 16 discussed above. Equipping the inflow tubing 28 with the male quick-connect fitting 96 is advantageous in that it provides a quick, easy, and convenient fashion to couple and de-couple the fluid inlet port 80 of the pump 26 to and from the female quick-connect fitting 19 of the first vascular cannula 16. The inflow tubing 28 may comprise any number of types of tubing of varying dimensions. In a preferred embodiment, the inflow tubing 28 is 3/8" x 9/16" Tygon^® tubing having a length of approximately 13 inches .

The magnetic drive cable assembly 30 of the present invention will now be described with combined reference to FIGS. 9-11 and FIGS. 19-20. Magnetic drive cable assembly 30 includes a pump coupling assembly 98, a motor coupling assembly 100, and a sheathed drive cable assembly 102 extending therebetween. The sheathed drive cable assembly 102 includes a drive cable 108 rotatably disposed within a generally flexible sheath or tubing member 110. The pump coupling assembly 98 includes a bearing housing cap 104 rigidly coupled to a portion 112 of the second housing member 74 which houses various bearing components associated with the shaft 90. These bearing components include a bearing 114, a spacer 116, a flanged bearing 118, and a retention ring 120. A seal 121 is also provided disposed about the shaft 90 near its connection to the impeller 86. The bearing housing cap 104 includes a sheath retainer 106 for fixedly receiving the sheath 110 of the drive cable assembly 102. The drive cable 108 extends through a lumen formed through the housing cap 104 for connection to the shaft 90. The pump coupling assembly 98 also includes a strain relief member 124 disposed about the sheath retainer 106 and an adjacent portion of the sheathed drive cable assembly 102. The motor coupling assembly 100 includes a magnet housing 126, a magnet housing cap 128, and a strain relief member 130. The magnet housing 126 is dimensioned to receive a magnet shaft assembly 132 comprising a shaft 134 fixedly coupled to the drive cable 108 and a magnet 136. The magnet shaft assembly 132 is rotatably disposed within the motor coupling assembly 100 through the use of a bearing 138 in the magnet housing 126 and a bearing 140 in the magnet housing cap 128. The magnet housing cap 128 includes a sheath retainer 142 and a lumen dimensioned to fixedly receive the sheath 110 of the sheathed drive cable assembly 102 therewithin. In this fashion, the drive cable 108 and magnetic shaft assembly 132 are hermetically sealed from the pumping chamber of the pump 26. The magnet housing 126 and the magnet housing cap 128 are dimensioned to be quickly and easily coupled to a motor (such as the motor 20 in FIG. 1) having a magnetic rotor capable of magnetically driving the magnet shaft assembly 132 into rotation. O-rings 144 and an engagement groove 146 may be provided to facilitate the quick and convenient coupling/de-coupling feature of the magnetic drive cable assembly 30 of the present invention. Under the direction of the magnetic rotor, the drive cable 108 will be forced into rotation within the sheath 110 to thereby cause the impeller assembly 76 to rotate within the pump 26. As will be discussed in greater detail below, the impeller assembly 76 is configured to rotate in a clockwise fashion within the pump 26 such that fluid will be drawn into the fluid inlet port 78 (after passing through the inlet tubing 28) and delivered in a generally tangential fashion out the fluid outlet port 82.

The miniature centrifugal pump 26 of the present invention will now be further described in detail with reference to FIGS. 12-18. Referring initially to FIGS. 12- 13, the first pump housing member 72 is preferably a molded component of unitary construction having a generally planar base portion 150 from which the fluid inlet port 80 extends in a generally perpendicular fashion. An annular ridge 152 is provided extending generally perpendicularly from the base portion 150 about the base of the fluid inlet port 80. A plurality of buttress members 154 extend between the annular ridge 152 and the base of the fluid inlet port 80.

A plurality of engagement ridges 156 are provided on the fluid inlet port 80 adjacent its open distal end to facilitate coupling the fluid inlet port 80 with the inflow tubing 28. This coupling may be augmented through various well-known techniques, including but not limiting to the use of adhesives and/or ultrasonic welding. The base portion 150 includes a first extending section 160 which, as will be described in further detail below, matingly engages with a corresponding portion of the second pump housing member 74 to define an aperture within which the female quick-connect fitting 84 may be bonded according to the present invention. The base portion 150 includes a second extending section 162 which, as will also be described in greater detail below, matingly engages with a corresponding portion of the second pump housing member 74 to define an aperture within which the luer-type priming port 34 may be bonded according to the present invention.

With reference to FIG. 13, the mating engagement of the first pump housing member 72 to the second pump housing member 74 is facilitated by molding an engagement ridge 164 as part of the first pump housing member 72 that extends generally perpendicularly from the interior surface of the base portion 150. As will be set forth in greater detail below, the engagement ridge 164 of the first pump housing member 72 is dimensioned to matingly cooperate with a corresponding engagement groove formed in the second pump housing member 74 to facilitate bonding the first and second pump housing members 72, 74 together during the manufacture of the miniature centrifugal blood pump 26 of the present invention. The engagement ridge 164 includes a first generally straight portion 166 and a second generally straight portion 168 which extend inward from the section 160 of the base member 150 for connection to a generally spiral portion 170. In a preferred embodiment, the generally spiral portion 170 has an expanding radius as it extends from the first generally straight portion 166 for connection to the second generally straight portion 168. The engagement ridge 164 also includes third and fourth generally straight portions 172, 174 which extend inward from the section 162 of the base member 150 for connection to the generally spiral portion 170. An abutment member 176 is disposed in between the first and second generally straight portions 166, 168 of the engagement ridge 164. The abutment member 176 helps define a seat against which the female quick-connect fitting 84 is brought to rest to ensure the fitting 84 is properly registered when it is bonded to the pump housing members 72, 74 during manufacture. A curved notch 178 may be formed on the underside of the section 160 of base 150 adjacent the abutment member 176 to conform to the contour of the portion of the female quick-connect fitting 84 that extends into the pump housing. In similar fashion, a curved notch 180 may be formed on the underside of the section 162 of base 150 to conform to the contour of the portion of the luer-type priming port 78 that extends into the pump housing. The underside of the base 150 is also characterized as including a generally planar surface 182 which has a width that expands radially corresponding to the radial expansion of the generally spiral portion 170 of the engagement ridge 164 along the base 150. Within this generally planar surface 182 are progressively curved surfaces 184, 186 which provide a smooth transition into the lumen defined within the fluid inlet port 80. The second pump housing member 74 of the present invention will now be described in detail with reference to FIGS. 14-18. Referring initially to FIG. 15, the second pump housing member 74 is preferably a molded component of unitary construction. The pump housing member 74 includes a generally planar base portion 190, a generally planar central portion 192 disposed in a generally raised and parallel fashion relative to the base portion 190, and a tiered bearing housing 194 extending generally perpendicularly from the central portion 192. A generally spiral volute portion 196 is also provided having a radially expanding width and a vertically increasing height as the volute portion 196 progresses counter-clockwise (as viewed in FIG. 15) along the base 190. The volute portion 196 includes a generally straight, partially tubular section 198 that extends outward from the base portion 190.

When the first and second pump housing members 72, 74 are coupled together, the generally straight section 198 cooperates with the first extending section 160 to define an aperture within which the female quick-connect fitting 84 is bonded according to the present invention. A generally straight, partially tubular portion 200 is also provided extending from the volute portion 196. During manufacture of the pump 26, the portion 200 cooperates with the second extending section 162 of the first pump housing member 72 to define an aperture within which a coupling mechanism (such as the luer-type priming port 78 shown above) may be bonded according to the present invention. As will be set forth in greater detail below, an air- evacuation aperture (not shown) is formed through the wall of the volute portion 196 within the tubular portion 200 such the coupling mechanism bonded therewithin may be employed with an air-evacuation device (such as the syringe 38 discussed above) to remove air from within the pump 26 to prime the pump 26 before use. With reference to FIGS. 14 and 16-18, the interior surface of the second pump housing member 74 is equipped with an engagement groove 204 dimensioned to matingly receive the engagement ridge 164 of the first pump- housing member 72 such that the first and second pump housing members 72, 74 may be bonded together during the manufacture of the miniature centrifugal pump 26 of the present invention. The engagement groove 204 includes a first straight portion 206 and a second straight portion 208 which extend inward from the generally tubular portion 198 for connection to a generally spiral portion 210. In a preferred embodiment, the generally spiral portion 210 has an expanding radius as it extends from the first generally straight portion 206 for connection to the second generally straight portion 208. The engagement groove 204 also includes third and fourth generally straight portions 212, 214 which extend inward from the partially tubular portion 200 for connection to the generally spiral portion 210. As will be appreciated, the portions 206-214 of the engagement groove 204 correspond to the portions 166-174 of the engagement ridge 164 discussed above. A curved notch 218 may be formed on the underside of the generally straight, partially tubular portion 198 to conform to the contour of the portion of the female quick-connect fitting 84 that extends into the pump housing. In similar fashion, a curved inner surface 220 of the tubular portion 200 conforms to the contour of the portion of a coupling mechanism (such as the luer-type priming port 78 disclosed above) so as to ensure proper registry during the bonding process. An air-evacuation port 222 is formed through the wall of the volute portion 196 to provide fluid communication between the coupling mechanism (i.e. priming port 78) and the interior of the pump 26 for priming purposes .

The interior of the second pump housing member 74 is also characterized as including a central region 224 having a generally planar surface corresponding to the central portion 192 discussed above with regard to the exterior of the second pump housing member 74. An annular seat 226 is provided within the central region 224 for receiving the rotor seal 121 discussed above. A shaft aperture 228 extends through the annular seat 226 such that the shaft 90 of the impeller assembly 76 may be passed therethrough for connection to the drive cable 108 of the present invention. As will be explained in greater detail below, the blades 88 of the impeller 86 are positioned generally within the central region 224 when the shaft 90 is passed through the shaft aperture 228. In an important aspect of the present invention, the impeller 86 cooperates with a volute 230 formed along the interior of the volute portion 196 discussed above to provide enhanced fluid pumping characteristics, such as increased fluid pressure for a given pump speed, and decreased hemolysis when pumping blood.

The volute 230 of the present invention has an origin (designated generally at 232) located a vertical distance above the surface of the central region 224. As it progresses in a clockwise fashion away from the origin 232, the shape of the volute 230 expands in both a vertically downward direction and a radially outward direction. In a preferred embodiment of the present invention, the rate of vertical expansion is approximately 2.5 degrees as the volute 230 progresses away from the origin 232, and the rate of radial expansion is approximately 5 degrees as the volute 230 progresses away from the origin 232. In this fashion, the volute 230 starts out above the surface of the central region 224 and then drops below the surface of the central region 224 at a location denoted generally at 234 and keeps expanding in a vertically downward fashion until approximately the beginning of the curved notch 218. It is to be readily understood that the scale and size of the first and second pump housing members 72, 74 may be selected and/or adjusted over a wide range such that the centrifugal pump 26 of the present invention may be dimensioned to be suitable for use in a wide variety of fluid pumping applications. For example, the rate of vertical and/or radial expansion of the volute 230 may be anywhere in the range of between 1 and 15 degrees without departing from the scope of the invention. The impeller assembly 76 of the present invention will now be discussed in detail with reference to FIGS. 21- 24. The impeller assembly 76 includes the shaft 90 rigidly coupled to the impeller 86, which is equipped with a plurality of rotor blades 88 for directing fluid within the pump 26. The shaft 90 may be constructed of any number of suitable materials, including but not limited to stainless steel. The impeller 86 and blades 88 may be constructed from any number of suitable materials, including but not limited to thermoplastics such as polycarbonate. The shaft 90 of the impeller assembly 76 is a generally cylindrical member of unibody construction. As shown most clearly in FIG. 21, the shaft 90 includes an impeller coupling portion 240, an upper cylindrical upper portion 244, a lower cylindrical portion 243, and an intermediate cylindrical portion 242. The impeller coupling portion 240 includes a plurality of intersecting threads 246 which, after the impeller 86 is molded thereabout during manufacture, serve to prevent the impeller 86 from unscrewing or becoming dislodged due to the rotational forces experienced during use. As shown in FIG. 24, the lower portion 243 of the shaft 90 is generally hollow having an internal lumen 248 for matingly receiving the drive cable 108 of the magnetic drive cable assembly 30. The drive cable 108 is preferably fixed to the shaft 90 by crimping the drive cable 108 within internal lumen 248 of the lower portion 243. The impeller 86 of the impeller assembly 76 is preferably constructed having a plurality of cut-out portions 260. The cut-out portions 260 define a plurality of bridging ribs 262 that extend radially away from the center of the impeller 86 for connection with the leading edge of a respective blade member 88.

As shown in FIGS. 9 and 11, the impeller assembly 76 of the present invention is disposed within the pump 26 such that the impeller 86 is located in between the first and second pump housing members 72, 74. With further reference to FIGS. 14-18, the shaft 90 is dimensioned to extend through the shaft aperture 228 and bearing housing 194 of the second pump housing member 74. In this arrangement, the upper portion 244 of the shaft 90 has the seal 121 disposed about its proximal end and the bearing 114 bounding its distal end. The lower portion 242 extends distally away from the upper portion 244 and is supported within the bearing housing 194 by the bearing 114, the spacer 116, and the flanged bearing 118. The retention ring 120 is provided to matingly engage within a groove 258 formed on the intermediate portion 242 of the shaft 90 for the purpose of maintaining the seals 114, 118 and spacer 116 in position around the lower portion 242. This allows the shaft 90 to rotate within the rotor bearing housing 194 under the direction of the motor 20 coupled to the magnetic drive cable assembly 30.

The dimensions and scale of the features and components comprising the centrifugal pump 26 of the present invention may be selected and/or adjusted over a wide range such that the centrifugal pump 26 may be dimensioned to be suitable for use in a wide variety of fluid pumping applications, including but not limited to pumping blood. When provided for use in pumping blood according to one embodiment of the present invention, the centrifugal pump 26 boasts a variety of advantageous characteristics, including but not limited to those shown and described by way of example with reference to FIG. 25.

FIG. 25 is a graph illustrating the flow versus pressure characterization of the centrifugal pump 26 of the present invention dimensioned for use as a blood pump according to an exemplary of the present invention.

The control console 22 will now be described in detail with reference to FIGS. 1 and 26-27. The control console 22 is a microcomputer-based system for controlling the operation of the blood pump 26. The control console 22 is designed to operate on standard line voltage (AC) or an internal battery (DC) capable of supplying emergency backup power in case of AC power failure. The console 22 may be factory-wired for either 100-120V or 220-240V AC power input. The internal battery (not shown) is preferably a nickel cadmium rechargeable battery having a fully charged voltage of approximately 26 volts. As shown in FIG. 1, the control console 22 has a control line 40 coupled to the motor 20 to provide the necessary electrical signals to drive the motor 20. The motor 20 is preferably a brushless DC motor having a hollow cylindrical region (not shown) formed within a stator (not shown) for removably receiving the motor coupling assembly 100 of the magnetic cable drive assembly 30. With the magnetic cable drive assembly 30 coupled to the motor 20, the control console 22 may then be employed to create a rotating magnetic field to magnetically drive the magnet shaft assembly within the motor coupling assembly 100.

In a preferred embodiment, the speed of the motor 20 (and hence pump 26) may be adjusted based on feedback regarding the flow within the pump assembly 24. One manner of accomplishing this is through the use of the flow probe 48, which is preferably coupled to the inflow tubing 28 and communicatively linked to the control console 22 via control line 50 to aid in determining the flow rate produced by the centrifugal pump assembly 24. Flow probe 48 may comprise any number of commercially available flow determination devices, including but not limited to the flow probes available from Transonics, Inc. In a preferred embodiment, the flow probe 48 is capable of monitoring flow rates in the range between 0.5 liters/minute and 8.0 liters/minute. A display screen 302 is provided to display this flow rate information to an operator, along with other information (as will be discussed in greater detail below) . Based on this flow feedback information, the flow rate may be adjusted by the operator through use of a speed adjustment knob 300 disposed on the front panel of the control console 22 for varying the speed of the motor 20 and thus the pump 26. Referring to FIG. 26, the front panel of the control console 22 includes an alarm fault indicator 304 and power indicator 306 in addition to the speed adjustment knob 300 and screen display 302. The alarm fault indicator 304 is preferably a red light-emitting diode designed to turn on when any of a variety of alarm conditions (to be described below) occurs. The power indicator 306 is preferably a green light-emitting diode designed to turn on when the control console 22 is operating on AC power and to turn off when the control console 22 is operating on its internal battery. The display screen 302 includes a host of system status information to be visually communicated to an operator, including Flow Rate (liters/minute) , Battery Voltage (volts) , Motor Current (amperes) , and Motor Voltage (volts) . This system status information also includes a Motor Speed bar graph 308 designed to present a visual display (in green, preferably) of the motor speed within the preferred range of 2500 RPM to 7500 RPM. The Set display 310 illustrates the desired motor speed as set via the speed adjustment knob 300. The Actual display 312 illustrates the actual motor speed with a range of plus or minus 100 RPM.

The screen display 302 may also include a variety of controls (preferably touch- screen) for operating the control console 22. These include a Motor Off control 314 and a Motor On control 316. The Motor Off control 314 turns off the motor 20 and, when touched, preferably changes to light green and reads "MOTOR IS OFF." The Motor On control 316 turns on the motor 20 and, when touched, preferably changes to light green and reads "MOTOR IS ON." The control console 22 includes an audible alarm designed to turn on when any of a variety of alarm conditions occurs. A Silence control 318 is provided to temporarily turn off the audible alarm. When touched, the Silence control 318 will turn off the audible alarm and read "ALARM IS SILENCED." If the alarm condition persists for a predetermined period, such as 30 seconds, the audible alarm will turn on again and the Silence control 318 will read "SILENCE."

The display screen 302 includes an Alarm/Messages Display 320 for visually presenting various messages to the operator, including alarm indications and suggested actions. The alarm indications and suggested actions may include, but are not necessarily limited to, the following:

Alarm Display Suggested Actions Low Flow Rate Check Pump and Pump Cable Check Motor

Check Flow Probe Cable

High Flow Rate Check Pump

Check Motor

Cannula Leakage Check Cannula

Low Battery Consider Replacing Battery

Motor Speed Mismatch Check Connection to Pump

Check Motor

High Motor Speed Replace Motor

Replace Controller

Low Motor Speed Replace Motor

Replace Controller

High Motor Current Replace Motor

Replace Controller

No Battery Check Battery Connection

Replace or Install Battery

High Controller Temp Turn Off Controller

Touch-Screen Failure Touch-Screen is Not Usable

With reference to FIG. 27, the back of the control console 22 includes a plurality of connectors, including a flow probe connector 322, a motor connector 324, and an AC power connector 326. The flow probe connector 322 is designed to receive the control line 50 for communicatively coupling the flow probe 48 to the control console 22. The motor connector 324 is designed to receive the control line 40 for communicatively coupling the motor 20 to the control console 22. A power switch 328 is also provided for turning the control console 22 on and off. A dual-LED display 330 is provided in conjunction with the power switch 328 to visually indicate whether the power is on or off. Although not shown, the control console 22 includes an internal fan to cool the circuitry along with air vents formed preferably along the bottom and sides of the control console 22.

Use of the control console 22 in conjunction with the cannula assembly 12 of the present invention will not be discussed. To prepare the control console 22 for use, a power cord (such as 332 in FIG. 1) must be connected to the AC power connector 326 on the back of the control console 22. After checking to ensure the AC power is set to the proper voltage (via line voltage indicator on AC power connector 326) , the power cord 332 may be plugged into the AC power source. The motor 20 should then be mounted near the patient, such as on the positioning assembly 30 shown in FIG. 1. In a preferred embodiment, the positioning assembly 30 is to be disposed near or within the surgical field. As described above, this allows the centrifugal pump assembly 24 to be positioned close to the patient so as to reduce the amount of tubing the blood is exposed to during the pumping process, thereby advantageously minimizing hemolysis. Once the motor 20 is positioned in this fashion, the control cable 40 can be employed to communicatively couple the control console 22 to the motor 20. This coupling process is facilitated by providing the control cable 40 with proximal and distal fittings that "click" into respective receptacles in the control console 22 and motor 20. The motor coupling assembly 100 of the magnetic cable drive assembly 30 may then be introduced into the hollow receptacle (not shown) within the motor 20 (as described above) to magnetically couple the impeller assembly 76 of the pump 26 to the motor 20. The flow probe 48 should then be coupled along the inlet tubing 28 of the pump assembly 24 and the control line 50 connected to the flow probe connector 322 on the back of the control console 22. The centrifugal blood pump assembly 24 may then be coupled to the pump and cannula assembly 12 as described in detail above.

With the pump and cannula assembly 12 coupled to the heart and pulmonary artery (as described above) , the control console 22 may be turned on using the power switch 328. In a preferred embodiment, the control console 22 is preprogrammed such that the motor 20 will automatically to start at 2500 RPM when the Motor On control 316 is activated independent of the position of the motor speed adjustment knob 300. From this point, the speed of the motor 20 may be increased by rotating the speed adjustment knob 300 clockwise, resulting in a motor speed ranging from approximately 2500 RPM to 7500 RPM in a preferred embodiment. Operating the motor 20 within this range preferably produces flow rates for the pump assembly 24 ranging approximately from 0.3 liters/minute to 8.0 liters/minute. In a preferred embodiment, a device may be employed to assess the cardiac output of the heart during the surgical procedure such that an operator can adjust the flow rate of the pump assembly 24 (by controlling motor 20) to ensure the patient's cardiac output is maintained at sufficient levels throughout the entire procedure. Such devices may comprise any of a variety of cardiac output monitoring devices or systems, including but not limited to those employed in the esophagus, within the heart itself (such as in the aorta), and those affixed on the aorta. Exemplary cardiac output monitoring devices include those commercially available from Deltex Medical, Inc. and Transonics, Inc. Ensuring adequate cardiac output in this fashion is advantageous in that it prevents complications that may otherwise result, such as reduced perfusion of the vital organs during periods of lower cardiac output . Such reductions in cardiac output may result (in the absence of the present invention) due to kinking or collapse of the pulmonary artery, aorta, and/or portions of the ventricular and atrial walls during surgery. This can occur particularly when the heart is manipulated to perform coronary artery bypass graft (CABG) procedures on the coronary arteries on the posterior and/or lateral regions of the heart . To disassemble the system following the surgical procedure, the second vascular cannula 18 should be clamped along the non-reinforced section 31 and the motor speed reduced to approximately 2500 RPM. The inlet tubing 28 should then be clamped. Clamping the cannula assembly 12 in this fashion prevents retrograde flow while the cannula assembly 12 is removed from the patient as described above. The motor 20 may now be turned off, such as by pressing the Motor Off control 314 on the screen display 302. The control console 22 may next be turned off via the power switch 328. The flow probe 48 may then be disconnected from the inlet tube 28 and the control console 22, after which point the pump assembly 24 may be disconnected from the motor 20 by removing the motor coupling assembly 100 of the magnetic cable drive assembly 30 from the hollow region of the motor 20. The motor 20 may then be disconnected from the control console 22 and removed from the positioning assembly 30, which can also be removed from its position near or within the surgical field. 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. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims .

Claims

1. A cannulation assembly for providing circulatory support during surgical procedures, comprising: a pumping system including a centrifugal blood pump having an inlet and an outlet, a motor coupled to a controller, and a cable drive assembly extending between the motor and the blood pump for driving the blood pump according to control signals communicated from the controller to the motor; and a cannula assembly defining a first flow path for transporting blood between the pump and a first predetermined location within the circulatory system of a patient, and a second flow path for transporting blood between the pump and a second predetermined location within the circulatory system of a patient.

2. The cannulation assembly of claim 1 and further, wherein the first and second flow paths of the cannula assembly are defined by first and second cannulas dimensioned to extend, in use, into the respective first and second predetermined locations through two separate incisions formed in the vascular system of the patient.

3. The cannulation assembly of Claim 1, wherein the cannula assembly and centrifugal blood pump are equipped with quick-connect fittings for coupling and decoupling the first flow path to the inlet of the centrifugal blood pump, and the second flow path to the outlet of the centrifugal blood pump.

4. The cannulation assembly of Claim 1, wherein the centrifugal blood pump has a priming port for removing air from within the centrifugal blood pump in preparation for use.

5. The cannulation assembly of Claim 4, wherein the priming port of the centrifugal blood pump is dimensioned to receive a syringe capable of withdrawing air from within the centrifugal blood pump.

6. The cannulation assembly of Claim 1, wherein the cable drive assembly is dimensioned such that the centrifugal blood pump may be disposed at or within the sterile surgical field.

7. The cannulation assembly of Claim 1, wherein the cable drive assembly includes a magnetic coupling dimensioned to be removably inserted into a lumen formed within a stator of the motor.

8. The cannulation assembly of Claim 1, wherein the motor is coupled to the controller via an electrical cable dimensioned such that the motor may be disposed at or within the sterile surgical field.

9. The cannulation assembly of Claim 1, wherein the controller includes a microcomputer programmed to regulate the speed of the motor.

10. The cannulation assembly of Claim 9, wherein the controller controls the speed of the motor based on feedback from a flow rate monitoring device coupled to the centrifugal blood pump.

11. The cannulation assembly of Claim 10, wherein the flow rate monitoring device is coupled to the inlet of the centrifugal blood pump.

12. The cannulation assembly of Claim 9, wherein the controller includes a manual speed adjustment control such that an operator may cause the microcomputer to adjust the speed of the motor to a range of approximately 2500 RPM to 7500 RPM.

13. The cannulation assembly of Claim 2, wherein the first and second cannulas each include a wire- reinforced elongated section having an open distal end and a non-reinforced clamping section.

14. The cannulation assembly of Claim 13, wherein the first cannula is dimensioned to be introduced such that the fluid inlet section is disposed within the right atrium and wherein the second cannula is dimensioned to be introduced such that the fluid outlet section is disposed in the pulmonary artery.

15. A method for providing circulatory support, comprising: providing a pumping system including a centrifugal blood pump having an inlet and an outlet, a motor coupled to a controller, and a cable drive assembly extending between the motor and the blood pump for driving the blood pump according to control signals communicated from the controller to the motor; providing a cannula assembly defining a first flow path for transporting blood between the pump and a first predetermined location within the circulatory system of a patient, and a second flow path for transporting blood between the pump and a second predetermined location within the circulatory system of a patient; and operating the control console to control the delivery of blood from the first predetermined location to the second predetermined location via the centrifugal blood pump.

16. The method for providing circulatory support of Claim 15 and further, wherein the first and second flow paths of the cannula assembly are defined by first and second cannulas dimensioned to extend, in use, into the respective first and second predetermined locations in the vascular system of the patient.

17. The method for providing circulatory support of Claim 15, wherein the cannula assembly and centrifugal blood pump are equipped with quick-connect fittings for coupling and decoupling the first flow path to the inlet of the centrifugal blood pump, and the second flow path to the outlet of the centrifugal blood pump.

18. The method for providing circulatory support of Claim 15, wherein the centrifugal blood pump has a priming port for removing air from within the centrifugal blood pump in preparation for use.

19. The method for providing circulatory support of Claim 18, wherein the priming port of the centrifugal blood pump is dimensioned to receive a syringe capable of withdrawing air from within the centrifugal blood pump.

20. The method for providing circulatory support of Claim 15, wherein the cable drive assembly is dimensioned such that the centrifugal blood pump may be disposed at or within the sterile surgical field.

21. The method for providing circulatory support of Claim 15, wherein the cable drive assembly includes a magnetic coupling dimensioned to be removably inserted into a lumen formed within a stator of the motor.

22. The method for providing circulatory support of Claim 15, wherein the motor is coupled to the controller via an electrical cable dimensioned such that the motor may be disposed at or within the sterile surgical field.

23. The method for providing circulatory support of Claim 15, wherein the controller includes a microcomputer programmed to regulate the speed of the motor.

24. The method for providing circulatory support of Claim 23, wherein the controller controls the speed of the motor based on feedback from a flow rate monitoring device coupled to the centrifugal blood pump.

25. The method for providing circulatory support of Claim 24, wherein the flow rate monitoring device is coupled to the inlet of the centrifugal blood pump.

26. The method for providing circulatory support of Claim 23, wherein the controller includes a manual speed adjustment control such that an operator may cause the microcomputer to adjust the speed of the motor to a range of approximately 2500 RPM to 7500 RPM.

27. The method for providing circulatory support of Claim 16, wherein the first and second cannulas each include a wire-reinforced elongated section having an open distal end and a non-reinforced clamping section.

28. The method for providing circulatory support of Claim 16, wherein the first cannula is dimensioned to be introduced such that the fluid inlet section is disposed within the right atrium and the second cannula is dimensioned to be introduced such that the fluid outlet section is disposed in the pulmonary artery.