Patent Publication Number: US-2021187272-A1

Title: Sheath assembly for catheter pump

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. patent application Ser. No. 15/812,471, filed Nov. 14, 2017, which claims priority to provisional Application No. 62/421,930, filed Nov. 14, 2016, and which is a continuation-in-part of U.S. patent application Ser. No. 13/801,833, filed Mar. 13, 2013, each of which is incorporated herein by reference in their entireties. 
    
    
     BACKGROUND 
     Field of the Invention 
     This application is directed to a catheter pump for mechanical circulatory support of a heart, and related components, systems and methods. In particular, this application is directed to reliable coupling of components that are subject to dynamic loads applied between a plurality of catheter bodies. 
     Description of the Related Art 
     Heart disease is a major health problem that has high mortality rate. Physicians increasingly use mechanical circulatory support systems for treating heart failure. The treatment of acute heart failure requires a device that can provide support to the patient quickly. Physicians desire treatment options that can be deployed quickly and minimally-invasively. 
     Intra-aortic balloon pumps (IABP) are currently the most common type of circulatory support devices for treating acute heart failure. IABPs are commonly used to treat heart failure, such as to stabilize a patient after cardiogenic shock, during treatment of acute myocardial infarction (MI) or decompensated heart failure, or to support a patient during high risk percutaneous coronary intervention (PCI). Circulatory support systems may be used alone or with pharmacological treatment. 
     In a conventional approach, an IABP is positioned in the aorta and actuated in a counterpulsation fashion to provide partial support to the circulatory system. More recently minimally-invasive rotary blood pump have been developed in an attempt to increase the level of potential support (i.e. higher flow). Rotary pumps have become more common recently for treating heart failure. A rotary blood pump is typically inserted into the body and connected to the cardiovascular system, for example, to the left ventricle and the ascending aorta to assist the pumping function of the heart. Other known applications include pumping venous blood from the right ventricle to the pulmonary artery for support of the right side of the heart. An aim of acute circulatory support devices is to reduce the load on the heart muscle for a period of time, to stabilize the patient prior to heart transplant or for continuing support. Rotary blood pumps generally utilize an electric motor which drives an impeller pump at relatively high speeds. In the case where the pump is remote from the motor, for example where the impeller is in the body and the motor is outside the body, there is a need for a robust and reliable connection between the motor and the impeller. There may also be the need for forming a flexible connection between the motor shaft and the impeller to allow free movement of various pump components during use and when pushing through the vasculature to the treatment location. There is also the continuing need to provide these system components in a compact, efficient form factor to allow for percutaneous approaches. 
     There is a need for improved mechanical circulatory support devices for treating acute heart failure. Fixed cross-section ventricular assist devices designed to provide partial or near full heart flow rate are either too large to be advanced percutaneously (e.g., through the femoral artery without a cutdown) or provide insufficient flow. 
     SUMMARY OF THE INVENTION 
     In one embodiment, a catheter pump includes a catheter body having at least one lumen therethrough, and comprising a distal end and a proximal end. An expandable impeller assembly includes an expandable impeller and an expandable cannula coupled to the distal end of the catheter body and housing the expandable impeller, the expandable cannula comprising a substantially straight segment having a distal inlet and a proximal outlet, the substantially straight segment configured to straddle an aortic valve. The catheter body comprises a proximal vessel contact zone and a distal vessel contact zone that are each proximal to the substantially straight segment, the proximal vessel contact zone and distal vessel contact zone configured to provide a force against an aortic arch to stabilize the expandable impeller assembly across the aortic valve. 
     In another embodiment, a catheter pump assembly is disclosed. The catheter pump assembly can include a pump including an impeller assembly and a catheter body disposed proximal to and supporting the pump. The catheter body can include relatively hard sections adjacent to a relatively softer middle section such that the middle section is configured to contact a wall of an aorta of a patient. The catheter body can include relatively hard sections adjacent to a relatively softer middle section such that the middle section facilitates bending relative to the relatively hard sections. The catheter body can include relatively hard sections adjacent to a relatively softer middle section such that when the pump assembly is positioned at a target location (e.g. across a valve), the middle section is configured to bend and the relatively hard sections are configured to remain substantially straight. 
     In another embodiment, a catheter pump assembly is disclosed. The catheter pump assembly can include a pump including an impeller assembly. A catheter body can be disposed proximally of and configured to couple with the impeller assembly, the catheter body having a vessel wall contact surface, the catheter body configured to cause the vessel wall contact surface to bear against an outer radius of an aortic arch. A bending section can be disposed between the vessel wall contact surface and the impeller assembly, the bending section being more flexible than the catheter body at the location of the vessel wall contact surface such that loads applied distal the vessel wall contact surface result in flexing at the bending section. 
     In another embodiment, a method is disclosed. The method can include advancing a distal portion of a catheter assembly including an impeller assembly and a catheter body to a treatment location of a patient. The method can include contacting an outer surface of the catheter body with a contact zone of an inner wall of an aorta of the patient to secure at least the distal portion of the catheter assembly against the aorta of the patient, the inner wall being located adjacent to the junction of the ascending aorta and the aortic arch. The method can include activating the impeller assembly to pump blood across the aortic valve. The method can include maintaining the contact between the outer surface of the catheter body and the contact zone while the impeller assembly is activated. 
     An aspect of at least one of the embodiments disclosed herein is the realization that the connection of a flexible proximal body to a more rigid distal segment of a catheter assembly can be better secured with an robust mechanical interface between one or more features of these components. For example, a distal end of the flexible proximal body can be fitted with a device or structure providing an interface that mechanically engages the flexible proximal body and that can be directly joined, e.g. welded, to a structure to which a load is applied. 
     In one embodiment, a catheter pump assembly is provided that includes an elongate polymeric catheter body, a cannula, and a tubular interface. The elongate polymeric catheter body has a proximal end and a distal end. The cannula has an expandable portion disposed distally of the elongate polymeric catheter body. The cannula can also have another tubular portion that is proximal to the distal portion. The tubular interface has an outer surface configured to be joined to the tubular portion of the cannula and an inner surface. The inner surface is disposed over the distal end of the elongate polymeric catheter body. The tubular interface has a plurality of transverse channels extending outward from the inner surface of the tubular interface. An outer surface of the elongate polymeric catheter body projects into the transverse channels to mechanically integrate the elongate polymeric catheter body with the tubular interface. 
     In another embodiment, a catheter pump assembly is provided that includes an elongate polymeric catheter body, a tubular member, and a mechanical interface. The elongate polymeric catheter body has a proximal end and a distal end. At least a portion of the tubular member is disposed distally of the elongate polymeric catheter body. The mechanical interface is disposed between a portion of the elongate polymeric catheter body and the tubular member. The mechanical interface is configured to mechanically integrate with a surface of the elongate polymeric catheter body. 
     In another embodiment, a catheter pump assembly is provided that includes an elongate catheter body, a metallic tubular member, and first and second mechanical interfaces. The elongate catheter body has a proximal portion and a distal portion. The metallic tubular member is disposed at least partially distally of the elongate catheter body. The first mechanical interface has a first portion joined to the distal portion of the elongate catheter body and a second portion welded to the metallic tubular member. The second mechanical interface is disposed on an outside surface of the catheter pump assembly. The second mechanical interface has a deflectable member configured to be disposed adjacent to the outside surface of the catheter pump assembly in a first configuration. The deflectable member is configured to be disposed inward of the outside surface of the catheter pump assembly in a second configuration. When in the second configuration, the deflectable member mechanically and securely engages the outside surface of the catheter pump assembly with a structure disposed inward of the second mechanical interface. 
     In another embodiment, a method is provided for coupling components of a catheter pump assembly together. An elongate polymeric tubular body is provided that has a proximal end and a distal end. A metallic tubular body is provided that has a proximal portion and a distal portion. A mechanical interface having a first interface zone and a second interface zone is positioned such that the first interface zone is disposed over a portion of the elongate polymeric tubular body adjacent to the distal end thereof The polymer is then caused to flow into the first interface zone, whereby the elongate polymeric tubular body becomes joined with the first interface zone of the mechanical interface. The metallic tubular body is coupled with the second interface zone of the mechanical interface. 
     In one approach, the polymer is caused to flow by heating the elongate polymeric tubular body to cause at least a portion of elongate polymeric tubular body adjacent to the distal end thereof to transition to a state with low resistance to deformation. 
     In another embodiment, a catheter pump assembly is provided that includes a proximal portion, a distal portion, and a catheter body having a lumen extending therebetween along a longitudinal axis. The catheter pump assembly also includes a torque assembly that has a first portion disposed in the lumen of the catheter body and a second portion disposed distal of the first portion. The second portion coupled with an impeller. The torque assembly causes the impeller to rotate upon rotation of the first portion of the torque assembly. The catheter pump assembly also includes a thrust bearing and a thrust bearing brace. The thrust bearing is disposed within the catheter pump assembly adjacent to the distal end of the catheter body. The thrust bearing resists movement of the torque assembly along the longitudinal axis. The thrust bearing brace is disposed on the outside surface of the torque assembly. The thrust bearing brace has a distal face that is directly adjacent to a proximal face of the thrust bearing. 
     In another embodiment, a catheter assembly is provided that includes an elongate flexible body, a torque assembly, a bearing assembly, and a sleeve. The elongate flexible body is disposed along a proximal portion of the catheter assembly and has a proximal infusate channel formed therein. The torque assembly extends through the elongate flexible body. The bearing assembly comprises a housing having an outer surface and a bearing surface disposed within the housing. The bearing surface provides for rotation of the torque assembly within the bearing housing. The sleeve comprises and an inner surface configured to be disposed over the outer surface of the housing of the bearing assembly and a fluid communication structure that extends through the walls of the sleeve. The catheter assembly also includes a distal infusate channel in fluid communication with the proximal infusate channel, the distal infusate channel disposed over the outer surface of the bearing housing and through side walls of the slot. 
     In another embodiment, a catheter pump assembly is provided that includes a proximal portion, a distal portion, and a catheter body having a lumen extending along a longitudinal axis between the proximal and distal portions. The catheter pump assembly also includes an impeller disposed at the distal portion and a stator disposed distal of the impeller to straighten flow downstream from the impeller. The stator is collapsible from a deployed configuration to a collapsed configuration. 
     In another embodiment, a catheter system is provided that includes an elongate polymeric catheter body, a cannula, and at least one expandable component disposed within the cannula. The elongate polymeric catheter body has a proximal end and a distal end. The cannula has an expandable portion disposed distally of the elongate polymeric catheter body. The catheter system also includes an elongate sheath body that has a retracted position in which the elongate sheath body is proximal of the expandable portion of the cannula and the at least one expandable component and a forward position in which the elongate sheath body is disposed over the expandable portion of the cannula and the at least one expandable component. A first segment of the elongate sheath body disposed over the expandable portion of the cannula and the at least one expandable component is configured to resist kinking to a greater extent than a second segment of the elongate sheath body disposed adjacent to the first segment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the subject matter of this application and the various advantages thereof can be realized by reference to the following detailed description, in which reference is made to the accompanying drawings in which: 
         FIG. 1  illustrates one embodiment of a catheter pump configured for percutaneous application and operation; 
         FIG. 2  is a plan view of one embodiment of a catheter adapted to be used with the catheter pump of  FIG. 1 ; 
         FIG. 3  show a distal portion of the catheter system similar to that of  FIG. 2  in position within the anatomy; 
         FIG. 4  is a perspective view of a distal portion of a catheter assembly according to one embodiment; 
         FIG. 5  is a perspective partial assembly detail view of a portion of the catheter assembly of  FIG. 4 . 
         FIG. 6  is a cross-sectional view of a portion of a connection zone of the catheter assembly of  FIG. 4 . 
         FIG. 6A  is a schematic view of embodiments of an outer sheath configured to enhanced delivery and retrieval performance. 
         FIG. 6B  is a schematic side view of a distal portion of a catheter assembly, in accordance with various embodiments. 
         FIG. 6C  is an enlarged view of the sheath assembly shown in  FIG. 6B . 
         FIG. 6D-1  shows an early portion of a method of positioning a catheter assembly of a catheter pump as disclosed herein. 
         FIG. 6D-2  shows a portion of a method following that shown in  FIG. 6D-1  in which a catheter assembly as described herein is advanced through the arterial vasculature until a distal portion thereof is disposed across an aortic valve of a patient. 
         FIG. 6D-3  shows a portion of a method following that shown in  FIG. 6D-2  in which contrast is provided to the aorta from the region of the aortic valve through the aortic arch. 
         FIG. 6D-4  shows a portion of a method following that shown in  FIG. 6D-3  in which an outer sheath of the catheter assembly has been retracted relative to an inner sheath to permit the cannula to expand in preparation for operating the catheter pump including the catheter assembly as disclosed herein. 
         FIG. 6D-5  shows an enlarged fluoroscopic view of a distal portion of the catheter assembly, showing the distal portion expanded in preparation for operation. 
         FIG. 7  is a perspective view of a distal portion of a catheter assembly according to another embodiment; 
         FIG. 8  is a perspective partial assembly detail view of a portion of the catheter assembly of  FIG. 7 ; 
         FIG. 9  is a detail view of a mechanical interface of a catheter assembly; 
         FIG. 10  is a cross-sectional view of a portion of a connection zone of the catheter assembly of  FIG. 9 ; 
         FIGS. 11-14  illustrate features of additional embodiments of catheter assemblies having robust mechanical interface; and 
         FIGS. 15-17  illustrate features of additional embodiments of catheter assemblies having robust mechanical interface. 
     
    
    
     More detailed descriptions of various embodiments of components for heart pumps useful to treat patients experiencing cardiac stress, including acute heart failure, are set forth below. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A high performance catheter pump is desired to provide sufficient output to approach and in some cases exceed natural heart output. Performance of this nature can be achieved with inventive components disclosed herein. 
       FIGS. 1-3  show aspects of a catheter pump  10  that can provide high performance including flow rates similar to full cardiac output. The pump  10  includes a motor driven by a controller  22 . The controller  22  directs the operation of the motor  14  and an infusion system  26  that supplies a flow of infusate in the pump  10 . A catheter system  80  that can be coupled with the motor  14  houses an impeller within a distal portion thereof. In various embodiments, the impeller is rotated remotely by the motor  14  when the pump  10  is operating. For example, the motor  14  can be is disposed outside the patient. In some embodiments, the motor  14  is separate from the controller  22 , e.g., to be placed closer to the patient. In other embodiments, the motor  14  is part of the controller  22 . In still other embodiments, the motor is miniaturized to be insertable into the patient. Such embodiments allow the drive shaft to be much shorter, e.g., shorter than the distance from the aortic valve to the aortic arch (about 5 mm or less). Some examples of miniaturized motors catheter pumps and related components and methods are discussed in U.S. Pat. Nos. 5,964,694; 6,007,478; 6,178,922; 6,176,848; and all of which are hereby incorporated by reference herein in their entirety for all purposes. 
       FIG. 3  illustrates one use of the catheter pump  10 . A distal portion of the pump  10  is placed in the left ventricle LV of the heart to pump blood from the LV into the aorta. The pump  10  can be used in this way to treat patients with a wide range of conditions, including cardiogenic shock, myocardial infarction, and acutely decompensated heart failure, and also to support a patient during a procedure such as percutaneous coronary intervention. One convenient manner of placement of the distal portion of the pump  10  in the heart is by percutaneous access and delivery using the Seldinger technique or other methods familiar to cardiologists. These approaches enable the pump  10  to be used in emergency medicine, a catheter lab and in other non-surgical settings. 
       FIG. 2  shows features that facilitate small blood vessel percutaneous delivery and high performance up to and in some cases exceeding normal cardiac output in all phases of the cardiac cycle. In particular, the catheter system  80  includes a catheter body  84  and a sheath assembly  88 . An impeller assembly  92  is coupled with the distal end of the catheter body  84 . The impeller assembly  92  is expandable and collapsible. In the collapsed state, the distal end of the catheter system  80  can be advanced to the heart. In the expanded state the impeller assembly  92  is able to pump blood at high flow rates.  FIGS. 2 and 3  illustrate the expanded state. The collapsed state can be provided by advancing a distal end  94  of an elongate body  96  distally over the impeller assembly  92  to cause the impeller assembly  92  to collapse. This provides an outer profile throughout the catheter assembly  80  that is of small diameter, for example 12.5 French as discussed further below. 
     In some embodiments, the impeller assembly  92  includes a self-expanding material that facilitates expansion. The catheter body  84  on the other hand preferably is a polymeric body that has high flexibility. When the impeller assembly  92  is collapsed, as discussed above, high forces are applied to the impeller assembly  92 . These forces are concentrated at a connection zone, where the impeller assembly  92  and the catheter body  84  are coupled together. These high forces, if not carefully managed can result in damage to the catheter assembly  80  and in some cases render the impeller within the impeller assembly  92  inoperable. A reliable mechanical interface is provided to assure high performance. While this interface is extremely beneficial for an assembly with an expandable impeller disposed in an expandable cannula, it also applies to assemblies including a fixed diameter impeller, which may be disposed in an expandable cannula or even in a non-expandable portion in fluid communication with an expandable cannula. In one variation, the impeller is disposed proximal of an expandable cannula in a rigid segment (e.g., a pump ring) and an expandable cannula is provided. The mechanical interfaces and inner and outer sheath assemblies facilitate the collapse of the cannula in such embodiments. A further design permits the impeller to be withdrawn into a rigid structure, e.g., a pump ring, to collapse the impeller before the cannula is collapsed. 
     The mechanical components rotatably supporting the impeller within the impeller assembly  92  permit high rotational speeds while controlling heat and particle generation that can come with high speeds. The impeller may be rotated as speeds above 6000 RPM, above 9000 RPM, above 10,000 RPM, above 15,000 RPM, above 20,000 RPM, above 25,000 RPM, or above 30,000 RPM. The infusion system  26  delivers a cooling and lubricating solution to the distal portion of the catheter system  100  for these purposes. However, the space for delivery of this fluid is extremely limited. Some of the space is also used for return of the infusate. Providing secure connection and reliable routing of infusate into and out of the catheter assembly  80  is critical and challenging in view of the small profile of the catheter body  84 . 
     Various aspects of the pump and associated components are similar to those disclosed in U.S. Pat. Nos. 7,393,181; 8,376,707; 7,841,976; 7,022,100; and 7,998,054, and in U.S. Pub. Nos. 2011/0004046; 2012/0178986; 2012/0172655; 2012/0178985; and 2012/0004495, the entire contents of each of which are incorporated herein for all purposes by reference. In addition, this application incorporates by reference in its entirety and for all purposes the subject matter disclosed in each of the following concurrently filed applications: application Ser. No. 13/802,556, which corresponds to attorney docket no. THOR.072A, entitled “DISTAL BEARING SUPPORT,” filed on Mar. 13, 2013; application Ser. No. 61/780,656, which corresponds to attorney docket no. THOR.084PR2, entitled “FLUID HANDLING SYSTEM,” filed on Mar. 13, 2013; application Ser. No. 13/802,570, which corresponds to attorney docket no. THOR.090A, entitled “IMPELLER FOR CATHETER PUMP,” filed on Mar. 13, 2013; application Ser. No. 13/801,528, which corresponds to attorney docket no. THOR.092A, entitled “CATHETER PUMP,” filed on Mar. 13, 2013; and application Ser. No. 13/802,468, which corresponds to attorney docket no. THOR.093A, entitled “MOTOR ASSEMBLY FOR CATHETER PUMP,” filed on Mar. 13, 2013. 
       FIGS. 4-6  show a first embodiment of a working end of a catheter assembly  100  forming a part of one embodiment of the catheter pump  10 . The catheter assembly  100  is similar to the catheter system  84  except as discussed differently below. The catheter assembly  100  includes an elongate catheter body  104 . A proximal end of the catheter body  104  can be coupled with a motor housing. A distal portion of the catheter body  104  is coupled to a cannula  108  configured to house a high flow rate impeller  112 . The exemplary catheter pump can be configured to produce an average flow rate of 4 liters/minute or more at physiologic conditions, e.g., at the typical systolic pressure of a patient needing treatment, such as 60 mmHg. In various embodiments, the pump can be configured to produce a maximum flow rate (e.g. low mm Hg) of greater than 4 Lpm, greater than 4.5 Lpm, greater than 5 Lpm, greater than 5.5 Lpm, greater than 6 Lpm, greater than 6.5 Lpm, greater than 7 Lpm, greater than 7.5 Lpm, greater than 8 Lpm, greater than 9 Lpm, or greater than 10 Lpm. In various embodiments, the pump can be configured to produce an average flow rate at 60 mmHg of greater than 2 Lpm, greater than 2.5 Lpm, greater than 3 Lpm, greater than 3.5 Lpm, greater than 4 Lpm, greater than 4.25 Lpm, greater than 4.5 Lpm, greater than 5 Lpm, greater than 5.5 Lpm, or greater than 6 Lpm. 
     In some embodiments both the cannula  108  and the impeller  112  are actuatable from a first configuration for delivery through a patient to a working site to a second configuration for generating high flow at the working site. The first configuration may be a low profile configuration and the second configuration may be an expanded configuration. The low profile configuration preferably enables access via a femoral artery or other peripheral blood vessel without excessive obstruction of blood flow in the vessel, as discussed further below. 
     The catheter body  104  preferably has a plurality of lumens, including a first lumen  140  adapted for housing a drive shaft  144 , a second lumen  140 B for conveying a medical fluid distally within the catheter body  104 , and a third lumen  140 C for anchoring a bearing housing  146  to the catheter body  104 . The drive shaft  144  extends proximally within the catheter body  104  from the impeller  112 . The drive shaft  144  couples with the motor at the proximal end and with the impeller  112  at the distal end thereof The drive shaft  144  can be formed with any suitable structure, but should be sufficient flexible to traverse at least from a peripheral (e.g., femoral) artery to a heart chamber, such as the left ventricle, as well as sufficiently durable to rotate at a high speed for several hours, for several days, and in some cases, months. The drive shaft  144  can be coupled with an impeller assembly  112  including an expandable impeller  112 A) disposed on a tubular body  112 B  FIGS. 4 and 6  shows these structures. The impeller  112 A preferably includes an elastomeric polymer structure that can be formed as a unitary body. The tubular body  112 B can be a metal hypotube. The tubular body  112 B can be received in a distal portion of the drive shaft  144 . 
     Any suitable material or combination of materials can be used for the catheter body  104  or catheter bodies  104 A and  304  discussed below and provided in some embodiments. In one embodiment, the catheter body  104  has an inner layer  148  surrounding the lumen  140  that comprises high density polyethylene (HDPE). For example, Marlex  4903  HDPE can be disposed about the lumen  140 . If a composite structure is used to form the catheter body  104 , the inner layer  148  has a thickness that is sufficient to withstand wear caused by interaction with the drive shaft  144 , which can be rotated at a very high speed in some applications, for example from 20,000-40,000 revolutions per minute. The inner layer can have a thickness of 0.003 inches. 
     The second lumen  140 B extends from a proximal end in fluid communication with a source of infusate, which can be a medical fluid (e.g., saline), to a distal end adjacent to the impeller assembly  112 . For example, the second lumen  140 B can have an outlet disposed adjacent to a flow channel formed in or about the bearing housing  146 . Examples of bearing housing flow channels are shown in  FIGS. 5, 10 , and in application Ser. No. 13/343618, which is hereby incorporated by reference. In one embodiment of the catheter body  104 A, the second lumen  140 B is generally circumferentially elongated, for example having two sides that are curved with an arc length of about 0.030 inches and two sides that are straight, disposed along a radial direction of the catheter body  104  and about 0.010 inches in length. A proximal end of the second lumen  140 B is coupled with a port, which may be similar to the luer  145  in  FIG. 2 , or other fluid connection device. Any suitable connection between a port and lumen can be used, e.g., a skived connection can be used. 
     The third lumen  140 C can be used to enhance the security of the connection between the catheter body  104 ,  104 A and the bearing housing  146 . For example, the third lumen  140 C can be sized to receive a plurality of, e.g., two, pull wires  160 . The pull wires  160  can take any suitable form, but preferably are sized to be easily received within the lumen  140 C. In one embodiment, the lumen  140 C is spaced apart from but about the same size as the second lumen  140 B and the pull wires are generally rectangular in shape, e.g., having a thickness of about 0.005 inches and a width of about 0.010 inches. The pull wires  160  can be formed of any material that is sufficiently rigid in tension, e.g., of stainless steel with pull strength of at least about 300 ksi. In one arrangement, the pull wires  160  extend at least about three inches into the elongate body  104  in the third lumen  140 C and extend out of the third lumen  140 C to overlay the bearing housing  146  as shown in  FIG. 5 . 
       FIG. 6  shows one approach to compactly arranging the pull wires  160  and structure coupled together thereby. In particular, a proximal portion  160 A of the wires is received within a distal length of the third lumen  140 C and a distal portion  160 C of the wires is disposed distal of the catheter body  104 . A transition  160 B is provided between the zones  160 A,  160 C causing the proximal portion  160 A to be disposed closer to the longitudinal axis of the impeller catheter assembly  100  than is the distal portion  160 C. This permits the outer surface of the catheter body  104  to be closer to the longitudinal axis of the catheter assembly  100  than if the pull wires were straight with the distal portion  160 C in the same position as illustrated. 
     Providing a plurality of pull wires provides redundancy in the connection between the catheter body  104 ,  104 A and the bearing housing  146 . In some cases, this redundancy is not needed and a single wire can be used. The redundancy is beneficial, however, because substantial tension force is applied at this connection point when the expandable cannula  108  is collapsed. In one technique relative motion is provided between the catheter body  104 ,  104 A and an outer sheath disposed over the catheter body until the outer sheath slides over a proximal portion of the cannula  108 . Further relative motion causes the cannula  108  to be compressed, but not without a substantial force being applied thereto. This force is born at several points, including at the junction between the catheter body  104 ,  104 A and the bearing housing  146 . Disconnection of the bearing housing  146  would be problematic, requiring complex procedures to extract the disconnected distal working end of the catheter assembly  100 . 
     The pull wires  160  preferably are located close together on the same side of the catheter body  104 ,  104 A. This arrangement enhances bending flexibility, which is beneficial if tortuous vasculature must be traversed to deliver the catheter assembly  100  to a treatment site, e.g., a heart chamber.  FIGS. 12-14  illustrate other techniques for enhancing the security of the connection of the bearing housing  146  to a catheter body. 
     In some embodiments, placing a radiopaque marker on a distal portion of the catheter assembly  100  is advantageous to confirm the location of the working end, e.g., of the cannula  108  and/or impeller  112  prior to and/or after deployment. 
     Gross mechanical properties of the catheter body  104  can be varied along the length thereof to provide appropriate flexibility and maneuverability within the vasculature to facilitate delivery and operation of the catheter pump into which the catheter assembly  100  is incorporated. For example, in one embodiment, the catheter body  104  is stiffest near the distal end where the catheter body  104  is joined to the working end. In one embodiment, a distal section of the catheter body  104  comprises a relatively soft or flexible material, such as Pebax®. Pebax® is a thermoplastic elastomer, such as a polyether block amide, marketed by Arkema of France. In various embodiments, the material has a hardness of about 100 D or less, 75 D or less, 72 D or less, 60 D or less, or 50 D or less. In various embodiments, the material has a flexural modulus of less than about 400 MPa, less than about 300 MPa, less than about 200 MPa, less than about 100 MPa, less than about 50 MPa, or less than about 30 MPa. A proximal section of the catheter body  104  may comprise a material, such as Vestamid®. In various embodiments the material has a hardness greater than about 40 D, greater than about 50 D, greater than about 60 D, or greater than about 72 D. In various embodiments, the material has a tensile strength of about 45 MPa. In various embodiments, the material has a flexural modulus of greater than about 20 MPa, greater than about 40 MPa, greater than about 75 MPa, greater than about 85 MPa, greater than about 120 MPa, greater than about 220 MPa, greater than about 350 MPa, or greater than about 1000 MPa. Vestamid is a thermoplastic elastomer marketed by Evonik Industries® of Germany known to have high elasticity and good recovery. Between these relatively hard sections ends, a middle section of the catheter body comprises a material having a lower hardness. In an exemplary embodiment, the middle section is formed of MX1205 Pebax®. In an exemplary embodiment, the relatively hard sections are formed of Vestamid. The low hardness section provides a softer structure in the vicinity of the aortic arch, where the catheter may be resting on the vessel wall in use. One or more intermediate hardness sections can be provided between the distal, proximal and middle sections. These arrangements are also relevant to the other inner catheter bodies discussed herein, including bodies  104 A,  304 . In various respects, the hardness of the material refers to the bending or torsional stiffness of the respective material. For example, in various embodiments, the relatively hard sections generally require a meaningfully higher moment before they bend relatively to the relatively softer materials. In various embodiments, the relatively hard section resist deformation in use compared to the relatively soft sections which are configured to deform (e.g. bend). 
     Alternately, or in addition to these features, the catheter body  104  can have different diameters along its length to provide several important performance benefits. The diameter of a proximal portion of the catheter body  104  can be relatively large to enhance pushability and trackability of the catheter assembly  100 . The diameter of a distal portion of the catheter body  104  can be relatively small to enhance flexibility of the distal tip and also to match the profile of the bearing housing  146  such that the lumens  140 B align with flow channels at least partly defined by the bearing housing (e.g., the slots  220  discussed below). The enlarged diameter and enhanced hardness at the proximal end both contribute to the maneuverability of the catheter assembly  100 . These arrangements are also relevant to the other inner catheter bodies discussed herein, including bodies  104 A,  304  and the catheter assemblies  100 A,  300 , and  400  (discussed below). 
     In addition to the foregoing structures for varying the stiffness along the length of the catheter body  104 , a separate stiffening component, such as a braid  188 , can be disposed in the catheter body  104 ,  104 A. In one embodiment, a 0.001 inch by 0.003 inch flat wire of 304V stainless steel is embedded in the catheter body  104 ,  104 A and the braid includes a 70 ppi configuration. The braid  188  can be positioned in any suitable location, e.g., between an inner layer  148  and an outer layer, as shown in  FIG. 9  of the drawings. 
     As discussed above, the catheter assembly  100  preferably also includes an outer sheath or sheath assembly  88  provided over the elongate body  104 ,  104 A to aid in delivering, deploying and/or removing the impeller  112 . The outer sheath  88  can include an elongate body  96  (see  FIG. 2 ) comprising an inner surface surrounding a lumen disposed therein. The inner lumen can comprise a low friction material or layer. For example, a thickness of PTFE can be provided adjacent the inner lumen. In one embodiment, one or more separate materials can be provided at an outer surface of the elongate body  96 . 
     The elongate body  96  preferably is connected at the proximal end with a proximal hub and/or a suitable connector, such as a Tuohy Borst connector. The proximal hub can include a luer fitting. 
     The outer sheath  88  also may have varied hardness or other gross mechanical properties along its length to provide appropriate flexibility and maneuverability within the vasculature to facilitate delivery and operation of the catheter pump into which the outer sheath is incorporated, and also to facilitate collapse of the cannula  108  after deployment thereof  FIGS. 6A  illustrates schematically bulk property variation in two embodiments of the sheath assembly  88 . In particular, an elongate body extending between the proximal and distal ends of the sheath assembly  88  has different hardness at different locations along the length. The different hardnesses enhance the maneuverability of the sheath assemblies  88 A,  88 B to minimize kinking of the elongate body as the catheter assembly  100  is tracking toward the heart and/or when the elongate body is used to collapse an expandable cannula or impeller, as discussed elsewhere herein. 
     The elongate body of the sheath assembly  88 A has a proximal portion “A” with a highest hardness. The proximal portion A can comprise vestamid or other similar material. A portion “B” distal of the proximal portion A and residing over a zone of the cannula in which the impeller I and the distal bearing support S (if present) are housed can have a hardness that is lower than that of the portion A. Portion B can comprise 55 D pebax. In some embodiments, as discussed further below a segment of portion B can act as a radiopaque marker for the sheath during delivery and/or removal of the catheter pump from the patient. A portion “C” disposed distal of the portion B can comprise a material with the lowest hardness of the elongate body of the sheath assembly  88 A, e.g., can comprise MX1205. A portion “D” at the distal end of the elongate body of the sheath assembly  88 A can have a relatively high hardness, e.g., 72 D pebax. The sheath assembly  88 A upon distal movement over the expanded cannula initially contacts the cannula with the relatively hard material of portion D. The relatively soft portion C may contact the vasculature as the catheter assembly  100  is advanced, and its relatively soft structure is biocompatible. Portion B has a hardness that is high enough to protect the zones I and S of the cannula, impeller, and support. Portion A is the hardest of the materials used in the sheath assembly  88 A, to aid in maneuverability. 
     The elongate body of the sheath assembly  88 B has a proximal portion and distal bearing zone portion “A” with a highest hardness. The proximal portion A can comprise vestamid or other similar material. A portion “B” between the proximal portion A and the distal bearing zone portion A. The portion B resides adjacent to the transition from the catheter body  104  to the cannula proximal portion  116  and can have a hardness that is lower than that of the portion A. Portion B can comprise 55 D pebax. Portions C and D in the sheath assembly  88 B are the same as in the sheath assembly  88 A. A portion E is disposed between the portions A and C, e.g., distal of the portion A disposed over the distal bearing support. Portion E can include a series of progressively softer lengths, e.g., a first length of 72 D pebax, a second length of 63 D pebax, and a third length of 55 D pebax. Other materials and hardnesses can be used that provide good resistance to kinking in the delivery of the catheter assembly  100  and/or in the process of re-sheathing the expanded cannula and impeller. 
       FIG. 6B  is a schematic side view of a distal portion of a catheter assembly  100 ′, in accordance with various embodiments. As with the embodiments described above, the catheter assembly  100 ′ can comprise an impeller assembly  92  having an impeller  112  disposed inside an expandable and collapsible cannula  108 . An inlet  151  and an outlet  152  can be defined in the cannula  108 , such that during operation of the catheter assembly  100 ′, the impeller  112  draws blood into the cannula  108  by way of the inlet  151  and expels blood out of the cannula  108  by way of the outlet  152 . An atraumatic tip  150  can be disposed distal the cannula  108 , and can be configured to provide an atraumatic contact interface when the tip  150  contacts the anatomy. As explained above, a sheath assembly  88 ′ can be disposed about a catheter body  104 , within which are provided one or more supply and waste lumens and a drive shaft that imparts rotation to the impeller  112 . 
       FIG. 6C  is an enlarged view of the sheath assembly  88 ′ shown in  FIG. 6B . The sheath assembly  88  can comprise a catheter body having an internal lumen. As shown in  FIGS. 6B and 6C , and as explained herein, the sheath assembly  88 ′ can be translated proximally P relative to the impeller assembly  92  to expose the impeller assembly  92 . As the impeller assembly  92  is exposed from the proximally sliding sheath assembly  88 ′ (or by relative motion between the sheath assembly  88 ′ and the impeller assembly  92  including by advancing the catheter body  104  relative to the sheath assembly  88 ′), the impeller  110  and the cannula  108  can self-expand into a deployed configuration. The pump, of which the catheter assembly  100 ′ is a part, can be activated to pump blood through the cannula  108 . In the deployed configuration, the pump can provide improved flow rates and patient outcomes as compared with non-expandable and other smaller diameter catheter pumps. After the procedure, the sheath assembly  88  can be moved distally D relative to the impeller assembly  92  to contact the cannula  108  and cause the cannula  108  and impeller  110  to move to a stored configuration. Relative motion between the sheath assembly  88 ′ and the impeller assembly  92  including by retracting the impeller assembly  92  into the sheath assembly  88 ′ can also be provided. Once stored, the impeller assembly  92  and sheath assembly  88  can be withdrawn from the anatomy. 
     The sheath assembly  88 ′ can include a sheath body  153  that defines an interior lumen in which the impeller assembly  92  is stored during insertion and/or removal of the catheter assembly  100 ′ from the anatomy. As shown in  FIG. 6C , the sheath body  153  can comprise a multi-layered structure of different materials. For example, an inner liner  158  can be provided to enable reduced friction during use. For example, the liner  158  can comprise a material with a low co-efficient of friction, such as one or more of a suitable polymer, such as polytetrafluoroethylene (PTFE). The sheath assembly  88 ′ can comprise an outer jacket  156  disposed about the inner liner  158 . The inner liner  158  can have a wall thickness sufficiently small so as to enable flexibility during use. The wall thickness of the inner liner  158  can be in a range of 0.001 inches to 0.005 inches, in a range of 0.001 inches to 0.004 inches, or in a range of 0.001 inches to 0.002 inches, e.g., about 0.0017 inches. 
     As explained above with respect to  FIG. 6A , the outer jacket  156  can be formed of a plurality of materials having different stiffnesses (e.g., varying along a length of the sheath assembly  88 ′) and/or elasticities to reduce kinking during use of the catheter assembly  100 . For example, the outer jacket  156  can comprise one or more of MX1205, Pebax 55 D, Pebax 72 D, and Vestamid. In one embodiment Vestamid is provided in a proximal portion  153 A that extends from a proximal end of the outer jacket  156  to a location adjacent to the distal end. The proximal portion  153 A has stiffness configured for advancing the catheter assembly  100 ′ to the heart by way of the aorta. A braided structure  157  can be provided along at least a portion of the length of the sheath assembly  88 ′ to provide reinforced mechanical strength, e.g., improved longitudinal or axial strength and improved radial strength. In one embodiment a stiffness contribution by the braided structure  157  varies along the length of the sheath assembly  88 ′, for example providing a denser braid in the proximal portion  153 A than in portions of the sheath assembly  88 ′ distal the proximal portion  153 A. The braided structure  157  can be provided radially between the outer jacket  156  and the inner liner  158  in various embodiments. In various other embodiments, the braided structure  157  can be integrated or embedded within the outer jacket  156  or within the inner liner  158 . The braided structure  157  can comprise a matrix or mesh of metallic material that is shaped in a tubular profile. In various embodiments, the braided structure  157  can comprise stainless steel, for example stainless steel 304V full hardness. The inner diameter of the sheath body  153  can be in a range of 0.1 inches to 0.2 inches, e.g., in a range of 0.155 inches to 0.17 inches (for example, about 0.163 inches). The outer diameter of the sheath body  153  can be in a range of 0.14 inches to 0.25 inches, or in a range of 0.16 inches to 0.21 inches, e.g., about 0.186 inches. A length of the sheath body  153  can be in a range of 90 cm to 110 cm, or in a range of 100 cm to 105 cm, e.g., about 102.5 cm+/−0.3 cm. 
     The sheath assembly can include a distal tip  154  at the distalmost end of the sheath assembly  88 ′, such that the distal tip  154  contacts the proximal portion of the cannula  108  (e.g., contacts the cannula mesh at or near the outlet  152 ) when the sheath assembly  88 ′ is urged distally D to collapse the impeller assembly  92 . Beneficially, the distal tip  154  can comprise a material that is suitably flexible so as to expand outwardly to accommodate forces imparted on the tip  154  by the wall of the cannula  108 . For example, when the distal tip  154  is urged distally D over the cannula  108 , the cannula  108  may impart radially outward forces to the distal tip  154 . The tip  154  can be sufficiently flexible as to accommodate the radially outward forces without excessively yielding or breaking, but may be sufficiently stiff so as to ensure collapse of the cannula  108 . For example, the distal tip  154  can expand radially outward to receive the cannula  108 , and portions of the jacket  158  directly proximal the tip  154  may provide a stiffer collapsing portion so as to cause the cannula  108  and impeller  112  to collapse into the sheath assembly  88 ′. In various embodiments, the distal tip  154  can be made of an elastic polymer, such as PTFE. In other embodiments, the distal tip can include a combination of materials including PEBAX. In one arrangement, a PEBAX cylindrical member is joined to a proximal portion of a distal-most portion  153 E by a folded over zone of the liner  158 . In other words, the liner  158  can be disposed on the inside of the sheath assembly  88 ′ and a length of the liner can be folded over and around the PEBAX cylindrical member such that the end of the liner  158  can be disposed proximal of the distal end of and around radially outward of the inside lumen of the sheath assembly  88 ′. In some embodiments, the outer diameter of the distal tip  154  can be slightly smaller than the outer diameter of the sheath body  153 . The outer diameter of the distal tip  154  can be in a range of 0.14 inches to 0.25 inches, or in a range of 0.16 inches to 0.21 inches, for example about 0.1895 inches. 
     In addition, the sheath assembly  88 ′ can comprise one or more position markers  155   a,    155   b,    155   c  that are configured to indicate to the clinician the position and/or orientation of the impeller assembly  92 . A second portion  153 B of the sheath body  153  disposed distal the proximal zone  153 A can extend from proximal of the markers  155   b,    155   c  to distal thereof The second portion  153 B can be configured with less stiffness than the proximal portion  153 A. The second portion  153 B can have a portion of the braided structure  157  that is less stiff, e.g., lower braid density, than the portion of the braided structure  157  in the proximal portion  153 A. The second portion  153 B can comprise a material that is less stiff than the material in the proximal portion  153 A. The second portion  153 B can be formed of 55 D PEBAX.  FIG. 6B  shows that the second portion  153 B can span the location of the markers  155   b,    155   c.  A third portion  153 C disposed distal the second portion  153 B can have a lesser stiffness than in the second portion  153 B. Any technique for providing a less stiff configuration in the third portion  153 C can be provided as discussed above. The third portion  153 C can extend from the second portion to a proximal end of the marker  155   a.  A fourth portion  153 D can correspond to the marker  155 A. The fourth portion  153 D can have any suitable configuration. In one embodiment, the fourth portion  153 D is stiffer than the third portion  153 C. In one embodiment, the fourth portion  153 D has the same stiffness as the second portion  153 B. 
     The position markers  155   a - 155   c  can comprise radiopaque markers that are visible to the clinician using, for example, an x-ray fluoroscope. The position markers  155   a - 155   c  can comprise a Pebax 55 D material with a radiopaque component, such as 60% tungsten. The distal-most marker  155   a  can be used during delivery of the catheter assembly  100  to provide the clinician with an estimated real-time position of the distal portion of the catheter assembly  100  as the catheter assembly  100  is inserted into, or removed from, the anatomy of the patient. For example, the clinician can view the distal-most marker  155   a  in real-time on a display device to guide the catheter assembly  100  to the treatment location. The middle marker  155   b  and the proximal marker  155   c  can be used to position the catheter assembly  100  relative to the treatment region to provide accurate of the catheter assembly  100  prior to unsheathing the cannula  108 . For example, in some embodiments, the clinician can view the middle and proximal markers  155   b,    155   c  to ensure that the markers  155   b,    155   c  are near (e.g., are straddling) the aortic valve before initiation of a left ventricular assist procedure. 
       FIG. 6D-1 to 6D-5  are fluoroscopic views of an example method for deploying the catheter assembly  100 ′ in connection with operating a pump. In  FIG. 6D-1  a catheter C is positioned on the aorta side of the aortic valve and contrast is injected into the aorta to identify the location of the aortic valve AV.  FIG. 6D-2  shows that hereafter, the catheter assembly  100 ′ is advanced into the patient, up the descending aorta AD, down the ascending aorta AA and into the heart across the aortic valve AV. In one technique, the position of the marker  155   a  can be confirmed to be in the left ventricle. The position of the proximal two marker bands  155   b,    155   c  can be confirmed to be at the aortic valve AV. In one technique, the band  155   b  can be distal the valve AV and the band  155   c  can be proximal the valve. The band  155   a  can be disposed over the inlet  151  and the bands  155   b,    155   c  can be at or distal to the outlet  152 . 
       FIG. 6D-3  shows that after the catheter assembly  100 ′ is positioned across the aortic valve AV and when so positioned, the catheter assembly  100 ′ follows the outer radius of the aortic arch AAr. 
       FIG. 6D-4  shows that following the deployment of the catheter assembly  100 ′ across the ventricle, the catheter assembly  100 ′ provides for proper positioning and orienting across the aortic valve. For example, it may be desired to provide a substantially straight segment  159  from proximal to the outlets  152 , through the aortic valve AV and into the ventricle. The straight segment  159  can include the location of the impeller  112  in one embodiment. The straight segment  159  can extend proximally and distally of the impeller  112  in one embodiment. In one approach, the configuration of the catheter assembly  100 ′ provides that a bending zone or bending section  160  is disposed proximal of the straight segment  159 . The bending zone  160  can be disposed distally of a distal vascular contact zone DVZ. The distal vascular contact zone DVZ can correspond to where an outside surface of the sheath body  153  contacts the wall of the ascending aorta. The vascular contact zone DVZ is located at or between the junction between the ascending aorta and the aortic arch such that the straight segment  159  is not required to bend to reach the aortic valve AV. 
     Further stability of the catheter assembly  100 ′ can be provided by a technique in which a proximal vessel contact zone PVZ is provided. The proximal vessel contact zone PVZ can be located at or distal the junction of the aortic arch and the descending aorta. The catheter assembly  100 ′ is configured by the stiffness and/or the resilience of the components thereof to generate a restoring force. The restoring force can arise due to stiffness of, the elasticity of, or the stiffness and the elasticity of the catheter assembly  100 ′ when the curved shaped is formed when the normally straight catheter assembly  100 ′ is deployed around the outer radius of the aortic arch. The restoring force can act on the walls of the aorta to provide an additional stabilizing force to help retain the catheter assembly  100 ′ in place around the outer radius of the aortic arch. This force combined with focusing the flex point between the distal contact zone DVZ and the outlet  152  provide greater stability of the working elements and outflow of the catheter pump. 
     As shown in  FIG. 6D-5 , for left ventricular assist procedures, the impeller assembly  92  can be positioned so that it straddles the aortic valve AV, with the inlet  151  disposed in the left ventricle LV and the outlet  152  disposed in the aorta Ao. The impeller assembly  92  can be activated to pump blood proximally from the left ventricle LV through the inlets  151  and into the cannula  108 . Blood can be ejected through the outlet  152  and into the aorta Ao. During pumping, it can be important to maintain the impeller assembly  92  at a relatively stable position relative to the aorta  192  and aortic valve  190 . Stability can be provided by the structures and techniques discussed above. Stable positioning can have a number of benefits including maintaining the pumping effectiveness of the catheter pump. Stability can reduce uncontrolled and repeated impact on the walls of the aorta in the aortic arch. Stability can reduce or eliminate the motion of the distal portion of the catheter assembly  100 ′ within the anatomy. Furthermore, the position of the inlet  151  and outlet  152  straddling the aortic valve AV can be maintained. That is, if the distal portion of the catheter assembly  100 ′ is mobile within the anatomy, there is a risk that both the inlet  151  and the outlet  152  will be in the aorta during some or all of the operation of the pump or the inlet  151  and the outlet  152  will be in the left ventricle LV during some or all of the operation of the pump. These conditions can prevent direct pumping from the heart and reduce the effectiveness of the heart pump. 
     Beneficially, the outer sheath assembly  88 ′ disclosed herein can have a variable stiffness along its length, as explained herein, which can enable the sheath assembly  88 ′ to bear gently but consistently against one or both of the proximal contact zone PVZ and the distal contact zone DVZ during operation of the catheter pump. In contrast, conventional catheter based heart pump devices are much more flexible and move cyclically from the outer radius of the aortic arch to the inner radius thereof, and then back to the outer radius. Advantageously, the sheath assembly  88 ′ can contact one or both of the distal and proximal contact zones DVZ, PVZ to maintain the position of the impeller assembly  92  during operation. This improvement over conventional catheter based heart pump helps to maintain stable relative position of these components, e.g., providing a more consistent tip-gap between an outer tip of the blades of the impeller  112  and the inner wall of the cannula  108 . This improvement over conventional catheter based heart pump devices also provides more consistent and predictable interaction between the atraumatic tip  150  and the inner walls of the ventricle to reduce any adverse side effects of disposing the distal portion of the catheter assembly  100 ′ within the left ventricle. 
       FIGS. 7-10  incorporate the discussion above and illustrate additional features and embodiments.  FIGS. 7 and 9  illustrate aspects of a mechanical interface between a bearing housing  146 A and the catheter body  104 A. In particular, a coupler  200  is provided between the bearing housing  146 A and the catheter body  104 A. The coupler  200  (also shown in  FIG. 6 ) is similar to the coupler  628  disclosed in U.S. application Ser. No. 13/343,618, which is hereby incorporated by reference herein. In this configuration a thrust bearing  204  is provided in the bearing housing  146 A. In some embodiments, a thrust bearing brace  208  is disposed just proximal of the thrust bearing  204 . The thrust bearing brace  208  can take any suitable form, but preferably provides a shoulder or other radial protrusion from the outer surface to the impeller shaft  112 B that abuts a proximal face of the thrust bearing  204 . The thrust bearing brace  208  minimizes or completely prevents movement of the thrust bearing  204  on the impeller shaft  112 B. Such movement is possible because the impeller on the impeller shaft  112 B generates significant distally oriented thrust. In some assemblies, the thrust bearing  204  is interference fit onto the impeller shaft  112 B. When sized and fit properly, this connection maintains the relative position of thrust bearing  204  to the impeller shaft  112 B under the thrust forces that are applied. The thrust bearing brace  208  provides redundancy of this connection. In one embodiment, the thrust bearing brace  208  comprises a short hypotube that is coupled with, e.g., laser welded to the impeller shaft  112 B. The weld completely prevents relative axial movement between the impeller shaft  112 B and the thrust bearing brace  208 . The abutment between the trust bearing  204  and the thrust bearing brace  208  prevent relative movement between the thrust bearing  204  and impeller shaft  112 B if the coupling between the impeller shaft  112 B and the thrust bearing  204  loosens. 
       FIG. 8  shows that an outer surface of the bearing housing  146 A can be covered by a cylindrical sleeve  216 . The sleeve has at least one slot  220  formed therein. The slot  220  can be circumferentially aligned to or otherwise in fluid communication with the second lumen  140 B such that infusate fluid flowing distally in the lumen enters the slot and can be directed distally in a space formed between the bearing housing  146 A, the sleeve  216  and an outer sleeve, that may be a proximal portion  222  of the frame-like structure of the cannula  108 . This structure is shown in  FIGS. 4 and 5 . In  FIG. 4 , the cannula  108  is displaced proximally to reveal the sleeve  216 , which would be covered by a proximal cylindrical portion  222  of the cannula  108  when the catheter assembly  100  is assembled. A difference between the impeller assembly/catheter body interface of the embodiment of  FIGS. 4-6  and the embodiment of  FIGS. 7-11  is that the sleeve  216 A includes recess  220 A in fluid communication with the lumen  140 B. The recesses  220 A are fluid flow structures. Other ports into the inside of the bearing housing  146 A can be accessed through apertures  224  that do not extend to the proximal end of the sleeve  216 . The apertures are fluid communication structures through which fluid can flow into the bearing housing. Flow from the lumen  104 B to the apertures  224  can be provided through a circumferential space defined between the outer surface of the sleeve  216  and an inner surface of the proximal portion  222  of the cannula  108 . See  FIG. 10 . In some cases, the apertures  224  are additionally or alternately adapted to receive components of secondary mechanical interface discussed below. In other embodiments, troughs are formed in an outer surface of the bearing housing are enclosed by the inner surface of the sleeve  216  to form enclosed flow channels for infusate. 
     Catheter pumps incorporating the catheter assembly and variation thereof can be configured to deliver average flow rates of over 4 liters/minute for a treatment period. For example, a treatment period can be up to 10 days for acute needs, such as patient in cardiogenic shock. Catheter pumps incorporating the catheter assembly  100  or such modifications thereof can be used for shorter periods as well, e.g., for support during high risk catheter or surgical procedures. 
     Also, catheter pumps incorporating the catheter assembly  100  or modifications thereof can be used for left or right side heart support. Example modifications that could be used for right side support include providing delivery features and/or shaping a distal portion that is to be placed through at least one heart valve from the venous side, such as is discussed in U.S. Pat. No. 6,544,216; 7,070,555; and US 2012-0203056A1, all of which are hereby incorporated by reference herein in their entirety for all purposes. For example, the catheter assembly  100  or modifications thereof can be configured to be collapsed to be deliverable through a 13 French introducer sheath and can be expanded to up to 24 French when deployed. In one embodiment, the outer profile of the catheter assembly  100  or modifications thereof is approximately 12 French, but can be any size that is insertable into a femoral artery without requiring surgical cutdown. The catheter assembly  100  can be as large as 12.5 F to be inserted through a 13 French introducer sheath. One method involves deployment of the cannula  108 , having an expandable nitinol structure, across the aortic valve. In this position, the impeller  112  can be disposed on the aorta side of the valve and a distal length of the cannula  108  within the ventricle. 
     In other embodiments, the outer profile of the catheter assembly  100  or modifications thereof is less than 12 French, e.g., about 10 French. The 10 French configuration can be useful for patients with lower flow needs, e.g., about 3 liters per minute or less at physiologic conditions. In another example, an 8 French configuration can be useful for patients with lower flow needs, e.g., about 2 liters per minute or less at physiologic conditions. 
       FIGS. 11-14  illustrate additional embodiments in which the structural integrity of a catheter assembly  300  is enhanced to provide security in connection with sheathing an expandable portion.  FIG. 11  shows that a distal portion of the catheter assembly  300  includes components similar to those hereinbefore described. In particular, the catheter assembly  300  includes a catheter body  304 , an expandable cannula  308  and an expandable impeller  312 . The catheter body can take any suitable form. In one embodiment, the catheter body  304  has variable hardness along its length. 
     The cannula  308  includes a self-expanding structure enclosed in a polymeric film. The self-expanding structure can be a distal portion of a member having a non-expanding tubular portion  316  proximal of the self-expanding structure. The tubular portion  316  plays a role in anchoring the cannula  308  to the catheter body  304 . 
       FIG. 11  shows that a support member  328  can be positioned within the cannula  308  to prevent unacceptable variance in the gap between the tip of the impeller  312  and the inside surface of the cannula. More details of this structure are set forth in concurrently filed application Ser. No. 13/802556, which corresponds to attorney docket no. THOR.072A, entitled “DISTAL BEARING SUPPORT,” filed on Mar. 13, 2013, which is incorporated hereby by reference herein for all purposes. Successful collapse of the cannula  308 , the impeller  312 , and the support  328  focuses forces on a joint between the cannula  308  and the catheter body  304 . 
       FIGS. 11-14  illustrate features that enhance the security of the connection catheter body  304  and the cannula  308 . In  FIG. 11 , no separate structure is shown between the catheter body  034  and the non-expanding tubular portion  316 . These structures are joined in other manners, such as indirectly by the force transfer capability of the pull wires discussed above and/or by an adhesive. In  FIG. 12 , the distal end of the catheter body  304  is coupled with a ferrule  336 . The ferrule  336  is an example of a structure to mechanically join the catheter body  304  to the cannula  308 . In one embodiment, the ferrule  336  includes a distal zone  340  for mechanically joining the ferrule  336  to the catheter body  304 . The distal zone  340  is also configured to mechanically couple with the cannula  308 , for example by welding. A plurality of apertures  344  is provided in one embodiment for mechanically joining the ferrule  336  to the catheter body  304 . The apertures  344  enable the material of the catheter body  304  to extend into the distal zone  340 . In one technique the ferrule  336  is disposed over the catheter body  304  which extends into the apertures  344 . 
     The apertures  344  can be arranged in multiple zones. In one embodiment a first zone is disposed distally of the second zone. The first zone can be disposed adjacent to the distal end of the ferrule  336  and the second zone is disposed proximal of the first zone. The first zone can include four apertures  344 A spaced evenly about the periphery of the body of the ferrule. The second zone can include a plurality of (e.g., four) apertures  344 B spaced evenly about the periphery of the body of the ferrule  336 . A specific advantageous embodiment provides four apertures  344 B in the second zone. The apertures  344 B of the second zone can be spaced evenly about the body of the ferrule  336 . Preferably the apertures  344  of the first and second zones are offset to provide a great deal of redundancy in the security of the connection of the catheter body  304  to the ferrule  336 . For example, the apertures  344  in the first and second zones can be offset by one-half the circumferential distance between adjacent apertures  344 . 
     The ferrule  336  also includes a proximal zone  348  disposed proximally of the aperture  344 . The proximal zone  348  preferably is configured to provide an excellent fluid seal between the ferrule and the non-expandable tubular portion  316  of the cannula  308 . In one embodiment, the proximal zone  348  includes a plurality of recesses  352  in the outer surface of the proximal portion  348 . The recesses  352  can take any form consistent with good sealing, and in one embodiment the recesses are turns of a continuous helical groove in the outer surface of the ferrule  336 . The helical groove is configured to receive a sealant that can bridge from the base of the grooves to the inner surface of the proximal portion  316  of the cannula  308 . In one embodiment, the sealant includes an adhesive that can flow into the helical groove and be adhered to the inner surface of the proximal portion  316  of the cannula  308 . 
     Although the weld and adhesive that can be formed or disposed between the ferrule  336  and the proximal portion  316  of the cannula  308  can provide excellent security between these components of the catheter assembly  300 , a supplemental securement device  360  can be provided in some embodiments.  FIG. 11  illustrates one embodiment in which a mechanical securement device  360  is provided. The mechanical securement device  360  includes a cantilevered member that can be deformed from the non-expandable proximal portion  316  of the cannula  308  into corresponding recesses disposed inward of the securement device. 
     In one embodiment, a recess  364  is provided within the catheter assembly  300  to receive the securement device  360 . The recesses  364  can be formed in an internal structure disposed within the proximal portion  316 . In a first variation, a sleeve  368  is provided immediately within the non-expandable proximal portion  316  of the cannula  308 . The sleeve  368  is provided and fills the volume between a bearing housing  372  and the proximal portion  316 . The bearing housing  372  facilitates rotation of the impeller shaft and the flow of infusate. The sleeve  368  has slots and/or other fluid communication structures formed therein that direct flow from channels in the catheter body  308  to flow channels in the bearing housing  372 . In one embodiment, the sleeve  368  has a plurality of small apertures that are disposed between flow slots. The apertures and slots can be similar is shape and form to the apertures  224  and slots  220  discussed above. 
     In other embodiment, apertures can be formed in the bearing housing  372 . For example, the bearing housing  372  can have a plurality of channels aligned with flow passages in the catheter body  304 . In such embodiment, apertures for receiving the securement device  360  can be provided directly in the bearing housing  372 . In another variation, apertures are provided that extend through the sleeve  368  and into the bearing housing  372 . 
     Modifications of catheter pumps incorporating the catheter assembly  300  can be used for right side support. For example, the elongate body  304  can be formed to have a deployed shape corresponding to the shape of the vasculature traversed between a peripheral vascular access point and the right ventricle. 
     Any suitable manufacturing method can be used to cause a portion of the catheter body  304  to be disposed in the apertures  344 . For example, in one the catheter body  304  and the cannula  308  are to be joined. The cannula  308  has the tubular portion  316  which is to be disposed over the catheter body  304 . The ferrule  336  is a metallic body that is an important part of one form of a mechanical interface. The ferrule  336  has an inner surface and apertures  344  that act as a first interface zone and an outer surface that acts as a second interface zone. The ferrule  336  is positioned such that the inner surface is disposed over the outer surface of short length of the catheter body  304  adjacent to the distal end thereof. 
     In one technique, the outer surface of the catheter body  304  is mechanically coupled to the ferrule  336  by a process that involves heating. The distal portion of the catheter body  304  and the ferrule  336  are heated sufficiently to cause at least a portion of the catheter body to transition to a state with low resistance to deformation. The low resistance state can be a fluid state or just a state in which the material of the catheter body  304  if more malleable. In the state having low resistance to deformation, the catheter body  304  flows through or protrudes into the apertures  344 . Because the material is formed continuously from a location inside the inner surface of the ferrule to outside the inner surface, a strong mechanical coupling is provided between these components. 
     The tubular portion  316  of the cannula  308  can be coupled with the ferrule  336  by any suitable technique. In one embodiment, the tubular portion  316  and the ferrule  336  are indirectly coupled through sleeve  368  discussed more below. In particular, the distal end of the ferrule  336  can be welded to the proximal end of the sleeve  368  and a second connection can be provided between the portion  316  and the sleeve as discussed elsewhere herein. In another embodiment, the ferrule  336  can be directly connected by a suitable technique, such as welding if suitable materials are provided. These structures are also illustrated in  FIG. 16  below, which shows further details of the connection by the ferrule  336 . 
     The foregoing technique of heating the catheter body  304  to cause the material thereof to be coupled with the proximal portion  160 A of the pull wire(s)  160 . Another technique for joining the pull wires  160  to the catheter body  304  is by an epoxy or other adhesive at the proximal end of the wires and/or catheter body  304 . A distal section of the pull wires  160  within the catheter body  304  can be left un-adhered to the catheter body, such that this section of the pull wires  160  can move relative to the catheter body or “float” to enhance flexibility of the distal portion of the catheter body in some embodiments. The proximal portion  160 A provides a first interface zone of a mechanical interface between the catheter body  104  and the bearing housing  146 . The distal portion  160 C provides a second interface zone that can be coupled with the bearing housing  146  by a suitable technique, such as welding In another embodiment, the sleeve  216 ,  216 A is formed of a material to which the pull wires can be welded or otherwise mechanically secured. 
       FIG. 11  illustrates an additional optional feature that can facilitate treatment with a catheter pump including the catheter assemblies disclosed herein or any of the pumps discussed in U.S. application Ser. No. 13/343,618 and Ser. No. 13/343,617, which are hereby incorporated herein by reference. A deployment system is provided by combining the catheter assembly  300  (or any other discussed or claimed herein) with a guide wire guide  240 . The guide wire guide  240  can be configured as a small elongate tubular member sized to be advanced in a lumen formed in the drive shaft  144 . The guide wire guide  240  includes a lumen that is sized to receive a guidewire (not shown). The wall thickness of the guide wire guide  240  is thin enough to fit within the allotted tolerance for tracking the catheter assemblies discussed herein through the vasculature. The guide wire guide  240  wall thickness is also thin enough to permit the guide wire guide  240  to be withdrawn from between the guide wire and the catheter assembly once the guidewire is in place without damaging either of these structures or disrupting the position of guidewire excessively. In various embodiments, the guide wire guide  240  includes a self-healing member that remains within the catheter assembly when the tubular portion is removed. The self-healing member has an end wall that re-seals when the guidewire is removed. Thus, the guide wire guide  240  facilitates loading the catheter assemblies onto a guidewire for a percutaneous delivery within a patient. 
       FIGS. 15-17  show details of a catheter assembly  400  having a stator assembly  402  disposed in a distal portion thereof The stator assembly  402  enhances the performance of a catheter pump including the catheter assembly  400 . The stator assembly  402  can include a stator blade body  404  having one or a plurality of, e.g., three, blades  408  extending outwardly from a central boy  412 . The stator blade body  404  is at a downstream location of the impeller  312 . In a percutaneous left ventricle application, the stator blade body  404  is disposed proximal of the impeller  312 . In a percutaneous right ventricle application, the stator blade body  404  is located distal of the impeller  312 . In a trans apical approach to aid the left ventricle, which might be provided through ports in the chest wall or via thoracotomy or mini-thoracotomy, the stator blade body  404  is disposed distal of the impeller  312 . 
     The stator blades  408  are configured to act on the fluid flow generated by the impeller  312  to provide a more optimal fluid flow regime downstream of the stator assembly  402 . This fluid flow regime can correspond to a more optimal fluid flow regime out of the outlet of the catheter pump. The stator blades  408  preferably convert at least the radial component of flow generated by the impeller  312  to a flow that is substantially entirely axial. In some cases, the stator blades  408  are configured to reduce other inefficiencies of the flow generated by the impeller  312 , e.g., minimize turbulent flow, flow eddies, etc. Removing the radial components of the flow can be achieved with blades that are oriented in an opposite direction to the orientation of the blades of the impeller  312 , for example, clockwise versus counterclockwise oriented blade surface. 
     While the stator blades  408  act on the flow generated by the impeller  312 , the fluids also act on the stator assembly  402 . For example, the stator blade body  404  experiences a torque generated by the interaction of the blades  408  with the blood as it flows past the stator assembly  402 . A robust mechanical interface  420  is provided between the central body  412  and a distal portion of the catheter assembly  400 . A bearing housing  424  is provided that is similar to the bearing housing  372 , except as described differently below. The bearing housing  424  includes an elongate portion  428  that projects into a lumen of the central body  412 . The elongate portion  428  preferably has an outer periphery that is smaller than an outer periphery of a portion of the bearing housing  424  immediately proximal of the elongate portion  428 . 
     This structure provides an interface  432  disposed between the elongate portion and the portion just distal thereto. The interface  432  can be a shoulder having a radial extent that is approximately equal to that of the central body  412 . In some embodiments, a flush surface is provided between the outer surface of the central body  412  and a distal outer surface of the sleeve  368  such that the radial extent of the shoulder of the interface  432  is less than that of the central body  412  by an amount approximately equal to the thickness of the sleeve  368 . The interface  432  can also or alternately includes an engagement feature between the inner surface of the lumen of the central body  412  and the outer surface of the elongate portion  428 . In one embodiment, the outer surface of the elongate portion  428  has a helical projection or groove and the central body  412  has corresponding and mating helical grooves or projections. These features can be or can be analogous to screw threads. Preferably the helix portion is arranged such that the torque felt by the stator assembly  402  generates a tightening of the engagement between the elongate portion  428  and the central body  412 . The projections or grooves in the central body  412  can be formed by molding the central body  412  over the elongate projection  428 . 
     A small gap is provided between the stator assembly  402  and the impeller  312  such that no or minimal contact is provided between these components, but the flow between the blades of these structures smoothly transitions between the blades thereof Such an arrangement is useful in that the impeller  312  rotates at more than 10,000 RPM while the stator assembly  412  is stationary. 
     While the robust mechanical interfaces between the catheter body  104  and the cannula  108  is important to the catheter assembly  300  the interface is even more important in certain embodiments of the catheter body  400  that are actuated to a collapsed state prior to being removed from the patient. In such embodiments, the deployed working end preferably is collapsed, including the cannula  308 , the stator blade body  404 , and the impeller  312 . This can be done by providing distal relative motion of the sheath assembly  88 . The forces applied by the sheath assembly  88  to the catheter body  400 , stator blade body  404 , and the impeller  312  and focused at the mechanical joints are enhanced due to the presence of the stator blade body  404 . 
     One will appreciate from the description herein that the catheter assembly may be modified based on the respective anatomy to suit the desired vascular approach. For example, the catheter assembly in the insertion state may be shaped for introduction through the subclavian artery to the heart. The catheter pump may be configured for insertion through a smaller opening and with a lower average flow rate for right side support. In various embodiments, the catheter assembly is scaled up for a higher flow rate for sicker patients and/or larger patients. 
     Although the inventions herein have been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present inventions. It is therefore to be understood that numerous modifications can be made to the illustrative embodiments and that other arrangements can be devised without departing from the spirit and scope of the present inventions as defined by the appended claims. Thus, it is intended that the present application cover the modifications and variations of these embodiments and their equivalents.