Patent Publication Number: US-2023149669-A1

Title: Guidewire guide configurations for implantable medical devices

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 63/280,803, filed on Nov. 18, 2021, titled Guidewire Guide Configurations for Implantable Medical Devices, the entire contents of which are hereby incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present disclosure relates generally to implantable medical devices, and more specifically, relates to guidewire guides for use in implantable medical devices. 
     BACKGROUND 
     Heart disease is a major health problem that has a 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. 
     A Percutaneous Heart Pump (PHP) system is one example of a ventricular assist device that may be used during high-risk percutaneous coronary interventions (PCI) performed electively or urgently in hemodynamically stable patients with severe coronary artery disease, when a heart team, including a cardiac surgeon, has determined high-risk PCI is the appropriate therapeutic option. Use of the PHP system in these patients may prevent hemodynamic instability, which can result from repeat episodes of reversible myocardial ischemia that occur during planned temporary coronary occlusions and may reduce pre-and post-procedural adverse events. PHP systems may also be used to treat cardiogenic shock in certain circumstances. 
     In at least some embodiments, the PHP system includes a distal septum to prevent blood from entering a fluid lumen of a catheter of the PHP system. In such embodiments, a guidewire guide (GWG) may extend through the distal septum for a period of time (e.g., while the PHP system is being stored), which may impact the sealing capabilities of the distal septum. Accordingly, it would be desirable to provide a GWG that facilitates reducing impacts on the sealing capabilities of the distal septum. 
     BRIEF SUMMARY OF THE DISCLOSURE 
     The present disclosure is directed to a guidewire guide (GWG) for use in a percutaneous heart pump. The GWG includes a hypotube and a sleeve section. The sleeve section is configured to extend across a distal septum of the percutaneous heart pump when the GWG is inserted into the percutaneous heart pump. The sleeve section also facilitates reducing deformation of the distal septum while the sleeve section extends across the distal septum. 
     The present disclosure is also directed to a catheter assembly for use in a percutaneous heart pump. The catheter assembly includes an impeller assembly that includes an impeller, an impeller tip positioned distal of the impeller, and a distal septum positioned between the impeller and the impeller tip. The catheter assembly also includes a flexible atraumatic tip (FAT) positioned distal of the impeller assembly, and a guidewire guide (GWG) coupled between the impeller assembly and the flexible atraumatic tip, wherein a proximal end of the guidewire guide is positioned distal of the distal septum. 
     The present disclosure is further directed to a catheter assembly for use in a percutaneous heart pump. The catheter assembly includes a guidewire guide (GWG) that includes a hypotube and a sleeve section coupled to a distal end of the hypotube. The sleeve section is configured to extend across a distal septum of the percutaneous heart pump when the GWG is inserted into the percutaneous heart pump. The sleeve section also facilitates reducing deformation of the distal septum while the sleeve section extends across the distal septum. 
     The foregoing and other aspects, features, details, utilities, and advantages of the present disclosure will be apparent from reading the following description and claims, and from reviewing the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         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    shows a distal portion of the catheter system similar to that of  FIG.  2    in position within the anatomy. 
         FIG.  4    is a schematic view of a catheter assembly and a drive assembly. 
         FIG.  4 A  is an enlarged view of a priming apparatus shown in  FIG.  4   . 
         FIG.  5    is a perspective view of a motor assembly as the drive assembly is being coupled to a driven assembly. 
         FIG.  6    is a plan view of the motor assembly once the drive assembly has been coupled and secured to a driven assembly. 
         FIG.  7    is a perspective view of the motor assembly of  FIG.  6   , with various components removed for ease of illustration. 
         FIG.  8    is a plan view of the motor assembly that illustrates a motor, a drive magnet, and a driven magnet, with various components removed for ease of illustration. 
         FIG.  9    is a perspective view of a first securement device configured to secure the drive assembly to the driven assembly, with various components removed for ease of illustration. 
         FIGS.  10 A- 10 C  are perspective views of a second securement device configured to secure the drive assembly to the driven assembly. 
         FIG.  11    illustrates a side schematic view of a motor assembly according to another embodiment. 
         FIGS.  12 A and  12 B  illustrate side schematic views of a motor assembly according to yet another embodiment. 
         FIG.  13    is a side view of a distal tip member disposed at a distal end of the catheter assembly, according to one embodiment. 
         FIG.  14    is a side cross-sectional view of a distal tip member disposed at a distal end of the catheter assembly, according to another embodiment. 
         FIG.  15    is a side cross-sectional view of a catheter assembly including an embodiment of a guidewire guide (GWG), according to one embodiment. 
         FIG.  16    is a perspective cross-sectional view of a catheter assembly including an alternative embodiment of a GWG, according to one embodiment. 
         FIG.  17    illustrates various embodiments of a distal portion of a GWG tube. 
         FIG.  18    illustrates an enlarged view of a portion of a catheter assembly including one embodiment of the various embodiments of the distal portion of the GWG tube shown in  FIG.  17    extending across a distal septum. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     The disclosure provides systems and methods for guidewire guides (GWGs) for use in a medical system. In various embodiments disclosed herein, a GWG may be configured to receive a guidewire therethrough. A clinician may maneuver the guidewire to the heart through the patient&#39;s vasculature. The clinician may then advance a distal portion of a catheter assembly over the guidewire, using the GWG, to position the distal portion (e.g., including an impeller) in a chamber of the heart. In some embodiments, the GWG may include a central lumen formed along the length of the catheter assembly. 
     Additional embodiments of this disclosure are directed to apparatuses for inducing motion of a fluid relative to the apparatus. For example, an operative device, such as an impeller, may be coupled at a distal portion of the apparatus. In particular, various embodiments disclosed herein generally relate to various configurations for a motor (also referred to herein as a “motor assembly”) adapted to drive an impeller at a distal end of a catheter pump (e.g., a percutaneous heart pump). The motor assembly may be disposed outside the patient in some embodiments. In other embodiments, the motor assembly may be miniaturized and sized to be inserted within the body. 
       FIG.  1    illustrates aspects of a catheter pump  10  that may provide high performance flow rates. Catheter pump  10  includes a motor  14  driven by a controller  22 . Controller  22  directs the operation of motor  14  and an infusion system  26  that supplies a flow of infusate in catheter pump  10 . A catheter assembly  80  that may be coupled to motor  14  houses an impeller within a distal portion thereof. In various embodiments, the impeller is rotated remotely by motor  14  when catheter pump  10  is operating. For example, motor  14  may be disposed outside the patient. In some embodiments, motor  14  is separate from controller  22  (e.g., to be placed closer to the patient). In other embodiments, motor  14  is part of controller  22 . In still other embodiments, motor  14  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 cm 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, and 6,176,848, all of which are incorporated herein by reference for all purposes in their entirety. Various embodiments of motor  14  are disclosed herein, including embodiments having separate drive and driven assemblies to enable the use of a GWG passing through catheter pump  10 . As explained herein, a GWG may facilitate passing a guidewire through catheter pump  10  for percutaneous delivery of catheter pump  10 &#39;s operative device to a patient&#39;s heart. 
       FIG.  2    illustrates features that facilitate small blood vessel percutaneous delivery and high performance, including up to and in some cases exceeding normal cardiac output in all phases of the cardiac cycle. In particular, catheter assembly  80  includes a catheter body  84  and a sheath assembly  88 . Catheter assembly  80  is also coupled to motor  14 , as described above. Impeller assembly  92  is coupled to a distal end of catheter body  84 . Impeller assembly  92  is expandable and collapsible. In the collapsed state, the distal end of catheter assembly  80  may be advanced to the heart, for example, through an artery. In the expanded state, impeller assembly  92  is able to pump blood at high flow rates.  FIGS.  2  and  3    illustrate the expanded state of impeller assembly  92 . The collapsed state may be provided by advancing a distal end  94  of an elongate body  96  distally over impeller assembly  92  to cause impeller assembly  92  to collapse. This provides an outer profile throughout catheter assembly  80  that is of small diameter, for example, to a catheter size of about 12.5 FR in various arrangements. 
     In some embodiments, impeller assembly  92  includes a self-expanding material that facilitates expansion. Catheter body  84  is preferably a polymeric body that has high flexibility. When impeller assembly  92  is collapsed, as discussed above, high forces are applied to impeller assembly  92 . These forces are concentrated at a connection zone, where impeller assembly  92  and catheter body  84  are coupled together. These high forces, if not carefully managed, may result in damage to catheter assembly  80  and, in some cases, render an impeller within impeller assembly  92  inoperable. Robust mechanical interface are provided to assure high performance. 
     The mechanical components rotatably supporting the impeller within impeller assembly  92  permit high rotational speeds while controlling heat and particle generation that may come with high speeds. Infusion system  26  (as shown in  FIG.  1   ) delivers a cooling and lubricating solution to the distal portion of catheter assembly  80  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 catheter assembly  80  is critical and challenging in view of the small profile of catheter body  84 . 
     When activated, catheter pump  10  (shown in  FIG.  1   ) may effectively increase the flow of blood out of the heart and through the patient&#39;s vascular system. In various embodiments, catheter pump  10  may 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, catheter pump  10  may be configured to produce an average flow rate at 62 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. 
     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, 7,998,054, 8,721,517, 9,358,329, 9,446,179, 9,872,947, and 10,449,279 and in U.S. Patent Publication Nos. 2011/0004046, 2012/0178986, 2012/0172655, 2012/0178985, and 2012/0004495, all of which are incorporated herein by reference for all purposes in their entirety. In addition, this disclosure incorporates by reference in its entirety and for all purposes the subject matter disclosed in the following filed application: Application No. 61/780,656, entitled “FLUID HANDLING SYSTEM,” filed on Mar. 13, 2013. 
       FIG.  3    illustrates one use of catheter pump  10  (shown in  FIG.  1   ). A distal portion of catheter pump  10 , which may include an impeller assembly  92 , is placed in the left ventricle (“LV”) of the heart to pump blood from the LV into the aorta. Catheter pump  10  may be used in this way to treat patients with a wide range of conditions, including cardiogenic shock, myocardial infarction, and other cardiac conditions, and also to support a patient during a procedure, such as percutaneous coronary intervention. One convenient manner of placement of the distal portion of catheter pump  10  in the heart is by percutaneous access and delivery using the Seldinger technique or other methods familiar to cardiologists. Various guide features disclosed herein enable catheter pump  10  to be advanced over a guidewire to the heart. These approaches enable catheter pump  10  to be used in emergency medicine, a catheter lab, and in other non-surgical settings. Modifications may also enable catheter pump  10  to support the right side of the heart. Example modifications that may 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 discussed in U.S. Pat. Nos. 6,544,216 and 7,070,555 and in U.S. Patent Publication No. 2012/0203056, all of which are incorporated herein by reference for all purposes in their entirety. 
       FIG.  4    illustrates another example of a catheter assembly, such as a catheter assembly  100 A (similar to catheter assembly  80  shown in  FIG.  2   ). Embodiments of catheter pumps, such as catheter pump  10  (shown in  FIG.  1   ) of this disclosure may be configured with a motor, such as motor  14  (shown in  FIG.  1   ) that is capable of coupling to (and in some arrangements optionally decoupling from) catheter assembly  100 A. This arrangement provides a number of advantages over a non-disconnectable housing. For example, access may be provided to a proximal end  1402  of catheter assembly  100 A prior to or during use. In one embodiment, catheter assembly  100 A is delivered over a guidewire  235 . In some embodiments, guidewire  235  may be conveniently extended through the entire length of catheter assembly  100 A and out of a proximal portion thereof that is completely enclosed in a coupled configuration. For this approach, connection of the proximal portion of catheter assembly  100 A to a motor housing of motor  14  may be completed after guidewire  235  has been used to guide the operative device of catheter assembly  100 A to a desired location within the patient (e.g., to a chamber of the patient&#39;s heart). In one embodiment, the connection between the motor housing and catheter assembly  100 A is configured to be permanent, such that catheter assembly  100 A, the motor housing, and motor  14  are disposable components. However, in other implementations, the coupling between the motor housing and catheter assembly  100 A is disengageable, such that motor  14  and motor housing may be decoupled from catheter assembly  100 A after use. In such embodiments, catheter assembly  100 A distal of motor  14  may be disposable, and motor  14  and the motor housing may be re-usable. In other embodiments, as explained in more detail below, guidewire  235  may be inserted through other types of guide features to guide catheter pump  10  to the heart. For example, in other embodiments, there may be no central lumen extending from proximal end  1402  to the distal end of catheter assembly  100 A. Rather, guidewire  235  may be inserted along the side of catheter assembly  100 A or along a short central lumen or a removable lumen. 
     Moving from the distal end of catheter assembly  100 A to proximal end  1402 , a priming apparatus  1400  may be disposed over an impeller assembly  116 A, such as impeller assembly  92  (shown in  FIGS.  2  and  3   ). As explained above, impeller assembly  116 A may include an expandable cannula or housing and an impeller with one or more blades. As the impeller rotates, blood may be pumped proximally (or distally in some implementations) to function as a cardiac assist device. 
       FIG.  4    also illustrates one example of priming apparatus  1400  disposed over impeller assembly  116 A near a distal end  170 A of an elongate body  174 A.  FIG.  4 A  is an enlarged view of priming apparatus  1400  shown in  FIG.  4   . Priming apparatus  1400  may be used in connection with a procedure to expel air from impeller assembly  116 A (e.g., any air that is trapped within the housing or that remains within elongate body  174 A near distal end  170 A). For example, a priming procedure may be performed before catheter pump  10  is inserted into the patient&#39;s vascular system, so that air bubbles are not allowed to enter and/or injure the patient. Priming apparatus  1400  may include a primer housing  1401  configured to be disposed around both elongate body  174 A and impeller assembly  116 A. A sealing cap  1406  may be applied to proximal end  1402  of primer housing  1401  to substantially seal priming apparatus  1400  for priming (i.e., so that air does not proximally enter elongate body  174 A and also so that priming fluid does not flow out of proximal end  1402  of housing  1401 ). Sealing cap  1406  may be coupled to primer housing  1401  in any way known to a skilled artisan. However, in some embodiments, sealing cap  1406  is threaded onto primer housing  1401  by way of a threaded connector  1405  located at proximal end  1402  of primer housing  1401 . Sealing cap  1406  may include a sealing recess disposed at the distal end of sealing cap  1406 . The sealing recess may be configured to enable elongate body  174 A to pass through sealing cap  1406 . 
     The priming procedure may proceed by introducing fluid into sealed priming apparatus  1400  to expel air from impeller assembly  116 A and elongate body  174 A. Fluid may be introduced into priming apparatus  1400  in a variety of ways. For example, fluid may be introduced distally through elongate body  174 A into priming apparatus  1400 . In other embodiments, an inlet, such as a luer, may optionally be formed on a side of primer housing  1401  to enable introduction of fluid into priming apparatus  1400 . 
     A gas permeable membrane may be disposed on a distal end  1404  of primer housing  1401 . The gas permeable membrane may permit air to escape from primer housing  1401  during priming. Further, priming apparatus  1400  may advantageously be configured to collapse an expandable portion of catheter assembly  100 A. Primer housing  1401  may include a funnel  1415  where the inner diameter of the housing decreases from distal to proximal. Funnel  1415  may be gently curved such that relative proximal movement of an impeller housing causes the impeller housing to be collapsed by funnel  1415 . During or after the impeller housing has been fully collapsed, distal end  170 A of elongate body  174 A may be moved distally relative to the collapsed impeller housing. After the impeller housing is fully collapsed and retracted into elongate body  174 A of a sheath assembly (such as sheath assembly  88  shown in  FIG.  2   ), catheter assembly  100 A may be removed from priming apparatus  1400  before a percutaneous heart procedure is performed (e.g., before catheter pump  10  is activated to pump blood). The embodiments disclosed herein may be implemented such that the total time for infusing the system is minimized or reduced. For example, in some embodiments, the time to fully infuse the system can be about six minutes or less. In other embodiments, the time to infuse may be about three minutes or less. In yet other embodiments, the total time to infuse the system may be about 45 seconds or less. It should be appreciated that lower times to infuse may be advantageous for use with cardiovascular patients. 
     Continue referencing to  FIG.  4   , elongate body  174 A extends proximally from impeller assembly  116 A to an infusate device  195  configured to enable for infusate to enter catheter assembly  100 A and for waste fluid to leave catheter assembly  100 A. A catheter body  120 A (which also passes through elongate body  174 A) may extend proximally and be coupled to a driven assembly  201 . Driven assembly  201  may be configured to receive torque applied by a drive assembly  203 , which is shown as being decoupled from driven assembly  201  and catheter assembly  100 A in  FIG.  4   . Although not shown in  FIG.  4   , a drive shaft may extend from driven assembly  201  through catheter body  120 A to couple to an impeller shaft at or proximal to impeller assembly  116 A. Catheter body  120 A may pass within elongate body  174 A such that elongate body  174 A may axially translate relative to catheter body  120 A. 
     In addition,  FIG.  4    illustrates guidewire  235  extending from a proximal guidewire opening  237  in driven assembly  201 . Before inserting catheter assembly  100 A into a patient, a clinician may insert guidewire  235  through the patient&#39;s vascular system to the heart to prepare a path for the operative device (e.g., impeller assembly  116 A) to the heart. In some embodiments, catheter assembly  100 A may include a guidewire guide (GWG) tube, such as GWG tube  312  shown in  FIG.  13   , passing through a central internal lumen of catheter assembly  100 A from proximal guidewire opening  237 . The GWG tube may be pre-installed in catheter assembly  100 A to provide the clinician with a preformed pathway along which to insert guidewire  235 . Thus, in the embodiment of  FIG.  4   , guidewire  235  may be advanced through a central lumen extending through the length of catheter assembly  100 A. Other embodiments may include different types of guide features, as explained herein. 
     In one approach, guidewire  235  is first placed in a conventional way, e.g., through a needle into a peripheral blood vessel, and along the path between that blood vessel and the heart and into a heart chamber (e.g., into the left ventricle). Thereafter, a distal end opening of catheter assembly  100 A and/or the GWG tube may be advanced over a proximal end of guidewire  235  to enable delivery to catheter assembly  100 A. After the proximal end of guidewire  235  is urged proximally within catheter assembly  100 A and emerges from proximal guidewire opening  237  and/or the GWG tube, catheter assembly  100 A may be advanced into the patient. In one method, guidewire  235  is withdrawn proximally while holding catheter assembly  100 A. 
     Alternatively, the clinician may insert guidewire  235  through proximal guidewire opening  237  and urge guidewire  235  along the GWG tube until guidewire  235  extends from a distal guidewire opening (not shown) in the distal end of catheter assembly  100 A. The clinician may continue urging guidewire  235  through the patient&#39;s vascular system until the distal end of guidewire  235  is positioned in the desired chamber of the patient&#39;s heart. As shown in  FIG.  4   , a proximal end portion of guidewire  235  may extend from proximal guidewire opening  237 . Once the distal end of guidewire  235  is positioned in the heart, the clinician may maneuver impeller assembly  116 A over guidewire  235  until impeller assembly  116 A reaches the distal end of guidewire  235  in the heart. The clinician may remove guidewire  235  and the GWG tube. In some embodiments, the GWG tube may also be removed before or after guidewire  235  is removed. Other embodiments for inserting guidewire  235  through different types of guide features are explained in more detail below. 
     After removing at least guidewire  235 , the clinician can activate a motor, such as motor  14  (shown in  FIG.  2   ) to rotate the impeller and begin operation of catheter pump  10 . One problem that arises when using guidewire  235  to guide the operative device to the heart is that a central lumen or tube (e.g., a GWG) is typically formed to provide a path for guidewire  235 . In some embodiments, it may be inconvenient or inoperable to provide a motor or drive assembly  203  having a lumen through which guidewire  235  may pass through. Moreover, in some implementations, it may be desirable to provide motor or drive assembly  203  separate from catheter assembly  100 A (e.g., for manufacturing or economic purposes). Thus, it may be advantageous to provide a means to couple drive assembly  203  to driven assembly  201 , while enabling the use of a GWG through which guidewire  235  may be passed. Preferably, drive assembly  203  may be securely coupled to driven assembly  201  such that vibratory, axial, or other external forces do not decouple drive assembly  203  from driven assembly  201  during operation. Moreover, the coupling should preferably enable the motor to operate effectively so that the drive shaft is rotated at the desired speed and with the desired torque. 
       FIG.  5    illustrates one embodiment of a motor assembly  206  as driven assembly  201  is being coupled to drive assembly  203 . Driven assembly  201  may include a flow diverter  205  and a flow diverter housing  207  that houses flow diverter  205 . Flow diverter  205  may include a plurality of internal cavities, passages, and channels that are configured to route fluid to and from the patient during a medical procedure. As discussed below, an infusate may be directed into flow diverter  205  from a source of the infusate. The infusate is a fluid that flows into catheter body  120 A to provide useful benefits, such as cooling moving parts and keeping blood from entering certain parts of catheter assembly  100 A. The infusate is diverted distally by flow channels in flow diverter  205 . Some of the infusate that flows distally is re-routed back through catheter body  120 A and may be diverted out of catheter assembly  100 A by flow diverter  205 . In various embodiments, a driven magnet  204  may be disposed within flow diverter  205 . For example, driven magnet  204  may be journaled for rotation in a proximal portion of flow diverter housing  207 . The proximal portion may project proximally of a proximal face of a distal portion of flow diverter housing  207 . In other embodiments, driven magnet  204  may be disposed outside flow diverter  205 . Driven magnet  204  may be configured to rotate freely relative to flow diverter  205  and/or flow diverter housing  207 . Catheter body  120 A may extend from a distal end of flow diverter housing  207 . Further, a drive shaft  208  may pass through catheter body  120 A from a proximal end of flow diverter housing  207  to distal end  170 A of elongate body  174 A (both shown in  FIGS.  4  and  4 A ). Drive shaft  208  may be configured to drive the impeller located at the distal end of catheter assembly  100 A. In some embodiments, a distal end of drive shaft  208  may be coupled to an impeller shaft, which rotates the impeller. 
     Drive assembly  203  may include a drive housing or a motor housing  211  having an opening  202  in a cap  212  of motor housing  211 . Motor housing  211  may also have a sliding member  213 , which may be configured to couple to the patient&#39;s body by way of, for example, connector  291  (shown in  FIG.  4   ) coupled to an adhesive or bandage on the patient&#39;s body. Because the motor and motor housing  211  may have a relatively high mass, it can be important to ensure that motor housing  211  is stably supported. In one embodiment, therefore, motor housing  211  may be supported by the patient&#39;s body by way of sliding member  213  and connector  291 . Sliding member  213  can slide along a track  214  located on a portion of motor housing  211 , such that relative motion between motor assembly  206  and the patient does not decouple sliding member  213  from the patient&#39;s body. Sliding member  213  and connector  291  may therefore be configured to provide a structural interface between motor housing  206  and a platform for supporting motor housing  211 . As explained above, in some arrangements, the platform supporting motor housing  211  may be the patient, since motor housing  211  may be positioned close to the insertion point. In other embodiments, the platform supporting motor housing  211  may be an external structure. 
     To couple drive assembly  203  to driven assembly  201 , the clinician or user may insert the proximal portion of flow diverter  205  into opening  202  in cap  212  of motor housing  211 . After passing through opening  202 , the proximal portion of flow diverter  205  may reside within a recess formed within motor housing  211 . In some embodiments, a securement device is configured to lock or secure drive assembly  203  to driven assembly  201  once driven assembly  201  is fully inserted into drive assembly  203 . In other embodiments, the securement device may be configured to secure drive assembly  203  to driven assembly  201  by inserting driven assembly  201  into drive assembly  203 , and then rotating drive assembly  203  with respect to driven assembly  201 . In some embodiments, coupling drive assembly  203  to driven assembly  201  may be irreversible, such that there may be no release mechanism to decouple drive assembly  203  from driven assembly  201 . In embodiments without a release mechanism, catheter assembly  100 A (including driven assembly  201 ) and motor housing  211  may be disposable components. In other embodiments, a release mechanism may be provided to remove drive assembly  203  from driven assembly  201 . Drive assembly  203  may thereby be used multiple times in some embodiments. 
       FIG.  6    illustrates motor assembly  206  in the assembled state, for example, after drive assembly  203  has been secured to driven assembly  201 . When drive assembly  203  is activated (e.g., a motor is activated to rotate an output shaft), driven assembly  201 , which is operably coupled to drive assembly  203 , is also activated. Activated driven assembly  203  may cause drive shaft  208  to rotate, which in turn causes the impeller to rotate to thereby pump blood through the patient. 
       FIGS.  7  and  8    illustrate motor assembly  206  with one wall of motor housing  211  removed so that various internal components in motor housing  211  may be better illustrated. A motor  220  may be positioned within motor housing  211  and mounted by way of a motor mount  226 . Motor  220  may be operably coupled to a drive magnet  221 . For example, motor  220  may include an output shaft  222  that rotates drive magnet  221 . In some embodiments, drive magnet  221  may rotate relative to motor mount  226  and motor housing  211 . Further, in some embodiments, drive magnet  221  may be free to translate axially between motor mount  226  and a barrier  224 . One advantage of the translating capability is to enable drive magnet  221  and driven magnet  204  to self-align by way of axial translation. Barrier  224  may be mounted to motor housing  211  and at least partially within cap  212  to support at least drive magnet  221 . In other embodiments, drive assembly  203  may include a plurality of motor windings configured to induce rotation of drive magnet  221 . In still other embodiments, the motor windings may operate directly on driven magnet  204  within driven assembly  201 . For example, the motor windings may be activated in phases to create an electric field and thereby commutate driven magnet  204 . 
     In  FIG.  8   , drive magnet  221  is illustrated in phantom, such that driven magnet  204  can be seen disposed within drive magnet  221 . Although not illustrated, the poles of drive magnet  221  may be formed on an interior surface of drive magnet  221 , and the poles of driven magnet  204  may be formed on an exterior surface of driven magnet  204 . As driven magnet  204  rotates the poles of drive magnet  221  may magnetically engage with corresponding, opposite poles of driven magnet  204  to cause driven magnet  204  to rotate with, or follow, drive magnet  221 . Because driven magnet  204  may be mechanically coupled to drive shaft  208 , rotation of drive magnet  221  may cause driven magnet  204  and drive shaft  208  to rotate at a speed determined in part by the speed of motor  220 . Furthermore, when driven magnet  204  is inserted into drive magnet  221 , the poles of each magnet may cause drive magnet  221  and driven magnet  204  to self-align. The magnetic forces between drive magnet  221  and driven magnet  204  may assist in coupling drive assembly  203  to driven assembly  201 . 
     Turning to  FIG.  9   , a perspective view of various components at the interface between drive assembly  203  and driven assembly  201  is shown. Various components have been hidden to facilitate illustration of one means to secure drive assembly  203  to driven assembly  201 . A first securement device  240  is illustrated in  FIG.  9   . First securement device  240  may include a first projection  240   a  and a second projection  240   b . Furthermore, a locking recess  244  may be formed in cap  212  around at least a portion of a perimeter of opening  202 . A lip  242  may also extend from the perimeter at least partially into opening  202 . As shown, lip  242  may also extend proximally from locking recess  244  such that a step is formed between locking recess  244  and lip  242 . Further, a flange  246  may be coupled to or formed integrally with flow diverter housing  207 . Flange  246  may include a plurality of apertures  247   a ,  247   b ,  247   c ,  247   d  that are configured to permit tubes and cables to pass therethrough to fluidly communicate with lumens within flow diverter  205 . In some embodiments, three tubes and one electrical cable may pass through apertures  247   a - d . For example, the electrical cable may be configured to electrically couple to a sensor within catheter assembly  100 A, e.g., a pressure sensor. The three tubes may be configured to carry fluid to and from catheter assembly  100 A. For example, a first tube may be configured to carry infusate into catheter assembly  100 A, a second tube may be configured to transport fluids to the pressure sensor region, and the third tube may be configured to transport waste fluid out of catheter assembly  100 A. Although not illustrated, the tubes and cable(s) may pass through apertures  247   a - d  of flange  246  and may rest against motor housing  211 . By organizing the routing of the tubes and cable(s), apertures  247   a - d  may advantageously prevent the tubes and cable(s) from becoming entangled with one another or with other components of catheter assembly  100 A. 
     When driven assembly  201  is inserted into opening  202 , first and second projections  240   a ,  240   b  may pass through the opening and engage locking recess  244 . In some embodiments, projections  240   a ,  240   b  and locking recess  244  may be sized and shaped such that axial translation of projections  240   a ,  240   b  through opening  202  causes a flange or tab  248  at a distal end of each projection  240   a ,  240   b  to extend over locking recess  244 . Thus, in some embodiments, once projections  240   a ,  240   b  are inserted through opening  202 , tabs  248  at the distal end of projections  240   a ,  240   b  are biased to deform radially outward to engage locking recess  244  to secure driven assembly  201  to drive assembly  203 . 
     Once driven assembly  201  is secured to drive assembly  203 , flow diverter housing  207  may be rotated relative to cap  212 . By permitting relative rotation between driven assembly  201  and drive assembly  203 , the clinician is able to position impeller assembly  116 A within the patient at a desired angle or configuration to achieve the best pumping performance. As shown in  FIG.  9   , lip  242  may act to restrict the relative rotation between driven assembly  201  (e.g., flow diverter housing  207 ) and drive assembly  203  (e.g. cap  212  and motor housing  211 ). As illustrated, flange  246  and apertures  247   a - d  may be circumferentially aligned with projections  240   a ,  240   b . Further, lip  242  may be circumferentially aligned with sliding member  213 , track  214 , and connector  291  of motor housing  211 . If flange  246  and projections  240   a ,  240   b  are rotated such that they circumferentially align with lip  242 , then the tubes and cable(s) that extend from apertures  247   a - d  may become entangled with or otherwise obstructed by sliding member  213  and connector  291 . Thus, it may be advantageous to ensure that sliding member  213  and connector  291  (or any other components on the outer surface of motor housing  211 ) do not interfere or obstruct the tubes and cable(s) extending out of apertures  247   a - d  of flange  246 . Lip  242  formed in cap  212  may act to solve this problem by ensuring that flange  246  is circumferentially offset from sliding member  213  and connector  291 . For example, flow diverter housing  207  may be rotated until one of projections  240   a ,  240   b  bears against a side of lip  242 . By preventing further rotation beyond the side of lip  242 , lip  242  may ensure that flange  246  and apertures  247   a - d  are circumferentially offset from sliding member  213 , track  214 , and connector  291 . 
     In one embodiment, once catheter assembly  100 A is secured to motor housing  211 , the connection between driven assembly  201  and drive assembly  203  may be configured such that drive assembly  203  may not be removed from driven assembly  201 . The secure connection between the two assemblies may advantageously ensure that motor housing  211  is not accidentally disengaged from catheter assembly  100 A during a medical procedure. In such embodiments, both catheter assembly  100 A and drive assembly  203  may preferably be disposable. 
     In other embodiments, it may be desirable to utilize a re-usable drive assembly  203 . In such embodiments, drive assembly  203  may be removably engaged with catheter assembly  100 A (e.g., engaged with driven assembly  201 ). For example, lip  242  may be sized and shaped such that when drive assembly  203  is rotated relative to driven assembly  201 , tabs  248  are deflected radially inward over lip  242  such that driven assembly  201  may be withdrawn from opening  202 . For example, lip  242  may include a ramped portion along the sides of lip  242  to urge projections  240   a ,  240   b  radially inward. It should be appreciated that other release mechanisms are possible. 
       FIGS.  10 A- 10 C  illustrate an additional means to secure drive assembly  203  to driven assembly  201 . As shown in the perspective view of  FIG.  10 A , a locking O-ring  253  may be mounted to barrier  224  that is disposed within motor housing  211  and at least partially within cap  212 . In particular, locking O-ring  253  may be mounted on an inner surface of drive assembly  203  or motor housing  211  surrounding the recess or opening  202  into which driven assembly  201  may be received. As explained below, locking O-ring  253  may act as a detent mechanism and may be configured to be secured within an arcuate channel formed in an outer surface of driven assembly  201  (e.g., in an outer surface of flow diverter  205  in some embodiments). In other embodiments, various mechanisms may act as a detent to secure driven assembly  201  to drive assembly  203 . For example, in one embodiment, a spring plunger or other type of spring-loaded feature may be cut or molded into barrier  224 , in a manner similar to locking O-ring  253  of  FIGS.  10 A- 10 C . The spring plunger or spring-loaded feature may be configured to engage the arcuate channel, as explained below with respect to  FIG.  10 C . Skilled artisans will understand that other types of detent mechanisms may be employed. 
       FIG.  10 B  illustrates the same perspective of drive assembly  203  as shown in  FIG.  10 A , except cap  212  has been hidden to better illustrate locking O-ring  253  and a second, stabilizing O-ring  255 . Stabilizing O-ring  255  is an example of a damper that may be provided between motor  220  and catheter assembly  100 A. In some embodiments, the damper may provide a vibration absorbing benefit. In other embodiment, the damper may reduce noise when catheter pump  10  (shown in  FIG.  1   ) is operating. In some embodiments, the damper may also both absorb vibration and reduce noise. Stabilizing O-ring  255  may be disposed within cap  212  and may be sized and shaped to fit along the inner recess forming the inner perimeter of cap  212 . Stabilizing O-ring  255  may be configured to stabilize cap  212  and motor housing  211  against vibrations induced by operation of motor  220 . For example, as motor housing  211  and/or cap  212  vibrate, stabilizing O-ring  255  may absorb the vibrations transmitted through cap  212 . Stabilizing O-ring  255  may support cap  212  to prevent cap  212  from deforming or deflecting in response to vibrations. In some embodiments, stabilizing O-ring  255  may act to dampen the vibrations, which may be significant given the high rotational speeds involved in the exemplary device. 
     In further embodiments, a damping material may also be applied around motor  220  to further dampen vibrations. The damping material may be any suitable damping material (e.g., a visco-elastic or elastic polymer). For example, the damping material may be applied between motor mount  226  and motor  220 . In addition, the damping material may also be applied around the body of motor  220  between motor  220  and motor housing  211 . In some embodiments, the damping material may be captured by a rib formed in motor housing  211 . In some embodiments, the rib may be formed around motor  220 . 
     Turning to  FIG.  10 C , a proximal end of driven assembly  201  is shown. As explained above, flow diverter  205  (or the housing of flow diverter  205  in some embodiments) can include an arcuate channel  263  formed in an outer surface of flow diverter  205 . Arcuate channel  263  may be sized and shaped to receive locking O-ring  253  when flow diverter  205  is inserted into opening  202  of drive assembly  203 . As flow diverter  205  is axially translated through the recess or opening  202 , locking O-ring  253  may be urged or slid over an edge of arcuate channel  263  and may be retained in arcuate channel  263 . Thus, locking O-ring  253  and arcuate channel  263  may operate to act as a second securement device. Axial forces applied to motor assembly  206  may thereby be mechanically resisted, as the walls of arcuate channel  263  bear against locking O-ring  253  to prevent locking O-ring  253  from translating relative to arcuate channel  263 . In various embodiments, other internal locking mechanisms (e.g., within driven assembly  201  and/or drive assembly  203 ) may be provided to secure driven and drive assemblies  201 ,  203  together. For example, driven magnet  204  and drive magnet  221  may be configured to assist in securing the two assemblies together, in addition to aligning the poles of the magnets. Other internal locking mechanisms may be suitable. 
       FIG.  10 C  also illustrates a resealable member  266  disposed within the proximal end portion of driven assembly  201  (e.g., the proximal end of catheter assembly  100 A as shown in  FIG.  4   ). As in  FIG.  4   , proximal guidewire opening  237  may be formed in resealable member  266 . As explained above with respect to  FIG.  4   , guidewire  235  may be inserted through proximal guidewire opening  237  and may be maneuvered through the patient&#39;s vasculature. After guiding the operative device of catheter pump  10  (shown in  FIG.  1   ) to the heart, guidewire  235  may be removed from catheter assembly  100 A by pulling guidewire  235  out through proximal guidewire opening  237 . Because fluid may be introduced into flow diverter  205 , it may be advantageous to seal the proximal end of flow diverter  205  to prevent fluid from leaking out of catheter assembly  100 A. Resealable member  266  may be formed of an elastic, self-sealing material that is capable of closing and sealing proximal guidewire opening  237  when guidewire  235  is removed. Resealable member  266  may be formed of any suitable material, such as an elastomeric material. In some embodiments, resealable member  266  may be formed of any suitable polymer (e.g., a silicone or polyisoprene polymer). Skilled artisans will understand that other suitable materials may be used. 
       FIG.  11    illustrates yet another embodiment of a motor assembly  206 A coupled to a catheter assembly, such as catheter assembly  100 A (shown in  FIG.  4   ). In  FIG.  11   , a flow diverter is disposed over and coupled to a catheter body  271  that may include a multi-lumen sheath configured to transport fluids into and away from the catheter assembly. Flow diverter  205 A may provide support to catheter body  271  and a drive shaft configured to drive an impeller assembly, such as impeller assembly  92  (shown in  FIGS.  2  and  3   ) and/or impeller assembly  116 A (shown in  FIG.  4   ). Further, motor assembly  206 A can include a motor  220 A that has a hollow lumen therethrough. Unlike the embodiments disclosed in  FIGS.  4 - 10 C , guidewire  235  may extend through proximal guidewire opening  237 A formed proximal to motor  220 A, rather than between motor  220 A and flow diverter  205 A. A resealable member  266 A may be formed in proximal guidewire opening  237 A such that resealable member  266 A may close opening  237 A when guidewire  235  is removed from the catheter assembly. A rotary seal  273  may be disposed inside a lip of flow diverter  205 A. Rotary seal  273  may be disposed over and may contact a motor shaft extending from motor  220 A. Rotary seal  273  may act to seal fluid within flow diverter  205 A. In some embodiments, a hydrodynamic seal maybe created to prevent fluid from breaching rotary seal  273 . 
     In the embodiment shown in  FIG.  11   , motor  220 A may be permanently secured to flow diverter  205 A and the catheter assembly. Because proximal guidewire opening  237  is positioned proximal to motor  220 A, motor  220 A need not be coupled with the catheter assembly in a separate coupling step. In this embodiment, motor  220 A and the catheter assembly may be disposable. Motor  220 A may include an output shaft and rotor magnetically coupled with a rotatable magnet in flow diverter  205 A. Motor  220 A may also include a plurality of windings that are energized to directly drive the rotatable magnet in flow diverter  205 A. 
       FIGS.  12 A and  12 B  illustrate another embodiment of a motor  420  coupling having a driven assembly  401  and a drive assembly  403 . Unlike the implementations disclosed in  FIGS.  4 - 10 C , the embodiment of  FIGS.  12 A and  12 B  may include a mechanical coupling disposed between an output shaft of motor  420  and a proximal end of a flexible drive shaft or cable. Unlike the implementations disclosed in  FIG.  11   , the embodiment of  FIGS.  12 A and  12 B  may include a guidewire guide (GWG) tube that terminates at a location distal to a motor shaft  476  that extends from motor  420 . As best shown in  FIG.  12 B , an adapter shaft  472  may be operably coupled to motor shaft  476  extending from motor  420 . A distal end portion  477  of adapter shaft  472  may be mechanically coupled to a proximal portion of an extension shaft  471  having a central lumen  478  therethrough. As shown in  FIG.  12 B , one or more trajectories  473  may be formed in channels within a motor housing  475  at an angle to central lumen  478  of extension shaft  471 . Motor housing  475  may enclose at least adapter shaft  472  and may include one or more slots  474  formed through a wall of housing  475 . 
     In some embodiments, a guidewire (not shown in  FIG.  12 B ) may pass through the GWG tube from the distal end portion of the catheter assembly and may exit the catheter assembly through central lumen  478  near distal end portion  477  of adapter shaft  472  (or, alternatively, near the proximal end portion of extension shaft  471 ). In some embodiments, one of extension shaft  471  and adapter shaft  472  may include a resealable member disposed therein to reseal central lumen  478  through which the guidewire passes, as explained above. In some embodiments, extension shaft  471  and adapter shaft  472  may be combined into a single structure. When the guidewire exits central lumen  478 , the guidewire may pass along angled trajectories  473  which may be formed in channels and may further pass through slots  474  to the outside environs. Trajectories  473  may follow from angled ports in adapter shaft  472 . A clinician may thereby pull the guidewire through slots  474  such that the end of the guidewire may easily be pulled from the patient after guiding the catheter assembly to the heart chamber or other desired location. Because the guidewire may extend out the side of motor housing  475  through slots  474 , motor shaft  476  and motor  420  need not include a central lumen for housing the guidewire. Rather, motor shaft  476  may be solid and the guidewire may simply pass through slots  474  formed in the side of motor housing  475 . 
     Furthermore, drive assembly  403  may be mechanically coupled to driven assembly  401 . For example, a distal end portion  479  of extension shaft  471  may be inserted into an opening in a flow diverter housing  455 . Distal end portion  479  of extension shaft  471  may be positioned within a recess  451  and may couple to a proximal end of a drive cable  450  that is mechanically coupled to the impeller assembly. A rotary seal  461  may be positioned around the opening and may be configured to seal motor  420  and/or motor housing  475  from fluid within flow diverter  405 . 
     Advantageously, the embodiments of  FIGS.  12 A and  12 B  enable motor  420  to be positioned proximal of rotary seal  461  in order to minimize or prevent exposing motor  420  to fluid that may inadvertently leak from flow diverter  405 . It should be appreciated that extension shaft  471  may be lengthened in order to further isolate or separate motor  420  from fluid diverter  405  in order to minimize the risk of leaking fluids. 
       FIG.  13    illustrates further features that may be included in various embodiments. In particular,  FIG.  13    illustrates a distal end portion  300  of a catheter assembly, such as catheter assembly  100 A (shown in  FIG.  4   ). As shown a cannula housing  302  may be coupled to a distal tip member  304 . Distal tip member  304  may be configured to assist in guiding the operative device of the catheter assembly (e.g., an impeller assembly, which may be similar to or the same as impeller assembly  116 A shown in  FIG.  4   ), along guidewire  235 . The exemplary distal tip member  304  is formed of a flexible material and has a rounded end to prevent injury to the surrounding tissue. If distal tip member  304  contacts a portion of the patient&#39;s anatomy (such as a heart wall or an arterial wall), distal tip member  304  will safely deform or bend without harming the patient. Distal tip member  304  may also serve to space the operative device away from the tissue wall. In addition, a guide feature or guidewire guide (GWG) tube  312  may be provided. GWG tube  312 , discussed above with reference to  FIG.  4   , may extend through a central lumen (such as central lumen  478  shown in  FIG.  12 B ) of the catheter assembly. Thus, GWG tube  312  may pass through the impeller shaft (not shown in  FIG.  13   , as the impeller is located proximal to distal end portion  300 ) and a lumen formed within distal tip member  304 . GWG tube  312  may include the central lumen extending throughout the length of the catheter assembly. In the embodiment of  FIG.  13   , GWG tube  312  may extend distally past the distal end of distal tip member  304 . As explained above, in various embodiments, the clinician may introduce a proximal end of guidewire  235  into the distal end of GWG tube  312 , which in  FIG.  13    extends distally beyond distal tip member  304 . In some embodiments, once guidewire  235  has been inserted into the patient, GWG tube  312  may be removed from the catheter assembly. 
     Distal tip member  304  may include a flexible, central body  306 , a proximal coupling member  308 , and a rounded tip  310  at the distal end of distal tip member  304 . Central body  306  may provide structural support for distal tip member  304 . Proximal coupling member  308  may be coupled to or integrally formed with central body  306 . Proximal coupling member  308  may be configured to couple the distal end of cannula housing  302  to distal tip member  304 . Rounded tip  310 , also referred to as a ball tip, may be integrally formed with central body  306  at the distal end of distal tip member  304 . Because rounded tip  310  is flexible and has a round shape, if distal tip member  304  contacts or interacts with the patient&#39;s anatomy, rounded tip  310  may have sufficient compliance so as to deflect away from the anatomy instead of puncturing or otherwise injuring the anatomy. As compared with other embodiments, distal tip member  304  may advantageously include sufficient structure by way of central body  306  such that distal tip member  304  may accurately track guidewire  235  to position the impeller assembly within the heart. Yet, because distal tip member  304  is made of a flexible material and includes rounded tip  310 , any mechanical interactions with the anatomy may be clinically safe for the patient. 
     One potential problem with the embodiment of  FIG.  13    is that it may be difficult for the clinician to insert guidewire  235  into the narrow lumen of GWG tube  312 . Since GWG tube  312  has a small inner diameter relative to the size of the clinician&#39;s hands, the clinician may have trouble inserting guidewire  235  into the distal end of GWG tube  312 , which extends past the distal end of distal tip member  304 . In addition, when the clinician inserts guidewire  235  into GWG tube  312 , the distal edges of GWG tube  312  may scratch or partially remove a protective coating applied on the exterior surface of guidewire  235 . Damage to the coating on guidewire  235  may harm the patient as the partially uncoated guidewire  235  is passed through the patient&#39;s vasculature. Accordingly, it may be desirable in various arrangements to make it easier for the clinician to insert guidewire  235  into distal end portion  300  of the catheter assembly, and/or to permit insertion of guidewire  235  into the catheter assembly while maintaining the protective coating on guidewire  235 . 
     Additionally, as explained herein, in some embodiments, cannula housing  302  (which may form part of an operative device) may be collapsed into a stored configuration such that cannula housing  302  is disposed within an outer sheath. When cannula housing  302  is disposed within the outer sheath, a distal end or edge of the outer sheath may abut distal tip member  304 . In some cases, the distal edge of the outer sheath may extend over distal tip member  304 , or the sheath may have an outer diameter such that the distal edge of the outer sheath is exposed. When the sheath is advanced through the patient&#39;s vasculature, the distal edge of the outer sheath may scratch, scrape, or otherwise harm the anatomy. Accordingly, there is a need to prevent harm to the patient&#39;s anatomy due to scraping of the distal edge of the sheath against the vasculature. 
       FIG.  14    is a side cross-sectional view of a distal tip member  304 A disposed at a distal end  300 A of the catheter assembly, according to another embodiment. Unless otherwise noted, the reference numerals in  FIG.  14    may refer to components similar to or the same as those in  FIG.  13   . For example, as with  FIG.  13   , distal tip member  304 A may be coupled to a cannula housing  302 A. Distal tip member  304 A may include a flexible, central body  306 A, a proximal coupling member  308 A, and a rounded tip  310 A at distal end of distal tip member  304 A. Furthermore, as with  FIG.  13   , a guide feature or guidewire guide tube (GWG)  312 A may pass through cannula housing  302 A and a lumen passing through distal tip member  304 A. 
     However, unlike the embodiment of  FIG.  13   , central body  306 A may include a bump  314  disposed near a proximal portion of distal tip member  304 A. Bump  314  illustrated may advantageously prevent the outer sheath from scraping or scratching the anatomy when the sheath is advanced through the patient&#39;s vascular system. For example, when cannula housing  302 A is disposed within the outer sheath, the sheath will advance over cannula housing  302 A such that the distal edge or end of the sheath will abut or be adjacent bump  314  of distal tip member  304 A. Bump  314  may act to shield the patient&#39;s anatomy from sharp edges of the outer sheath as distal end  300 A is advanced through the patient. Further, the patient may not be harmed when bump  314  interact with the anatomy because bump  314  includes a rounded, smooth profile. Accordingly, bump  314  may advantageously improve patient outcomes by further protecting the patient&#39;s anatomy. 
     Furthermore, GWG tube  312 A does not extend distally past the end of distal tip member  304 A. Rather, in  FIG.  14   , the central lumen passing through distal tip member  304 A may include a proximal lumen  315  and a distal lumen  313 . As shown in  FIG.  14   , proximal lumen  315  may have an inner diameter larger than an inner diameter of distal lumen  313 . A stepped portion or shoulder  311  may define the transition between proximal lumen  315  and distal lumen  313 . As illustrated in  FIG.  14   , the inner diameter of proximal lumen  315  is sized to accommodate GWG tube  312 A as it passes through a portion of distal tip member  304 A. However, the inner diameter of distal lumen  313  is sized to be smaller than the outer diameter of GWG tube  312 A such that GWG tube  312 A is too large to pass through distal lumen  313  of distal tip member  304 A. In addition, in some embodiments, the thickness of GWG tube  312 A may be made smaller than the height of the stepped portion or shoulder  311  (e.g., smaller than the difference between the inner diameter of proximal lumen  315  and the inner diameter of distal lumen  313 ). By housing GWG tube  312 A against shoulder  311 , shoulder  311  may protect the outer coating of a guidewire (such as guidewire  235  shown in  FIG.  4   ) when the guidewire is inserted proximally from distal lumen  313  to proximal lumen  315 . 
     The embodiment illustrated in  FIG.  14    may assist the clinician in inserting the guidewire into distal end  300 A of the catheter assembly. For example, GWG tube  312 A may be inserted through the central lumen of the catheter assembly. For example, GWG tube  312 A may pass distally through a portion of the motor, the catheter body, the impeller assembly, and cannula housing  302 A, and through proximal lumen  315  of distal tip member  304 A. GWG tube  312 A may be urged further distally until the distal end of GWG tube  312 A reaches shoulder  311 . When the distal end of GWG tube  312 A reaches shoulder  311 , shoulder  311  may prevent further insertion of GWG tube  312  in the distal direction (e.g., shoulder  311  may have a smaller diameter that the diameter of GWG tube  312 A). Because the inner diameter of distal lumen  313  is smaller than the outer diameter of GWG tube  312 A, the distal end of GWG tube  312 A may be disposed just proximal of shoulder  311 , as shown in  FIG.  14   . Shoulder  311  may be made of a flexible material, which may result in expansion of shoulder  311  when a distal end of GWG tube  312 A is pushed against shoulder  311 . Therefore, in some embodiments, shoulder  311  may be coupled to a rigid ring (not shown) that forms a non-deformable ledge. The ring facilitates maintaining the diameter of shoulder  311  and prevents GWG  312 A from expanding shoulder  311  and moving beyond shoulder  311 . 
     The clinician may insert the proximal end of the guidewire proximally through distal lumen  313  passing through rounded tip  310 A at the distal end of distal tip member  304 A. Because distal tip member  304 A is flexible, the clinician may easily bend or otherwise manipulate the distal end of distal tip member  304 A to accommodate the small guidewire. Unlike GWG tube  312 A, which may be generally stiffer than distal tip member  304 A, the clinician may easily deform distal tip member  304 A to urge the guidewire into distal lumen  313 . Once the guidewire is inserted in distal lumen  313 , the clinician may urge the guidewire proximally past stepped portion or shoulder  311  and into a larger GWG tube  312 A, which may be positioned within proximal lumen  315 . Furthermore, since most commercial guidewires include a coating (e.g. a hydrophilic or antimicrobial coating, or PTFE coating), GWG tube  312 A and shoulder  311  advantageously avoid damaging or removing the coating. When the wall thickness of GWG tube  312 A is less than the height of the step or shoulder  311 , shoulder  311  may substantially prevent GWG tube  312 A from scraping the exterior coating off of the guidewire. Instead, the guidewire easily passes from distal lumen  313  to proximal lumen  315 . The guidewire may then be urged proximally through the impeller and catheter assembly until the guidewire protrudes from the proximal end of the system, such as through proximal guidewire opening  237  described above with reference to  FIG.  4   . 
     The GWG features (e.g., GWG tubes  312 ,  312 A) illustrated in  FIGS.  13  and  14    include a central lumen passing through the catheter assembly along its length. In some embodiments, it may be desirable to omit the central lumen through the catheter assembly. For example, removing the central lumen from the drive cable and motor assembly may advantageously simplify the manufacturing process and may reduce the profile (e.g., diameter) of the catheter assembly. 
       FIG.  15    is a side cross-sectional view of a catheter assembly  1500 , such as catheter assembly  100 A (shown in  FIG.  4   ). Catheter assembly  1500  includes an embodiment of a guidewire guide (GWG) tube  1502 , similar to GWG tubes  312  and  312 A (shown in in  FIGS.  13  and  14   ). Catheter assembly  1500  also includes a distal septum  1504 , an expandable cannula  1506  (shown in a collapsed state in  FIG.  15   ), a flexible atraumatic tip (FAT)  1508 , a distal end  1510  of an impeller, and a gap  1512  extending between FAT  1508  a distal end  1510 . GWG tube  1502  extends across gap  1512  and extends through cannula  1506 . GWG  1502  also extends through distal end  1510  and across distal septum  1504 . 
       FIG.  16    is a perspective cross-sectional view of an alternative catheter assembly  1600 , such as catheter assembly  100 A (shown in  FIG.  4   ). Catheter assembly  1600  includes a guidewire guide (GWG)  1602 , a proximal end  1604  of GWG  1602 , an impeller tip  1606 , a distal septum  1608 , a cannula  1610 , a flexible atraumatic tip (FAT)  1612 , similar to FAT  1508  (shown in  FIG.  15   ), and a distal end  1614  of GWG  1602 . In this embodiment, GWG  1602  is permanently coupled between FAT  1612  and impeller tip  1606  (e.g., GWG  1602  remains in catheter assembly  1600  prior to a procedure, such as a percutaneous heart procedure, and during the procedure). GWG  1602  is flexible and resilient to facilitate (a) not kinking as catheter assembly  1600  is delivered to the left ventricle of a patient&#39;s heart and (b) not increasing a rigid length of catheter assembly  1600 . 
     GWG  1602  may be made of flexible alloys, such as nitinol, a grade of stainless steel, and/or advanced polymers such as polyamide, HDPE, LLDPE, FEP, PET, Pebax, etc. Any of these materials may include a pattern cut into them to improve flexibility and prevent kinking. GWG  1602  may also include a reinforced sheath (e.g., a thin braid structure) that also improves flexibility and prevents kinking (particularly in embodiments where GWG  1602  rotates during operation of catheter assembly  1600 ). 
     As shown in  FIG.  16   , proximal end  1604  of GWG  1602  is located distal of distal septum  1608 . Accordingly, GWG  1602  does not extend across distal septum  1608 . Accordingly, by permanently including GWG  1602  in catheter assembly  1600 , the only time distal septum  1608  is pierced is when a user (e.g., a clinician) passes a guidewire through GWG  1602  prior to a procedure. The guidewire may subsequently be removed, for example, as soon as catheter assembly  1600  is delivered inside the patient, thereby allowing distal septum  1608  to be sealed quickly (e.g., in less than one hour). 
     As cannula  1610  is sheathed, FAT  1612  moves distally by approximately  0 . 25  inches relative to impeller tip  1606 . To accommodate this, in the embodiment shown in  FIG.  16   , distal end  1614  of GWG  1602  is coupled to FAT  1612  using a slip fit. Further, in the embodiment shown, GWG  1602  is coupled to FAT  1612 , such that GWG  1602  is capable of rotating or spinning relative to FAT  1612  (and rotating with the impeller) during operation of catheter assembly  1600 . In other embodiments, where GWG  1602  is not rotatable or spinnable with the impeller, at least one bearing (not shown) is included in catheter assembly  1600 , such that the at least one bearing is configured to secure GWG  1602  inside catheter assembly  1600  and allow the impeller to rotate relative to GWG  1602 . 
       FIG.  17    illustrates various embodiments of a distal portion of a GWG tube (also referred to herein as a hypotube) that may be used to implement, for example, GWG tubes  312  and  312 A (shown in  FIGS.  13  and  14   ). 
     A first hypotube  1700  shown in  FIG.  16    represents a known configuration of a GWG tube. First hypotube  1700  may include a relatively rigid hypodermic tubing made of stainless steel. Hypotubes  1702 ,  1704 ,  1706 ,  1708 , and  1710  are alternative embodiments of hypotube  1700  with generally the same cut length as hypotube  1700 . However, a distal tip  1712  of each hypotube  1702 ,  1704 ,  1706 ,  1708 , and  1710  is different than distal tip  1714  of hypotube  1700 . 
     Each distal tip  1712  includes a polymeric sleeve or flexible tubular lumen, thereby making the distal end of the GWG tube (which contacts the inner lumen of the sealing septum and/or rigid transition, as shown in  FIG.  16   ) more conformable and expandable. 
     Second hypotube  1702  includes a sleeve  1716  (e.g., a polymeric sleeve or flexible tubular lumen) that may be extruded or constructed from any of a number of polymeric materials similar to a tip of a balloon, such as polyamide elastomers (similar to inner members of balloon catheters), polyethylene copolymers, PTFE blends, or combination thereof. Sleeve  1716  may be compliant, expandable, electrospun, braided, mesh-like, webbing-like, and/or similar to a wrap or tubular lumen. Sleeve  1716  may also be coated to further reduce friction between contact components. The coating may include silicone or mineral oil based materials, hydrophobic materials, hydrophilic materials, or other materials suitable for coating sleeve  1716  to function, as described herein. Further, in some embodiments, sleeve  1716  includes an end terminus  1718  that may include an oval or circular lumen that may expand during a guidewire insertion, for example, through the GWG tube. Sleeve  1716  may also be straight-cut or angled to reduce the total surface area of material around the guidewire, potentially that would enlarge the distal septum during storage post-manufacturing prior to use. 
     Third hypotube  1704  includes a lased sleeve  1720  that may be constructed from a flexible alloy, such as nitinol or a grade of stainless steel (with exemplary compositions of  16 % to 25% chromium and between 6% to 25% nickel). Lased sleeve  1720  may be cut with different patterns (e.g., including the one shown in  FIG.  17   ) and may include a coating for reduced friction. The coating may include similar materials to those described above with respect to sleeve  1716 . Lased sleeve  1720  may include an end terminus  1722  that employs a cylindrical collar to ensure that no snagging on other components occurs. Lased sleeve  1720  may include relatively small outer diameter at end terminus  1722 , and segments having different expansion capabilities. Lased sleeve  1720  may also include a lased transition  1724 . 
     GWG tube may, in some embodiments, include combinations of expandable sleeves and lased transitions. For example, fourth hypotube  1706  includes a sleeve  1726  having both an expandable braided sleeve  1728  and a lased transition section  1730 . 
     Fifth hypotube  1708  includes a lased sleeve  1732  and a lased transition  1734 . Sixth hypotube  1710  includes a lased expandable sleeve  1736 . Each hypotube  1702 ,  1704 ,  1706 ,  1708 , and  1710 , described above, is more “septum friendly” than at least some known GWG tubes, since each of the hypotubes has a distal tip  1712  that is more flexible and/or has a reduced footprint (e.g., smaller outer diameter), reducing friction between the hypotube and other components (e.g. tail, nose, distal septum  1504 , cannula  1506 , FAT  1508 , distal end  1510  of the impeller (all shown in  FIG.  15   ), and other components that may be in contact with the hypotubes). With distal tip  1712  capable of expanding only temporarily or a minimal amount of time (e.g., for less than thirty seconds during guidewire insertion by the physician), septum sealing efficiency is maintained and a material “memory” of the septum would not be impacted. 
     Additionally, each hypotube  1702 ,  1704 ,  1706 ,  1708 , and  1710  may include diameters or gauge sizes smaller or larger than existing GWG tube outer diameters and/or inner diameters, in order to accommodate guidewires of varied dimensions dependent on coronary, peripheral, neurovascular, biliary, or alternate anatomies. For example, the dimensions of hypotubes  1702 ,  1704 ,  1706 ,  1708 , and  1710  may include an outer diameter ranging from 0.0120-0.0125 inches, a wall thickness of approximately 0.002 inches, and an inner diameter ranging from 0.0075-0.0090 inches. 
       FIG.  18    is an enlarged view of a portion of catheter assembly  1800 , such as catheter assembly  1500  (shown in  FIG.  15   ). Catheter assembly  1800  includes a hypotube  1802 , such as of one of the hypotubes shown in  FIG.  17   . Hypotube  1802  includes a lased sleeve  1804  that may be constructed from a flexible alloy, such as nitinol, a grade of stainless steel, or advanced polymers, such as polyamide, HDPE, LLDPE, FEP, PET, Pebax, etc. Lased sleeve  1804  may be cut with different patterns (e.g., including the patterns shown in  FIG.  17   ) and may include a coating for reduced friction. The coating may include similar materials to those described above with respect to the sleeve described in  FIG.  17   . 
     As shown in  FIG.  18   , the diameter of lased sleeve  1804  decreases across a septum  1810 , allowing septum  1810  to substantially close. Once lased sleeve  1804  exits septum  1810  distally, lased sleeve  1804  expands back out to a larger diameter (which may be the same as or smaller than a diameter of portions of the associated hypotube that are proximal of septum  1810 ). 
     The embodiments described herein provide systems and methods for guidewire guides in implantable medical devices. Although certain embodiments of this disclosure have been described above with a certain degree of particularity, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this disclosure. All directional references (e.g., upper, lower, upward, downward, left, right, leftward, rightward, top, bottom, above, below, vertical, horizontal, clockwise, and counterclockwise) are only used for identification purposes to aid the reader&#39;s understanding of the present disclosure, and do not create limitations, particularly as to the position, orientation, or use of the disclosure. Joinder references (e.g., attached, coupled, connected, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, joinder references do not necessarily infer that two elements are directly connected and in fixed relation to each other. It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not limiting. Changes in detail or structure may be made without departing from the spirit of the disclosure as defined in the appended claims. 
     When introducing elements of the present disclosure or the preferred embodiment(s) thereof, the articles “a”, “an”, “the”, and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including”, and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. 
     As various changes could be made in the above constructions without departing from the scope of the disclosure, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 
     The examples and illustrations included herein show, by way of illustration and not of limitation, specific embodiments in which the subject matter may be practiced. As mentioned, other embodiments may be utilized and derived there from, such that structural and logical substitutions and changes may be made without departing from the scope of this disclosure. Such embodiments of the inventive subject matter may be referred to herein individually or collectively by the term “invention” merely for convenience and without intending to voluntarily limit the scope of this application to any single invention or inventive concept, if more than one is, in fact, disclosed. Thus, although specific embodiments have been illustrated and described herein, any arrangement calculated to achieve the same purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all adaptations or variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, will be apparent to those of skill in the art upon reviewing the above description.