Patent Publication Number: US-2022233840-A1

Title: Mechanical circulatory support systems and methods

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     The present application claims the benefit of priority to U.S. Provisional Application No. 62/861,985, filed Jun. 14, 2019, which is incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The present technology relates to mechanical circulatory support systems and associated methods of use. In particular embodiments, the present technology relates to mechanical circulatory support systems for use in conjunction with catheter-based heart therapies. 
     BACKGROUND 
     Over the past 15 years, transcatheter (or percutaneous) procedures to address cardiovascular diseases have become increasingly popular, especially in the last 5 years as long-term data for these devices has been published. Transcatheter Aortic Valve Replacement (TAVR), (also referred to as Transcatheter Aortic Valve Implantation (TAVI)), Transcatheter Mitral Valve Repair (TMVr), and Transcatheter Mitral Valve Replacement (TMVR) all access the heart percutaneously through the arteries or veins. Prior to the transcatheter approach, valve replacement or repairs were done through “open” procedures that required a sternotomy. The adverse events of a sternotomy were common and severe including prolonged recovery times, pain, infection, and other morbidity. [1][2] The transcatheter approach has made these procedures safer and easier to recover from and has made therapies accessible to patients who would otherwise be too sick to undergo an open surgery. 
     Aortic stenosis is the calcification and narrowing of the valve between the left ventricle and the aorta. The disease can be asymptomatic, but progression can lead to angina, syncope, or heart failure. [ 3 ] Aortic stenosis has a prevalence of 0.4% in the general population and affects about 1.3 million people in the United States. [4] Treatments include balloon aortic valvotomy (BAV), in which a balloon is placed across the aortic valve and inflated to fracture the calcification and restore mobility to the valve leaflets, surgical aortic valve replacement (SAVR), an open procedure in which a mechanical or bio-prosthetic valve is implanted, and the increasingly popular transcatheter aortic valve replacement (TAVR or TAVI), in which a prosthetic valve is implanted percutaneously through the femoral artery, transapically, or through direct aortic access. [5] Though TAVR was originally indicated for high-risk patients who were not likely to tolerate open surgery, further studies have shown that TAVR and SAVR have similar risk profiles, driving increasing popularity of the transcatheter approach. [6][7] 
     Mitral valve regurgitation is a condition in which the mitral valve does not close properly, causing abnormal leaking of blood backwards from the left ventricle, through the mitral valve, into the left atrium, when the left ventricle contracts. Most patients are asymptomatic until there is left ventricular (LV) enlargement and systolic dysfunction, pulmonary hypertension, or the onset of atrial fibrillation. Symptoms include fatigue and labored breathing. [8] Mitral valve regurgitation affects 1.7% of the United States adult population, approximately 3.9 million people. [9] Mitral valve repair (MVR) and mitral valve replacement (MVRx), both “open” procedures, have good results in young, low surgical risk patients but are associated with high mortality and morbidity in older, higher surgical risk patients. The “MitraClip”, a device for transcatheter mitral valve repair became commercially available in the United States in 2014, has been shown over a series of studies to be a viable treatment option for high risk surgical patients. [10][11][12] 
     Mitral valve stenosis is a condition that causes mechanical obstruction between the left atrium and left ventricle. It is most commonly a secondary condition to rheumatic heart disease that causes a narrowing of the valve due to immobile mitral valve leaflets, fibrosis, thickening, shortening, fusion, and calcification of the chordae tendineae. The narrowing creates a pressure gradient across the valve which causes the left atrium to work harder. Over time mitral valve stenosis can cause congestive heart failure, systematic arterial embolism, hemoptysis, pulmonary hypertension and death. [13][14] Treatment of mitral valve stenosis includes percutaneous mitral balloon valvotomy, in which a balloon is placed across the valve and inflated, valve repair, which can be open commissurotomy and include placement of an annuloplasty ring, valve replacement, which can be done in an open or closed procedure, or transcatheter mitral valve replacement (TMVR), which is percutaneous delivery of a prosthetic valve. TMVR is still investigational in the United States. 
     In addition, there are other therapies which involve catheterization of the heart, such as RF Ablation of the left atrium and pulmonary veins to prevent atrial fibrillation or other rhythm abnormalities, placement of occlusion devices in the left atrial appendage to prevent stroke in patients with atrial fibrillation, and other therapies. 
     Despite the benefits of transcatheter procedures, the patient population eligible for these procedures is generally still very high risk. While the procedures offer long-term benefit, they can cause temporary disruption and stress to the heart. Patients are more likely to become hemodynamically unstable, leading to cardiogenic shock, heart failure, and/or death. In particular, repair or replacement of the mitral valve places an extra strain on the left ventricle over a period of hours or days as the ventricle adjusts to ejecting a lower stroke volume against a higher pressure. This improves the long-term health of the patient by reducing or eliminating regurgitant flow but can cause a dangerous period of short-term stress. Currently, patients with low left ventricular ejection fractions are not considered safe candidates for transcatheter mitral valve repair or replacement due to this increased acute strain on the ventricle. 
     In the recovery and readjustment period, it would be advantageous to “unload” the heart or decrease the demand placed on the heart&#39;s pumping capacity, thus decreasing the heart&#39;s need for oxygen and nutrients. By shifting work to a short-term mechanical circulatory assist device, the unloaded heart is more likely to remain hemodynamically stable and allow for recovery and fewer adverse events. [15][16] 
     Mechanical assist devices draw blood from the arterial system, either from inside the heart (left atrium or left ventricle) or from just beyond the aortic valve (ascending aorta or descending aorta). Blood is pumped using centrifugal, screw, peristaltic, impeller, or roller pumps. Blood can be returned to the circulatory system in several different ways. If the device is intraluminal, blood may be returned a few centimeters downstream in the aorta via the same catheter with the in-line pump. Other devices draw the blood out of the body, through an extracorporeal pump, and return it to the arterial system through the femoral artery or another major peripheral artery of the body. Alternatively, blood can be drawn from the venous circulation, such as from the inferior vena cava or right atrium, and run through an oxygenator as well as a pump before being returned to the arterial system. 
     There are also intra-aortic balloon pumps (IABP) that use counter pulsation to reduce systolic pressure and increase diastolic pressure, thereby increasing cardiac output and forward blood flow. The IABP balloon is placed in the descending aorta and rapidly inflated and deflated using helium. During diastole, the balloon inflates, which increases blood flow to the body&#39;s tissues, including the coronary arteries and driving heart perfusion. During systole, the balloon deflates, lowering aortic pressure and decreasing the afterload on the heart. 
     Existing mechanical assist devices require multiple complex steps to gain the necessary access to the appropriate portions of the circulatory system, such as the creation of transseptal access to access the left atrium from the femoral vein. These steps typically involve the introduction of new devices. These steps add cost, take additional time and cause additional stress to the patient. Accordingly, improved systems and methods for providing mechanical circulatory support are needed. 
     SUMMARY 
     The present technology relates to mechanical circulatory support systems and associated methods of use. In particular embodiments, the present technology relates to mechanical circulatory support systems for use in conjunction with catheter-based heart therapies. The subject technology is illustrated, for example, according to various aspects described below, including with reference to  FIGS. 1-27 . Various examples of aspects of the subject technology are described as numbered clauses (1, 2, 3, etc.) for convenience. These are provided as examples and do not limit the subject technology.
         1. A system for providing cardiopulmonary support to patients undergoing transcatheter procedures, wherein the same catheter used for delivering the therapy is also used to withdraw blood from the cardiovascular system.   2. The system of Clause 1, wherein the catheter comprises a guide catheter having a steerable distal portion.   3. The system of Clause 2, wherein the guide catheter comprises one or more positioning features extending into a lumen of the guide catheter, the positioning features configured to position a delivery catheter within the guide catheter lumen.   4. The system of Clause 2 or Clause 3, wherein the guide catheter comprises one or more holes in a distal portion of the guide catheter, the holes configured to receive blood therethrough.   5. The system of any one of Clauses 2 to 4, wherein the distal portion of the guide catheter is at least partially coated with heparin or another anti-coagulant coating.   6. The system of any one of Clauses 2 to 5, wherein the guide catheter is at least partially coated with heparin or another anti-coagulant coating   7. The system of any one of Clauses 2 to 6, wherein the guide catheter comprises a distal end portion, a proximal end portion, and an intermediate portion therebetween, wherein the intermediate portion is configured to be positioned within an artery or a vein of a patient.   8. An adaptor for accessing a guiding catheter to allow its use as a drainage cannula.   9. A guiding catheter which also has features which allow it to be used as a drainage cannula.   10. A method of treatment which allows for cardiopulmonary support during or immediately after cardiovascular procedures without the need for new cannulation.   11. A method of treatment comprising:   positioning a catheter with a distal portion disposed within or adjacent a heart of a patient;   advancing a treatment device through the catheter and into the heart;   withdrawing blood from the heart through the catheter to an extracorporeal pump; and   returning blood from the pump to a blood vessel of the patient.   12. The method of Clause 11, wherein the treatment device comprises a prosthetic valve.   13. The method of Clause 11, wherein the treatment device comprises a valve repair device.   14. The method of Clause 11, wherein the positioning the catheter comprises positioning the catheter into the ascending aorta or the left ventricle.   15. The method of Clause 14, wherein the catheter is advanced through the descending aorta.   16. The method of Clause 11, wherein positioning the catheter comprises positioning the catheter into the left atrium.   17. The method of Clause 16, wherein the catheter is advanced through the inferior vena cava.   18. A method of treatment comprising:   positioning a catheter with a distal portion disposed within or adjacent a heart of a patient and an intermediate portion disposed within an artery or a vein of the patient;   advancing a treatment device through the catheter and into the heart;   withdrawing blood from the heart through the catheter to an extracorporeal pump; and returning blood from the pump to a blood vessel of the patient.   19. The method of Clause 18, wherein the positioning the catheter comprises positioning a distal end portion of the catheter into the ascending aorta or the left ventricle.   20. The method of Clause 18, wherein positioning the catheter comprises positioning a distal end portion of the catheter into the left atrium.   21. A system for providing cardiac support to a patient, the system comprising:   a first elongated shaft defining a first lumen extending therethrough, the first shaft having a proximal end portion and a distal end portion, wherein the distal end portion is configured to be intravascularly positioned at a first cardiovascular location, and wherein the lumen of the first shaft is configured to slidably receive a catheter housing an interventional element in a low-profile state;   a second elongated shaft defining a second lumen extending therethrough, the second shaft having a proximal end region and a distal end region, wherein the distal end region is configured to be intravascularly positioned at a second cardiovascular location within an artery of the patient; and   a pressure source configured to generate pressure within the first lumen and the second lumen, wherein the pressure source is configured to be coupled to the proximal end portion of the first shaft and the proximal end region of the second shaft, and wherein pressure generated by the pressure source pulls blood from the first location proximally through the first shaft to the pressure source, then pushes the blood distally through the second shaft and into circulatory flow at the second cardiovascular location, thereby providing mechanical circulatory support to the patient.   22. The system of Clause 21, wherein the pressure source is configured to generate the blood flow while the catheter is positioned within and/or extending distally from the distal end portion of the first shaft.   23. The system of Clause 21 or Clause 22, wherein the pressure source is configured to be extracorporeally positioned while generating pressure.   24. The system of any one of Clauses 21 to 23, wherein the pressure source is configured to generate negative pressure in the first shaft and positive pressure in the second shaft.   25. The system of any one of Clauses 21 to 23, further comprising an oxygenator configured to oxygenate the blood as it flows between the distal end portion of the first shaft and the distal end region of the second shaft.   26. The system of any one of Clauses 21 to 25, wherein the first cardiovascular location is within one of the left ventricle, the left atrium, or the ascending aorta.   27. The system of any one of Clauses 21 to 26, wherein the second cardiovascular location is within one of the ascending aorta, the aortic arch, the descending aorta, the subclavian artery, or the femoral artery.   28. The system of any one of Clauses 21 to 27, wherein the distal end portion of the first shaft comprises a steerable region configured to bend at an angle relative to a longitudinal axis of the first shaft.   29. The system of Clause 28, wherein the steerable region is a first steerable region and the distal end portion of the first shaft further comprises a second steerable region configured to bend at a second angle relative to the longitudinal axis of the first shaft.   30. The system of Clause 29, wherein the first angle is equal to the second angle.   31. The system of Clause 29, wherein the first angle is greater than the second angle.   32. The system of any one of Clauses 21 to 31, wherein the distal end portion of the first shaft comprises a plurality of openings extending through a sidewall of the first shaft.   33. The system of any one of Clauses 21 to 32, wherein a radial dimension of the distal end portion of the first shaft decreases in a distal direction.   34. The system of any one of Clauses 21 to 33, wherein the first shaft comprises a plurality of projections extending radially inward from an inner surface of the first shaft.   35. The system of Clause 34, wherein some or all of the projections comprise a curved surface that is convex toward the first lumen.   36. The system of Clause 34 or Clause 35, wherein the projections are evenly distributed around a circumference of the inner surface of the first shaft.   37. The system of Clause 34 or Clause 35, wherein the projections are asymmetrically distributed around a circumference of the inner surface of the first shaft.   38. The system of Clause 37, wherein the projections are configured to position the catheter against a portion of the inner surface of the first shaft.   39. The system of any one of Clauses 21 to 38, wherein the proximal end portion of the first shaft comprises an outflow channel configured to fluidly couple to the pressure source.   40. The system of Clause 39, wherein the outflow channel is disposed at an angle relative to a longitudinal axis of the first shaft.   41. The system of any one of Clauses 21 to 40, wherein the proximal end portion of the first shaft is flared in a proximal direction.   42. The system of any one of Clauses 21 to 41, wherein the proximal end portion of the first shaft comprises a valve.   43. The system of any one of Clauses 21 to 41, wherein the proximal end portion of the first shaft comprises a seal.   44. The system of Clause 42 or Clause 43, wherein the valve or seal is configured to limit air and/or fluid displacement through the valve or seal under negative and/or positive pressure.   45. The system of any one of Clauses 21 to 44, wherein an outer surface of the proximal end portion of the first shaft includes threads or a lip configured to engage with a connector.   46. The system of any one of Clauses 21 to 45, wherein the proximal end portion of the first shaft is configured to engage with a cap such that the proximal end portion of the first shaft comprises a closed lumen.   47. The system of any one of Clauses 21 to 46, wherein the distal end region of the second elongated shaft comprises at least one opening through a sidewall of the second elongated shaft.   48. The system of any one of Clauses 21 to 47, wherein the distal end region of the second elongated shaft comprises an atraumatic distal terminus.   49. The system of any one of Clauses 21 to 48, wherein the distal end region of the second elongated shaft comprises an open lumen.   50. The system of Clause 49, wherein the distal terminus of the second elongated shaft is beveled.   51. The system of any one of Clauses 21 to 50, further comprising a connector configured to fluidly couple the proximal end portion of the first shaft and the pressure source.   52. The system of Clause 51, wherein the connector comprises a coupler configured to detachably couple to (a) the proximal end portion of the first shaft and/or (b) the pressure source.   53. The system of Clause 51, wherein the connector comprises a coupler and tubing configured to detachably couple to the coupler.   54. The system of Clause 52 or Clause 53, wherein the coupler comprises a hollow shaft defining a lumen extending therethrough, wherein the shaft is configured to be received within the first lumen of the first shaft.   55. The system of Clause 54, wherein a radial dimension of the hollow shaft decreases in a distal direction.   56. The system of Clause 54 or Clause 55, wherein the hollow shaft is configured to be inserted through and hold open the valve or seal of the first shaft.   57. The system of any one of Clauses 52 to 56, wherein the coupler comprises an attachment portion configured to receive the proximal end portion of the first shaft.   58. The system of Clause 57, wherein the attachment portion comprises threads.   59. The system of Clause 57, wherein the attachment portion comprises a snap-fit mechanism.   60. The system of Clause 57, wherein the attachment portion comprises a locking screw configured to engage an outer surface of the proximal end portion of the first shaft.   61. The system of any one of Clauses 52 to 60, the coupler further comprising a valve positioned within the lumen of the hollow shaft.   62. The system of Clause 61, wherein the valve is generally conical.   63. The system of any one of Clauses 52 to 62, the coupler further comprising a seal.   64. The system of Clause 63, wherein the seal is an elastomeric o-ring.   65. The system of any one of Clauses 52 to 64, wherein the coupler comprises an outflow channel configured to fluidly couple to the pressure source.   66. The system of Clause 65, wherein the outflow channel is disposed at an angle relative to the shaft.   67. The system of Clause 65 or Clause 66, wherein an outer surface of the outflow channel is threaded or barbed.   68. The system of any one of Clauses 52 to 67, wherein the coupler comprises a flush port.   69. The system of any one of Clauses 21 to 68, further comprising a connector configured to fluidly couple the proximal end region of the second shaft and the pressure source.   70. The system of Clause 69, wherein pressure generated by the pressure source causes blood to flow from the first location into the distal end portion of the first shaft, then proximally through the first lumen and first connector to the pressure source, then distally from the pressure source through the second connector and the second lumen to the distal end region of the second shaft, then into the artery.   71. The system of Clause 69 or Clause 70, wherein pressure generated by the pressure source causes deoxygenated blood to flow from a third cardiovascular location into the first shaft, then proximally through the first lumen and first connector to the pressure source, then distally from the pressure source through the second connector and the second lumen to the distal end region of the second shaft, then into the artery.   72. The system of any one of Clauses 21 to 71, wherein the first location is a left atrium.   73. The system of any one of Clauses 21 to 71, wherein the first location is a left ventricle.   74. The system of any one of Clauses 21 to 71, wherein the first location is an aorta.   75. The system of any one of Clauses 21 to 74, wherein the distal end portion of the first shaft is configured to be positioned across a septum.   76. The system of any one of Clauses 21 to 75, wherein the interventional element comprises a prosthetic mitral valve.   77. The system of any one of Clauses 21 to 75, wherein the interventional element comprises a prosthetic aortic valve.   78. The system of any one of Clauses 21 to 75, wherein the interventional element comprises a heart valve repair device.   79. A system comprising:   a bypass device comprising a first end region with an inlet, a second end region with an outlet, and a fluid path extending therebetween, wherein the first end region is configured to be intravascularly delivered to and positioned at a first cardiovascular location, and wherein the second end region is configured to be intravascularly delivered to and positioned at a second cardiovascular location within an artery of the patient; and   a pressure source disposed along the fluid path between the inlet and the outlet,   wherein a portion of the bypass device between the pressure source and the inlet is configured to receive a catheter containing an interventional device, and wherein, when the pressure source is activated, the pressure source pulls blood from the first cardiovascular location into the inlet, through the fluid path, and ejects the blood from the outlet to the second cardiovascular location.   80. The system of Clause 78, wherein the pressure source is configured to aspirate blood from the first location and eject blood to the second location while the catheter is positioned within the bypass device.   81. The system of Clause 79 or Clause 80, wherein the pressure source is configured to aspirate blood from a third cardiovascular location comprising deoxygenated blood.   82. The system of any one of Clauses 79 to 81, wherein the third cardiovascular location is a right atrium of the patient.   83. The system of any one of Clauses 79 to 82, wherein the third cardiovascular location is an inferior vena cava of the patient.   84. The system of any one of Clause 79 to 83, further comprising an oxygenator configured to oxygenate the blood as it flows between the first end region and the second end region of the bypass device.   85. The system of any one of Clauses 79 to 84, wherein the pressure source is a pump.   86. The system of Clause 85, wherein the pump is a centrifugal pump, a peristaltic pump, a pulsatile pump, or a roller pump.   87. A method of providing mechanical circulatory support to a patient, the method comprising:   positioning a distal end portion of a first elongated shaft at a first cardiovascular location proximate a treatment site at or near the patient&#39;s heart, the first shaft defining a first lumen therethrough;   advancing a delivery catheter through the first lumen of the first shaft to the treatment site, wherein the delivery catheter contains an interventional device in a low-profile delivery state;   performing an interventional procedure at the treatment site with the interventional device; positioning a distal end region of a second elongated shaft at a second cardiovascular location within an artery of the patient, the second shaft defining a second lumen therethrough; and   generating pressure within the first and second lumens to pull blood from the first cardiovascular location through the first shaft and the second shaft and eject the blood from the distal end region of the second shaft at the second cardiovascular location.   88. The method of Clause 87, further comprising withdrawing the delivery catheter from the first shaft prior to generating the pressure in the first and second lumens.   89. The method of Clause 87, wherein the pressure is generated while the delivery catheter is at least partially positioned within the first shaft.   90. The method of Clause 87, further comprising withdrawing the delivery catheter from the first shaft after generating the pressure in the first and second lumens.   91. The method of Clause 87, wherein positioning the distal end portion of the first shaft at a treatment location comprises a retrograde transfemoral approach.   92. The method of Clause 87, wherein positioning the distal end portion of the first shaft at the treatment site comprises an antegrade transseptal approach.   93. The method of Clause 87, wherein positioning the distal end portion of the first shaft at the treatment site comprises a transaortic approach.   94. The method of Clause 87, wherein positioning the distal end portion of the first shaft at the treatment site comprises a transapical approach.   95. The method of Clause 87, wherein positioning the distal end portion of the first shaft at the treatment site comprises a trans-subclavian approach.   96. The method of Clause 87, wherein positioning the distal end portion of the first shaft at the treatment site comprises a transaxillary approach.   97. The method of any one of Clauses 87 to 96, wherein the first cardiovascular location is within one of the left ventricle, the left atrium, or the ascending aorta.   98. The method of any one of Clauses 87 to 96, wherein the second cardiovascular location is within one of the ascending aorta, the aortic arch, the descending aorta, the subclavian artery, or the femoral artery.   99. The method of any one of Clauses 87 to 98, wherein the treatment site is the same as the first cardiovascular location.   100. The method of any one of Clauses 87 to 99, wherein the interventional procedure is a transcatheter aortic valve replacement.   101. The method of any one of Clauses 87 to 99, wherein the interventional procedure is a transcatheter mitral valve replacement.   102. The method of any one of Clauses 87 to 99, wherein the interventional procedure is a transcatheter mitral valve repair.   103. The method of any of Clauses 87 to 102, further comprising oxygenating the blood via an oxygenator in-line with the fluid pathway.   104. A system for providing cardiac support to a patient, the system comprising:       

     an inlet catheter defining a first lumen extending therethrough, the inlet catheter having a proximal end portion and a distal end portion, wherein the distal end portion is configured to be intravascularly positioned at a first arterial location, and wherein the lumen of the inlet catheter is configured to slidably receive a delivery catheter housing a prosthetic heart valve in a low-profile state;
         an outlet catheter defining a second lumen extending therethrough, the outlet catheter having a proximal end region and a distal end region, wherein the distal end region is configured to be intravascularly positioned at a second arterial location; and   a pump configured to be coupled to the proximal end portion of the inlet catheter and the proximal end region of the outlet catheter, and wherein pressure generated by the pump pulls blood from the first arterial location proximally through the inlet catheter to the pump, then pushes the blood distally through the outlet catheter and into circulatory flow at the second arterial location, thereby providing mechanical circulatory support to the patient.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Instead, emphasis is placed on illustrating clearly the principles of the present disclosure. 
         FIG. 1  depicts a mechanical circulatory support system of the present technology configured for use in conjunction with a typical TMVR and/or TMVr procedure. 
         FIG. 2  depicts a mechanical circulatory support system of the present technology configured for use in conjunction with a typical TAVR procedure. 
         FIG. 3  depicts a mechanical circulatory support system of the present technology configured for use in conjunction with a typical TAVR procedure. 
         FIGS. 4A-4D  each depict a distal end portion of a second elongated shaft configured to be positioned within an arterial blood vessel in accordance with the present technology. 
         FIG. 5  depicts a first elongated shaft and a delivery catheter in accordance with several embodiments of the present technology. 
         FIGS. 6A and 6B  are axial and isometric views, respectively, of a first elongated shaft and a delivery catheter in accordance with several embodiments of the present technology. 
         FIGS. 7A and 7B  are axial and isometric views, respectively, of a first elongated shaft and a delivery catheter in accordance with several embodiments of the present technology. 
         FIG. 8  depicts a first elongated shaft and a delivery catheter in accordance with several embodiments of the present technology. 
         FIG. 9  depicts a first elongated shaft in accordance with several embodiments of the present technology. 
         FIG. 10  is a cross-sectional view of a proximal end portion of a first elongated shaft and a delivery catheter in accordance with several embodiments of the present technology. 
         FIG. 11A  is a cross-sectional view of a proximal end portion of a first elongated shaft and a delivery catheter in accordance with several embodiments of the present technology. 
         FIG. 11B  is an axial view of the valve of  FIG. 11A . 
         FIG. 12  is a cross-sectional view of a proximal end portion of a first elongated shaft in accordance with several embodiments of the present technology. 
         FIG. 13  is a cross-sectional view of a proximal end portion of a first elongated shaft and a delivery catheter in accordance with several embodiments of the present technology. 
         FIG. 14  is a cross-sectional view of a proximal end portion of a first elongated shaft and a delivery catheter in accordance with several embodiments of the present technology. 
         FIG. 15  is a cross-sectional view of a proximal end portion of a first elongated shaft in accordance with several embodiments of the present technology. 
         FIG. 16  is a cross-sectional view of a proximal end portion of a first elongated shaft and a cap in accordance with several embodiments of the present technology. 
         FIG. 17  depicts a proximal end portion of a first elongated shaft in accordance with several embodiments of the present technology. 
         FIG. 18  depicts a proximal end portion of a first elongated shaft in accordance with several embodiments of the present technology. 
         FIG. 19A  is a cross-sectional view of a coupler in accordance with several embodiments of the present technology. 
         FIG. 19B  is a cross-sectional view of the coupler of  FIG. 19A  attached to a first elongated shaft and tubing, each in accordance with several embodiments of the present technology. 
         FIG. 20  is a cross-sectional view of a coupler in accordance with several embodiments of the present technology. 
         FIG. 21  is a cross-sectional view of a distal attachment portion of a coupler in accordance with several embodiments of the present technology. 
         FIG. 22  is a cross-sectional view of a distal attachment portion of a coupler in accordance with several embodiments of the present technology. 
         FIG. 23  is a cross-sectional view of a distal attachment portion of a coupler in accordance with several embodiments of the present technology. 
         FIG. 24  is an isometric view of a distal end portion of a second elongated shaft in accordance with several embodiments of the present technology. 
         FIG. 25  is an isometric view of a distal end portion of a second elongated shaft in accordance with several embodiments of the present technology. 
         FIG. 26  is an isometric view of a distal end portion of a second elongated shaft in accordance with several embodiments of the present technology. 
         FIG. 27  is an isometric view of a distal end portion of a second elongated shaft in accordance with several embodiments of the present technology. 
     
    
    
     DETAILED DESCRIPTION 
     The present technology relates to systems and methods for providing mechanical circulatory support to patients undergoing or who have undergone catheter-based cardiovascular therapy. Some embodiments of the present technology, for example, are directed to providing mechanical circulatory support during or following transcatheter aortic valve replacement (TAVR) (also known as transcatheter aortic valve implantation (TAVI)), transcatheter aortic valve repair, transcatheter mitral valve replacement (TMVR), and/or native mitral valve repair (TMVr). The support systems of the present technology take advantage of existing access to the certain portions of the circulatory system established during a catheter-based procedure (such as any of the aforementioned heart valve therapies). Unless specifically stated otherwise, the terms “circulatory system” or “circulatory path,” “vascular” or “vascular system,” and “cardiovascular” or “cardiovascular system,” as used herein, refer to the blood vessels, the heart, or both. Likewise, “arterial” refers to any portion of the heart or blood vessels containing oxygenated blood. By obviating the complex steps required to introduce new devices to gain access to the appropriate portions of the circulatory system, the support systems and methods of the present technology save time and money and reduce patient stress and recovery time. Specific details of several embodiments of the technology are described below with reference to  FIGS. 1-27 . 
     I. Support System Overview 
       FIG. 1  depicts a support system  100  (or “system  100 ”) configured in accordance with several embodiments of the present technology. In some embodiments, for example as shown in  FIG. 1 , the system  100  comprises a first elongated shaft  120 , a second elongated shaft  170 , and a pressure source  180  configured to be fluidly coupled to both the first and second elongated shafts  120 ,  170 . The first elongated shaft  120  has a proximal end portion  120   b  configured to be coupled to the pressure source  180  and a distal end portion  120   a  configured to be positioned at a first location within the circulatory system. The second elongated shaft  170  has a proximal end portion  170   b  configured to be coupled to the pressure source  180  and a distal end portion  170   a  configured to be positioned at a second location, typically within the arterial system. When activated, the pressure generated by the pressure source  180  directs blood from the first location through the first and second shafts  120 ,  170  to the second location, thereby providing mechanical support to the heart. 
     In some embodiments, the proximal end portion  120   b  of the first shaft  120  connects directly to the pressure source  180 . For example, the proximal end portion  120   b  of the first shaft  120  may comprise a coupling portion (not shown) integrally formed with the proximal end portion  120   b  of the first shaft  120 . In some embodiments, for example as shown in  FIG. 1 , the first shaft  120  connects to the pressure source  180  via a connector  146 . The connector  146  may comprise one or more couplers  150  configured to detachably couple to the proximal end portion  120   b  of the first shaft  120  and/or the pressure source  180 . Additionally or alternatively, the connector  146  may comprise tubing  148  configured to detachably couple to the proximal end portion  120   b  of the first shaft  120 , the pressure source  180 , and/or one or more couplers  150  (should the system  100  include any couplers  150 ). In some embodiments, the proximal end portion  120   b  of the first elongated shaft  120  is directly coupled to the tubing  148 . For example, the proximal end portion  120   b  may comprise an integral coupling portion that connects directly to the tubing  148  without additional couplers. Additional details regarding the connection between the first shaft  120  and the pressure source  180  are discussed below. 
     In some embodiments, the proximal end portion  170   b  of the second shaft  170  connects directly to the pressure source  180 . For example, the proximal end portion  170   b  of the second shaft  170  may comprise a coupling portion (not shown) integrally formed with the proximal end portion  170   b  of the second shaft  170 . In some embodiments, for example as shown in  FIG. 1 , the second shaft  170  connects to the pressure source  180  via a connector  146 . The connector  146  may comprise one or more couplers  150  configured to detachably couple to the proximal end portion  170   b  of the second shaft  170  and/or the pressure source  180 . Additionally or alternatively, the connector  146  may comprise tubing  148  configured to detachably couple to the proximal end portion  170   b  of the second shaft  170 , the pressure source  180 , and/or one or more couplers  150  (should the system  100  include any couplers  150 ). In some embodiments, the proximal end portion  170   b  of the first elongated shaft  170  is directly coupled to the tubing  148 . For example, the proximal end portion  170   b  may comprise an integral coupling portion that connects directly to the tubing  148  without additional couplers. Additional details regarding the connection between the second shaft  170  and the pressure source  180  are discussed below. 
     The pressure source  180  may be a pump, such as a centrifugal pump, a screw pump, a peristaltic pump, an impeller pump, a roller pump, and others. When coupled to the first and second shafts  120 ,  170  and in use, the pressure source  180  may be extracorporeally positioned, or may be implanted within the patient. The pressure source  180  may be configured to generate a negative pressure (i.e., suction) within a lumen of the first shaft  120  to increase the pressure differential between the patient&#39;s physiologic blood pressure and the pressure within the lumen of the first shaft  120 , thereby drawing more blood into the first shaft  120 . The pressure source  180  may be configured to generate a positive pressure within a lumen of the second shaft  170 . This positive pressure is typically higher than the arterial pressure of the patient, causing blood to flow out of the second shaft  170  into the patient&#39;s arterial system. 
     As previously mentioned, the system  100  is configured to provide mechanical circulatory support during or following a catheter-based heart therapy, such as TAVR, transcatheter aortic valve repair, TMVR, or TMVr, using some or all of the same delivery system components used to perform the heart therapy. The first shaft  120 , for example, defines a lumen sized to slidably receive therethrough one or more delivery system components and/or treatment elements configured to treat or facilitate treatment of one or more structures of the heart. The delivery system may comprise a guidewire, a delivery catheter, an elongated push member, and/or other components. The treatment element may be advanced through the guide catheter in a low-profile delivery state, either housed within a delivery catheter or exposed. Non-limiting examples of treatment elements include a prosthetic mitral valve implant, a prosthetic aortic valve implant, a mitral valve repair device, an aortic valve repair device, a patent foramen  ovale  (PFO) closure device, a left atrial appendage (LAA) occlusion device, an atrial septal defect (ASD) closure device, an ablation catheter, a ventricular partitioning device, a myocardial anchoring system, and other interventional elements for catheter-based heart therapies. The pressure source  180  may be coupled to the first shaft  120  during the transcatheter heart therapy, or may be coupled to the first shaft  120  after the delivery catheter has been withdrawn from the first shaft  120 . 
     The specific location within the circulatory system for placement of the distal end portion  120   a  of the first shaft  120  depends on the type of transcatheter procedure/heart structure being treated. For example, the distal end portion  120   a  of the first shaft  120  may be configured to be positioned at a first cardiovascular location (a) within the left atrium, (b) within the left ventricle, and/or (c) within the aorta at a location just downstream of the aortic valve. When the system  100  is used in conjunction with a TMVR and/or a TMVr procedure, for example, the distal end portion  120   a  of the first shaft  120  may be positioned in the left atrium or the left ventricle. When the system  100  is used in conjunction with a TAVR or transcatheter aortic valve repair procedure, the distal end portion  120   a  of the first shaft  120  may be positioned within the left ventricle and/or within the aorta at a location just downstream of the aortic valve (such as along the ascending aorta, aortic arch, or descending aorta). 
     Regardless of the procedure, the distal end portion  170   a  of the second shaft  170  is configured to be positioned at a second cardiovascular location within the arterial circulation. For example, the second cardiovascular location may be at or within the femoral artery, the subclavian artery, the descending aorta, the ascending aorta, or the aortic arch. 
     In some embodiments, blood can be drawn from the venous circulation, such as from the inferior vena cava or right atrium. In such embodiments, the system  100  may include an oxygenator, the blood pulled from the circulation can pass through the oxygenator as well as the pressure source  180  before being returned to the arterial system. 
     As previously mentioned, in some embodiments the system  100  is configured for use in conjunction with a TMVR and/or TMVr procedure. In such embodiments, the first shaft  120  may be a guide catheter sized to receive a delivery catheter containing an interventional device for replacing and/or repairing the mitral valve. As shown in  FIG. 1 , a distal end portion  120   a  of the first shaft  120  can be positioned in the left atrium and the distal end portion  170   a  of the second shaft  170  can be positioned in the femoral artery. The first shaft  120  may be delivered to the left atrium through the femoral vein, iliac vein, inferior vena cava and right atrium via an antegrade transseptal approach (as shown) or through the femoral artery, aorta, and left ventricle via a retrograde transfemoral approach. In some embodiments, the first shaft  120  is a guide catheter configured to be delivered to the left atrium and/or left ventricle via an antegrade transseptal approach. In such embodiments, when the system  100  is in use and providing circulatory support, the first shaft  120  extends distally from the pressure source  180  through a patient&#39;s inferior vena cava, into the right atrium of the patient&#39;s heart, and across the septum into the left atrium, as shown in  FIG. 1 . The second shaft  170  may be configured to be advanced into the femoral artery, iliac artery, or descending aorta such that the distal end region  170   a  of the second elongated shaft  170  is positioned within one of these vessels, or into the aortic arch. 
       FIG. 2  depicts a system  200  of the present technology positioned within the cardiovascular system for use in conjunction with a TAVR procedure. The system  200  may comprise a first elongated shaft  220  having distal and proximal end portions  220   a ,  220   b  and a second elongated shaft  270  having distal and proximal end portions  270   a ,  270   b . The proximal end portion  202   b  of the first elongated shaft  220  and/or the proximal end portion  270   b  of the second elongated shaft  270  may be configured to be attached to a pressure source  280 . As shown in  FIG. 2 , at least when used in conjunction with a TAVR procedure, the distal end portion  220   a  of the first elongated shaft  220  may be positioned within the left ventricle or ascending aorta, and the distal end portion  270   a  of the second elongated shaft  270  can be positioned within the arterial system, such as within the femoral artery, iliac artery, or descending aorta. According to some embodiments, for example as shown in  FIG. 3 , the distal end portion  320   a  of the first elongated shaft  320  can be positioned within the left ventricle. 
     The distal end portion of the second shaft is typically positioned within a patient&#39;s arterial system. While  FIGS. 1 and 2  depict the distal end portion of the second shaft positioned within the femoral artery, in some embodiments the distal end portion of the second shaft may be positioned elsewhere within the patient&#39;s cardiovascular system. For example, the distal end portion  470   a  of the second shaft may be configured to be positioned within a subclavian artery ( FIG. 4A ), an ascending aorta ( FIG. 4B ), a descending aorta ( FIG. 4C ), and/or a femoral artery ( FIG. 4D ). 
     II. Selected First Shaft Embodiments 
     A first elongated shaft of the present technology may be formed of a polymeric and/or elastomeric material such as Pebax®, polyurethane, and other suitable materials. In some embodiments, an inner surface and/or an outer surface of the first shaft may include a coating configured to reduce or prevent clotting, damage to the vessel and/or heart wall, and/or an inflammatory response resulting from placement of the first shaft within a patient&#39;s cardiovascular system. Additionally or alternatively, the first shaft may include a reinforcement member, such as a coil, a braid, and others. In some embodiments, the reinforcement member is positioned within a sidewall of the first shaft, such as between the inner and outer surfaces. 
     According to some embodiments, the first shaft comprises at least one steerable region configured to bend along the longitudinal axis of the first shaft to reduce or prevent contact between the first shaft and the vessel walls as the first shaft is advanced through the vasculature. As such, the steerable regions herein reduce or prevent trauma to the vessel and/or formation of embolic debris, facilitate directing the shaft into the desired location, and facilitating delivery of an interventional device or other device to the appropriate location. The steerable region(s) may be controlled by a tensioning mechanism such as a longitudinal pull-wire positioned within the sidewall of the first shaft. Although longitudinal pull-wires are described herein, any suitable tensioning mechanism may be employed. The longitudinal pull-wire may be attached to the outer side of the inner surface and/or the inner side of the outer surface such that tensioning of the longitudinal pull-wire causes the first shaft to flex. In some embodiments, the first shaft comprises multiple steerable regions. For example, a first longitudinal pull-wire may be attached to the first shaft at a first location and a second longitudinal pull-wire may be attached to the first shaft at a second location proximal of the first location. The steerable regions may be configured to advantageously flex independently of one another. For example, when used in conjunction with a TAVR procedure, the first shaft may be positioned within the ascending aorta for delivery of a prosthetic aortic valve. To position the first shaft within the ascending aorta, the first (i.e., distal) steerable region may be flexed via tensioning of the pull-wire as the distal end portion of the first shaft is advanced from the descending aorta into the aortic arch and further into the ascending aorta. After the valve is delivered, the distal end portion of the first shaft may be advanced through the aortic valve into the left ventricle so that it can be used to withdraw blood from the left ventricle. During this advancement, the first steerable region may be flexed or straightened to minimize damage to the aortic valve and the second steerable region may be flexed while positioned within the aortic arch. The first shaft may comprise any number of suitable steerable regions. 
     A first elongated shaft of the present technology may have an outer diameter between about 14 and about 36 French, an inner diameter between about 12 and about 32 French, and/or a length between about 70 and about 160 cm. In some embodiments, the inner diameter of the first shaft may be greater than an outer diameter of a delivery catheter configured to be slidably received within the first shaft. For example, the first shaft may have a 30 French outer diameter and a 26 French inner diameter when configured for use with a delivery catheter having an outer diameter of 18 French. Oversizing of the first shaft relative to the delivery catheter may facilitate advancement of the delivery catheter through the first shaft to perform a therapeutic procedure. Additionally or alternatively, an oversized first shaft may permit blood to be withdrawn and/or mechanical circulatory support to be provided during the procedure by drawing blood through the annular space around the valve delivery catheter. Upon completion of the procedure, the oversized first shaft permits greater rates of blood flow through the first shaft as compared to a first shaft comprising a smaller inner diameter. 
       FIG. 5  is an isometric view of a distal end portion  520   a  of a first elongated shaft  520  and a delivery catheter  590  in accordance with several embodiments of the present technology. The first shaft  520  comprises an outer surface  522 , an inner surface  524 , and a lumen  526  defined by the inner surface  524 . As shown, the delivery catheter  590  can be slidably received through the lumen  526  of the first shaft  520 . In some embodiments, for example when the first shaft  520  is oversized relative to the delivery catheter  590 , a radial dimension of the distal end portion  520   a  decreases in a distal direction. Distal tapering of the first shaft  520  can enable precise placement and orientation of the delivery catheter  590  during an interventional procedure. 
     Additionally or alternatively, a first elongated shaft of the present technology may comprise internal features to facilitate positioning of the delivery catheter relative to one or both of the first shaft and the anatomy at the treatment site. For example,  FIGS. 6A and 6B  show axial and isometric views, respectively, of a first elongated shaft  620  having a plurality of guide members in accordance with several embodiments of the present technology. As shown, the guide members may comprise protrusions  628  extending inwardly towards the lumen  626  from the inner surface  624  of the shaft  620 . The protrusions  628  may engage the outer surface of a delivery catheter (such as delivery catheter  690 ) while positioned in the lumen  626  to stabilize and guide advancement of the catheter  690 . In some embodiments, the protrusions  628  are spaced apart about the circumference of the inner surface  624  such that, even when the delivery catheter  690  is positioned within the first shaft  620 , blood can flow through the unobstructed regions of the lumen  626  between the protrusions  628 . 
     The protrusions  628  may be positioned along one or more discrete portions of the first shaft  620  or may extend continuously along the entire length of the first shaft  620 . In some embodiments, the protrusions  628  are positioned along only a distal end portion  620   a  of the shaft  620  (as shown in  FIG. 6A ), only a proximal end portion, or only an intermediate portion. In some embodiments, the protrusions  628  are equally spaced around a circumference of the inner surface  624 , for example to center the delivery catheter  690  within the lumen  626 . According to several embodiments, the protrusions  628  may be asymmetrically arranged (for example as discussed below with reference to  FIGS. 7A and 7B ). 
     The protrusions  628  may be separate components coupled to the shaft  620  or may be unitarily formed with the shaft  620  (for example, via an extrusion process). The protrusions  628  may have any suitable cross-sectional shape, such as a hemispherical or rounded shape (see  FIG. 6A ), a square, a rectangle, a quadrilateral, a trapezoid (see  FIG. 7A ), a polygon, or any other suitable shape. All of the protrusions of a given shaft  620  may have the same shape and/or size, or some or all of the protrusions may have a different shape and/or size. In some embodiments, one, some, or all of the protrusions  628  comprise a rounded surface that is convex towards the lumen  626  and free of corners, for example as shown in  FIG. 6A . Rounded protrusions may be advantageous for minimizing thrombus formation, whereas quadrilateral protrusions may be advantageous for stabilizing the delivery catheter and/or for ease of manufacture. 
     While  FIG. 6A  shows a first shaft  620  with four protrusions  628 , in some embodiments the first shaft  620  may include more or fewer protrusions. For example, the first shaft  620  may include 1-20 protrusions, 2-18 protrusions, 3-15 protrusions, 3-8 protrusions, 4-10 protrusions, or other suitable numbers of protrusions. 
       FIGS. 7A and 7B  are axial and isometric views, respectively, of a delivery catheter  790  positioned within a first elongated shaft  720  having an outer surface  722 , an inner surface  724 , and a lumen  726  defined by the inner surface  724 . The first shaft  720  comprises guide members in the form of protrusions  728  extending radially inward from the inner surface  724 . Here, the protrusions  728  are positioned asymmetrically around only a portion of a circumference of the inner surface  724  to position the delivery catheter  790  against or near the other portion of the inner surface  724  without protrusions  728  (see  FIG. 7A ). The semilunar space between the delivery catheter  790  and the opposing portion of the inner surface  724  may permit greater blood flow through the first shaft  720 , as compared to the symmetrical annular space between the delivery catheter  690  and the inner surface  624  of the first shaft  620  in  FIG. 6A . In some embodiments, the protrusions  728  may be positioned on the inner curvature of the distal end portion  720   a  of the first shaft  720  when it is flexed, so the delivery catheter  790  follows the outer curvature of the first shaft  720 . In some embodiments, a tapered-tip dilator used to introduce the first shaft  720  over a guidewire may have corresponding slots to accommodate the protrusions  728 . 
       FIG. 8  shows a distal end portion  820   a  of a first elongated shaft  820  comprising an outer surface  822 , an inner surface  824 , and a sidewall extending therebetween. The first shaft  820  is shown in  FIG. 8  with a delivery catheter  890  positioned in its lumen  826 . In some embodiments, for example as shown in  FIG. 8 , the first shaft  820  can comprise one or more openings  830  extending through the sidewall to permit blood flow into the first shaft  820 . The openings  830  may allow a sufficient volume of blood to flow into the first shaft to compensate for the tapered distal end portion of the delivery catheter  890 . In some embodiments, the openings  830  are located at the distalmost 1-3 centimeters of the first shaft  820 . The positioning of the openings  830  can be based at least in part on the intended blood withdrawal location (e.g., left atrium, left ventricle, aorta, etc.). 
     The number and locations of openings through a sidewall of the first shaft may be based at least in part on the geometry of the first shaft and/or the intended positioning of the first elongated shaft within the patient&#39;s heart and/or vasculature. For example,  FIG. 9  depicts a distal end portion  920   b  of a first shaft  920  comprising a plurality of openings  930  around the circumference of the first shaft  920 . The first shaft  920  of  FIG. 9  comprises a greater number of openings  930  than the first shaft  820  of  FIG. 8  and may thereby be configured for increased blood flow through the first shaft  920 . The first shaft  920  may comprise any suitable number of openings. The openings  930  may be placed along a length of the first shaft  920  and/or about a circumference of the first shaft  920  to withdraw blood from a specific location within the patient&#39;s heart and/or vasculature. For example, if the distal end portion  920   b  of the first shaft  920  is intended to be placed in the left atrium via the inferior vena cava and right atrium (e.g., as depicted in  FIG. 1 ), the portions of the first shaft  920  positioned within the right atrium and/or inferior vena cava may include openings  930 . Such openings  930  allow more blood to be withdrawn through the first shaft  920 , the blood withdrawn from the right atrium and inferior vena cava is deoxygenated. The system may comprise an oxygenator to add oxygen to such deoxygenated blood prior to reintroducing the blood into the patient&#39;s arterial system. The openings  930  may be sufficiently small to prevent kinking of the first shaft  920  or inadvertent passage of a delivery catheter through an opening  930 . 
     To prevent blood leakage from the first shaft and/or air leakage into the first shaft, in some embodiments the proximal end portion of the first shaft comprises an adapter, a handle, and/or a housing to allow advancement, retraction, and/or torqueing of the first shaft. The proximal end portion of the first shaft may also comprise controls of any steerable region(s) of the first shaft. In some embodiments, the proximal end portion of the first shaft is configured to be attached to a rack along with a delivery catheter to stabilize the system components for precise delivery of an interventional element. 
       FIG. 10  is a cross-sectional view of a proximal end portion  1020   b  of a first elongated shaft  1020  of the present technology. The proximal end portion  1020   b  may also have the aforementioned handle and steering controls, not shown here. The first shaft  1020  comprises an outer surface  1022 , an inner surface  1024 , and a lumen  1026  defined by the inner surface. The proximal end portion  1020   b  of the first shaft  1020  may comprise an outflow channel  1032  disposed at an angle relative to a longitudinal axis of the first shaft  1020 . The outflow channel  1032  may be configured to be coupled to a pressure source and/or a second elongated shaft of the present technology. In some embodiments, the angle between the outflow channel  1032  and the longitudinal axis of the first shaft  1020  is between about 30 degrees and about 330 degrees. In some embodiments, the angle between the outflow channel  1032  and the longitudinal axis of the first shaft  1020  is about 90 degrees, for example to minimize the length of the first shaft  1020 . 
     The outflow channel  1032  may be configured to be coupled to tubing which is in turn coupled to the pressure source and/or the second shaft. In some embodiments, the outer surface  1022  of the outflow channel may be barbed, threaded, or otherwise configured to interlock with the pressure source, the tubing, and/or the second shaft. The outflow channel  1032  may be integrally formed with the first shaft  1020  (see  FIG. 10 ), detachably coupled to the first shaft  1020 , and/or rotatably coupled to the first shaft  1020 . If rotatably coupled, the connection of the outflow channel  1032  to the first shaft  1020  may include o-rings or other seals to prevent leakage of air or fluid. In some embodiments, the proximal end portion  1020   b  of the first shaft  1020  comprises a port (not pictured) configured to remove air and/or blood from the lumen  1026  of the first shaft  1020  and/or introduce saline, radiopaque contrast dye, anticoagulants, medications, etc. into the lumen  1026  of the first shaft  1020 . 
     As previously mentioned, a proximal end portion  1020   b  of the first shaft  1020  may be configured to receive a delivery catheter therethrough. To prevent blood leakage from the first shaft  1020  and/or the introduction of air into the blood stream, the proximal end portion  1020   b  of the first shaft  1020  may comprise a valve  1034  that receives and/or conforms to the delivery catheter  1090 . 
     A proximal end portion of the first elongated shaft of the present technology may comprise a hemostatic valve or seal  1034  to prevent blood from advancing proximally beyond the valve or seal. The valves and seals described herein may be formed of any suitable material including synthetic rubbers or thermoplastics. In some embodiments, a single valve or seal may provide sufficient leakage protection. However, in some embodiments a reinforced or adjustable valve or seal and/or multiple valves or seals may be advantageous for providing leakage protection while mechanical circulatory support is being performed and pressure is being generated within the first shaft. The multiple valves or seals might be oriented in different directions, so that one prevents egress of air or fluid, and another prevents ingress of air or fluid. Valves and seals such as those described herein may also be employed in a second elongated shaft of the present technology. 
     In some embodiments, for example as shown in  FIGS. 11A and 11B , the proximal end portion  1120   b  of the first shaft  1120  may comprise a valve  1134  having an annular portion  1134   a  and a plurality of flaps  1134   b . The annular portion  1134   a  of the valve  1134  may be received within a recess  1136  in the sidewall of the proximal end portion  1120   b  of the first shaft  1120 . The flaps  1134   b  may be separated by slits such that an individual flap is movable relative to the other flaps towards the center of the valve  1134 . Accordingly, the flaps  1134   b  may be configured to generally conform to a delivery catheter  1190  inserted through the valve  1134  and prevent blood or air passage through the valve  1134 . 
       FIG. 12  depicts a proximal end portion  1220   b  of a first elongated shaft  1220  in accordance with several aspects of the present technology. As shown in  FIG. 12 , in some embodiments, the proximal end portion  1220   b  comprises a duckbill-style valve  1234  having two or more flaps received within a recess  1236  in the sidewall of the proximal end portion  1220   b  of the first shaft  1220 . The tips of the flaps may be positioned in contact to prevent blood flow from the first shaft  1220  from progressing proximally beyond the valve  1234 . This valve may be advantageous for preventing blood leakage during mechanical circulatory support initiated after an interventional procedure has been completed and a delivery catheter has been removed from the first shaft. Additionally or alternatively, the tips of the flaps may conform to a delivery catheter positioned within the first shaft (as shown in  FIG. 10 ) to prevent blood leakage during mechanical circulatory support provided while the delivery catheter is positioned within the first shaft. The valve  1234  might also comprise a second valve oriented in the opposite direction. For example, the proximal end portion  1220   b  of the first shaft  1220  may comprise a second valve  1234  oriented in the opposite direction from the valve  1234  shown in  FIG. 10  to prevent air and/or fluid ingress into the first shaft  1220 . 
     In some embodiments, for example as shown in  FIG. 13 , a proximal end portion  1320   b  of a first shaft  1320  can comprise a valve  1334  configured to prevent blood leakage during mechanical circulatory support provided during an interventional procedure and/or while a delivery catheter  1390  is positioned within the first shaft  1320 . The valve  1334  depicted in  FIG. 13  comprises a generally continuous ring with a generally circular opening positioned at the center of the ring. The delivery catheter  1390  may be received through the opening in the valve  1334 . The valve  1334  may have a generally conical shape, as shown in  FIG. 13 . 
       FIG. 14  is a cross-sectional view of a proximal end portion  1420   b  of a first elongated shaft  1420  including an o-ring seal  1434  received within a recess  1436  within a sidewall of the first shaft  1420 . A delivery catheter  1490  may be received through the opening of the seal  1434  such that blood flow proximal of the seal  1434  is prevented while the delivery catheter  1490  is positioned within the first shaft  1420 . 
       FIG. 15  shows a cross-sectional view of a proximal end portion  1520   b  of a first shaft  1520  comprising a two-stage valve  1534  configured to prevent blood leakage and/or air inflow during mechanical circulatory support. This may be most advantageous when mechanical circulatory support is provided while an interventional procedure is being performed and a delivery catheter  1490  is positioned within the first shaft  1520 . As shown in  FIG. 15 , the two-stage valve  1534  may comprise an o-ring seal positioned distal of a duckbill-style valve. Any combination of suitable valves or seals, such those described elsewhere herein, may be positioned in series to form a two-stage valve. 
     A lumen of a proximal end portion of a first shaft may be completely closed when mechanical circulatory support is initiated after a delivery catheter has been removed from the first shaft. For example, as shown in  FIG. 16 , a proximal end portion  1620   b  of the first shaft  1600  may comprise an attachment portion  1638  configured to attach a cap  1640  to the first shaft  1600  and thereby close the lumen  1656  of the first shaft  1600 . The attachment portion  1638  may comprise threads, barbs, or any other suitable attachment mechanism. In some embodiments, a cylindrical member may be positioned within the lumen  1626  of the proximal end portion  1620   b  and/or inserted through the valve(s) after the delivery catheter has been removed to prevent air or fluid leakage through the valve(s). 
     According to some embodiments, a proximal end portion of a first elongated shaft of the present technology may be configured to be attached to a connector.  FIG. 17  depicts a proximal end portion  1720   b  of a first elongated shaft  1720  configured to attach to a connector in accordance with several embodiments of the present technology. The outer surface  1722  of the proximal end portion  1720   b  comprises threads  1740  configured to engage with female threads of a connector. The first shaft  1720  can comprise any suitable mechanism for attaching to a connector. For example, the proximal end portion  1820   b  depicted in  FIG. 18  comprises a lip  1842  configured to engage with a corresponding attachment portion of a connector. 
     III. Selected Coupler Embodiments 
     According to some embodiments, a system of the present technology may comprise a connector configured to attach a proximal end portion of a first shaft to a pressure source. The connector may comprise a tube and/or a coupler. In some embodiments, the tube is formed integrally with the coupler. The tube and coupler may be detachably coupled. In some embodiments, the first shaft is connected directly to the pressure source, to just a tube, or to just a coupler. The connector may be attached to the proximal end portion of the first shaft before, during, and/or after an interventional procedure (e.g., TAVR, TMVR, etc.). In some embodiments, the pressure source may be integral with the coupler. 
       FIGS. 19A and 19B  are cross-sectional views of a coupler  1950  in accordance with several embodiments of the present technology and a coupler  1950  attached to a proximal end portion  1920   b  of a first elongated shaft  1920  and a tube  1948 , respectively. As shown in  FIG. 19A , the coupler  1950  may comprise a shaft  1952  configured to be received within a lumen  1926  of the first shaft  1920  and/or to penetrate a valve and/or seal  1934  within the lumen  1926  of the first shaft  1920 . Accordingly, the shaft  1952  may have a radial dimension that decreases in a distal direction (i.e., distally tapers) to penetrate the seal  1934  and hold the seal  1934  in an open position. In some embodiments, the shaft  1952  has a constant diameter to maximize the diameter of the lumen  1953 . In some embodiments, the coupler  1950  may comprise a removable obturator configured to facilitate penetration seal  1934  of the first shaft by the coupler  1950  without damaging the seal  1934 . 
     A lumen  1953  extending through the shaft  1952  is configured to permit blood to flow proximally from the first shaft  1920  through the lumen  1953  of the shaft  1952  of the coupler  1950 . The coupler  1950  may comprise a one-way valve  1962  within the lumen  1953  of the shaft  1952  to prevent blood from flowing in the other direction through the lumen  1953  when mechanical circulatory support is not being supplied (i.e., no pressure is being generated in the lumen of the first shaft). In some embodiments, the coupler  1950  includes a port  1964  for withdrawing blood and/or air from the lumen  1953 . It may be advantageous to maximize the diameter of the lumen  1953  to maximize blood flow during mechanical circulatory support. The wall thickness of the shaft  1952  may be minimized to maximize the diameter of the lumen  1953 . The shaft  1952  may be formed of a polymer, metal, or another suitable material. However, forming the shaft  1952  of metal may facilitate minimizing the wall thickness of the shaft  1952 . 
     The coupler  1950  comprises an outflow channel  1956  extending proximally from the shaft  1952  and having a lumen  1957  extending through the outflow channel  1956 . The distal end portion of the lumen  1957  of the outflow channel  1956  is open to the lumen  1953  of the shaft  1952  and the proximal end portion of the lumen  1957  of the outflow channel  1956  is open to a lumen  1949  of the tube  1948  leading to the pressure source. An outer surface of the outflow channel  1956  may comprise a mechanism for attaching to the tube  1948 . For example, the outflow channel  1956  shown in  FIGS. 19A and 19B  comprises a hose barb. The mechanism for attaching to the tube  1948  can comprise threads, barbs, CPC fittings, or any other suitable tubing connection mechanisms. 
     The coupler  1950  may comprise an attachment portion  1954  configured to securely attach the coupler  1950  to a proximal end portion of a first shaft. For example, as shown in  FIGS. 19A and 19B , the attachment portion  1954  may comprise female threads  1958  configured to receive male threads of  1940  the proximal end portion  1920   b  of the first shaft  1920 . In some embodiments, the attachment portion  1954  comprises an elastomeric seal  1960  (e.g., an o-ring seal or flat seal) to improve the coupling between the coupler  1950  and the first shaft  1920 . The proximal end portion  1920   b  of the first shaft  1920  may not be designed with threads or other attachment features, in which case the coupler  1950  might comprise a specialized clamp designed to engage the housing or handle of proximal end portion  1920   b  of the first shaft and hold coupler  1950  against it, preventing air and fluid leakage and inadvertent detachment for the period of mechanical support. The clamp might be designed to engage specific features of the proximal end portion  1920   b  of the first shaft  1920  to hold it securely while also being ergonomically acceptable to be in close proximity to the patient for the period of mechanical support. For example, the clamp might have rounded edges and minimal size and weight. 
       FIG. 20  is a cross-sectional view of a coupler  2050  comprising a shaft  2052 , an attachment portion  2054 , and an outflow channel  2056  in accordance with several aspects of the present technology. A lumen  2053  extends through the shaft  2052 . The distal end portion of the lumen  2053  may be open to be configured to connect to a proximal end portion of a first elongated shaft. The proximal end portion of the lumen  2053  may be open to receive a delivery catheter through the lumen  2053 . The coupler  2050  may comprise a hemostatic valve  2062  positioned within the lumen  2053  as shown in  FIG. 20  to prevent blood leakage and/or air inflow. The hemostatic valve  2062  may comprise seals, flaps, plugs, caps, or other suitable features to prevent fluid or air passage through the hemostatic valve  2062 . 
     In some embodiments, for example as shown in  FIG. 20 , the coupler  2050  may comprise an outflow channel  2056  positioned at an angle relative to a longitudinal axis of the coupler  2050 . The distal end portion of the lumen  2057  of the outflow channel  2056  can be open to the lumen  2053  of the shaft and the proximal end portion of the lumen  2047  of the outflow channel  2056  can be open to a lumen of tubing leading to the pressure source and/or a second elongated shaft to fluidly connect the first elongated shaft with the other components of the system. The outflow channel  2056  may also be directly connected to the pressure source, and the pressure source may be a part of the coupler  2050 . The outer surface of the outflow channel  2056  may comprise a hose barb or other suitable tubing connection mechanism as previously described. In some embodiments, for example as shown in  FIG. 20 , the outflow channel  2056  can be integrally formed with the shaft  2052  and/or attachment portion  2054  of the coupler  2050 . The outflow channel  2056  may be detachably coupled to the shaft  2052  and/or attachment portion  2054 . In some embodiments, the outflow channel  2056  rotates relative to the shaft  2052  and/or attachment portion  2054 . 
     The attachment portion  2054  of the coupler  2050  is configured to securely and/or removably attach a first elongated shaft to the coupler  2050 . As shown in  FIG. 20  and previously described regarding  FIGS. 19A and 19B , the attachment portion  2054  may comprise threads  2058  and/or an elastomeric ring  2060 .  FIGS. 21-23  depict various embodiments of attachment portions in accordance with the present technology. For example, a coupler may comprise an attachment portion  2154  with threads (see  FIG. 21 ), an attachment portion  2254  comprising a snap-fit mechanism (see  FIG. 22 ), an attachment portion  2354  comprising a set screw mechanism (see  FIG. 23 ), or a clamp. In some embodiments, an attachment portion of the present technology does not comprise an elastomeric ring. 
     A connector in accordance with the present technology may comprise a coupler (as previously described) and/or a tube. In some embodiments, a coupler is attached to a proximal end portion of an elongated shaft (i.e., first or second elongated shaft) and a distal end portion of the tube is attached to an outflow channel of the coupler. In some embodiments, the distal end portion of the tube is directly attached to the proximal end portion of an elongated shaft. A proximal end portion of the tube may be attached to another tube, a pressure source, or another elongated shaft. For example, in some embodiments, a distal end portion of the tube attaches to an outflow channel of a coupler and a proximal end portion of the tube attaches to a pressure source. In some embodiments, the pressure source is directly coupled to or a part of the coupler. 
     The tube may comprise medical grade tubing formed of a suitable material such as polyvinyl chloride (PVC). The tube may have an inner diameter between about 0.250 inches to 0.5 inches. In some embodiments, the inner surface of the tube is coated with an anti-coagulant such as heparin or another suitable coating to minimize clotting, blood damage, and/or inflammatory response. 
     The tube can connect the coupler to the pressure source and the pressure source to the second elongated shaft. In some embodiments, for example when the pressure source comprises a roller pump, the tube may be inserted into the pressure source. The pressure source can comprise a centrifugal pump, a peristaltic pump, a pulsatile pump, roller pump, or any other pump suitable for moving blood. In some embodiments. the pump comprises an oxygenator to introduce oxygen into the blood before the blood is advanced out of the distal end region of the second shaft into a patient&#39;s artery. According to some embodiments, the pressure source is directly connected to or integral with the first elongated shaft, the coupler, the tube, and/or the second elongated shaft. 
     IV. Selected Second Shaft Embodiments 
     According to some embodiments, a system of the present technology comprises a second elongated shaft configured to be positioned within an arterial vessel of the patient such that a distal end portion of the second shaft is positioned downstream of a distal end portion of a first shaft. In some embodiments, the second shaft is a return cannula. The second shaft can comprise an outer diameter between about 12 French and about 24 French, an inner diameter between about 10 French and about 22 French, and/or a length between about 8 cm and about 50 cm. The outer diameter, inner diameter, and/or length of the second shaft may be any suitable value based on the anatomy of the patient to be treated. The second shaft may be formed of a material such as a thermoplastic elastomer (e.g., Pebax®), polyurethane, or another material suitable for forming catheters or return cannulas. The second shaft may comprise a material such as, but not limited to, wire, a coil, or a braid, within a sidewall of the second shaft for reinforcement, and/or kink-resistance. The second shaft may comprise one or more steerable regions, as described elsewhere herein. 
     The second elongated shaft is configured to deliver blood to a patient&#39;s arterial circulatory system. Accordingly, the second elongated shaft comprises one or more openings for release of blood from the second shaft.  FIGS. 24-27  illustrate various embodiments of such openings. A distal end portion  2470   a  of the second elongated shaft may comprise an open lumen  2474  having a generally blunt distal end as shown in  FIG. 24 . In some embodiments, the distal end portion  2570   a  comprises an open lumen  2574  but the distal end has a beveled shape, for example as shown in  FIG. 25 . According to some embodiments, the distal end portion  2670   a  of the second shaft comprises a closed and/or atraumatic distal terminus and a side hole  2676  extending through a sidewall of the second shaft (see  FIG. 26 ). The distal end portion  2770   a  may comprise a plurality of side holes  2776  as shown in  FIG. 27 . 
     V. Conclusion 
     Although many of the embodiments are described above with respect to systems and methods for mechanical circulatory support related to transcatheter heart valve repair or replacement, the present technology is applicable to other applications and/or other approaches, such as any transcatheter heart therapy. Moreover, other embodiments in addition to those described herein are within the scope of the technology. Additionally, several other embodiments of the technology can have different configurations, components, or procedures than those described herein. A person of ordinary skill in the art, therefore, will accordingly understand that the technology can have other embodiments with additional elements, or the technology can have other embodiments without several of the features shown and described above with reference to  FIGS. 1-27 . 
     The descriptions of embodiments of the technology are not intended to be exhaustive or to limit the technology to the precise form disclosed above. Where the context permits, singular or plural terms may also include the plural or singular term, respectively. Although specific embodiments of, and examples for, the technology are described above for illustrative purposes, various equivalent modifications are possible within the scope of the technology, as those skilled in the relevant art will recognize. For example, while steps are presented in a given order, alternative embodiments may perform steps in a different order. The various embodiments described herein may also be combined to provide further embodiments. 
     As used herein, the terms “generally,” “substantially,” “about,” and similar terms are used as terms of approximation and not as terms of degree, and are intended to account for the inherent variations in measured or calculated values that would be recognized by those of ordinary skill in the art. 
     Moreover, unless the word “or” is expressly limited to mean only a single item exclusive from the other items in reference to a list of two or more items, then the use of “or” in such a list is to be interpreted as including (a) any single item in the list, (b) all of the items in the list, or (c) any combination of the items in the list. Additionally, the term “comprising” is used throughout to mean including at least the recited feature(s) such that any greater number of the same feature and/or additional types of other features are not precluded. It will also be appreciated that specific embodiments have been described herein for purposes of illustration, but that various modifications may be made without deviating from the technology. Further, while advantages associated with certain embodiments of the technology have been described in the context of those embodiments, other embodiments may also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages to fall within the scope of the technology. Accordingly, the disclosure and associated technology can encompass other embodiments not expressly shown or described herein. 
     VI. References 
     
         
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