Catheters with enhanced flexibility and associated devices, systems, and methods

#The present technology is related to catheters. In particular, at least some embodiments are related to neuromodulation catheters having one or more cuts and/or other features that enhance flexibility, such as to facilitate intravascular delivery via transradial or other suitable percutaneous transluminal approaches.

#The sympathetic nervous system (SNS) is a primarily involuntary bodily control system typically associated with stress responses. Fibers of the SNS extend through tissue in almost every organ system of the human body and can affect characteristics such as pupil diameter, gut motility, and urinary output. Such regulation can have adaptive utility in maintaining homeostasis or in preparing the body for rapid response to environmental factors. Chronic activation of the SNS, however, is a common maladaptive response that can drive the progression of many disease states. Excessive activation of the renal SNS in particular has been identified experimentally and in humans as a likely contributor to the complex pathophysiology of hypertension, states of volume overload (e.g., heart failure), and progressive renal disease.

#Sympathetic nerves of the kidneys terminate in the renal blood vessels, the juxtaglomerular apparatus, and the renal tubules, among other structures. Stimulation of the renal sympathetic nerves can cause, for example, increased renin release, increased sodium reabsorption, and reduced renal blood flow. These and other neural-regulated components of renal function are considerably stimulated in disease states characterized by heightened sympathetic tone. For example, reduced renal blood flow and glomerular filtration rate as a result of renal sympathetic efferent stimulation is likely a cornerstone of the loss of renal function in cardio-renal syndrome, (i.e., renal dysfunction as a progressive complication of chronic heart failure). Pharmacologic strategies to thwart the consequences of renal sympathetic stimulation include centrally-acting sympatholytic drugs, beta blockers (e.g., to reduce renin release), angiotensin-converting enzyme inhibitors and receptor blockers (e.g., to block the action of angiotensin II and aldosterone activation consequent to renin release), and diuretics (e.g., to counter the renal sympathetic mediated sodium and water retention). These pharmacologic strategies, however, have significant limitations including limited efficacy, compliance issues, side effects, and others.

#Many aspects of the present technology 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 technology. For ease of reference, throughout this disclosure identical reference numbers may be used to identify identical or at least generally similar or analogous components or features.

#FIG. 1 is a partially schematic perspective view illustrating a therapeutic system including a neuromodulation catheter configured in accordance with an embodiment of the present technology.

#FIG. 2 is an enlarged partially cut-away side view of a shaft of the neuromodulation catheter shown in FIG. 1 illustrating a hypotube of the shaft and a cut extending along a helical path having varying pitch along the length of the shaft.

#Neuromodulation catheters configured in accordance with at least some embodiments of the present technology include elongate shafts having one or more cuts and/or other features that enhance flexibility without unduly compromising desirable axial stiffness (e.g., pushability or other responsiveness to axial force) and/or desirable torsional stiffness (e.g., torqueability or other responsiveness to torsional force). For example, a neuromodulation catheter configured in accordance with a particular embodiment of the present technology is sufficiently flexible in some respects to facilitate deployment via a relatively long and/or tortuous intravascular path without excessive resistance, while still being sufficiently stiff in other respects so as to allow intravascular navigation or other suitable manipulation via an extracorporeal handle. Desirable axial stiffness can include, for example, the capability of the shaft to be advanced or withdrawn along the length of an intravascular path without significantly buckling or elongating. Desirable torsional stiffness can include, for example, the capability of the shaft to distally transfer rotational motion (e.g., from a handle at a proximal end portion of the shaft to a neuromodulation element operably connected to the shaft via a distal end portion of the shaft) with close correspondence (e.g., at least about one-to-one correspondence). In addition or alternatively, desirable torsional stiffness can include the capability of the shaft to distally transfer rotational motion without causing whipping and/or diametrical deformation of the shaft. Desirable axial and torsional stiffness together can facilitate predictable and controlled transmission of axial and torsional force from the proximal end portion of the shaft toward the distal end portion of the shaft while a neuromodulation catheter is in use.

#Metal hypodermic (needle) tubing, aka hypotubing, is commonly incorporated into small-diameter shafts of medical catheters to utilize the wire-like physical properties of such material along with the useable lumen extending therethrough. However, solid-walled metal tubing also has known limitations regarding flexibility and kink resistance, and various designs have utilized slits, slots or other openings in the tubing wall to achieve improvements in flexibility. Such modifications to the wall structure have always brought about compromises in physical properties in tension, compression, and torsion. Thus, in at least some conventional neuromodulation catheters, imparting flexibility can require unduly sacrificing axial stiffness and/or torsional stiffness. For example, creating a continuous helical cut in a relatively rigid hypotube of a shaft tends to increase the flexibility of the shaft, but, in some instances, the resulting coils between turns of the cut may also tend to separate to an undesirable degree in response to tension on the shaft and/or torsion on the shaft in at least one circumferential direction. In some cases, this separation can cause a permanent or temporary change in the length of the shaft (e.g., undesirable elongation of the shaft), a permanent or temporary diametrical deformation of the shaft (e.g., undesirable flattening of a cross-section of the shaft), and/or torsional whipping. Such shaft behavior can interfere with intravascular navigation and/or have other undesirable effects on neuromodulation procedures.

#Due, at least in part, to enhanced flexibility in combination with desirable axial and torsional stiffness, neuromodulation catheters configured in accordance with at least some embodiments of the present technology can be well-suited for intravascular delivery to treatment locations (e.g., treatment locations within or otherwise proximate to a renal artery of a human patient) via transradial approaches (e.g., approaches that include the radial artery, the subclavian artery, and the descending aorta). Transradial approaches are typically more tortuous and longer than femoral approaches and at least some other commonly used approaches. Transradial approaches can be desirable for accessing certain anatomy, but other types of approaches (e.g., femoral approaches) may be desirable in particularly tortuous anatomy or vessels having relatively small diameters. In some instances, however, use of transradial approaches can provide certain advantages over use of femoral approaches. In some cases, for example, use of transradial approaches can be associated with increased patient comfort, decreased bleeding, and/or faster sealing of the percutaneous puncture site relative to use of femoral approaches.