Catheter And Treatment Methods For Lower Leg Ischemia

Abstract

A method of treating lower leg ischemia includes advancing a wire guide upstream through a vascular access sheath extending into an artery, and increasing a downstream flow of blood at least in part by dilating a constriction in the artery with a treatment mechanism guided into the constriction via the wire guide. The method further includes withdrawing a catheter which is coupled with the treatment mechanism from the patient at the percutaneous entry point via sliding the catheter downstream through the vascular access sheath. A low profile balloon may be used as the treatment mechanism, and is advanced through the artery while the vascular access sheath protects the artery from irritation such that spasm of the artery is less likely to occur. Reduced risk of spasm advantageously enables retrograde access to chronic total occlusions such that multiple entry points into a patient's body are not necessary.

1 . A method of treating lower leg ischemia in a patient comprising the steps of:
 advancing a wire guide in an upstream direction through a vascular access sheath extending into an artery of the patient at a percutaneous entry point in the lower leg;   guiding a treatment mechanism into a constriction in the artery via sliding a catheter coupled with the treatment mechanism over the wire guide from the percutaneous entry point;   increasing a flow of blood in a downstream direction through the artery at least in part by dilating the constriction with the treatment mechanism; and   withdrawing the catheter from the patient at the percutaneous entry point via sliding the catheter in the downstream direction through the vascular access sheath.   
     
     
         2 . The method of  claim 1  further comprising a step of crossing the constriction at least in part by pushing a tip of the wire guide through material occluding the artery at a location upstream of the vascular access sheath. 
     
     
         3 . The method of  claim 2  wherein the step of crossing further includes puncturing a fibrous cap of material located at a downstream end of the constriction while maintaining the tip of the wire guide within the true lumen of the artery. 
     
     
         4 . The method of  claim 3  further comprising a step of limiting buckling of the wire guide in response to a resistance of the fibrous cap of material during the crossing step at least in part via a microcatheter positioned to provide a barrier between the wire guide and the vascular access sheath. 
     
     
         5 . The method of  claim 2  wherein the treatment mechanism includes a balloon, and the step of increasing a flow of blood further includes dilating the constriction by inflating the balloon. 
     
     
         6 . The method of  claim 1  further comprising a step of injecting a vasodilator into the artery through the vascular access sheath. 
     
     
         7 . The method of  claim 6  wherein the step of injecting occurs subsequent to the withdrawing step. 
     
     
         8 . The method of  claim 1  further comprising a step of establishing the percutaneous entry point in the foot or ankle of the patient. 
     
     
         9 . The method of  claim 6  wherein the step of establishing further includes establishing the percutaneous entry point into the pedal artery. 
     
     
         10 . A catheter for treating lower leg ischemia in a patient comprising:
 a compound catheter body having a proximal body end and a distal body end, the compound catheter body further having an outer tubular body piece defining a longitudinal axis, and a coaxial inner tubular body piece, the outer and inner tubular body pieces together defining an inflation lumen extending axially between the proximal and distal body ends;   a balloon coupled with the compound catheter body, the balloon having a proximal neck attached to the outer tubular body piece, a distal neck attached to the inner tubular body piece, and the balloon defining a cavity in fluid communication with the inflation lumen;   the outer tubular body piece further defining an inlet port to the inflation lumen for connecting with a supply of inflation fluid, and the inner tubular body piece further defining a wire guide lumen opening at each of the proximal and distal body ends such that the catheter may be slid over a wire guide extending through the compound catheter body;   wherein the balloon is in a rest configuration and defines a first outer diameter dimension which is equal to about 0.7 millimeters or less, such that the catheter may be advanced into or withdrawn from the patient through a vascular access sheath extending into an artery at a percutaneous entry point in the patient's lower leg, and wherein the balloon is inflatable via the inflation fluid to an expanded configuration at which the balloon defines a second outer diameter dimension which is equal to about 1.2 mm or greater, for dilating a constriction in the artery.   
     
     
         11 . The catheter of  claim 10  wherein the first outer diameter dimension is equal to about 0.64 millimeters or less, and the second outer diameter dimension is equal to about 1.28 millimeters or greater. 
     
     
         12 . The catheter of  claim 11  wherein the balloon includes three longitudinal folds, and the second outer diameter dimension is equal to between about 1.30 millimeters and about 1.70 millimeters. 
     
     
         13 . The catheter of  claim 12  wherein the balloon further includes a double wall balloon having an outer surface, and an inner surface defining the cavity, and the balloon further having a wall thickness from the inner surface to the outer surface which is between about 0.02 millimeters and about 0.03 millimeters, such that the balloon defines a burst pressure greater than about 25 atmospheres. 
     
     
         14 . The catheter of  claim 10  wherein each of the outer tubular body piece and the inner tubular body piece is formed of a polyimide base material and a PEEK coating. 
     
     
         15 . The catheter of  claim 14  wherein each of the outer and inner tubular body pieces includes an outer surface and an inner surface, and defines a wall thickness from the corresponding outer surface to the corresponding inner surface which is between about 0.03 millimeters and about 0.06 millimeters. 
     
     
         16 . The catheter of  claim 15  wherein the wall thickness is between about 0.046 millimeters and about 0.051 millimeters. 
     
     
         17 . The catheter of  claim 10  further comprising a side arm having a first end which includes a fitting, a second end attached to the outer tubular body piece, and defining an inflation fluid conduit extending from the fitting to the second end, and the inflation fluid conduit fluidly connecting with the inlet port at the second end. 
     
     
         18 . A method of treating lower leg ischemia via retrograde access through a lower leg artery in a patient comprising the steps of:
 sliding a vascular access sheath over a first wire guide extending into the artery at a percutaneous entry point in the patient's lower leg, the vascular access sheath having an outer diameter dimension less than about 2 mm and an inner diameter dimension greater than about 1 mm;   advancing a second wire guide through the vascular access sheath from the percutaneous entry point such that a tip of the second wire guide crosses a constriction in the artery located upstream of the vascular access sheath;   guiding a catheter into the constriction in the artery via sliding the catheter over the second wire guide from the percutaneous entry point, the catheter having an outer diameter dimension less than about 0.7 mm;   increasing a flow of blood in a downstream direction through the artery at least in part by dilating the constriction with a treatment mechanism of the catheter; and   withdrawing the catheter from the patient at the percutaneous entry point, including sliding the catheter through the vascular access sheath such that the artery is protected from irritation.   
     
     
         19 . The method of  claim 18  wherein the step of sliding the vascular access sheath further includes sliding an assembly of the vascular access sheath and a stiffening dilator over the first wire guide at a percutaneous entry point into the pedal artery. 
     
     
         20 . The method of  claim 19  wherein the step of increasing a flow of blood further includes increasing the flow of blood via dilating the constriction with a balloon comprising the treatment mechanism.