Ultrahigh-Pressure PTA for Hemodialysis
These new applications using the Conquest PTA Balloon Dilatation Catheter can preserve vascular access in hemodialysis patients.
The maintenance of an adequately functioning vascular access is one of the most significant clinical challenges of long-term hemodialysis. As more individuals are diagnosed with end-stage renal disease and become chronically dependent on hemodialysis, efforts to preserve vascular access become even more critical. By extending vascular-access longevity, morbidity and mortality in the hemodialysis patient population can be decreased. Preservation of vascular-access patency decreases the number of missed hemodialysis treatments, as well as the rate of hospitalization associated with vascular-access complications and interventions.1
The polytetrafluoroethylene (PTFE) graft is the most widely used means of hemodialysis vascular access in the US, yet synthetic dialysis grafts are susceptible to progressive development of intimal hyperplastic stenoses. Indeed, stenosis leading to thrombosis is the most common cause of graft failure and may occur at the graft-vein anastomosis or anywhere along the native venous outflow tract.2-5 Stenoses also occur within the graft itself (midgraft), and these cases are usually attributed to pseudointimal hyperplasia and fibroblastic ingrowth through needle puncture tracts.3,6
In native arteriovenous (AV) fistulae, a similar pathologic process of intimal hyperplastic growth and thickening of the vein wall may occur just distal to the site of the arterial needle puncture.3 In patients with previous long-term catheter insertion into the subclavian vein, central vein stenosis is a common occurrence and often leads to vascular-access failure. Thus, patients who rely on a hemodialysis vascular access as their lifeline are vulnerable to the development of stenoses, regardless of the type of vascular access they use.
Hemodynamically significant stenoses should be treated to maintain patency in dialysis grafts and primary AV fistulae. The National Kidney Foundation Kidney Disease Outcomes Quality Initiative (NKF-DOQI) states that the rate of thrombosis and graft loss can be reduced, and the average use-life of a vascular access can be prolonged, if interventions are performed for stenoses.7 For stenoses found to be >50% of the lumen diameter and associated with hemodynamic abnormalities, the recommended treatment options are percutaneous transluminal angioplasty (PTA) or surgical revision.7 In recent years, there has been an increasing trend for using PTA to treat stenosis because of the several advantages of PTA over surgical approaches.2,3,8 The expected outcome for repairing a graft by surgical methods is only 50% unassisted patency at 1 year. Even when this result is achieved, patency is obtained at the expense of using additional native vein—a precious resource in the end-stage renal disease patient population—whereas treatment of stenoses by PTA allows for preservation of the native veins.3 With endovascular techniques, stenotic lesions can be treated in situ, while maintaining patency and functionality of the existing graft. PTA also can be performed quickly—often on the same day that the graft-related problem is discovered. Immediate repair of the stenosis can eliminate the need for temporary hemodialysis catheters and decrease the number of missed hemodialysis treatments.1
Despite the advantages of using endovascular techniques to treat stenoses in dialysis grafts and AV fistulae, standard PTA approaches sometimes result in limited success rates. The technical, or immediate, success rate of PTA in the repair of intimal hyperplastic can be as low as 80%,3 which suggests that a subset of stenoses are not able to be resolved successfully by conventional PTA. It has been reported that residual stenosis can occur due to an inability to fully dilate the stenotic lesion,9 and the occurrence of acute restenosis from elastic recoil represents another potential obstacle to maintaining patency.9 Even in the cases of failing grafts or fistulae successfully repaired by standard PTA, the primary patency rate at 6 months is only 50% to 60%,2,4,7,10 and repeated angioplasty procedures are often necessary to maintain function and preserve patency. Finally, some venous stenoses are simply resistant to routine angioplasty and are characterized by balloon rupture at pressures as high as 22 atm to 28 atm.11 Studies have reported venous stenoses so rigid that they required dilatation at pressures >30 atm—pressures that are not compatible with conventional angioplasty balloons.12 An alternate approach to the treatment of resistant stenoses involves the use of ultrahigh-pressure, noncompliant PTA balloons.
Introducing and Inflating the PTA Balloon Catheter in a Dialysis Graft or Fistula
At our facility, we have experienced favorable results using the Conquest PTA Balloon Dilatation Catheter (Bard Peripheral Vascular, Tempe, AZ) (Figure 1). Introducing the device has typically been performed on an outpatient basis using the standard Seldinger technique. Before using the balloon catheter in a dialysis graft (Figures 2 and 3) or fistula (Figure 4), a diagnostic fistulogram was obtained to assess the stenotic lesion. The optimal location for access into the graft or fistula was determined by physical examination, and the appropriately sized balloon was selected. Although the manufacturer recommends that the expanded diameter of the balloon not exceed that of the vessel just proximal to the stenosis, the balloon size selected for the cases reported herein was 1 mm to 2 mm larger than the diameter of the graft or the normal vessel.
A local anesthetic was administered at the puncture site before initiating PTA. The balloon catheter was prepared according to the manufacturer's instructions. Under fluoroscopic observation, a guidewire was passed into the graft or fistula, followed by catheter placement over the guidewire to confirm the stenotic lesion. The balloon was then passed over the guidewire up to the site of the stenosis. Once the balloon was visualized within the lesion and proper positioning was confirmed, a syringe (recommended capacity of 10 mL or larger) or inflator was used to inflate the balloon. Inflation pressure was monitored during the dilatation procedure using a pressure gauge. Although the manufacturer recommends not exceeding the maximum rated burst pressure (30 atm for the smallest diameter balloons), pressure >30 atm was used if necessary in some cases. Once complete inflation was achieved and the waist of the balloon had disappeared, the inflated balloon was typically left inflated for 2 minutes. A syringe was used to deflate the balloon by applying suction to the balloon lumen, and a final fistulogram was obtained to confirm repair of the stenosis. The patients were then immediately returned to the dialysis clinic or discharged.
Using the PTA Balloon Catheter in Conjunction With a Self-Expanding Stent
Based on the case history of the patient and the degree of severity of the stenosis, a self-expanding nitinol stent was used along with the balloon catheter in a subset of cases. This combination procedure may fully restore flow and extend the longevity of a patient's failing vascular access (usually by about 6 months). In this application, the stent was first introduced into the stenosis by standard methods. Once the stent was positioned, a balloon catheter was inflated inside the stent to 33 atm to fully open and restore flow (Figure 4). In no case was the balloon diameter greater than the stent diameter. Although inflation of the balloon using ultrahigh pressure may rupture the stenotic vessel, the stent prevented extravasation and allowed blood to follow its normal circuit.
In our facility, the Conquest Balloon Catheter has been successfully used to treat severe cases of stenosis in more than 100 patients. In one quarter of these cases, high pressure (up to 30 atm) was used; in 15 cases, we attained pressures as high as 37 atm without rupturing the balloon. Although the manufacturer recommends that inflation of the balloon not exceed the rated burst pressure of 30 atm, we have found that the balloon is able to withstand even higher pressure. We report that stenoses normally resistant to treatment by conventional PTA can be repaired successfully by means of a noninvasive endovascular procedure.
Perhaps the most important application of this balloon catheter is that it allows clinicians to maintain and extend the longevity of vascular accesses in their patients by endovascular, rather than surgical, approaches. Some venous stenoses are resistant to standard PTA—characterized by balloon rupture at pressures of 22 atm to 28 atm—and then require further intervention by open surgical revision or aggressive interventional techniques. Yet, for hemodialysis patients who rely on long-term vascular access as their lifeline, native veins are a precious resource for future vascular access preservation; surgical revision of a failing access requires the sacrifice of native veins.
Because there is increasing impetus to use PTA approaches for the repair of stenoses in dialysis grafts and fistulae, clinicians are finding that the majority of PTA balloons currently available are not reliable at pressures as high as 22 atm to 28 atm or greater. Ultrahigh-pressure PTA with a noncompliant balloon catheter is a safe and effective alternative to surgical treatments for resistant venous stenoses in hemodialysis access circuits. Moreover, the availability of such a tool eliminates the need for clinicians to rely on an expanded inventory of different types of angioplasty balloons for endovascular procedures. For more routine stenotic lesions, as well as rigid stenoses that are resistant to pressures in the higher range, the Conquest Balloon is an ideal tool to help preserve and extend vascular access in hemodialysis patients. n
John R. Ross, MD, is Chief of Surgery, Bamberg County Hospital, Bamberg, South Carolina. He is a consultant for Bard Peripheral Vascular. Dr. Ross may be reached at (803) 245-4435; JRRsurgery@aol.com.
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