Pilot Study Results Disappointing for Initial Treatment of Venous Stenosis

One of the most frequent complications involving dialysis access is recurrent venous stenosis. Cryoplasty, or angioplasty with a balloon that freezes the tissues, has been used in peripheral arteries.

The results of a preliminary study on treatment of restenosis in dialysis access with cryoplasty were promising, which prompted this pilot study for using cryoplasty as the initial balloon treatment for dialysis access stenosis.

The objective of the pilot study was to evaluate the safety and feasibility of cryoplasty as the initial balloon treatment for dialysis access venous stenoses.

The results of this study show that cryoplasty on dialysis access is safe; however, they do not suggest any patency benefit compared with conventional angioplasty.

Design/Participants
20 patients enrolled in a non-randomized prospective study.

Methods
All patients had at least 50% stenosis in an open dialysis access on angiography. Only 1 lesion was treated with cryoplasty in each patient. Mean stenosis was 62%, with a mean length of 2.5 cm. All lesions were treated with the PolarCath peripheral balloon system, sometimes used with conventional angiography to achieve an acceptable anatomic result (<30% residual stenosis).

Results
The anatomic success rate of cryoplasty alone was 35%. In total, 80% of patients underwent supplemental angioplasty with a high-pressure balloon. Anatomic and procedure success was achieved in 80% of patients. All patients reported pain during cryoplasty at the angioplasty site with a severity of 7 to 10 on a scale of 1 to 10.

The primary circuit patency (meaning the patency of the entire graft system) was 82% at 3 months and 19% at 6 months. Primary (index) lesion patency rates were 88% at 3 months and 25% at 6 months. The only complication related to cryoplasty itself was transient spasm. Four other procedure-related complications occurred.

Conclusions/Reviewer’s Comments
The goal of cryoplasty is to cause apoptosis in endothelial cells, not cell necrosis, which prevents an inflammatory response and decreases incidence of neointimal hyperplasia and subsequent luminal narrowing.

These results show that cryoplasty on dialysis access is safe, with minimal complications related to the use of the device itself.

However, they do not suggest any patency benefit compared with conventional angioplasty, and the primary patency results are lower than in most studies like this.

The 6-month circuit patency of 19% is similar to other trials of this kind.

The authors believe that the freezing of a superficial vein that is close to the skin might be the cause of the severe pain.

Limitations of the study included the inability to create a pressure gradient of >8 atm(most stenoses needed ≥15 atm to dilate) and the inability to use a balloon >8 mm.

Currently, these results do not support further research with the currently available materials. The authors still believe that better outcomes with decreased intimal hyperplasia may be achieved in dialysis accesses if larger and higher pressure cryoplasty balloons are made available.

Author: Sharon Gonzales, MD

Reference:
Gray RJ, Varma JD, et al. Pilot Study of Cryoplasty With Use of PolarCath Peripheral Balloon Catheter System for Dialysis Access.  J Vasc Interv Radiol; 2008; (October): 1460-1466.