Cutting balloon angioplasty versus conventional balloon angioplasty in hemodialysis access stenoses: Multicenter prospective randomized comparison of primary patency rates.

Cutting balloon angioplasty versus conventional  balloon angioplasty in hemodialysis access stenoses: Multicenter prospective randomized  comparison  of primary patency rates.

Ahmed Kanud Gabra, MD; Hossam M  SaJeha, MD; Mohammed M  Tawjika, MD; HeshamAbouellaifb, lv!D; Tarek H Elkamashc, MD

a) Vascular Surgery Department, Ain Shams University b) Nephrology Department, Ain Shams University

c) Radiodiagnosis Department, Suez Canal University

Purpose:  To compare primary patency rates of cutting balloon percutaneous transluminal angioplasty and conventional balloon percutaneous transluminal angioplasty in the treatment of different types of hemodialysis access stenosis.

Patients  and  methods:   58  patients  with  different  types  of hemodialysis  access  stenosis in  whom  PTA  was indicated   were prospectively,  randomized  to have  either  conventional balloon percutaneous transluminal  angioplasty or cutting balloon percutaneous transluminal angioplasty   The  study  was  performed  at  3 medical  centers  in  Saudi  Arabia  {Al-Moosa Specialized  hospital  Al-Ahsaa,  Tabuk University,  & Saudi  German  Hospital  Riyadh).  The primary patency rates of conventional PTA group & cutting balloon PTA group were compared The patients were followed up for 15 months. Primary patency rates  for lesions were calculated with the Kaplan-Meier method according to the type of stenosis.compared  the two groups

by using the log-rank test to determine statistical significance.

Results:  In the cutting PTA group, 26 patients with 29 stenoses achieved clinical success. In the conventional PTA group, 25 patients with 30 stenoses achieved clinical success. In patients with graft-to vein anastomotic  stenosis, the primary patency rate was significantly higher for cutting PTA than for conventional PTA (P = .037).In patients with autogenous venous stenosis, intragraft  stenosis and arterial anastomotic  stenosis, no significant difference in the primary patency rate was noted between groups (P = .360, .371 & .921 respectively).

Conclusion: Primary patency rates are significantly higher for cutting PTA in the treatment of graft-to-vein  anastomotic  stenosis, however, no significant differences in primary patency rates  exist  between  these  PTAs in  the  treatment  of autogenous  venous stenosis, intragraft stenosis, or arterial anastomotic stenosis.

Introduction:

Autogenous    arteriovenous    fistulas (AVF) and prosthetic arteriovenous  grafts (AVG) are necessary for chronic end-stage renal failure patients on hemodialysis. Hemodialysis  accesses  are  prone  to  failure due to thrombosis, usually concomitant  with stenosis   over  the  anastomosis   or  outflow vein. Access thrombosis frequently requires semi-emergent salvage intervention. Patients eventually   may   require   multiple   salvage

procedures to restore functionality or creation of  a  new  access.  The  Dialysis  Outcomes Quality  Initiative guidelines  of the National Kidney Foundation recommend that balloon percutaneous       transluminal       angioplasty (PTA)  be  performed  to  treat  hemodialysis access stenosis.  With  use of  PTA, it is not difficult  to  achieve  the  reasonable  patency goals     described     in   these     guidelines.l-5

Furthermore, secondary patency can typically be maintained with repeated PTA.2 However,

since patients undergoing long-term dialysis require hemodialysis  access for long periods of  time,  improvement  in  primary  patency rates would reduce the number of PTAs performed.  Thus, the  purpose  of our  study was  to  compare  primary  patency  rates  of cutting balloon PTA and conventional balloon PTA in the treatment of different types of hemodialysis access stenosis.

Patients and methods:

Study Design: From November 2011 to October 2013, 58 patients with different types ofhemodialysis access stenosis in whom PTA was indicated were prospectively, randomized (using an internet randomization  service6) to have either conventional balloon percutaneous transluminal angioplasty (conventional PTA) or cutting balloon percutaneous transluminal angioplasty  (cutting  PTA).  The primary patency rates of conventional balloon PTA group & cutting balloon  PTA group were compared. In the present study, primary subjects were those with stenoses in whom clinical  success  was achieved  by using balloon  angioplasty  alone  without  stenting. The study was performed at 3 medical centers in  Saudi Arabia  (Al-Moosa  Specialized hospital Al-Ahsaa, Tabuk University, & Saudi German hospital Riyadh).   The vascular surgeon evaluated the indications for PTA; performed PTA, including conventional PTA and cutting PTA; measured vessel diameters; and monitored each patient's clinical course. Demographic  Table (1) and procedural  data were  obtained;  these  data  included  access type and location, technical details of the procedure, complications, and procedure outcome. In some patients with thrombotic occlusion,  balloon PTA was performed after surgical   thrombectomy.   All   complications that occurred during PTA & post PTA follow­ up were recorded and evaluated, including (balloon rupture, vascular injury, hemorrhage, hypotension, allergic reaction, and infection, and  pulmonary  embolism,  ischemia  of  the hand, hypoxia, and death).

Patients:  In  all  patients,  an  autogenous

fistula   or   polytetrafluoroethylene    (PTFE)

graft  (6 mm in diameter  or 4-7mm tapered

graft) was placed in either the forearm or the upper arm. None of the patients underwent previous PTA.

Criteria for PTA: According to Dialysis Outcomes Quality Initiative guidelines, all PTAs were performed  in patients with more than 50% stenosis and clinical abnormalities. 1

Clinical   abnormalities   included   abnormal

physical examination findings (changes in bruits, thrills, pulse, etc.); abnormal urea recirculation   measurements,   as  defined  in the Dialysis Outcomes Quality Initiative protocol; elevated venous pressure during dialysis; decreased access flow; previous thrombosis  in the  access  line; development of collateral veins; limb swelling; low arterial pressure during dialysis; and/or unexplained decreases in dialysis dose.l

Exclusion  criteria:  Previous  PTA for the same lesion. PTA combined  with stenting Associated significant (>50%) central venous stenosis.   Positive  pregnancy  test  within  7 days  before  enrollment.   Patient  scheduled for a kidney transplant. Life expectancy <6 months. Documented allergy to heparin or radiographic contrast material.

Cutting      PTA     Group:      Patients      who

underwent cutting PTA comprised 29 patients with   36   stenoses   (17   men,   12  women). Included patients with significant dialysis access stenosis in whom clinical success was achieved by using cutting PTA alone. In this group, three ofthe 29 patients with thrombotic occlusion underwent surgical thrombectomy before PTA.

Conventional  PTA Group:  Conventional

PTA was performed  in 29 patients  with 38 stenoses (13 men,  16 women). Included patients  with  significant  dialysis  access stenosis  in whom  clinical  success  was achieved  by using  conventional  PTA alone. In this group, two of the 29 patients with thrombotic occlusion underwent surgical thrombectomy.

Assessment of Stenoses: Diagnostic fistulography  was performed to identify and evaluate the target lesion and to evaluate the outflow veins. All lesions were characterized by location,  length,  and degree of stenosis. The   angiographic    criteria   were   assessed

and satisfied before any treatment was performed.  The target lesion was imaged in two  orthogonal  planes.  The  imaging  plane that demonstrated the greatest degree of stenosis was used for subsequent anatomic measurements.   Anatomic   measurements were made with use of a calibrated reference marker  or the  computer-  assisted  edge detection software within the angiographic imaging system. The reference vessel was defined  as  an  adjacent  segment  of  normal vein located upstream from the target lesion. The degree of stenosis was reported as the maximum diameter reduction compared with the reference vessel diameter Table (2).

Procedures    and     clinical     success:    All

procedures were performed by the vascular surgeon   under  local  anesthesia   (lidocaine

2%)   Anticoagulants   (intravenous   heparin,

2000 IU) were administered at the beginning of angioplasty procedures. Initial balloon size was determined with the same technique used to determine the expected vessel diameter in a fistula or the diameter of the adjacent graft. A

5-7-F introducer sheath was used as an access device for balloon angioplasty in all patients. In patients with an autogenous fistula, the introducer sheath was placed in the draining vein. In patients with a graft, the  introducer sheath  was  placed  in the  graft  or  drainage vein.   Clinical  success  of  conventional   or cutting balloon  PTA was  defined as an improvement in hemodialysis access failure and resumption of normal dialysis for at least one dialysis session after PTA.

Technique for cutting PTA: In cutting PTA, a 1-2 em-long cutting balloon (Peripheral Cutting Balloon; Boston Scientific) rated as having a burst pressure of 10 atm and with inflation diameter of 5-8  mm was used. The lesion was crossed by using a 0.018- inch guidewire (Transend; Boston Scientific), over which  the  cutting  balloon  was  introduced. First, the cutting balloon was inflated for 60 seconds  at 4 atm. for two attempts.  On the third inflation, if the balloon waist remained at the same pressure as on the second inflation, pressure  was  subsequently   increased  by  2 atm. & inflated repeatedly  until the  balloon waist  disappeared.   Once  the  balloon   was

completely inflated for 60 seconds on any attempt, the inflation procedure was stopped. Maximum pressure was set at 10 atm., even if the balloon waist  remained  after inflation at 10 atm., the inflation procedure was terminated. After inflation end, the deflated cutting  balloon  catheter  was  rolled  before the next inflation. The reason for rolling the cutting balloon catheter was so the blade attached to the balloon would cut the vessel wall at a different site each time. At the end of the procedure, a final fistulogram was obtained Figures (1-2).

Technique for conventional PTA: In conventional PTA, 2--4-cm long conventional balloons (Synergy; Boston Scientific) rated as having a burst pressure of 18 atm., and with an inflation diameter of 5-8  mm were used. The lesion was crossed by using a 0.035- inch guidewire (Terumo Medical Corporation, USA), over which the balloon was introduced. Each balloon  was  inflated to  a level  below the  rated  burst  pressure  recommended   by the manufacturer until the balloon waist disappeared;   then   it  was   inflated  for   60 seconds. If the balloon waist still remained when  the rated burst pressure  was reached, the balloon  was inflated for  60 seconds  for no more than three attempts until the balloon waist disappeared below the rated burst pressure. Even if the balloon waist remained after inflation at rated burst pressure the inflation procedure was terminated without further attempt. At the end of the procedure, a final fistulogram was obtained Figures (3,4).

Total procedure time: The total procedure

time was documented for each study patient. The  start  of  the  procedure  was  defined  as the moment when the physician gained percutaneous access into the graft. The end of the procedure was defined as the completion of  final  postprocedural   fistulography.  The mean procedure times for conventional PTA and cutting PTA treatment were 49.6 minutes and 61.2 minutes, respectively (P= .642).

Follow-up:     In     both     groups,     clinical

findings   (change   in   bruits,  thrills,   pulse, etc) were noted at physical examination, venous    dialysis    pressure    was    recorded during    each    hemodialysis    session,    and

monthly measurements of dialysis dose and urea   recirculation   were   obtained.   Access flow measurements were obtained with ultrasonography (US) every 2-3 months. Fistulography was performed when abnormal results were obtained. The mean duration of follow-up was 15 ±3 month.

Statistical   analysis:     Balloon    diameter,

percent  diameter  stenosis  before  PTA, residual percent diameter stenosis after PTA, and percent diameter dilatation (ie, residual percent diameter stenosis after PTA minus percent diameter stenosis before PTA) in the cutting PTA group and the conventional  PTA group were compared by using the Mann­ Whitney U test. Hemodialysis access stenosis was  divided  into  the following  four  types: (a)   autogenous   venous   stenosis   (stenosis of venous runoff from arterial-venous anastomosis  to  central  veins),  (b)  graft-to­ vein anastomotic stenosis, (c) intragraft stenosis, and (d) arterial anastomotic stenosis. For these four types, the patency rates were assessed   with   the   Kaplan-Meier   method and compared with the results of log-rank statistics in the cutting and conventional PTA groups.

Primary patency for the lesion was defined

as  uninterrupted  patency  of the treated  site after balloon PTA. The end point of patency was decided at the time of treatment for hemodialysis access failure due to restenosis of the treated site. However, when a lesion other than that at the treated site caused hemodialysis access failure, primary patency for the lesion was not interrupted.

As the sample size was small, the X2 test

or Fisher exact test was used to compare patency  rates  for  various  time  points  (3rd,

6th, 9th, 12th, and 15th months) between cutting and conventional  PTA groups for the four types  of stenosis.  P values of less than

.05 were considered to indicate a statistically

significant difference. All analyses were performed by using Stat- View, version  5.0, software (SAS Institute, Cary, NC).

Results

Cutting     PTA:    From     November     2011 to  October  2013,  29  patients  (17  men,  12

women;  mean  age,  60.4  years  ±10.1)  with

36   stenoses,   underwent   cutting   PTA.  26 patients   89%   with   29   stenoses   achieved clinical  success  with  cutting  PTA. Clinical success  could  not be  achieved  with cutting PTA  alone   in  three   patients   with   seven stenoses;  these  patients  required  additional stent   implantation   (1  patient)   or  surgical reconstruction (2 patients). Of the 29 stenoses, (18 were autogenous venous stenoses, 5 were graft-to-vein   anastomotic  stenoses,  4  were intragraft  stenoses,  and  2  were  in  arterial anastomotic   stenosis).   Two  patients   with thrombotic  occlusion  were  included  among the   26  patients  in  whom  clinical  success was   achieved.   The   inflation   diameter   of the  cutting  balloons  used, the  mean loaded maximum   pressure  used  are  illustrated  in Table (3). the mean percent diameter stenosis before  PTA,  after  PTA, and  mean  percent diameter  dilatation  after  PTA, respectively, were 80.9 ±12.0, 30.8 ±15.5, and 50.1 ±18.5 for autogenous venous stenosis; 82.1 ±16.2,

34.9 ±12.7, and 47.2 ±11.0 for graft-to-vein

anastomotic stenosis; 68.1 ±18.9, 38.9 ±16.0, and  29.2  ±13.3  for  intragraft  stenosis;  and

74.8  ±5.5,  34.9  ±11.2,  and  40.9  ±11.0  for

arterial anastomotic stenosis Table (2).

Conventional   PTA:  Of  the  29  patients who had 38 stenoses.  25 patients 86% with

30 stenoses (13 men, 16 women; mean age,

61.9 years ± 10.2) achieved clinical success with   conventional   PTA.   Clinical   success could not be achieved with conventional PTA alone in four patients who required additional stent implantation (one patient) or surgical reconstruction   (2  patients)   graft  insertion (one patient). Of the 30 stenoses, (17 were autogenous venous stenoses, 7 were graft-to­ vein anastomotic stenoses, 3 were intragraft stenoses, and 3 were in arterial anastomotic stenosis). The inflation diameter of the cutting balloons used, the mean loaded maximum pressure  used  are  illustrated   in  Table (3). The mean percent diameter stenosis before PTA, after PTA, and mean percent diameter dilatation    after   PTA,   respectively,    were

74.1 ±14.3, 26.8 ±13.0, and 47.3 ±17.7 for autogenous   venous   stenosis;   67.9   ±13.4,

32.0 ±12.3, and 35.9 ±14.3 for graft-to-vein

Figure (1): Dilatation of cephalic venous stenosis of mid-forearm radio-cephalic fistula using cutting balloon angioplasty. a. Stenosis, b. cutting balloon inflation to dilate the stenosis without waist, c. completion venography after balloon dilatation.

Figure {2): Forearm loop graft with graft-to-vein  anastomotic stenosis. a. before and b. after cutting balloon dilatation.

Figure {3): Conventional  balloon  angioplasty  of cephalic  venous stenosis in  radiocephalic fistula. a. Fisulogram showing the stenotic segment of the cephalic vein at the level of the elbow, b. Conventional  balloon inflation dilating  the stenotic  sement  without  waist, c. Completion venography after conventional balloon dilatation.

anastomotic stenosis; 63.0 ±9.5, 27.9 ±8.7, and  35.1±14.1  for  intragraft  stenosis; and

72.1 ±6.1, 24.1  ±15.0, and 48.0 ±13.7 for rutetial anastomotic stenosis Table (2).

Cutting     PTA   and    conventional    PTA

groups:     No    significant    differences    in balloon diameter between cutting PTA and conventional PTA groups were seen for any type  of  stenosis  Table (3).   No  significant

differences in percent diameter stenosis were seen between cutting PTA and conventional PTA groups  before  PTA for graft-to-vein anastomotic stenosis (P =.060), intragraft stenosis (P =.858), or ruterial anastomotic stenosis (P =.328). A significant difference in percent diameter stenosis was seen between the groups for autogenous venous stenosis (P

=.0 11) Table (2).  No significant differences

Figure (4): Brachiocephalicfistula with arterial anastomotic stenosis. a. Before and b. After conventional balloon dilatation.

Table (1): Demographic characteristics of the study population.

Table (2): Percent diameter stenosis before PTA and residual percent diameter stenosis after

PTA.

*Pvalues were detived fi:om compruisons between cutting and conventional  PTA groups and were calculated with the Mann-Whitney U test.

between cutting  PTA and conventional  PTA groups were seen in residual percent diameter stenosis after PTA for autogenous venous stenosis (P =.328), graft-to-vein anastomotic stenosis (P =.371), or rutetial anastomotic stenosis (P =.096). A significant difference in

residual percent diameter stenosis was seen between the groups  for intragraft stenosis (P

=.028). No significant differences between cutting  PTA and  conventional   PTA groups were   seen   in   percent   diameter   dilatation after PTA for autogenous venous stenosis (P

Table (3): Diameter and loaded maximum pressure of balloons.

*Pvalues were denved from compansons  between cuttmg and conventiOnal PTA groups and

were calculated with the Mann-Whitney Utest

Table 4: Patency rates for autogenous venous stenosis.

*Pvalues were denved from compansons  between cuttmg and conventiOnal PTA groups and

were calculated with the X2 test or Fisher exact test.

Table (5): Patency rates for graft-to-vein anastomotic  stenosis.

*Pvalues were derived from comparisons between cutting and conventional  PTA groups and were calculated with the X2 test or Fisher exact test.

=.312),   graft-to-vein   anastomotic   stenosis (P  =.100),  intragraft  stenosis  (P  =. 287),  or arterial anastomotic stenosis (P =.141).

Primary   patency   rates   for   autogenous

venous stenosis:  For cutting PTA group, the

6-month patency rate was 83% and the 1-year patency rate was 56% according to Kaplan­ Meier analysis results. For conventional PTA

group,  the  6-month  patency  rate  was  53% and the 1-year patency rate was 47%, as calculated with the Kaplan-Meier method. No significant differences (P =.360) in primary patency rates were identified between the two groups by using Kaplan-Meier analysis. With use of the X2 or Fisher exact tests, patency rates  in  the  cutting  PTA group  were found

Table (6): Patency rates for intragraft stenosis.

*Pvalues were denved from compansons between cuttmg and conventwnal  PTA groups and

were calculated with the X2 test or Fisher exact test.

Table (7): Arterial anastomotic stenosis.

* Pvalues were denved from compansons between cuttmg and conventwnal  PTA groups and

were calculated with the X2 test or Fisher exact test.

to be significantly higher than those in the conventional  PTA group in the   6th, and 9th months (P =.013, and P =.003, respectively) Table (4).

Primary Patency Rates for Graft-to-Vein Anastomotic    Stenosis:    For   cutting    PTA alone, the 6-month patency rate was 80% and the  1-year  patency  rate  was  60%  according to Kaplan-Meier analysis results. For conventional PTA alone, the 6-month patency rate was 71% and the 1-year patency rate was

42% according to Kaplan- Meier analysis results.  With  use  of  Kaplan-Meier  methods, the  primary   patency  rate  was  significantly higher for cutting PTA than for conventional PTA (P =.037). With use of the X2 or Fisher exact tests, the patency rate was significantly higher for cutting PTA than for conventional PTA in the 9th month (P =.032) Table (5).

Primary     Patency     Rates     for    Intragraft

Stenosis: For cutting PTA alone, the 6-month patency rate was 75% and the 1-year patency rate was 50% according to Kaplan-Meier analysis results.  For conventional  PTA alone,

the  6-month  patency  rate was  67%  and the

1-year  patency  rate  was 33%,  as calculated with   the   Kaplan-Meier   method.   With  use of Kaplan-Meier analysis, no significant differences in primary patency rates were identified   between   the   groups   (P  =.371). With use of the X2 or Fisher exact tests, no significant differences in patency rates were identified between the  groups at any follow­ up point Table (6).

Primary  Patency  for  arterial  anastomotic

stenosis:  For cutting PTA alone, the 6-month patency rate was 100% and the 1-yearpatency rate was 50% according to Kaplan-Meier analysis results. For conventional  PTA alone, the 6-month  patency rate was 100%  and the

1-year  patency  rate  was 67%,  as calculated with the Kaplan-Meier method. No significant differences in primary patency rates were noted between the groups with use of the Kaplan­ Meier method  (P =.921). With use of the X2 or Fisher exact tests, no significant differences in patency rates were identified between the groups at any time point Table (7).

Complications  in cutting PTA: Balloon rupture   occurred   in  one  of  36  stenoses, but subsequent angiography revealed no extravasation, but angiography performed 3 months after cutting PTArevealed aneurysmal dilatation at the site of balloon inflation. Diameter  of aneurysmal  dilatation  was less than   2   em.   Follow-up   testing   conducted

1 year after PTA showed no aneurysmal diameter increase, and aneurysmal dilatation did not affect hemodialysis. Cutting PTA did not cause any other complications.

Complications   in  conventional  PTA: Balloon   rupture  occurred   during  inflation in two of the 38 stenoses, but angiography revealed no extravasation. Extravasation occurred immediately  after balloon inflation in one patient, and hemostasis  was achieved by  inflating  the  same  balloon  with  2  atm of pressure in the same location to apply compression from inside the vessel and by manually  applying external compression  for

5  minutes.   Extravasation   disappeared   and

clinical success was achieved. Conventional

PTA did not cause any other complications.

Discussion:

Percutaneous transluminal angioplasty (PTA) is the main stay of treatment in hemodialysis  access stenosis.  PTA is a safe and useful intervention to restore access patency   and   preserve   venous   capital   for future  AVF or AVG creation.7 PTA restores the luminal diameter of venous fistula by stretching and dissection of the vessel wall. This   induces   vascular   damage   and   may cause subsequent restenosis.8 whether the mechanism  of  venous  restenosis  is  similar to arterial restenosis is uncertain. However, venous restenosis seems to recur more frequently than that of its arterial counterpart. Cutting  balloon  angioplasty  reduces  the amount of arterial wall damage by inducing a controlled fracture of atherosclerotic  plaque. It is uncertain if cutting balloon angioplasty will reduce the recurrence rate of venous stenosis as compared to conventional balloon angioplasty.9

The   cutting   balloon   was   designed   to

conventional  balloon  angioplasty.  In  1991, Barath             and       colleagues10   described   their experience  with  use  of  the  cutting  balloon in   normal   porcine       arteries.   By   creating longitudinal  incisions  into the  medial  layer of  the  vascular  wall  while  simultaneously dilating   the     lesion,   the      cutting   balloon causes  less stretching  and less injury to the surrounding  vascular smooth  muscle.  These investigators   suggested   that   limiting   the extent  of  angioplasty  induced  injury  could reduce the expression of proliferative growth factors  and thereby  decrease  the neointimal hyperplasic   response.10  This   concept   was clinically verified by Kondo and colleagues,11 who used the coronary cutting balloon to treat

127 atherosclerotic lesions in the coronary arteries of 110 patients. In the subgroup of patients who were treated with only the cutting balloon,  there was a significant  decrease  in the degree of restenosis. In addition, the acute gain in luminal  diameter  was  greater when the cutting balloon was used compared  with conventional angioplasty.

Vorwerk and  colleagues 12 were  the  first

group to report the use of the cutting balloon for treatment of hemodialysis  related venous stenoses. Fifteen patients with 19 venous stenosis  underwent   treatment   with  use  of

3-mm,  5-mm,  and  6-mm  cutting  balloons.

However, 68% of these lesions were also treated  with  conventional  angioplasty balloons during the same procedure. Vorwerk et al12 achieved  a 6-month  primary  patency rate of 64%, but these results are confounded by the concurrent use of conventional angioplasty. This is a widespread problem that is found in other published reports describing the use of the cutting balloon for treatment of vascular access-related venous stenosis.13-17

The results of these studies include patients who underwent concurrent treatment with the cutting balloon and conventional angioplasty. Singer-Jordan et ai15 described the use ofthe cutting balloon as "primary" treatment for fistula-  related  venous  stenoses.  However,

40% of the 42 study patients also underwent

conventional  angioplasty  immediately  after use of the  cutting  balloon and two  patients

reported   the  results   of  treatment  with  the cutting  balloon  in three patients,  all of whom also    underwent   conventional   angioplasty and  stent  placement after  use  of the  cutting balloon.  In the majority of these  published reports,   the   cutting   balloon   was   used   to treat stenoses that failed to respond to high pressure balloon angioplasty. However, under these  circumstances, the  long-term   patency rate is not necessarily reflective of the cutting balloon.  As previously described, the  cutting balloon is designed  to reduce vascular trauma and  thereby reduce   neointimal hyperplasia and improve long-term patency ofthe vascular access.   One  could  theorize   that  concurrent use of a high-pressure angioplasty balloon would negate these conceptual benefits.

Several  studies  compared the use of high­

pressure  balloon  angioplasty versus  the Peripheral Cutting  Balloon for treatment of stenoses in autogenous fistulas & reported equivalent immediate results.l8-20 T. Vesely et ai21 in 2005  comparing use of the  cutting balloon   PTA  versus   Conventional  balloon

PTA for treatment of hemodialysis-related venous   stenoses   &  demonstrated that   the cutting    balloon    PTA   provides    equivalent

6-month  patency   to  PTA  for   stenotic   and thrombosed grafts.  Kariya  S,  et  al compare primary   patency   rates   of  cutting   balloon percutaneous transluminal angioplasty (PTA) with  their   older   experience  in  the  use  of conventional balloon  PTA  in  the  treatment of   different   types   of   hemodialysis  access stenosis, & reported higher  primary  patency rates  for  cutting   PTA  in  comparison  with conventional PTA in the treatment of graft-to­ vein anastomotic stenosis,22 which  is similar to  our  results.   Some  investigators  reported the,  safety,  high  technical success   rate,  low complication rates  & lower  restenosis rate when  cutting  balloon  PTA used  in resistant venous       stenoses           of                dialysis      access,23-25 others  reported  that cutting  balloon  PTA did not  improve  patency compared to published results  of conventional PTA, but may  lower the frequency of required re-interventions.26

We found that in patients  with autogenous

venous stenosis  and those with graft-to-vein anastomotic  stenosis,  the   primary   patency

rate  for  cutting  PTA  was  higher   than  that for conventional PTA. As our results  of log­ rank testing  show, a longer period  of primary patency  achieved  by performing cutting  PTA might be expected  only in patients  with graft­ to  vein  anastomotic stenosis; however,  the sample  size  was  insufficient to  determine  if there  was a significant  difference. However,

Kaplan-Meier and  the  results  of  X2  testing

indicate a possibility that longer periods of primary  patency  achieved  by performing cutting  PTA could be expected for autogenous venous stenosis  and graft to-vein anastomotic stenosis after PTA. Despite the prospective randomized nature  our study  was limited  by the small number  of subjects, future larger studies  are warranted.

When  cutting  PTA was performed  to treat

intragraft stenosis,  primary  patency  was  not significantly improved, and  residual  percent diameter  stenosis   was   greater   for   cutting PTA than for conventional PTA. The reasons for  this  may  be  because  of  the  presence  of a  circumferential  artificial   structure  in  the vascular   wall,   no  structurally  weak   areas were   present,    even   when    high    pressure was  applied,   and  minimal   vascular  damage resulted from dissection and vessel stretching. As  a result,  no  advantage   was  obtained  by using  a  cutting  balloon  in the  treatment of intragraft stenosis. In the cutting  PTA group, aneurysmal dilatation at the site  of inflation was  seen  during  follow-up in  one  stenosis. However,   aneurysmal   dilatation   did   not increase  in size and did not cause any dialysis failure.   Aneurysmal  dilatation  could   have been  caused  by  an incision  in  the  vascular wall created  by a blade; thus, patients need to be monitored for a certain period of time after cutting  PTA. In conclusion, primary  patency rates are significantly higher  for cutting  PTA than for conventional PTA in the treatment of graft-to-vein anastomotic stenosis. However, no  significant  differences  are  apparent   in primary  patency  rates  between  cutting  PTA and conventional PTA groups in the treatment of   autogenous  venous    stenosis,  intragraft stenosis,  or   arterial    anastomotic  stenosis. These  data suggest that cutting  PTA could be performed to treat  graft-to-vein anastomotic

stenosis.

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