1 Department of Cardio-Vascular Radiology, Clinique St-Gatien, 2 Department of Surgery, Clinique de l'Archette, Olivet, 3 Department of Nephrology-Hemodialysis, Centre Hospitalier Universitaire, Tours cedex, 4 Department of Hemodialysis, Clinique St-Côme, Blois, 5 Hemodialysis Center, Châteauroux, 6 Department of Nephrology-Hemodialysis, Hôpital de La Source, Orléans and 7 Department of Hemodialysis, Clinique de l'Archette, Olivet, France
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Abstract |
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Methods. Over a 6-year period, 52 dysfunctional and 17 thrombosed immature forearm fistulas (mean age 10 weeks) were treated by interventional radiology. Angiography was performed by puncture of the brachial artery but dilation of underlying stenoses was performed after cannulation of the fistula itself, whenever possible, with a balloon never smaller than 5 mm. Embolization or ligation of any type of vein was never indicated and never performed. For thrombosed fistulas, significant clots were removed by manual catheter-directed aspiration. A covered stent (Passager®) was used in cases of dilation-induced rupture not controlled by balloon tamponade.
Results. An underlying stenosis was diagnosed in 100% of cases. Half of them were located in the anastomotic area. The initial success rate of interventional radiology was 97%. Dilation-induced rupture occurred in nine cases (13%) but stents were necessary in only two cases. The rate of significant clinical complications was 2.8% (bacteraemia, pseudoaneurysm). Primary and secondary patency rates at 1 year were 39 and 79%, respectively.
Conclusions. Delayed maturation of native fistulas should lead systematically to imaging as an underlying stenosis is diagnosed in all cases. Interventional radiology can treat the majority of cases and achieve a 97% success rate but early recurrence of stenoses can occur. Multidisciplinary re-evaluation of the patient must, therefore, be performed after radiological salvage of the fistula.
Keywords: arteriovenous fistula; declotting (thrombolysis, thromboaspiration, thrombectomy); percutaneous transluminal angioplasty; stents and prostheses
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Introduction |
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In centres working with a real team approach, surgeons and nephrologists are now aware and have been convinced for many years of the potential of interventional radiology alternatives, logically leading them to refer immature fistulas to radiologists.
We report 6 years of encouraging experience of a single European centre in the angiographic evaluation and endovascular treatment of forearm fistulas that failed to mature spontaneously.
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Subjects and methods |
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The definition of an immature fistula used in this retrospective study is either a fistula created less than 3 months earlier (62 patients) or a fistula of more than 3 months but used for less than 1 month for dialysis (seven patients). Mean fistula age was 10.25 weeks (range 426) at the time of the first percutaneous intervention. Fifty-two fistulas were dysfunctional but still patent and 17 were thrombosed.
Fistula dysfunction was assessed clinically on the basis of insufficient development after 1 month, difficulties in cannulation, or impossibility of achieving 300 ml/min dialysis flow rate without recirculation.
Patients were referred to the radiologist by six haemodialysis centres comprising 18 nephrologists and three surgeons. Sixty-three were radio-cephalic and six were ulnar-basilic fistulas. The less numerous cases of immature upper arm fistulas treated during the same period were not included in this study because recent surgical and radiological publications have shown different long-term outcomes between forearm and upper arm fistulas [2,7].
All radiological interventions were outpatient procedures. There were no contraindications to angiography: diluted iodine was used in the seven patients who had not previously been haemodialysed, gadolinium (the contrast medium used in magnetic resonance imaging) was used in two cases of severe allergy to iodine [8].
Apart from local infection, the contraindications to dilation were anastomotic stenoses in fistulas of less than 6 weeks duration (risk of disruption of the anastomosis) and this occurred in two cases: one was operated on and the other was dilated after 6 weeks and not operated on because of concomitant downstream stenoses. The contraindications to declotting were local infection and fistulas unsuccessfully used at least once for dialysis if the vein was not clinically palpable in the forearm. Such previously unused thrombosed fistulas were definitively abandoned and a new vascular access had to be created.
Treatment of dysfunctional but patent fistulas
The predominance of inflow and cannulation problems necessitated perfect evaluation of the fistula and precluded cannulation of the vein itself. Diagnostic angiography was subsequently performed in more than 90% of cases by puncture of the brachial artery at the elbow with an 18G needle and placement of only the dilator of a 4F introducer sheath. Digital subtraction imaging was performed at a rate of three to six images per second with an iodine injection rate of 5 ml/s for 1 s.
The status of vascularization of the hand was systematically checked as well as patency of the palmar arch and the antegrade or retrograde filling of the distal segment of the artery feeding the fistula (radial or ulnar). The anastomosis was then studied by additional runs when necessary for optimal visualization. The veins were then studied up to the thorax.
Once stenosis had been diagnosed, dilation was performed by cannulation of the fistula itself. For stenoses located in the artery or at the anastomosis, a retrograde approach was used from the vein in the upper third of the forearm or from the elbow. If this retrograde approach was unsuccessful, the arterial stenosis was treated by antegrade cannulation of the brachial artery at the elbow and selective catheterization of the feeding artery. In contrast, antegrade cannulation of the fistula close to the anastomosis was used for stenoses located in the vein far from the anastomosis.
After placement of a 5 or 6F introducer-sheath, a dilation balloon never smaller than 5 mm was used for venous stenoses and never smaller than 4 mm for arterial or anastomotic stenoses. High-pressure balloons inflatable up to 25 atm (Blue-Max, Medi-Tech®, Natick, MA, USA or Centurion, Bard®, Covington, GA, USA) were used when necessary to abolish the waist of the stenosis on the balloon. The final result was assessed both clinically and angiographically.
In cases of dilation-induced rupture of the vein, the dilation balloon was first reinflated locally at low pressure (24 atm) for periods of 10 min. If the leakage persisted despite 30 min of balloon tamponade, stent placement was the only way to save the fistula. The stent used was the Passager (Boston-Scientific® Europe, La Garennes-Colombes, France), a wide mesh nitinol puncturable stent covered with Dacron.
Treatment of thrombosed fistulas
The methods of declotting of thrombosed native fistulas have been detailed previously [9,10]. Placement of a tourniquet at the elbow to make the non-thrombosed outflow segment swell and puncturable or antegrade cannulation of the feeding artery from the brachial artery at the elbow were often necessary to gain access to the fistula. Once a guide wire had been successfully pushed both into the arterial inflow and the venous outflow, the success of the procedure was predictable because the clot burden was always very small or non-existent, due to the small vein diameter. Removal of the thrombus by manual catheter-directed aspiration was never a problem. Sufficient dilation of the underlying stenoses was the only requirement to success.
Statistics
Success rates, patency rates, and complications were defined in agreement with the guidelines and reporting standards of the American Society of Cardio-Vascular and Interventional Radiology (SCVIR) [10,11]. Anatomic success was, therefore, defined angiographically as less than 30% residual stenosis and clinical success as the ability to perform at least one full dialysis treatment at a 300 ml/min flow rate without recirculation.
Major complications were defined as those resulting in admission to a hospital for therapy (for outpatient procedures), an unplanned increase in the level of care, prolonged hospitalization, permanent adverse sequelae, or death [12].
Primary patency was considered to begin on the day of the first radiological procedure and to end on the day of access failure or further re-intervention (radiological or surgical). Secondary patency included all further radiological therapy (dilation, stent placement, declotting) but ended with any surgical intervention [11]. Death and renal transplantation with a patent fistula were considered to be the end of follow-up.
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Results |
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Nine acute ruptures occurred during dilation (13%) and seven were sealed by prolonged balloon inflation. Only two of them, located in cannulation areas, required a stent and they were controlled by placement of a Passager®. They were then routinely cannulated for 10 and 24 months, respectively.
There were two significant complications (2.8%). The early complication was severe bacteraemia, resulting from overlooked infection of the (8-week-old) anastomotic scar, and leading to urgent ligation of the fistula at day 7. The delayed complication was the development of a pseudoaneurysm 6 weeks after initially controlled dilation-induced rupture.
No patient died within 1 month of the radiological procedure. No complication occurred at the brachial artery puncture site. During follow-up, three patients underwent renal transplantation (at 7, 7, and 10 months, respectively) and 13 patients died (at 1, 2, 5, 5, 7, 7, 9, 10, 10, 12, 15, 17, 20, 22, 22, and 24 months, respectively).
Patency rates are detailed in Figure 2. Primary and secondary patency rates were 56±7% and 83±5% at 6 months, 39±8% and 79±7% at 1 year, and 26±10% and 75±10% at 2 years, respectively.
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Secondary patency rates were 84 (n=34) and 82% (n=12) at 6 months, and 81 (n=21) and 74% (n=8) at 1 year, respectively.
Late failures involved 12 early recurring stenoses, which were treated surgically by a new anastomosis some centimetres above the first in three cases (with a 100% 1-year primary patency rate) and by the creation of a new vascular access in nine cases (with a low 11% 1-year primary patency rate).
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Discussion |
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In currently immature fistulas, ultrasound evaluation can also show when the stenosis is located at the anastomosis only and when direct surgical creation of a new anastomosis a few centimetres above can, therefore, be planned without angiography.
Results of the radiological approach
Although the success rate of our endovascular approach is high, primary patency rates are more disappointing since the 1-year rate of 39% is comparable with the results achieved after dilation of prosthetic grafts [1]. It must, however, be borne in mind that the vast majority of the radiological interventions were last resort salvage procedures and that most of these fistulas were close to being abandoned at the time of the first radiological intervention. In addition, it has previously been reported that the younger the dysfunctional vascular access (and immature fistulas are very young accesses), the faster the recurrence after dilation [7]. The same article also reported similar outcomes for thrombosed and non-thrombosed mature fistulas after endovascular treatment. There is, however, a slight selection bias between the two groups in the present series as, unlike dysfunctional but patent fistulas, thrombosed fistulas were treated only if they had previously successfully been used at least once for dialysis, which means that the arterial inflow was appropriate and that one arterialized venous segment was puncturable.
Radiology or surgery?
Surgery can save immature fistulas only when the stenosis is located near the anastomosis in the distal forearm: a new anastomosis can be created a few centimetres above and does not sacrifice a long segment of vein. No comparative study between surgery and dilation has ever been performed. However, 1-year primary patency rates after construction of forearm fistulas range from 65 to 84% in the literature [3,5,1314] whereas the best rate after dilation is 51% [7] and surgical revision of the anastomosis in three cases in this series achieved excellent results.
Interventional radiology has, however, the advantage of being able to treat all types of stenosis in any location and can be considered more effective as a first approach. This study indicates that the majority of non-maturing fistulas can be salvaged radiologically and that the availability of wide mesh, thus puncturable covered stents, is helpful to optimize the results in cases with complications. The future of a radiologically salvaged immature fistula must, however, be rapidly discussed in a multidisciplinary fashion. In cases of early recurrence of stenosis, for example within 3 months, what is the best strategy: redilation or creation of a new fistula?
In cases of early restenosis close to the anastomosis, the surgical creation of a new anastomosis a few centimetres above is probably the best solution. In all other circumstances, each patient is a specific case.
If, according to pre-operative venous mapping, there is a good chance of being more successful in the creation of a new native fistula in the opposite forearm, we believe this surgical alternative is preferable to redilation every 3 months or even to every 6 months, although this must nevertheless be performed as long as the new fistula is not usable. On the other hand, if the only alternative surgery available is placement of a prosthetic graft, it is possible that preservation of the native fistula might be preferable from a strategical point of view, even with redilation every 3 months, as statistics show that secondary failure of grafts is frequent and can also eventually necessitate reintervention every 3 months [1].
Influence on surgical strategy?
The potential of interventional radiology might influence the overall vascular access strategy. It can encourage surgeons to intervene in more marginal cases. For example, Ascher et al. [4] achieved a 100% primary success rate at 3 months and Wolowczyk et al. [5] achieved 80% at 6 weeks in the creation of forearm fistulas, but they arterialized only cephalic veins greater than 3 mm in diameter. Similarly, Silva et al. [3] reported a low 8% immediate failure rate using only cephalic veins greater than 2.5 mm at the wrist. If veins smaller than 2.5 mm were inappropriate for fistula creation, it would not be possible to create such fistulas in children but they are routinely performed. Microsurgery is, however, mandatory in such cases according to Bourquelot and Bagolan [15,16]. Finally, despite their apparently disappointing results (34% clinical success rate at 6 months), Miller et al. [6] were probably working in the right direction in attempting creation of native forearm fistulas even in marginal cases and it can be hypothesized that their results might have been improved by the help of interventional radiology.
Iodine or not?
Iodine injection is a concern in previously non-haemodialysed patients. Carbon dioxide gas cannot be used for brachial artery injection because of the risk of neurologic complications in cases of reflux into the cerebral arteries [17]. Some teams have proposed using gadolinium instead of iodine [8]. Unfortunately, gadolinium is at least 10 times more expensive than iodine and is 3.5 times less radio-opaque than iodine at the concentration routinely used in vascular imaging (300 g/l). Nobody has clearly demonstrated that gadolinium is less nephrotoxic than diluted iodine to warrant this expense and it will obviously be interesting to verify the value of prophylactic oral administration of acetylcysteine in this subgroup of patients with particularly advanced renal insufficiency [18].
It is likely that screening of such patients by ultrasound can be especially valuable to select those who can undergo direct surgical repair (short stenoses close to the anastomosis) from those who need contrast injection for the endovascular approach (either long stenoses or those far from the anastomosis).
Our differences from the previously published literature
The findings and techniques of this article are not in agreement with those of the only previously published article on this topic [19]. However, the populations, diagnostic evaluations, and treatment are significantly different in the two series.
Concerning the population, thrombosed fistulas and fistulas with inadequate inflow were excluded from Beathard's study. In addition, the fistulas included were significantly more mature as their mean age at the time of treatment was 5 months (vs 2.5 in our series).
From a diagnostic point of view, our series indicates that there is no delayed maturation or immature fistula failure without underlying tight stenosis, whereas Beathard et al. described stenosis in only 21 of 63 of their cases. Our 100% underlying stenosis rate might be explained by the fact that initial angiographic evaluation was achieved by puncture of the brachial artery. We share the opinion of Lui et al. [20], that direct cannulation of the vein, as reported by Beathard, has several drawbacks: it can induce local spasm which creates a pseudostenosis modifying the kinetics of the fistula, and it is never possible to be sure of not cannulating a side branch instead of the main arterialized vein. In addition, the arterial inflow can be studied only by reflux after placement of a pressure cuff on the upper arm. The dye then fills the whole forearm venous system and creates so many superimpositions that the anastomosis may not be analysable. When appropriate reflux is achieved, such unphysiological opacification of the arteries prohibits any functional interpretation of the inflow (which part of the artery really feeds the fistula: proximal or distal?).
In terms of treatment, our difference from Beathard is that we simply dilate stenoses and never embolize or ligate collaterals. From long-standing experience of angiography in native fistulas, we know that, apart from fistulas with excessively high flow, there is no opacification of collaterals without underlying stenosis of the main outflow vein. If there are collaterals, a stenosis or occlusion is localized in all cases on the main outflow vein somewhere downstream (in relation to direction of blood flow) from the ostia of the collaterals. The collaterals simply divert the excess flow that cannot run through the stenosis.
The general rule is that it is more effective to treat the cause of a problem than its consequences. In immature fistulas, our experience indicates that sufficient dilation of the underlying stenosis renders the fistula usable for dialysis, prevents thrombosis and will make the subsequent collaterals disappear, whereas ligation or embolization of collaterals leaves stenosis untreated which can worsen and lead to fistula thrombosis.
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Conclusion |
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Acknowledgments |
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Notes |
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References |
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