ORIGINAL ARTICLE
J Vasc Access 2014 ; 15 ( Suppl 7 ): S96-S100 DOI: 10.5301/jva.5000254
Endovascular techniques for cannulation difficulties in dialysis access Steven Powell, Tze Chan Royal Liverpool Hospital, Liverpool - UK
ABSTRACT Although the arteriovenous fistula (AVF) is the access of choice for dialysis, its success as an access is limited by its high rate of failing to mature and its development of venous stenoses. This makes cannulation difficult or even impossible for dialysis staff. A variety of endovascular techniques exist for improving cannulation rates in AVFs. These include coil embolization of tributaries and balloon-assisted maturation in immature fistulae and fistuloplasty, stents and thrombus removal in mature failing access. This article aims to discuss the methods and evidence related to these techniques. Key words: Arteriovenous fistula, Dialysis, Embolization, Endovascular, Fistuloplasty Accepted: March 7, 2014
INTRODUCTION Although the arteriovenous fistula (AVF) is the access of choice for dialysis, its success as an access is limited by its high rate of maturation failure (38-60%) (1-3) and its development of intimal hyperplasia and stenosis in the venous segment. Venous stenosis is the most common cause of late failure of AVFs (4) and in most centres lead to a high number of interventions to maintain patency. The cannulating practitioner expects certain metrics to be met. For successful cannulation, the venous segment should be more than 6 mm in diameter and less than 6 mm deep for a length of 6 cm in the arm to allow the positioning of two needles sufficiently far apart to eliminate recirculation. Even when it is not easily palpable or accessible to the cannulating practitioner, the AVF should have an adequate flow rate of more than 600 ml/min for a forearm fistula and more than 1 l/min for an upper arm fistula. These parameters provide a useful guide to predict successful cannulation of newly formed AVFs, but it may be oversimplified. The biology behind AVF maturation and venous wall thickening is complex and not yet fully understood. Cannulation problems arise when these parameters are not met or when the wall of the vein has not thickened sufficiently. Even with adequate flow, diameter and depth, a thin walled venous segment may still present cannulating difficulties including extravasation and difficulty in achieving haemostasis. Failure of the AVF to satisfy these parameters can occur early S96
as a result of maturation difficulties or late as a result of stenotic disease. Failure to mature is the result of any number of variables. These include the surgical technique employed at the time of creation, inadequacy of arterial flow, the presence of competing collateral vessels and negative venous remodelling, which in itself may be related to any number of biological factors. There are now a gamut of minimally invasive techniques described in the literature to improve maturation rates. These include coil embolization of collateral veins, balloon-assisted maturation (BAM), angioplasty of the inflow artery and even far infrared light (FIR) exposure. Postmature cannulation difficulties are usually the result of stenotic disease. The position of the stenosis relative to the puncture zone is the single most important factor for the development of signs and symptoms. A stenosis closer to the anastomosis relative to the puncture zone will result in an access that feels soft and underfilled (Fig. 1). It may be difficult to needle without “double walling” the vessel. Needles may clot more easily and adequate flow rates may be difficult to achieve. The dialysis machine will read a low arterial pressure and may alarm. An access with a stenosis beyond the puncture zone in the venous segment will feel more pulsatile and will be hypertense (Fig. 2). Although this may be easy to cannulate initially, the dialysis machine will alarm due to high venous pressure and arterial pressure. The patient may also experience extravasation, prolonged bleeding times postdialysis, and in severe venous hypertension, the needles can be pushed out causing acute haemorrhage. The most frequently used
© 2014 Wichtig Publishing - ISSN 1129-7298
Powell and Chan
arriving from the artery, hence leaving insufficient flow at the puncture zone. In such situations, coil embolization represents an alternative to surgical ligation and has reported similar efficacy (5). It is the authors’ opinion that this technique should be used sparingly and only following detailed Doppler and flow rate evaluation of the venous structures of the arm of the patient. More commonly, collaterals are present in response to venous hypertension caused by an outflow stenosis in the venous segment of the AVF. Prior to any coil embolization of collaterals, the patient’s arm should be examined with ultrasound Doppler to determine whether any of the collaterals are competing significantly for flow. Minor collaterals will typically only take a small amount of the total flow volume (10-20 ml/min) and hence can be ignored. Major collaterals may represent good puncture zones for future cannulation and this should be considered before any attempt at embolization. Any stenosis within the venous segment must be detected and eliminated either by fistuloplasty or surgical patchplasty before embolization. Collaterals will often fill in the presence of outflow venous stenotic disease but should resolve following fistuloplasty, negating the need for embolization or surgical ligation. The embolization technique typically uses an antegrade puncture of the venous segment. A 5 or 6 French (F) vascular sheath is inserted. A short steerable catheter is then used to select the unwanted collateral branches. Coils can then be deployed until occlusion is achieved. Coil size selection will be related to the size of the vessel being targeted. Multiple vessels can be embolized in one session (Fig. 3). As these veins are typically superficial, patients should be advised that coils may be palpable and superficial venous thrombosis can cause discomfort. This technique has also been described using the Amplatzer Plug device.
Fig. 1 - Peri-anastomotic venous stenosis.
Fig. 2 - Outflow venous stenosis.
therapy for either of these scenarios is percutaneous fistuloplasty using angioplasty balloons and/or stents. An alternative cause of postmature cannulation difficulty is wall adherent thrombus in dilated aneurysmal venous segments. Percutaneous techniques have been described for its removal. The use of the Trerotola percutaneous thrombectomy device is probably the most commonly used, but the authors own experience is that surgical removal and correction is highly successful. The purpose of this article is to discuss the methods and evidence related to these techniques. FAILURE TO MATURE TECHNIQUES Coil embolization of collateral veins Collateral veins arising from the anastomosed draining vein of an AVF may take a proportion of the flow volume
Balloon-assisted angioplasty BAM is a relatively new technique with conflicting evidence as to its adequacy. In the presence of a small (
J Vasc Access 2014 ; 15 ( Suppl 7 ): S96-S100 DOI: 10.5301/jva.5000254
Endovascular techniques for cannulation difficulties in dialysis access Steven Powell, Tze Chan Royal Liverpool Hospital, Liverpool - UK
ABSTRACT Although the arteriovenous fistula (AVF) is the access of choice for dialysis, its success as an access is limited by its high rate of failing to mature and its development of venous stenoses. This makes cannulation difficult or even impossible for dialysis staff. A variety of endovascular techniques exist for improving cannulation rates in AVFs. These include coil embolization of tributaries and balloon-assisted maturation in immature fistulae and fistuloplasty, stents and thrombus removal in mature failing access. This article aims to discuss the methods and evidence related to these techniques. Key words: Arteriovenous fistula, Dialysis, Embolization, Endovascular, Fistuloplasty Accepted: March 7, 2014
INTRODUCTION Although the arteriovenous fistula (AVF) is the access of choice for dialysis, its success as an access is limited by its high rate of maturation failure (38-60%) (1-3) and its development of intimal hyperplasia and stenosis in the venous segment. Venous stenosis is the most common cause of late failure of AVFs (4) and in most centres lead to a high number of interventions to maintain patency. The cannulating practitioner expects certain metrics to be met. For successful cannulation, the venous segment should be more than 6 mm in diameter and less than 6 mm deep for a length of 6 cm in the arm to allow the positioning of two needles sufficiently far apart to eliminate recirculation. Even when it is not easily palpable or accessible to the cannulating practitioner, the AVF should have an adequate flow rate of more than 600 ml/min for a forearm fistula and more than 1 l/min for an upper arm fistula. These parameters provide a useful guide to predict successful cannulation of newly formed AVFs, but it may be oversimplified. The biology behind AVF maturation and venous wall thickening is complex and not yet fully understood. Cannulation problems arise when these parameters are not met or when the wall of the vein has not thickened sufficiently. Even with adequate flow, diameter and depth, a thin walled venous segment may still present cannulating difficulties including extravasation and difficulty in achieving haemostasis. Failure of the AVF to satisfy these parameters can occur early S96
as a result of maturation difficulties or late as a result of stenotic disease. Failure to mature is the result of any number of variables. These include the surgical technique employed at the time of creation, inadequacy of arterial flow, the presence of competing collateral vessels and negative venous remodelling, which in itself may be related to any number of biological factors. There are now a gamut of minimally invasive techniques described in the literature to improve maturation rates. These include coil embolization of collateral veins, balloon-assisted maturation (BAM), angioplasty of the inflow artery and even far infrared light (FIR) exposure. Postmature cannulation difficulties are usually the result of stenotic disease. The position of the stenosis relative to the puncture zone is the single most important factor for the development of signs and symptoms. A stenosis closer to the anastomosis relative to the puncture zone will result in an access that feels soft and underfilled (Fig. 1). It may be difficult to needle without “double walling” the vessel. Needles may clot more easily and adequate flow rates may be difficult to achieve. The dialysis machine will read a low arterial pressure and may alarm. An access with a stenosis beyond the puncture zone in the venous segment will feel more pulsatile and will be hypertense (Fig. 2). Although this may be easy to cannulate initially, the dialysis machine will alarm due to high venous pressure and arterial pressure. The patient may also experience extravasation, prolonged bleeding times postdialysis, and in severe venous hypertension, the needles can be pushed out causing acute haemorrhage. The most frequently used
© 2014 Wichtig Publishing - ISSN 1129-7298
Powell and Chan
arriving from the artery, hence leaving insufficient flow at the puncture zone. In such situations, coil embolization represents an alternative to surgical ligation and has reported similar efficacy (5). It is the authors’ opinion that this technique should be used sparingly and only following detailed Doppler and flow rate evaluation of the venous structures of the arm of the patient. More commonly, collaterals are present in response to venous hypertension caused by an outflow stenosis in the venous segment of the AVF. Prior to any coil embolization of collaterals, the patient’s arm should be examined with ultrasound Doppler to determine whether any of the collaterals are competing significantly for flow. Minor collaterals will typically only take a small amount of the total flow volume (10-20 ml/min) and hence can be ignored. Major collaterals may represent good puncture zones for future cannulation and this should be considered before any attempt at embolization. Any stenosis within the venous segment must be detected and eliminated either by fistuloplasty or surgical patchplasty before embolization. Collaterals will often fill in the presence of outflow venous stenotic disease but should resolve following fistuloplasty, negating the need for embolization or surgical ligation. The embolization technique typically uses an antegrade puncture of the venous segment. A 5 or 6 French (F) vascular sheath is inserted. A short steerable catheter is then used to select the unwanted collateral branches. Coils can then be deployed until occlusion is achieved. Coil size selection will be related to the size of the vessel being targeted. Multiple vessels can be embolized in one session (Fig. 3). As these veins are typically superficial, patients should be advised that coils may be palpable and superficial venous thrombosis can cause discomfort. This technique has also been described using the Amplatzer Plug device.
Fig. 1 - Peri-anastomotic venous stenosis.
Fig. 2 - Outflow venous stenosis.
therapy for either of these scenarios is percutaneous fistuloplasty using angioplasty balloons and/or stents. An alternative cause of postmature cannulation difficulty is wall adherent thrombus in dilated aneurysmal venous segments. Percutaneous techniques have been described for its removal. The use of the Trerotola percutaneous thrombectomy device is probably the most commonly used, but the authors own experience is that surgical removal and correction is highly successful. The purpose of this article is to discuss the methods and evidence related to these techniques. FAILURE TO MATURE TECHNIQUES Coil embolization of collateral veins Collateral veins arising from the anastomosed draining vein of an AVF may take a proportion of the flow volume
Balloon-assisted angioplasty BAM is a relatively new technique with conflicting evidence as to its adequacy. In the presence of a small (
