Saving Fistula in Case of Distal Ischemia or High Flow: Literature Review of Current Surgical and Endovascular Techniques with Proposal of Decisional Algorithm

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Marco Taurisano

DOI: 10.69097/42-01-2025-06

Marco Taurisano¹, Cosma Cortese², Andrea Mancini³, Marcello Napoli⁴

1 UO Nefrologia e Dialisi, Ospedale “Santa Caterina Novella”, Galatina, Lecce
2 UOC Nefrologia, Dialisi e Trapianto Policlinico di Bari
3 UOC Nefrologia e Dialisi, Ospedale “Di Venere”, Bari
4 UOC Nefrologia e Dialisi, Ospedale “Vito Fazzi”, Lecce

Corresponding author:
Marco Taurisano
UO Nefrologia e Dialisi, Ospedale “Santa Caterina Novella”, Galatina, Lecce
Via Roma, 73013 Galatina LE
Cell. +39 3801843301
E-mail: taurisanomarco@tiscali.it

 

Abstract

Arteriovenous fistulas (AVFs) are the preferred vascular access for chronic hemodialysis patients due to their lower rates of infectious and thrombotic complications, reduced morbidity and mortality, and increased durability compared to central venous catheters. However, the creation of AVFs has become increasingly challenging due to the rising prevalence of chronic diseases like diabetes, hypertension, and cardiovascular conditions, which are leading causes of end-stage renal disease (ESRD). These comorbidities, coupled with the aging dialysis population, have led to an increase in peripheral vascular diseases, complicating AVF management. This paper discusses two major complications of AVFs: Hemodialysis Access-Induced Distal Ischemia (HAIDI) and high-flow AVFs. HAIDI is characterized by ischemia in extremities due to reduced capillary perfusion, potentially leading to severe outcomes such as tissue necrosis and digital amputations. Approximately 5% of hemodialysis patients with AVFs develop HAIDI, necessitating corrective treatment. High-flow AVFs, defined by excessive blood flow that disrupts overall circulatory dynamics, pose another significant challenge, particularly in patients with cardiovascular compromise. The management of these complications is complex and often requires specialized techniques to preserve the AVF and avoid its closure. This review presents both surgical and endovascular techniques aimed at reducing AVF flow and improving distal perfusion. Techniques discussed include vein approach like ligation, plication, banding, prosthetic graft interposition, and various arterial interventions like distal radial artery ligation and embolization. Additionally, the review presents techniques for anastomosis remodeling, offering innovative approaches to managing AVF complications. The review concludes with a proposed decision-making algorithm to guide clinicians in selecting appropriate interventions based on the specific AVF-related complications, ensuring optimal outcomes for hemodialysis patients. This comprehensive overview highlights the importance of individualized treatment strategies in the management of AVF complications.

Keywords: High Flow Fistula, HAIDI, AVF, Surgical, Endovascular

Introduction

The preferred vascular access in chronic hemodialysis patients is represented by arteriovenous fistula (AVF), considering lower incidence of infectious and thrombotic complications, reduced morbidity and mortality, and longer durability compared to central venous catheters [1, 2]. However, currently, setting up AVFs with native vessels is becoming increasingly challenging due to the increasing prevalence of chronic diseases such as the leading causes of end-stage renal disease (ESRD) (diabetes, hypertension, heart diseases) coupled with the aging of the dialysis population, resulting in an increase in peripheral vascular diseases [3]. In this scenario distal fistulas are often created in patients with advanced peripheral vascular diseases or proximal fistulas. The major issues in such conditions, as known, are represented by distal ischemic syndrome associated with hemodialysis access (Hemodialysis Access-Induced Distal Ischemia – HAIDI) and high-flow AVF.

HAIDI is characterized by the onset of ischemia of varying severity at the extremities of the limb where the AVF is present due to reduced capillary perfusion caused by reduced blood arrival or resistance to its outflow [4]. This condition can occur acutely within a few hours after fistula creation (more frequently in grafts) with serious consequences up to possible loss of hand function. The chronic form (more commonly observed in AVFs with autologous vessels), albeit rare, is more common and usually of milder severity but can still result in tissue necrosis, sometimes necessitating digital amputations [5, 6]. It is estimated that about 5% of all hemodialysis patients with AVF develop distal ischemic syndrome requiring corrective treatment [7]. From an etiopathogenetic point of view, the involved mechanisms appear complex and not yet fully defined.

According to some authors, the main factor would be the drop in arterial pressures towards the hand due to a non-physiological readjustment of the arterial circulation after fistula creation (especially in patients with advanced vascular diseases due to diabetes, older age with severe atherosclerosis) with poor or absent remodeling, resulting in a progressive loss of perfusion pressures towards the periphery [8]. Healthy individuals’ arteries are sufficiently elastic and capable of initiating such remodeling, maintaining perfusion pressures downstream. Conversely, diabetic and vasculopathic patients often have high arterial wall stiffness or actual stenotic lesions, not guaranteeing adequate wall remodeling [9]. Another mechanism implicated to varying degrees in the determination of HAIDI is the “steal” phenomenon that physiologically occurs in AVFs created without terminalization of the artery. The principle underlying the determination of a retrograde (centripetal) flow from the hand to the anastomosis is related to the fact that the distal artery “prefers” to channel flow into a low-resistance district (the efferent vein) rather than a high-resistance district (the resistive arterial vessels of the hand). This mechanism occurs “physiologically” in all AVFs where the distal artery of the anastomosis is not terminalized. The steal becomes pathological, causing distal ischemia when it is quantitatively excessive, as in the case of high-flow AVFs with excessively large anastomoses (this is referred to as true steal) or in case of maladaptation of the distal arterial circulation as explained earlier [10]. Also, preexisting or subsequently formed proximal or distal arterial stenotic lesions in the AVF can be responsible for worsening distal ischemia after AVF creation [11, 12]. Finally, another cause of distal ischemia can be represented by venous blood stagnation in the hand caused by the presence of arterialized venous collaterals directed towards the hand or in the presence of venous outflow stenosis. This is referred to as stagnant venous ischemia [13]. From what has been said, the etiopathological mechanisms determining distal ischemia can be multiple and often concomitant and not always easy to identify (Table 1).

Mechanisms Causes
Proximal or distal preexisting arterial inflow reduction Arterial stenosis
Arterial system maladaptation Vasculopathy with calcification and increased arterial stiffness
True steel High flow fistula with big anastomosis
Stagnant venous ischemia Hand directed venous collaterals, outflow stenosis
Table 1. HAIDI etiopathogenesis. This table shows the main causes with the respective mechanisms underlying the development of distal ischemia in arteriovenous fistulas.

The definition of high-flow AVF varies and is ambiguous. Certainly, AVFs with high flow are those in which hemodynamics are influenced by blood flow far exceeding that required for hemodialysis, compromising overall circulatory dynamics [14]. The cardiovascular tolerance of a high-flow AVF is variable, with young patients able to tolerate flows of up to 3 liters per minute without hemodynamic compromise [15]. Some authors have identified a cut-off value between 1.5 and 2 l/min to define a high-flow AVF even in the absence of symptoms [16–18]. The Vascular Access Society indicates values above 1-1.5 l/min and associates an additional parameter, the “cardiopulmonary recirculation” (CPR), which is the ratio between the flow of the AVF and the cardiac output. When this index is >20%, there may be a risk of high-output decompensation. In short, it is not the absolute value of AVF flow that defines high flow but the ratio between its flow and the cardiovascular system’s capacity of that patient to maintain adequate cardiac output to manage the increased venous return without going into failure [19].

Distal ischemia and high-flow fistula conditions represent major issues in hemodialysis patients, difficult to manage outside specialized centers. Frequently, AVF ligation is the method used to resolve the issue, but it results in the loss of access for the patient. Bearing in mind the importance of maintaining AVF as a preferred vascular access, this work will present commonly used surgical and endovascular techniques, as well as new proposals, to restore proper AVF functioning by resolving ischemic issues or excessive flow. The techniques mentioned here can be classified into techniques involving intervention on the vein or artery and techniques of “remodeling” the anastomosis.

 

Vein

Vein Ligation

With this technique, the efferent vein of the anastomosis is exposed, and a silk ligature is applied and knotted to reduce the vein diameter (Figure 1a) aiming to decrease its flow rate [20]. Some authors suggest applying multiple ligatures to achieve an effective reduction in flow rate [21]. Some authors have developed a percutaneous, ultrasound-guided procedure, without surgical incision, for reducing the diameter of the efferent vein using a silk ligature [22]. The procedure involves using two needles, one in its normal configuration and the other curved; the curved needle, under ultrasound guidance, is used to pass beneath the venous vessel to be ligated, near the anastomosis. Through this needle, a silk ligature is then passed. The straight needle is passed above the vessel; through this, the silk ligature is brought back to the initial point for knotting. In the 26 patients treated this way, the authors describe a reduction in flow rate from 2196 to 679 ml/min, with these values maintained at one year follow-up, and a procedure duration of only 8.5 minutes.

Intraoperative monitoring of flow using color Doppler in procedures for reducing the diameter of the efferent vein can guide the extent and concomitant reduction of flow to the desired value [21, 23].

Figure 1. In this picture are presented main vein techniques to manage pathological AVFs.
Figure 1. In this picture are presented main vein techniques to manage pathological AVFs.

Miller Technique

An improvement over the previous technique involves ligating the efferent vein with a ligature assisted by the presence of an inflated angioplasty balloon inside the lumen to define controlled ligature caliber (Figure 1b). This is referred to as minimally invasive limited ligation endoluminal-assisted revision (MILLER) [24, 25]. This technique has shown technical success close to 100%, with clinical success in 50% of patients with distal ischemia and 100% of patients with high-flow fistulas [26]. Some authors have applied the same principle of controlling the extent of ligature.

Vein Plication

In this technique, after isolating the efferent vein of the AVF, a continuous suture is performed on the vein using a Satinsky clamp, resulting in a reduction in diameter (Figure 1c). Flow monitoring using Doppler helps determine the extent of plication before venoplasty [27]. Some authors have shown technical success in all cases treated, with symptom reduction in 92% and an average flow reduction of 600 ml/min [28].

Vein Banding

Like vein ligation but using a PTFE strip to create a sleeve approximately 20-30 mm in length wrapped around the efferent vein shortly after the anastomosis (Figure 1d). This technique has shown good success rates and maintenance of access functionality at 1 year [29]. Complications reported with this technique include band migration or venous aneurysmal dilatation both pre- and post-anastomosis [30]. To avoid these issues, some authors have proposed T-banding, characterized by using a portion of a PTFE prosthesis that is longitudinally opened and trimmed to fashion a structure capable of wrapping around the anastomotic chamber with the afferent and efferent arteries and the segment of the efferent vein, reducing its diameter but avoiding the complications [31]. With this method, these authors have shown a 44% reduction in flow with a primary and secondary clinical success of 72% and 90%, respectively.

Prosthetic Graft Interposition

After surgical dissection with isolation of the efferent vein, it is sectioned and a 5 mm prosthetic segment is interposed, 5 to 2 cm away from the anastomotic chamber (Figure 1e). This technique has shown technical success in 100% of 25 patients, with clinical improvement in 96% of treated patients [32]. Advantages include a lower recurrence rate of high flow, with a higher risk of access infections or thrombosis compared to simple banding [33].

Endovascular Vein Diameter Reduction

Several endovascular techniques have been described to reduce the diameter of the efferent vein, resulting in reduced flow. Some authors have placed a covered stent, flared at one end, at the post-anastomotic segment of the efferent vein, resulting in a reduction in the usable lumen diameter (Figure 1f), with improvement in ischemic symptoms and fistula flow reduction [34]. Other authors have used a similar technique in three patients, but in which a larger caliber, longer covered stent is inserted into a smaller caliber and shorter covered stent, creating an hourglass-shaped structure (Figure 1g), adhering at the ends to the vein wall but having an internal segment of smaller caliber, reducing flow in the AVF [35].

Management of Stagnant Venous Ischemia

In this condition, the presence of arterialized venous collateral vessels directed towards the hand, with or without obstruction in proximal outflow vessels, can result in increased pressure in the capillary venous side of the hand, resulting in “warm” ischemia, associated with edema. This condition can be resolved by ligating the vessels directed towards the hand with possible treatment of venous stenotic lesions when indicated (Figure 1h) [36].

 

Artery

Distal Artery Ligation

In distal forearm fistulas constructed with the radial artery, which is non-terminalized, distal radial artery ligation (DRAL) (Figure 2a) can be a resolving method for improving ischemic syndrome by interrupting retrograde flow from the hand to the fistula [37]. This procedure should only be performed after assessing the capacity of the ulnar artery, with the palmar arch, to provide adequate vascularization of the hand and is indicated for the treatment of distal ischemic syndrome [38].

Figure 2. In this picture are presented main artery techniques to manage pathological AVFs.
Figure 2. In this picture are presented main artery techniques to manage pathological AVFs.

Proximal Artery Ligation

Proximal radial artery ligation (PRAL) (Figure 2b) is used to reduce flow in AVFs with the radial artery in the distal forearm. AVF patency will be ensured by retrograde flow from the distal radial artery, through the palmar arch and the ulnar artery. In this case as well, the patency of these structures should be established before the procedure to avoid complete closure of the fistula. Burquelot et al. demonstrated a success rate of flow reduction in 92% of cases, with primary patency at 1 and 2 years of 88% and 74%, respectively, in 37 patients [39].

Distal Radial Artery Embolization

Unlike the previously described techniques, interruption of arterial flow in the distal radial artery can be performed endovascularly, using embolization coils [38, 40, 41] (Figure 2c). The endovascular approach can allow simultaneous treatment of stenotic lesions of the brachial, proximal radial, or ulnar arteries [42], reducing procedural times with less invasiveness compared to surgical approaches.

Angioplasty of Stenotic Lesions

The presence of stenotic lesions in the arterial system supplying the AVF can cause various forms of distal ischemic injury. Stenosis on the ulnar side can cause reduced blood flow to the hand in patients with distal radio-cephalic fistulas due to physiological “steal” from the radial artery [42, 43], or in proximal accesses with brachial artery stenosis and associated radial or ulnar artery lesions [44]. Endovascular treatment of such lesions with angioplasty can lead to rapid improvement in patient symptoms, with minimally invasive and rapid procedures (Figure 2d). The presence of calcified stenotic lesions can pose challenges. Recently, new techniques have been developed and used by vascular surgeons and cardiologists. Intravascular lithotripsy (IVL) allows for the fragmentation of calcium by emitting sound waves from a device placed inside the vessel [45]. We have recently begun using this equipment in the treatment of pre-existing arterial stenotic lesions at the time of fistula creation [46, 47] or in failed fistulas during maturation [48]. This opens the possibility of using this tool in the future for the treatment of calcified stenotic lesions causing distal ischemic syndrome.

Anastomosis

RUDI

Revision Using Distal Inflow (RUDI) is a surgical technique used to revise the anastomosis in fistulas with the brachial artery associated with distal ischemia with or without high flow. The technique involves isolating the anastomosis, ligating the efferent vein, and applying a prosthetic bridge between the post-ligation vein segment and the radial or ulnar artery [49, 50] (Figure 3a). This method remodels a proximal fistula with the brachial artery into a “distal” fistula by distal transposition of the inflow. This results in a reduction in access flow as well as reduced steal from the brachial artery. Variants of this technique have been described, involving ligation of the efferent vein, its sectioning with transposition and anastomosis with the radial or ulnar artery [51]. Literature reports a 50% reduction in access flow, improvement in symptoms and ischemic lesions, with primary patency at 3 and 12 months of 80% and 100% respectively [52]. Other authors described primary and secondary patency at 3 years of 48% and 84% respectively, with a postoperative flow reduction of approximately 65% [53]. Mallios recently described a new technique, performed on a patient, named endo-RUDI, in which he created an anastomosis between the proximal radial artery and the radial vein using the Ellipsys endovascular system and subsequently, during surgical time, anastomosed the basilic vein (efferent of the previous brachio-basilic access) with the radial vein, ligating the previous anastomosis. This achieved distalization of the inflow [54].

Figure 3. In this picture are presented main techniques to remodeling AVFs anastomosis
Figure 3. In this picture are presented main techniques to remodeling AVFs anastomosis

DRILL

Distal Revascularization with Interval Ligation (DRILL) is used to treat distal ischemic syndromes with or without high flow by “proximalizing” the bifurcation of the brachial artery in patients with proximal fistulas with the brachial artery. A prosthetic bridge (or using autologous veins such as the saphenous) is placed between the artery (brachial or axillary) upstream of the anastomosis and the brachial artery downstream of the anastomosis, followed by ligation of the artery between the anastomosis (with the vein) and the new distal anastomosis (Figure 3b). This remodels the pathological access as if it were a fistula with a terminalized radial or ulnar artery [55]. A challenge with this technique is that distal arterial perfusion depends on graft patency; therefore, some authors recommend not ligating the artery between the two anastomoses, although this limits the effectiveness of the procedure in reducing access flow. Literature reports an 80% technical success rate [56] with primary access patency rates at 12 and 24 months of 87% and 79% respectively [57].

PAI

Proximalization of Arterial Inflow (PAI). By placing a junctional prosthetic bridge between the brachial or axillary artery and the efferent vein of the fistula with ligation of the vein in the iuxtanastomotic tract, the access is remodeled by “recreating” a high bifurcation of the artery, eliminating the previous anastomosis (Figure 3c). In this procedure, useful for reducing symptoms related to distal ischemia in AVFs with or without high flow, the brachial artery is not ligated as in DRILL, avoiding possible complications of distal vascularization in case of graft thrombosis [58]. Graft thrombosis will result in non-functioning of the vascular access, without compromising upper limb vascularization. With this technique, primary and secondary patency rates of 87% and 90% at 1 year and 67% and 78% at 3 years are described, with a significant improvement in ischemic symptoms [59].

Radial Artery Transposition

This technique described by Bourquelot [60] reduces the flow of a pathological access with the brachial artery by dissecting the radial artery, proximally transposing it, and anastomosing it with the efferent vein of the previous AVF, suppressing the old anastomosis (Figure 3d). This creates a new end-to-end anastomosis with the radial artery, effectively reducing its flow through a modification of the inflow, which will be supplied by the radial artery. Technical success is reported in 91% of cases, with a 66% reduction in fistula flow. Primary patency at one and three years was 61% and 40% respectively, with secondary patency of 89% and 70%.

From the preceding chapters, it is evident that the techniques currently used to reduce the flow of a vascular access or to improve distal perfusion are diverse. These techniques may involve the venous compartment, the arterial compartment, or act through “remodeling” of the anastomosis. There are both surgical and endovascular techniques, some well-established and others emerging. Some of the described procedures have a greater impact on the flow of the AVF, while others focus on improving distal perfusion. As previously described, the pathophysiological aspects of high-flow fistulas and distal ischemic syndrome are often intertwined. Therefore, in practical terms, we may encounter three types of issues, which are easy to diagnose: high-flow fistulas without distal ischemic syndrome, high-flow fistulas with distal ischemic syndrome, and fistulas with distal ischemic syndrome without high flow. The aim of this review is to propose a decision-making algorithm, based on literature data, to indicate which procedures to implement for addressing these three categories (Table 2, Figure 4).

Reducing flow Reducing ischemia
Vein
Vein ligature +++ +
Miller technique +++ +
Vein plication +++ +
Vein banding +++ +
Prosthetic interposition +++ +
Endovascular vein caliper reduction +++ +
Artery
DRAL + ++
PRAL ++ –
Distal radial artery embolization + ++
Stenotic lesion angioplasty – +++
Anastomosis
RUDI + +++
DRILL + +++
PAI + +++
Radial artery transposition ++ +
Table 2. Available techniques. This table represents the effectiveness of the various techniques described in achieving flow rate reduction and/or improvement of ischemia in arteriovenous fistulas.
Figure 4. In this picture are presented decisional make algorithm to hang AVFs pathology in case of high flow with or without associated ischemia.
Figure 4. In this picture are presented decisional make algorithm to hang AVFs pathology in case of high flow with or without associated ischemia.

 

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  45. Madhavan MV, Shahim B, Mena-Hurtado C, Garcia L, Crowley A, Parikh SA. Efficacy and safety of intravascular lithotripsy for the treatment of peripheral arterial disease: An individual patient-level pooled data analysis. Catheter Cardiovasc Interv. 2020 Apr 1;95(5):959-968. https://doi.org/10.1002/ccd.28729. Epub 2020 Jan 20. PMID: 31957955; PMCID: PMC7187419.
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  50. Callaghan CJ, Mallik M, Sivaprakasam R, Iype S, Pettigrew GJ. Treatment of dialysis access-associated steal syndrome with the “revision using distal inflow” technique. J Vasc Access. 2011 Jan-Mar;12(1):52-6. https://doi.org/10.5301/jva.2010.5985. PMID: 21058261.
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Platelet-To-Lymphocyte Ratio and Arteriovenous Fistula for Hemodialysis: An Early Marker to Identify AVF Dysfunction

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Roberta Maria Messina

DOI: 10.69097/41-06-2024-12

Roberta Maria Messina1, Vincenzo Calabrese2, Fortunata Zirino1, Antonella Lipari1, Alfio Edoardo Giuffrida1, Concetto Sessa1, Dario Galeano1, Ivana Alessandrello1, Giulio Distefano1, Viviana Scollo1, Carmelo Zuppardo1, Domenico Santoro2, Walter Morale1

1 Department of Nephrology and Dialysis “Maggiore” Hospital Modica, Ragusa, 97015, Italy
2 Department of Clinical and Experimental Medicine, Unit of Nephrology and Dialysis, A.O.U. “G. Martino”, University of Messina, Messina, 98125, Italy

Corresponding author:
Roberta Maria Messina
Tel: +39 34076769584
E-mail: robertamaria.messina@asp.rg.it

 

Abstract

The KDOQI guidelines (Kidney Disease Outcomes Quality Initiative) recommend autologous arteriovenous fistula (AVF) as the primary vascular access in hemodialysis patients because of the higher quality of life and lower complication rates if compared to arteriovenous grafts (AVGs) or central venous catheter (CVC). Several studies used various inflammatory biomarkers to evaluate the association between systemic inflammation and AVF dysfunction. A novel inflammatory biomarker, the platelet–lymphocyte ratio (PLR), is a useful and easy laboratory parameter that can reveal systemic inflammation. Our study aimed to evaluate the relationship between PLR value changes over time and AVF dysfunction. The impact of PLR on our outcome showed a trend close to the significance (OR: 4,9; 95%CI: [0.84-28.5]; p = 0.08) but the slope was not linear. Therefore, we performed the same analysis splitting the patients by the median PLR value and we highlighted a significant relationship between our outcome and the PLR (log-transformed) for PLR-value under the median value (OR: 9.97; 95%CI: [2.53-39.25]; p = 0.001). Furthermore, in patients with PLR above the median value, the interaction visit-PLR showed an impact close to the statistical significance (OR: 7.7; 95%CI: [0.81-72.97]; p = 0.07). PLR (log-transformed) was positively correlated with AVF age (Rho: 0.254, p = 0.002).

Keywords: AVF, chronic kidney disease, hemodialysis, platelet-lymphocite ratio, thrombosis

Introduction

The KDOQI guidelines (Kidney Disease Outcomes Quality Initiative) recommend autologous arteriovenous fistula (AVF) as the primary vascular access in hemodialysis patients because of the higher quality of life and lower complication rates if compared to arteriovenous grafts (AVGs) or central venous catheter (CVC) [1–3]. Several studies evaluated the association between systemic inflammation and AVF dysfunction using various inflammatory biomarkers [4, 5, 10].

A novel inflammatory biomarker, the platelet-lymphocyte ratio (PLR), is a useful and easy laboratory parameter that can reveal systemic inflammation [1]. Various studies showed how the PLR values are linked to chronic inflammation in different clinical conditions [8, 12]. Our study aimed to evaluate the relationship between PLR value changes over time and AVF dysfunction (both stenotic and/or thrombotic complications) in our group of patients undergoing chronic hemodialysis (HD) at our center.

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Stenotic FAV: Success of the Collaboration Between Spoke and HUB

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Ramona Nicotera

DOI: 10.69097/41-04-2024-09

Ramona Nicotera1, Armando Pingitore2, Pietro Prunestì3, Salvatore Chiarella4, Cinzia Donato5, Giovanni Mazzitello1, Margherita Bovino1, Pierpaolo Cannistrà6

1 Dirigente Medico SSD Nefrologia e Dialisi, P.O. Soverato
2 Dirigente Medico U.O. Radiologia (Interventistica), P.O. Pugliese-Ciaccio- Catanzaro
3 Direttore SSD Nefrologia e Dialisi, P.O. Soverato
4 Direttore S.O.C. Nefrologia e Dialisi, P.O. Pugliese-Ciaccio- Catanzaro
5 Dirigente Medico S.O.C. Nefrologia e Dialisi, P.O. Pugliese-Ciaccio-Catanzaro
6 Infermiere Professionale SSD Nefrologia e Dialisi, P.O. Soverato, specializzato in accessi vascolari per emodialisi

Corresponding author:
Ramona Nicotera
SSD di Nefrologia e Dialisi
P.O. Soverato (CZ)
Via Carlo De Cardona n°98
Tel/Fax 0961912516
Cell 3408795163
E-mail: ramona.nicotera@gmail.com

 

Abstract

The arteriovenous fistula constitutes the vascular access of first choice in hemodialysis. We present three clinical cases that highlight the resolution in interventional radiology of venous stenosis, one of the major complications.
Clinical monitoring and instrumental diagnostics with color Doppler ultrasound have prevented the failure of the AVF due to high risk of thrombosis.
The angiographic interventions, thanks to the collaboration between Spoke and Hub, were completed without complications.

Keywords: hemodialysis, stenosis, AVF, interventional radiology, color Doppler ultrasound, PTA

Sorry, this entry is only available in Italiano.

Introduzione

La fistola artero-venosa (FAV) per il paziente in dialisi costituisce l’accesso vascolare di prima scelta, in quanto meno gravato da complicanze a medio-lungo termine e per la maggiore sopravvivenza rispetto alla protesi e al catetere venoso centrale permanente [1]. L’Ecocolordoppler (ECD) ormai da anni rappresenta l’esame diagnostico meno invasivo per il mapping dei vasi pre-confezionamento FAV e per il monitoraggio delle complicanze (stenosi, trombosi, ematomi, aneurismi e pseudoaneurismi) venose e arteriose [2–6]. Sono più frequenti le stenosi venose che le stenosi arteriose [7, 8]; si distingue poi ulteriormente tra stenosi dell’inflow (vaso afferente) e stenosi dell’outflow (vaso efferente). Tra le stenosi venose, le stenosi iuxta-anastomotiche (entro i 2 cm dall’anastomosi) sono più frequenti rispetto alle stenosi distali [7, 8].

Il primum movens della stenosi venosa è l’iperplasia neointimale. Costituiscono fattori concomitanti lo stress chirurgico, lo stato pro-infiammatorio legato alla malattia renale cronica, la predisposizione genetica, le venipunture ripetute. Il processo che si determina è un’anomala proliferazione e migrazione delle cellule muscolari lisce, con espressione di citochine, chemochine, e mediatori come l’endotelina, il TGFβ, l’ossido nitrico, l’osteopontina e l’apolipoproteina. Spiegherebbe la riduzione del lume vascolare anche la migrazione di fibroblasti dall’avventizia all’intima [9–11].

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Triple stenosis of brachio-basilic arteriovenous fistula: percutaneous transluminal angioplasty utility, case report and literature review

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Marco Taurisano

Marco Taurisano, Andrea Mancini, Filomena D’Elia

UOC di Nefrologia e Dialisi Ospedale di Venere Bari

Corresponding author:
Andrea Mancini
Cell 3474402862
UOC di Nefrologia e Dialisi
Ospedale Di Venere
Via Ospedale Di Venere Bari
E-mail: andreadot@libero.it

 

Abstract

The major haemodialysis arteriovenous fistula (AVF) complication is stenotic disease. It is represented by a reduction of the arterial or venous caliper forming the AVF. Most frequently it is located in the juxta- anastomotic region of the venous segment.
There are a lot of mechanisms responsible for the stenosis formation; some are correlated by the shear stress in the wall of venous tract with a lot of biochemical mechanisms, others are associated with the repetition of venipuncture during haemodialisys treatment
It is recommended that each dialysis center activate an AVF monitoring program capable of identifying and treating stenosis.
We describe a clinical case of a young woman with a multiple stenosis disease of a brachio-basilical transposed AVF.

Keywords: AVF, haemodialysis, stenosis, PTA, ecoguided PTA

Sorry, this entry is only available in Italiano.

Introduzione

Tra le complicanze della fistola arterovenosa (FAV) per emodialisi (Tabella I), vanno annoverate le stenosi; trattasi di una complicanza strutturale a cui è esposta la FAV. Le stenosi delle FAV native possono interessare sia il versante venoso che quello arterioso. L’incidenza di stenosi coinvolgenti il sistema venoso della FAV risulta essere di gran lunga maggiore rispetto a quello arterioso [1–5]. Le stenosi sono senza dubbio la causa più frequente di failure della fistola arterovenosa; la caduta di portata di cui sono responsabili riduce l’efficienza dialitica con calo del Kt/V, inoltre sono causa di un incremento della pressione negativa nel circuito, ostacolano il ritorno venoso, favoriscono il ricircolo [6, 7].

COMPLICANZE STRUTTURALI COMPLICANZE EMODINAMICHE
Ridotto/assente inflow (stenosi vaso afferente) Ridotta portata della FAV per perdita dell’inflow
Ridotto/assente outflow (stenosi del vaso efferente) Sindrome da furto (Steal syndrome)
Stenosi della porzione centrale del vaso efferente Presenza di collaterali venose che riducono la portata
Ematoma Scompenso cardiaco congestizio
Aneurisma Edema del braccio
Pseudoaneurisma –
Calcificazioni –
Tabella I: complicanze della FAV (Meola M: Ecografia clinica in nefrologia. Fistola arterovenosa, p 1308. Meola M. Eureka editore 2015).

Alcuni autori hanno classificato le stenosi del versante venoso della FAV in iuxta-anastomotiche o distali, a seconda che la sede della stenosi sia rispettivamente entro o oltre i 2 cm dall’anastomosi; anche se per Tessitore [8] vanno considerate tali anche le stenosi entro i 5 cm dall’anastomosi; questo sottotipo è responsabile dell’80 % delle stenosi.

Altra possibile classificazione riguardante la sede delle stenosi prevede la distinzione di stenosi centrali, iuxta-anastomotiche e stenosi riguardanti il tratto di vena compreso tra queste due regioni. Infine, da un punto di vista emodinamico, possiamo classificarle in stenosi dell’inflow e stenosi dell’outflow. Le prime determinano, da un punto di vista emodinamico, una riduzione della portata della fistola e riguardano le stenosi arteriose e le stenosi venose iuxta-anastomotiche; le seconde, invece, sono le stenosi venose distali che determinano un ostacolo al deflusso venoso anche in presenza di una valida portata [9].

La sede più frequente di stenosi è la porzione iuxta-anastomotica [10–13], ma sono frequenti anche le stenosi della porzione centrale della vena efferente sede di venopuntura. Possiamo definire critica una stenosi quando la riduzione del diametro del lume vasale è superiore al 50 % rispetto a quello misurato nella porzione prestenotica. Ma tale definizione non può prescindere dalle alterazioni emodinamiche causate dalla stenosi: una riduzione della portata, l’aumento degli indici di resistenza, l’incremento della velocità di picco sistolico in corrispondenza della stenosi e, non ultima, l’inadeguata efficienza dialitica che accompagnano la stenosi [14].

La FAV è un “bene prezioso” per il paziente emodializzato; il patrimonio vascolare non è illimitato e il ricorso al catetere venoso centrale dovrebbe essere una seconda scelta. La stenosi deve essere considerata come l’iniziale processo di chiusura della FAV: se precocemente riconosciuta e trattata può evitare la chiusura definitiva dell’accesso vascolare.

 

Case report

Descriviamo il caso di una paziente di 54 anni, ipertesa, uremica in trattamento emodialitico da 3 anni, affetta da sindrome Nail-Patella. All’avvio al trattamento veniva confezionata una FAV radio-cefalica distale all’avambraccio sinistro previo mapping preoperatorio dell’arto che evidenziava una vena cefalica di 2 mm che incrementava il suo diametro a più del 50% dopo posizionamento del laccio emostatico; arteria radiale di 2,2 mm con portata di 15 ml/m e un test dell’iperemia reattiva che mostrava una caduta delle resistenze e incremento della portata.

Dopo 6 mesi la FAV andava incontro a failure, per cui veniva posizionato un catetere venoso centrale definitivo in vena giugulare destra. Allestita una nuova FAV distale radio-cefalica a carico dell’avambraccio di destra, quest’ultima andava incontro ad early failure nonostante il mapping preoperatorio mostrasse vasi aggredibili con buona compliance vascolare. Veniva quindi allestita una FAV prossimale brachio-basilica a carico del braccio sinistro con trasposizione della basilica. La portata della fistola, calcolata sull’arteria brachiale, dopo 7 giorni dall’allestimento era pari a 765 ml/m e incrementava a 1130 ml/m dopo 30 giorni.

Durante i trattamenti emodialitici si riscontravano pressioni venose elevate nell’accesso vascolare e pressioni arteriose eccessivamente negative. Veniva intrapreso quindi un follow-up ecografico e veniva posticipata la rimozione del CVC definitivo. Un controllo a distanza di 8 mesi mostrava una caduta della portata a 880 ml/m. L’accesso vascolare, monitorato nei mesi successivi, mostrava una progressiva riduzione di portata: 760 ml/m dopo 10 mesi dall’allestimento; 600 ml/m dopo 13 mesi. Giunge alla nostra osservazione a marzo 2022. L’esame doppler metteva in evidenza una portata pari a 465 ml/min. IR pari a 0,5 e l’evidenza di 3 stenosi lungo il decorso della vena basilica trasposta. Di queste, una si presentava in regione iuxta-anastomotica, con velocità di picco sistolico (PSV) calcolata in corrispondenza della stenosi pari a 350 cm/sec e le due restanti in regione distale con PSV rispettivamente di 617 cm/sec e 387 cm/sec. Si concludeva dunque per FAV malfunzionante con patologia stenotica multipla, con impatto emodinamico significativo. Per difficoltà operativa nel reperire un accesso unico che consentisse di trattare tutte e tre le stenosi contemporaneamente, veniva pianificato un trattamento di PTA in due tempi:

  1. PTA delle due stenosi distali con approccio anterogrado.
  2. PTA della stenosi iuxta-anastomotica con approccio retrogrado.

Veniva eseguita una prima procedura di PTA ecoguidata con balloon non compliante ad alta pressione delle dimensioni di 6 x 30 mm gonfiato fino a 24 atmosfere con completa distensione delle due lesioni stenotiche. Immediatamente dopo la procedura la portata dell’accesso vascolare risultava essere di 1100 ml/min con IR pari a 0,42 (Figure 1-5).

Figura 1: B-Mode. Scansione longitudinale su vena basilica efferente la FAV. Si nota esteso tratto stenotico.
Figura 1: B-Mode. Scansione longitudinale su vena basilica efferente la FAV. Si nota esteso tratto stenotico.
Figura 2: Color-doppler. Portata calcolata su arteria brachiale: 465ml/min; IR 0.5.
Figura 2: Color-doppler. Portata calcolata su arteria brachiale: 465ml/min; IR 0.5.
B-Mode. Gonfiaggio del pallone per angioplastica nel lume
Figura 3: B-Mode. Gonfiaggio del pallone per angioplastica nel lume venoso in corrispondenza del tratto stenotico. Si notano due incisure disegnate sul profilo del pallone, sede di maggiore resistenza della stenosi, che verranno completamente sfiancate al raggiungimento di 24 atmosfere.
B-Mode. Risultato finale della procedura. Assenza di recoil della stenosi, omogeneo il lume vascolare.
Figura 4: B-Mode. Risultato finale della procedura. Assenza di recoil della stenosi, omogeneo il lume vascolare.
Color-doppler. Portata calcolata su arteria brachiale successivamente alla procedura.
Figura 5: Color-doppler. Portata calcolata su arteria brachiale successivamente alla procedura. Si nota un incremento della portata a 1094 ml/min con riduzione indici di resistenza a 0,41.

A distanza di 15 giorni veniva eseguita seconda proceduta di PTA ecoguidata su stenosi iuxta-anastomotica. Veniva utilizzato balloon non compliante ad alta pressione delle dimensioni di 6 x 30 mm gonfiato fino a 24 atmosfere con completa risoluzione della stenosi (Figure 6-10).

Scansione longitudinale su vena basilica efferente la FAV in corrispondenza della regione iuxta-anastomotica stenotica.
Figura 6: B-Mode. Scansione longitudinale su vena basilica efferente la FAV in corrispondenza della regione iuxta-anastomotica stenotica.
Figura 7: Color-doppler. Portata calcolata su arteria brachiale: 920 ml/min con IR 0.49.
Figura 7: Color-doppler. Portata calcolata su arteria brachiale: 920 ml/min con IR 0.49.
Gonfiaggio del pallone per angioplastica nel lume venoso in corrispondenza del tratto stenotico.
Figura 8: B-Mode. Gonfiaggio del pallone per angioplastica nel lume venoso in corrispondenza del tratto stenotico. Pallone completamente disteso, gonfiato a 24 atmosfere.
Figura 9: B-Mode. Risultato finale della procedura. Assenza di recoil della stenosi, omogeneo il lume vascolare.
Figura 9: B-Mode. Risultato finale della procedura. Assenza di recoil della stenosi, omogeneo il lume vascolare.
Portata calcolata su arteria brachiale successivamente alla procedura
Figura 10: Color-doppler. Portata calcolata su arteria brachiale successivamente alla procedura. Si nota un incremento della portata a 1756 ml/min con riduzione indici di resistenza a 0,37.

La portata dell’accesso al termine della procedura risultava pari a 1600 ml/min con IR pari a 0,37. Contestualmente nella stessa seduta operatoria veniva rimosso CVC giugulare definitivo destro. In Figura 11 è riportato l’andamento della portata della FAV dal suo allestimento fino all’espletamento dell’ultima procedura descritta.

Figura 11: Il grafico, portata/tempo, mostra l’andamento del flusso prima e dopo le due procedure di angioplastica.
Figura 11: Il grafico, portata/tempo, mostra l’andamento del flusso prima e dopo le due procedure di angioplastica.

 

Discussione

Il primum movens del processo di stenosi è rappresentato dall’iperplasia neointimale, a sua volta legata ad un incremento dello shear-stress di parete per l’imponente incremento di flusso cui è sottoposto il vaso dopo la creazione dell’anastomosi. Concorrono, al processo di stenosi, anche lo stato pro infiammatorio proprio della malattia renale cronica, le venipunture ripetute, lo stress chirurgico, fattori genetici. Tutti questi elementi sono responsabili del rimodellamento della parete vascolare e di una anomala proliferazione [15] e migrazione delle cellule muscolari lisce mediata da una serie di fattori: citochine, chemochine, ossido di azoto, endotelina, osteopontina, apolipoproteina [10, 16-21].

È inoltre dimostrata una migrazione di fibroblasti dall’avventizia all’intima e la loro trasformazione in miofibroblati che contribuisce in maniera significativa alla riduzione del lume vascolare [22–28]. Alcuni studi hanno incentrato l’attenzione sulla natura delle cellule che costituiscono la neointima: la loro identificazione pone infatti le basi per azioni terapeutiche volte a inibire il processo di proliferazione neointimale. In particolare la recente evidenza di fibroblasti migrati dall’avventizia all’intima e trasformati in miofibroblasti ha sottolineato il ruolo fondamentale di queste cellule nella produzione di matrice extracellulare della neointima. Tutto questo rimarca l’importanza dell’avventizia come attore in prima linea nel processo di iperplasia neointimale e la pone al centro dell’attenzione di interventi terapeutici che mirino al controllo di tutti questi elementi cellulari (fibroblasti, miofibroblasti, cellule muscolari lisce). Da ciò la proposta di alcuni autori di utilizzare farmaci antiproliferativi ad azione perivascolare [29-31]. Non ultima la necessità di una corretta manipolazione chirurgica intraoperatoria finalizzata a preservare l’avventizia e i vasa vasorum [29]; è dimostrato infatti che il ridotto traumatismo della parete vasale riduce in maniera significativa l’iperplasia neointimale [32].

Il malfunzionamento dell’accesso vascolare è una temuta complicanza del paziente in trattamento emodialitico: la sorveglianza clinica e il monitoraggio strumentale della FAV tendono a scongiurare questo pericolo. Negli anni si sono sviluppati programmi di sorveglianza clinico/strumentale spesso dissociati in quanto il nefrologo non sempre è il fulcro di questa sorveglianza, demandando al chirurgo vascolare o al radiologo la parte tecnico/strumentale. Nel nostro centro da tempo è stata posta l’attenzione a questo tipo di problematica e un team dedicato, oltre ad effettuare una sorveglianza clinica (esame ispettivo della FAV, Kt/V, ricircolo dell’accesso, monitoraggio delle pressioni venose ed arteriose intradialitiche), provvede al monitoraggio ecografico delle FAV a rischio di chiusura. L’ecocolordoppler infatti va ritenuto l’unica indagine capace di fornire informazioni strutturali e funzionali sull’accesso vascolare [33-36]; la metodica, infatti, oltre ad identificare deficit funzionali, mediante la valutazione della portata [35–47], è in grado di individuare stenosi e trombosi da correggere mediante interventi di angioplastica, anch’essi ecoguidati, con i quali lo stesso nefrologo può cimentarsi.

Va comunque precisato che i programmi di sorveglianza degli accessi vascolari a tutt’oggi sono oggetto di discussione, in quanto lì dove studi osservazionali indicano che la correzione preventiva delle stenosi riduca la percentuale di fallimento dell’accesso vascolare [47] e le stesse linee guida NKF-K-DOQI [48] consigliano di sottoporre gli emodializzati portatori di FAV ad un programma di sorveglianza dell’accesso vascolare, ci sono pareri discordanti che attribuiscono una scarsa efficacia a detti programmi [49–51].

I dati presenti in letteratura mostrano come vi sia una tendenza alla recidiva della stenosi dopo trattamento mediante PTA.

Le varie casistiche identificano una pervietà della FAV tra il 50-60% ad un anno dal trattamento. L’ipotesi eziopatogenetica è identificata nella iperplasia reattiva dei miociti della parete del vaso sottoposto a stretching durante la procedura con conseguente reazione sclerotico-cicatriziale e riformazione della stenosi [52]. A tal ragione vengono usati con maggiore frequenza balloon medicati (DCB), ricoperti da farmaci antiproliferativi come il Placitaxel, che rilasciati nella parete vascolare durante la dilatazione della stenosi vanno ad inibire la proliferazione reattiva. Grazie all’utilizzo di tali dispositivi si è ottenuta una pervietà primaria maggiore rispetto ai ballon convenzionali: fino all’80% a 6 mesi [53].

 

Conclusioni

La FAV va considerata l’accesso vascolare di prima scelta, la sua sopravvivenza deve essere garantita con l’utilizzo di tutti i mezzi a nostra disposizione: osservazione clinica e strumentale, monitoraggio intradialitico, accuratezza nella venopuntura. Le stenosi rappresentano la causa più frequente di malfunzionamento della FAV, se precocemente riconosciute e trattate l’accesso vascolare “sopravvive”. È nostra esperienza che la restenosi di una FAV, sottoposta ad angioplastica, è una evenienza possibile, ma proprio la sorveglianza di queste FAV a rischio ci consente di reintervenire concedendo all’accesso vascolare un ulteriore periodo di utilizzo.

 

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