Endovascular treatment of hemodialysis access stenosis under color Doppler ultrasound guidance

Hemodialysis (HD) is aimportant treatment method for patients with end-stage renal failure. The construction of a smooth and effective HD access is a necessary prerequisite for ensuring that patients with end-stage renal failure maintain effective HD treatment. When a patient needs HD treatment within 1 year, or has a creatinine clearance <25 ml/min, serum creatinine >4 mg/dl, and is expected to undergo HD after 6 months, the establishment of a hemodialysis access should be considered. Arterio-venous fistulas (AVF) and arterio-venous grafts (AVG) are currently the preferred methods of access construction. Intimal hyperplasia or thrombosis caused by repeated punctures, infection, compression, and arteriosclerosis are common causes of access stenosis and occlusion. The K/DOQI guidelines developed by the National Kidney Foundation clearly indicate that when HD does not reach the expected blood flow or hemodynamic parameters show stenosis of the fistula vessel, active intervention treatment is needed. Epidemiological data show that more than 30% of HD patients require hospitalization for additional treatment due to stenosis or occlusion of the hemodialysis access. With the development of intravascular treatment technology, percutaneous transluminal angioplasty (PTA) has been widely used in the treatment of AVF/AVG stenosis or occlusion. PTA is a minimally invasive intravascular treatment that avoids the related risks of excessive central venous catheterization, maximizes the preservation of the patient's limited vascular resources, is more effective than traditional surgical treatment, and has become the preferred treatment method for hemodialysis access stenosis.

1. Difficulties in Interventional Treatment of Hemodialysis Access Stenosis

The Japanese Society for Dialysis Therapy published the "Guidelines for Construction and Maintenance of Hemodialysis Access in Chronic Dialysis" which states:If AVF anastomosis blood flow <180 ml/min, near anastomosis or outflow vein stenosis diameter <2.5 mm as measured by DSA, and stenosis exists simultaneously, and blood flow decreases significantly during dialysis, it indicates AVF stenosis. For proximal vein stenosis of AVF and anastomosis stenosis or arterial stenosis where the guidewire can pass, PTA is the preferred treatment. Increased venous pressure in the artificial vessel leads to recirculation, and recirculation rate ≥10%, or prolonged dialysis time, increased venous pressure, reduced thrill, and vessel diameter <2.5 mm indicate AVG stenosis. If the vessel pressure exceeds 15 atm (1 atm = 101325 Pa), a non-compliant or semi-compliant balloon can be used for PTA. For difficult-to-open stenosis, ultra-high-pressure balloons or cutting balloons can be used. For AVF/AVG stenosis, if elastic recoil and non-central venous blood flow obstruction occur after PTA treatment, stent implantation is recommended; if restenosis occurs within 3 months after PTA, hematoma after dilation causes blood flow obstruction, increasing the risk of re-occlusion, stent implantation can also be considered.

DSA interventional treatment of hemodialysis access presents a series of difficulties. The arteriovenous anastomosis and the venous outflow tract 2-5 cm nearby are common sites of AVF stenosis and occlusion. At the same time, cephalic vein and radial artery side-to-side or end-to-side anastomosis easily form obvious vascular angulation and tortuosity. Currently, the mainly used are semi-compliant PTA balloons designed for lower limb arteriosclerosis occlusion. The balloon is difficult to pass through the angled and tortuous stenosis sites via the brachial artery route. The intimal hyperplasia proximal to the anastomosis caused by the high-flow, high-shear environment at the venous site of AVF/AVG is relatively hard and difficult to fully expand, leading to an increased risk of restenosis or occlusion. The diameter of coronary artery balloons is relatively small, and currently, high-pressure balloons or cutting balloons are mostly used for expansion treatment abroad.

2. Intravascular Treatment Guided by Color Doppler Ultrasound

With the improvement in the precision of ultrasound instruments,color Doppler ultrasound can clearly display the peripheral vascular structure and intravascular interventional devices. In 1983, the concept of interventional ultrasound (INVUS) was proposed and rapidly implemented clinically. The European INVUS treatment guidelines published in 2015 have clearly indicated that INVUS can be used for interventional treatment of arterial and venous diseases in multiple parts of the body, including hemodialysis access. Compared with traditional DSA interventional treatment, INVUS has lower requirements for equipment and venues, can flexibly change the probe section, perform multi-angle observation, and can observe the relationship between the guidewire, balloon catheter, and blood vessels in real time during operation. DSA can only display blood flow, while ultrasound can also display the vessel wall and extravascular structures. Under ultrasound guidance, vascular puncture does not require contrast agents, avoiding contrast agent-related adverse reactions, reducing balloon recoil time, and causing basically no radiation damage to doctors and patients. Bacchini et al. reported 12 cases of ultrasound-guided PTA treatment of AVG stenosis, with good surgical results and no complications. Wakabayashi et al. reported 4896 cases of ultrasound-guided intravascular treatment of hemodialysis access, with a treatment success rate of 97.1% for stenotic lesions and 91.9% for occlusive lesions, and a complication rate of only 0.2%, confirming that ultrasound-guided intravascular treatment of hemodialysis access is safe and effective. For AVG stenosis,ultrasound-guided PTA treatment can reduce the risk of thrombosis by 64%, and the patency rate at 18 months is significantly better than surgical treatment.

Ultrasound-guided intravascular treatment of hemodialysis access can be completed in an outpatient setting, withobvious advantages such as short hospitalization time and low cost, and can also be used for the expansion of arterial stenosis before AVF construction. The ultrasound-guided vascular puncture time and PTA operation time are significantly shorter than DSA interventional treatment, and the immediate success rate of the surgery is higher. Antegrade brachial artery puncture is the main approach for upper limb DSA interventional treatment. Because the brachial artery to radial artery segment has many vascular branches, when the guidewire is advanced along the brachial artery path, it often enters the vascular branches, and multiple adjustments are required to enter the main branch of the radial artery. Adjusting the direction of the guidewire and sheath or multiple punctures to adjust the position can easily lead to perivascular hematoma and pseudoaneurysm formation, and the incidence of interventional treatment failure is also significantly increased. However, ultrasound-guided retrograde venous puncture is relatively easy, shortens the puncture time, and avoids blind arterial puncture damage to the blood vessels. Compared with the brachial artery route, ultrasound-guided retrograde venous puncture as the approach for PTA treatment can avoid the tortuous segment between the radial artery and the cephalic vein, improving the ability of the guidewire and balloon to pass through the stenosis, shortening the distance to the anastomosis and proximal vein stenosis, thereby improving the success rate of treatment.

3. Stenosis and Occlusion of Hemodialysis Access Guided by Color Doppler UltrasoundIntravascular treatment methods

3.1 Percutaneous balloon angioplasty guided by color Doppler ultrasound

Preoperative ultrasound examination of AVF/AVG to identify the location and diameter of stenosis.Disinfect and drape the surgical field, cover the ultrasound probe with a sterile film, and cover the operating interface with a sterile film. After locating the stenosis of AVF with ultrasound, puncture the venous end of AVF 5-8cm above the stenosis site in a retrograde manner under local anesthesia, insert a 5F or 6F vascular sheath, and insert a 0.035in (1in=0.0254 m) ultra-smooth guidewire through the sheath. If the guidewire is difficult to pass through the severely angled, tortuous, or occluded site of arteriovenous fistula, a V-18 guidewire or Pilot 50 guidewire with better passability can be replaced. After the guidewire passes through the lesion, select a peripheral vascular balloon or coronary artery balloon with an appropriate diameter according to the angiographic vessel diameter, and advance the balloon to the stenotic lesion along the guidewire. Expand it fully multiple times (1-2 min/time, pressure 6-12 atm) until the balloon crease disappears.

If the vascular stenosis is still >30%, a balloon with a diameter increased by 1-2mm can be usedfor another dilation or a high-pressure balloon to increase the dilation pressure. If the desired effect is still not achieved, the double-wire double coronary non-compliant balloon dilation technique can be used, that is, two PTA guidewires are inserted through the stenosis, and two small-diameter (2.0-3.5mm) coronary non-compliant balloons are inserted along the two guidewires according to the vessel diameter, and pressurized simultaneously until the balloon crease disappears. Routine heparinization is performed during the operation, and the sheath is removed and pressure dressing is applied after the operation. The technical successcriteria are that the residual stenosis at the lesion site is <30% after treatment, and the clinical success criteria are that HD can be successfully completed once or more after treatment.

3.2 Thrombolysis guided by color Doppler ultrasound

Compared with AVF, AVG has a higher incidence of acute thrombosis, which isan important cause of stenosis and occlusion of AVG. For acute thrombosis of hemodialysis access, theoretically, transcatheter drug thrombolysis, mechanical thrombectomy, Fogarty catheter thrombectomy, Angiojet system thrombectomy, thrombectomy/endothelialectomy, etc. can all be performed under ultrasound guidance. However, at present, it is only limited to case attempts in individual centers, and the success rate and safety are unknown, and there are no large-scale literature reports. Ultrasound-guided fine-needle puncture thrombolysis (lyse-and-wait technique) of hemodialysis access is a safe and effective treatment method reported more frequently at present.

Under ultrasound guidance, a No. 7 scalp puncture needle is used to directly puncture the thrombussite, and the pulsed injection method is used for drug administration, which ensures a certain pressure, so that the drug solution is accurately injected into the thrombus, and avoids strong stimulation to the blood vessels, ensuring the local drug concentration and reducing the amount of urokinase used. Puncture the arterial side of the AVG artificial blood vessel. Domestically, urokinase thrombolysis is often given (maintenance dose 6×10⁴~10×10⁴U/h), while foreign countries mostly use recombinant tissue plasminogen activator (rt-PA), and ordinary heparin is given at the same time. The dose is adjusted according to the pulsation, tremor and ultrasound monitoring results. During thrombolysis, the number of puncture points of the artificial blood vessel can be increased to promote the dissolution of thrombus in the venous anastomosis or hemodialysis puncture segment of the artificial blood vessel. It is not necessary to puncture and draw blood thrombus again to reduce blood loss and damage to blood vessels. At the same time, during the operation, avoid tying a tourniquet to avoid slowing down blood flow and causing thrombus re-formation. Thrombolytic therapy has high requirements for thrombolysis time. Generally, the effect is better within 6 hours of thrombus formation, and the effect is very poor after 48 hours.

The 2010 National Hemodialysis Standard Operating Procedure points out that forfistula thrombus formed within 24 hours, local intravascular injection of urokinase thrombolysis can be used. During the thrombolysis process, ultrasound monitoring should be performed every 30min to evaluate the thrombolysis effect and the degree of vascular recanalization.

4. Summary

Ultrasound examination plays an important role in the diagnosis and treatment of vascular surgical diseases. Ultrasoundguided endovascular treatment of stenosis and occlusion of hemodialysis access can effectively avoid some disadvantages of DSA interventional therapy, with advantages such as short operation time, high success rate of endovascular treatment, and low incidence of complications, which is worthy of clinical promotion and application. With the development of ultrasound instruments and interventional devices, more endovascular operations will be performed in the form of outpatient surgery under ultrasound guidance in the future, greatly improving medical efficiency.

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