Overview
Definition:
The HeRO graft (Hemodialysis Reliable Outflow graft) is a synthetic vascular access device designed to provide a reliable outflow pathway for hemodialysis in patients with challenging venous anatomy, particularly those with central venous stenosis or occlusion
It consists of a short segment of reinforced expanded polytetrafluoroethylene (ePTFE) graft that connects to a percutaneous valved venous conduit
The valved conduit acts as a one-way valve, preventing venous outflow obstruction and facilitating repeated access for dialysis
This system aims to overcome limitations of traditional AV fistulas and grafts in complex cases.
Epidemiology:
Central venous stenosis and occlusion are common complications in patients on long-term hemodialysis, affecting an estimated 30-60% of patients requiring repeat access
The HeRO graft is indicated in a subset of these patients where conventional access methods have failed or are not feasible due to severe venous disease, making its use specific to complex cases rather than a widespread initial intervention.
Clinical Significance:
For patients with end-stage renal disease (ESRD) requiring hemodialysis, a functioning vascular access is life-sustaining
Central venous stenosis presents a significant challenge, leading to access failure, suboptimal dialysis, arm swelling, and pain
The HeRO graft offers a solution for these patients, potentially restoring access, improving dialysis efficiency, and preventing further complications related to poor venous outflow
Successful implantation is crucial for maintaining dialysis adequacy and improving patient quality of life, making it a vital procedure for vascular surgeons.
Indications
Primary Indications:
Failure of traditional AV fistula or AV graft due to central venous stenosis or occlusion
Absence of suitable peripheral venous or arterial sites for creation of an AV fistula
Recurrent venous stenosis despite angioplasty or stenting
Patients requiring repeated access interventions due to complex venous anatomy.
Contraindications:
Active infection at the proposed insertion site
Uncorrected coagulopathy
Severe peripheral arterial disease precluding arterial inflow if an arterial component is needed (though HeRO primarily addresses venous outflow)
Patient refusal or inability to tolerate surgery and post-operative care.
Patient Selection Criteria:
Thorough pre-operative venous mapping to confirm the nature and extent of central venous stenosis/occlusion
Assessment of arterial inflow
Evaluation of patient's overall health status and ability to comply with post-operative care and monitoring.
Preoperative Preparation
Vascular Mapping:
Duplex ultrasound mapping is essential to assess the arterial inflow, identify the optimal arterial anastomosis site, and evaluate the venous system for the proposed outflow conduit and to confirm the presence and severity of central venous stenosis.
Imaging Studies:
Venography with pressure measurements may be performed to precisely delineate the anatomy of central venous stenosis/occlusion and assess the impact on venous pressure
CT angiography or MR venography can also provide detailed anatomical information.
Medical Optimization:
Correction of anemia, electrolyte imbalances, and coagulopathies
Optimization of cardiac and pulmonary function
Review and adjustment of antihypertensive and anticoagulant medications as per institutional protocol.
Antibiotic Prophylaxis:
Intravenous administration of appropriate antibiotics (e.g., cefazolin) 30-60 minutes prior to incision, according to institutional guidelines, to reduce the risk of surgical site infection.
Procedure Steps
Anesthesia And Positioning:
Typically performed under local anesthesia with sedation, or general anesthesia, depending on patient factors and surgeon preference
The patient is positioned supine with the ipsilateral arm extended and prepped and draped sterilely.
Arterial Anastomosis:
A suitable arterial inflow site (e.g., radial artery, brachial artery, or axillary artery) is selected based on vascular mapping
An appropriate length of the ePTFE graft is tunneled subcutaneously to the chosen arterial site
An end-to-side or side-to-side arterial anastomosis is created using fine non-absorbable sutures (e.g., Prolene).
Graft Tunneling And Venous Outflow Conduit Placement:
The remaining segment of the ePTFE graft is tunneled subcutaneously towards the venous outflow conduit insertion site, typically in the subclavian or jugular vein
The valved venous conduit is then advanced into the central vein, ideally positioned across the stenosis or into a patent segment of the superior vena cava (SVC) or right atrium, secured with a purse-string suture to the skin and fascia.
Graft Connection And Hemostasis:
The distal end of the tunneled ePTFE graft is anastomosed to the superior aspect of the venous outflow conduit using fine sutures
Meticulous hemostasis is achieved at all anastomosis sites and along the graft tunnel
The patency of the graft and the outflow conduit is confirmed by palpation and by observing pulsatile flow.
Wound Closure:
Subcutaneous tissues and skin are closed in layers with absorbable and non-absorbable sutures
Sterile dressings are applied.
Postoperative Care
Early Monitoring:
Close monitoring of vital signs, graft pulsation, thrill, and bruit
Assessment for signs of bleeding, infection, or limb ischemia
Serial Doppler ultrasound evaluation may be performed to confirm patency.
Pain Management:
Adequate analgesia provided with oral or intravenous pain medications as needed
Early mobilization of the arm is encouraged.
Anticoagulation:
Post-operative anticoagulation is typically not required unless there are specific indications (e.g., thrombophilia, concurrent interventions)
However, aspirin may be prescribed for long-term graft patency.
Infection Prevention:
Continued wound care and monitoring for signs of infection
Prompt treatment of any suspected infection with appropriate antibiotics
Emphasis on meticulous hand hygiene by healthcare providers and patients.
Dialysis Initiation:
Dialysis can usually be initiated 24-48 hours after implantation, provided graft patency and hemostasis are satisfactory
The valved conduit allows for percutaneous cannulation.
Complications
Early Complications:
Bleeding or hematoma at surgical sites
Graft or conduit thrombosis
Infection of the graft or conduit
Pseudoaneurysm formation
Steal phenomenon
Nerve injury.
Late Complications:
Venous outflow conduit stenosis or thrombosis
Graft occlusion
Catheter-related bloodstream infections (CRBSI) if the conduit is used for long-term catheterization
Graft infection
Fistula stenosis (if arterial inflow compromised).
Prevention Strategies:
Meticulous surgical technique with careful anastomosis and hemostasis
Adequate graft tunneling to prevent kinking
Appropriate patient selection and pre-operative imaging
Prophylactic antibiotics and strict sterile technique during cannulation
Regular monitoring for early signs of complications
Early intervention for any evidence of stenosis or thrombosis.
Key Points
Exam Focus:
Understand the primary indication for HeRO graft (central venous stenosis)
Differentiate it from other AV access types
Recall the basic components: ePTFE graft and valved venous conduit
Key complications like thrombosis and infection are high-yield
Remember the importance of vascular mapping.
Clinical Pearls:
In cases of suspected central venous stenosis, always consider a HeRO graft as a salvage option when other accesses fail
Meticulous attention to hemostasis at the venous conduit anastomosis is critical to prevent early thrombosis
Educate patients on the importance of avoiding kinks in the graft tunnel and maintaining hygiene around the conduit site.
Common Mistakes:
Incorrect placement of the venous outflow conduit, leading to inadequate relief of stenosis or direct impingement
Inadequate arterial inflow assessment, leading to graft failure
Failure to recognize and promptly manage graft or conduit thrombosis
Underestimating the risk of infection with the valved conduit.