Loay Salman

Accuracy of Physical Examination in the Detection of Arteriovenous Fistula Stenosis

BACKGROUND AND OBJECTIVES Physical examination has been highlighted to detect vascular access stenosis; however, its accuracy in the identification of stenoses when compared with the gold standard (angiography) has not been validated in a systematic manner. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS A prospective study was conducted of 142 consecutive patients who were referred for an arteriovenous fistula dysfunction to examine the accuracy of physical examination in the detection of stenotic lesions when compared with angiography. The findings of a preprocedure physical examination and diagnosis were recorded and secured in a sealed envelope. Angiography from the feeding artery to the right atrium was then performed. The images were reviewed by an independent interventionalist who had expertise in endovascular dialysis access procedures and was blinded to the physical examination, and the diagnosis was rendered. Cohens kappa was used as a measurement of the level of agreement beyond chance between the diagnosis made by physical examination and angiography. RESULTS There was strong agreement between physical examination and angiography in the diagnosis of outflow (agreement 89.4%, kappa = 0.78) and inflow stenosis (agreement 79.6%, kappa = 0.55). The sensitivity and specificity for the outflow and inflow stenosis were 92 and 86% and 85 and 71%, respectively. There was strong agreement beyond chance regarding the diagnosis of coexisting inflow-outflow lesions between physical examination and angiography (agreement 79%, kappa = 0.54). CONCLUSIONS The findings of this study demonstrate that physical examination can accurately detect and localize stenoses in a great majority of arteriovenous fistulas.

Patency rates for angioplasty in the treatment of pacemaker-induced central venous stenosis in hemodialysis patients: results of a multi-center study.

While hemodialysis access ligation has been used to manage pacemaker (PM) and implantable cardioverter‐defibrillator (ICD) lead‐induced central venous stenosis (CVS), percutaneous transluminal balloon angioplasty (PTA) has also been employed to manage this complication. The advantages of PTA include minimal invasiveness and preservation of arteriovenous access for hemodialysis therapy. In this multi‐center study we report the patency rates for PTA to manage lead‐induced CVS. Consecutive PM/ICD chronic hemodialysis patients with an arteriovenous access referred for signs and symptoms of CVS due to lead‐induced CVS were included in this analysis. PTA was performed using the standard technique. Technical and clinical success was examined. Technical success was defined as the ability to successfully perform the procedure. Clinical success was defined as the ability to achieve amelioration of the signs and symptoms of CVS. Both primary and secondary patency rates were also analyzed. Twenty‐eight consecutive patients underwent PTA procedure. Technical success was 95%. Postprocedure clinical success was achieved in 100% of the cases where the procedure was successful. The primary patency rates were 18% and 9% at 6 and 12 months, respectively. The secondary patency rates were 95%, 86%, and 73% at 6, 12, and 24 months, respectively. On average, 2.1 procedures/year were required to maintain secondary patency. There were no procedure‐related complications. This study finds PTA to be a viable option in the management of PM/ICD lead‐induced CVS. Additional studies with appropriate design and sample size are required to conclusively establish the role of PTA in the management of this problem.

Stent graft for nephrologists: concerns and consensus.

The role of the stent graft is emerging in the management of arteriovenous dialysis access. Physicians are incorporating this device in the management of three distinct problems--vein-graft anastomotic stenosis, pseudoaneurysm formation, and cephalic arch stenosis--with varying degrees of success. Indeed, a recent randomized, controlled trial to evaluate the role of angioplasty plus stent graft versus angioplasty alone for the management of stenosis at the vein-graft anastomosis led to the approval of the stent graft by the Food and Drug Administration; however, several elements of the management of stenosis at the vein-graft anastomosis/cephalic arch as well as the repair of pseudoaneurysms by stent graft remain controversial. The situation is further complicated and warrants a cost-to-benefit ratio analysis when the added cost of the device is appended to the procedure. In contrast to the controversies, angioplasty-induced complete vascular rupture is one situation in which a stent graft is indicated beyond any doubt. With recent conditional Food and Drug Administration approval, it is anticipated that the use of stent grafts might increase in our patients. In this context, it is critically important that nephrologists be familiar with the current controversies and consensus that surround the use of stent grafts for dialysis access. Just as therapeutic interventions are analyzed in other disciplines within nephrology, these experts must appraise the use of this device for dialysis access. This report presents an up-to-date synopsis on the use of the stent graft that would assist renal physicians in requesting or rejecting the device for the optimal management of their patients vascular access dysfunction.

Accuracy of physical examination in the detection of arteriovenous graft stenosis.

Physical examination has recently been demonstrated to detect vascular access stenosis in patients with arteriovenous fistulae. However, its accuracy in the identification of stenoses when compared with the gold standard (angiography) in patients with arteriovenous grafts has not been studied in a systematic fashion. We conducted a prospective study to examine the accuracy of physical examination in the detection of stenotic lesions when compared with angiography. Forty‐three consecutive cases referred for an arteriovenous graft dysfunction were included in this analysis. Preprocedure physical examination was performed. The findings of the examination and diagnosis were recorded and secured in a sealed envelope. Angiography from the feeding artery to the right atrium was performed. The images were reviewed by an independent interventionalist with expertise in endovascular dialysis access procedures and the diagnosis was rendered. The reviewer was blinded to the physical examination. Cohen’s Kappa was used as a measurement of the level of agreement beyond chance between the diagnosis made by physical examination and angiography. There was a strong agreement between the physical examination and the angiography in the diagnosis of vein‐graft anastomotic stenosis (kappa = 0.52). The sensitivity and specificity for this lesion was 57% and 89%, respectively. There was a moderate agreement beyond chance regarding the diagnosis of intragraft (kappa = 0.43) and inflow stenoses (kappa = 0.40). The sensitivity and specificity for the intragraft and inflow stenosis was 100%, 73% and 33%, 73%; respectively. The findings of this study demonstrate that physical examination can assist in the detection and localization of stenoses in arteriovenous grafts.

Stent Graft Infection and Protrusion Through the Skin: Clinical Considerations and Potential Medico-Legal Ramifications

Stent grafts have been used for a variety of arteriovenous access associated issues. This article presents three cases of stent graft infection and a case of protruded metal piece of the stent graft through the skin. All four required surgical treatment and three cases required a tunneled dialysis catheter to provide long‐term dialysis therapy. This report highlights that stent graft problems can occur that may result in loss of the access. Additionally, strut protrusion can pose a medical hazard to those performing preparation and cannulation of the arteriovenous access.

Impact of Surgeon Selection on Access Placement and Survival Following Preoperative Mapping in the “Fistula First” Era

According to the “Fistula First Initiative” surgeon selection should be based on best outcomes, willingness, and ability to provide access services. This analysis presents arteriovenous access placement and outcomes in 75 patients when surgery was performed by one of two dedicated high‐volume vascular access surgeons (community [surgeon I] and academic medical center [surgeon II]). Preoperative vascular mapping was performed in all the patients. Demographic characteristics were similar except that patients referred to surgeon I (n = 40) were older (52.7 ± 16.2 years vs. 45.4 ± 13.7 years; p = 0.04) and tended to have more previously failed accesses (50% vs. 29%; p = 0.06) and black race (65% vs. 43%; p = 0.055) including a history of previously failed accesses (50% for surgeon I and 29% for surgeon II; p = 0.06). Similarly, there was no significant difference in the size of forearm ([surgeon I: 2.0 ± 1.0 mm], [surgeon II: 1.9 ± 0.8 mm]; p = 0.45) or upper arm veins (cephalic vein: surgeon I = 3.2 ± 1.4 mm, surgeon II = 2.9 ± 1.2 mm, p = 0.34; basilic vein: surgeon I = 5.0 ± 1.2 mm, surgeon II = 4.7 ± 1.3 mm, p = 0.25). Fistulae placement occurred in 98% vs. 71% (p = 0.001) for surgeon I and II, respectively. Characteristics predictive of fistula placement over an arteriovenous graft were surgeon selection (odds ratio [OR] = 19.52; p = 0.01) and no history of diabetes (OR = 7.61; p = 0.016). Kaplan–Meier analysis revealed 6 and 12 months overall access survival rates of 82%, 58% and 82% and 47% for surgeon I and II, respectively (p = 0.007). This analysis demonstrates that surgeon selection can have a significant impact on the rate of fistula placement and its overall survival despite similar findings on preoperative vascular mapping.

A Novel Technique for Tethered Dialysis Catheter Removal Using the Laser Sheath

Traction and cutdown techniques can successfully remove a tunneled dialysis catheter (TDC) in a great majority of patients. However, these methods may not be successful in patients with catheters that are tethered or attached to the central veins or the atrium. A forceful application of traction can lead to catheter breakage with subsequent retention of the broken piece and carries a potential risk of vascular and atrial wall avulsion. Open thoracotomy has been employed to remove an attached TDC. However, this procedure is invasive and bears a significant morbidity. This report presents three cases of tethered TDCs that underwent laser sheath extraction. The TDCs had been in place for an average of 26 months. The patients underwent initial unsuccessful removal attempt using the traction method with surgical exploration all the way to the venotomy site. The laser technique that is used to remove pacemaker/implantable cardioverter defibrillator leads was then applied to these stuck catheters. All three catheters were successfully removed without any damage to the catheter, central veins, or the right atrium. There were no retained catheter fragments left in the central veins or the atrium. One patient demonstrated a significant thrombus that extended from the tip of the catheter all the way to the right ventricle. The external sheath of the laser device successfully aspirated the thrombus. There were no procedure‐related complications. In this small series, a laser sheath successfully extracted tethered dialysis catheters. The study found the procedure to be effective, easy to perform, and minimally invasive. We suggest that this approach be considered for the removal of tethered catheters that cannot be removed using traditional approaches.

Origin of Neointimal Cells in Arteriovenous Fistulae: Bone Marrow, Artery, or the Vein Itself?

To elucidate the source of neointimal cells, experimental fistulas were created in Lewis wild‐type (WT) and transgenic rats that constitutively expressed the green fluorescent protein (GFP) in all tissues. Arteriovenous fistula (AVFs) were created by anastomosing the left renal vein to the abdominal aorta. The contribution of bone marrow (BM)‐derived cells to the AVF neointima was examined in lethally irradiated WT rats that had been rescued with GFP BM cells. Neointimal cells in these chimeric rats were mostly GFP negative indicating the non‐BM origin of those cells. Then, the contribution of arterial cells to the AVF neointima was assessed in a fistula made with a GFP aorta that had been implanted orthotopically into a WT rat. Most of the neointimal cells were also GFP negative demonstrating that AVF neointimal cells are not derived from the feeding artery. Finally to study local resident cells contribution to the formation of neointimal lesions, a composite fistula was created by interposing a GFP vein between the renal vein and the aorta in a WT recipient rat. GFP neointimal cells were only found in the transplanted vein. This study suggests that neointimal cells originate from the local resident cells in the venous limb of the fistula.

Epicardial Cardiac Rhythm Devices for Dialysis Patients: Minimizing the Risk of Infection and Preserving Central Veins

Transvenous leads of cardiac rhythm devices (CRDs) are known to cause central stenosis and are vulnerable to contamination during hemodialysis access‐related bacteremia. In this retrospective study, nine consecutive chronic hemodialysis patients with transvenous CRD infection due to dialysis access‐related bacteremia and recurrent central stenosis are presented. Four patients with tunneled hemodialysis catheters (TDCs) and three with arteriovenous grafts experienced access‐related bacteremia that spread to the transvenous CRD. Two patients required repeated angioplasty procedures (less than 3 months apart) for central venous stenosis. Transvenous CRD was removed and replaced with an epicardial system in all. One patient with TDC switched to peritoneal dialysis and did not experience infection of the epicardial system despite two episodes of peritonitis. The remaining TDC (n = 3) and graft patients (n = 3) received a new TDC after the resolution of bacteremia. While all six experienced on average 1.5 episodes of catheter‐related bacteremia (average follow‐up = 14.5 months), none developed infection of the epicardial system. The patients with central stenosis have required only one angioplasty each for the past 8 and 6 months. To the best of our knowledge this is the first study to suggest that an epicardial approach might be a preferred method over transvenous leads for chronic hemodialysis patients.

Interventional Nephrology: Physical Examination as a Tool for Surveillance for the Hemodialysis Arteriovenous Access

The prospective recognition of stenosis affecting dialysis vascular access and its prospective treatment is important in the management of the hemodialysis patient. Surveillance by physical examination is easily learned, easily performed, quickly done, and economical. In addition, it has a level of accuracy and reliability equivalent to other approaches that require special instrumentation. Physical examination should be part of any education to all hemodialysis care givers. This review presents the basic principles of physical examination of the hemodialysis vascular access and discusses the evidence behind its value.