The Experts below are selected from a list of 3816 Experts worldwide ranked by ideXlab platform

Michael Allon - One of the best experts on this subject based on the ideXlab platform.

  • A Patient with Recurrent Arteriovenous Graft Thrombosis
    Clinical journal of the American Society of Nephrology : CJASN, 2015
    Co-Authors: Michael Allon
    Abstract:

    Arteriovenous Grafts (AVGs) are prone to frequent thrombosis that is superimposed on underlying hemodynamically significant stenosis, most commonly at the Graft-vein anastomosis. There has been great interest in detecting AVG stenosis in a timely fashion and performing preemptive angioplasty, in the belief that this will prevent AVG thrombosis. Three surveillance methods (static dialysis venous pressure, flow monitoring, and duplex ultrasound) can detect AVG stenosis. Whereas observational studies have reported that surveillance with preemptive angioplasty substantially reduces AVG thrombosis, randomized clinical trials have failed to confirm such a benefit. There is a high frequency of early AVG restenosis after angioplasty caused by aggressive neointimal hyperplasia resulting from vascular injury. Stent Grafts prevent AVG restenosis better than balloon angioplasty, but they do not prevent AVG thrombosis. Several pharmacologic interventions to prevent AVG failure have been evaluated in randomized clinical trials. Anticoagulation or aspirin plus clopidogrel do not prevent AVG thrombosis, but increase hemorrhagic events. Treatment of hyperhomocysteinemia does not prevent AVG thrombosis. Dipyridamole plus aspirin modestly decreases AVG stenosis or thrombosis. Fish oil substantially decreases the frequency of AVG stenosis and thrombosis. In patients who have exhausted all options for vascular access in the upper extremities, thigh AVGs are a superior option to tunneled internal jugular vein central vein catheters (CVCs). An immediate-use AVG is a reasonable option in patients with recurrent CVC dysfunction or infection. Tunneled femoral CVCs have much worse survival than internal jugular CVCs.

  • when should a patient receive an Arteriovenous Graft rather than a fistula
    Seminars in Dialysis, 2013
    Co-Authors: Howon Lee, Michael Allon
    Abstract:

    There has been a dramatic increase in the placement and use of Arteriovenous fistulas (AVF) in US patients with chronic kidney disease over the past few years, in accordance with strong recommendations by Fistula First Initiative and KDOQI guidelines. However, AVF nonmaturation remains a substantial obstacle to achieving functional AVFs in a subset of patients, despite the widespread use of preoperative vascular mapping to assist surgeons in planning access surgery, and the growing use of interventions to salvage nonmaturing AVFs. In the right patient, aggressive efforts result in a functioning AVF, which provides adequate dialysis with relatively few interventions required to maintain its long-term patency for dialysis. In the wrong patient, aggressive efforts to achieve a mature AVF may result in numerous failed surgical and percutaneous procedures and prolonged catheter dependence, with all its associated complications. Thus, strict recommendations to place an AVF in all dialysis patients might not benefit every patient, and may actually harm some patients. There are no randomized clinical trials to address which patients are more suitable for placement of an Arteriovenous Graft (AVG), rather than an AVF. However, there is a wealth of observational studies, which taken cumulatively, may assist clinicians in identifying those patients who should receive an AVG. In this article, we review the relevant published literature regarding this topic and provide suggestions for stratifying patients who should receive each type of vascular access.

  • Arteriovenous Graft placement in predialysis patients a potential catheter sparing strategy
    American Journal of Kidney Diseases, 2011
    Co-Authors: Roman Shingarev, Ivan D Maya, Jill Barkerfinkel, Michael Allon
    Abstract:

    Background When predialysis patients are deemed unsuitable candidates for an Arteriovenous fistula, current guidelines recommend waiting until just before or after initiation of dialysis therapy before placing a Graft. This strategy may increase catheter use when these patients start dialysis therapy. We compared the outcomes of patients whose Grafts were placed before and after dialysis therapy initiation. Study Design Retrospective analysis of a prospective computerized vascular access database. Setting & Participants Patients with chronic kidney disease receiving their first Arteriovenous Graft (n = 248) at a large medical center. Predictor Timing of Graft placement (before or after initiation of dialysis therapy). Outcome & Measurements Primary Graft failure, cumulative Graft survival, catheter dependence, and catheter-related bacteremia. Results The first Graft was placed predialysis in 62 patients and postdialysis in 186 patients. Primary Graft failure was similar for pre- and postdialysis Grafts (20% vs 24%; P = 0.5). Median cumulative Graft survival was similar for pre- and postdialysis Grafts (365 vs 414 days; HR, 1.22; 95% CI, 0.81-1.98; P = 0.3). Median duration of catheter dependence after Graft placement in the postdialysis group was 48 days and was associated with 0.63 (95% CI, 0.48-0.79) episodes of catheter-related bacteremia per patient. Limitations Retrospective analysis, single medical center. Conclusion Grafts placed predialysis have primary failure rates and cumulative survival similar to those placed after starting dialysis therapy. However, postdialysis Graft placement is associated with prolonged catheter dependence and frequent bacteremia. Predialysis Graft placement may decrease catheter dependence and bacteremia in selected patients.

  • Arteriovenous Graft infection: a comparison of thigh and upper extremity Grafts.
    Clinical Journal of The American Society of Nephrology, 2011
    Co-Authors: Abha Harish, Michael Allon
    Abstract:

    Summary Background and objectives There are a limited number of publications on the features of Arteriovenous Graft infection in hemodialysis patients. The authors compared the clinical presentation, complications, and outcomes of infections of thigh and upper extremity Grafts. Design, setting, participants, & measurements The authors queried a prospective access database at a large university medical center and identified 132 patients with Graft infections (40 in the thigh and 92 in the upper extremity) requiring surgical excision. The authors collected information regarding the microbiology, complications, and clinical outcomes. Results The two Graft groups were similar in age, gender, race, and frequency of diabetes. The median age of infected Grafts was 162 days for thigh Grafts versus 168 days for upper extremity Grafts ( P = 0.35). Thigh Graft infections were more likely than upper extremity Graft infections to be caused by a Gram-negative rod (31% versus 4%; P = 0.003), and more likely to result in a metastatic infection (15% versus 3%; P = 0.02). The duration of hospitalization associated with Graft infection was similar (10.8 ± 5.4 versus 8.7 ± 6.3 days; P = 0.09). Finally, median catheter dependence was longer after thigh Graft than upper arm Graft infections (319 versus 237 days; P = 0.04). Conclusions As compared with upper extremity Graft infections, thigh Graft infections requiring excision are more likely to be caused by Gram-negative bacteria and to result in serious metastatic complications. These differences may require different empiric antibiotics and a higher index of suspicion for infection in hemodialysis patients with thigh Grafts.

  • effect of dipyridamole plus aspirin on hemodialysis Graft patency
    The New England Journal of Medicine, 2009
    Co-Authors: Bradley S Dixon, Laura M Dember, Michael Allon, Gerald J Beck, Miguel A Vazquez, Arthur Greenberg, James A Delmez, Jonathan Himmelfarb, Jennifer J Gassman, Tom Greene
    Abstract:

    Background Arteriovenous Graft stenosis leading to thrombosis is a major cause of complications in patients undergoing hemodialysis. Procedural interventions may restore patency but are costly. Although there is no proven pharmacologic therapy, dipyridamole may be promising because of its known vascular antiproliferative activity. Methods We conducted a randomized, double-blind, placebo-controlled trial of extended-release dipyridamole, at a dose of 200 mg, and aspirin, at a dose of 25 mg, given twice daily after the placement of a new Arteriovenous Graft until the primary outcome, loss of primary unassisted patency (i.e., patency without thrombosis or requirement for intervention), was reached. Secondary outcomes were cumulative Graft failure and death. Primary and secondary outcomes were analyzed with the use of a Cox proportional-hazards regression with adjustment for prespecified covariates. Results At 13 centers in the United States, 649 patients were randomly assigned to receive dipyridamole plus as...

James S Kaufman - One of the best experts on this subject based on the ideXlab platform.

  • randomized controlled trial of prophylactic repair of hemodialysis Arteriovenous Graft stenosis
    Kidney International, 2004
    Co-Authors: Laura M Dember, Erika F Holmberg, James S Kaufman
    Abstract:

    Randomized controlled trial of prophylactic repair of hemodialysis Arteriovenous Graft stenosis. Background Previous nonrandomized studies suggest that prophylactic repair of hemodialyisis Arteriovenous (AV) Graft stenosis reduces thrombosis rates and increases cumulative Graft survival. The present study is a randomized trial comparing prophylactic repair of AV Graft stenosis with repair at the time of thrombosis. Methods Sixty-four patients with elevated static venous pressure measured in an upper extremity AV Graft were randomized to Intervention or Observation. Monthly static venous pressure/systolic blood pressure ratios (SVPR) were determined for all patients throughout the duration of study participation. Patients in the Intervention group underwent angiography and repair of identified stenoses if the monthly SVPR was elevated (≥0.4). Patients in the Observation group underwent stenosis repair only in the event of access thrombosis or clinical evidence of access dysfunction. The primary end point was access abandonment. Results Access abandonment occurred in 14 patients in the Intervention group and 14 patients in the Observation group during the 3.5-year study period. Time to access abandonment did not differ significantly between the treatment groups (hazard ratio for randomization to Intervention 1.75, 95% CI 0.80–3.82, P = 0.16). The proportion of patients with a thrombotic event was greater in the Observation group (72%) than in the Intervention group (44%) ( P = 0.04), but overall thrombosis rates were similar in the groups. Conclusion Compared with a strategy of observation and repair of accesses only in the event of thrombosis, prospective static venous pressure monitoring with prophylactic stenosis repair did not prolong Graft survival.

  • value of static venous pressure for predicting Arteriovenous Graft thrombosis
    Kidney International, 2002
    Co-Authors: Laura M Dember, Erika F Holmberg, James S Kaufman
    Abstract:

    Value of static venous pressure for predicting Arteriovenous Graft thrombosis Background Static venous pressure elevation has been shown to have both high sensitivity and high specificity for hemodialysis Arteriovenous (AV) Graft venous anastomosis stenosis. However, it is not known how well static venous pressure elevation predicts subsequent AV Graft thrombosis. Methods Monthly static venous pressure measurements were made during two consecutive dialysis sessions in all patients with a functioning upper extremity AV Graft in two hemodialysis units during a 16-month period. Static venous pressure was normalized to systolic blood pressure and corrected for the height difference between the AV Graft and the dialysis machine pressure transducer to yield the static venous pressure ratio (SVPR). Results Fifty-four patients (38%) had a thrombotic event during the study period and thus were labeled as clotters. Among the clotters, SVPR just prior to thrombosis was 0.51 ± 0.16 (mean ± SD), and mean time to thrombosis following an elevated SVPR (≥0.4) was 118 ± 106 days. Receiver operating characteristic (ROC) curves were generated using the sensitivities and specificities of a range of SVPR values for access thrombosis within one, two, three and four months. The areas under the curve (AUCs) for the ROC curves ranged from 0.557 to 0.638, reflecting the absence of SVPR values with both high sensitivity and high specificity for access thrombosis. An increase in SVPR over time was not a better predictor of access thrombosis than absolute SVPR. Conclusion Static venous pressure measurement is not an optimal screening test for identifying AV Grafts at risk for thrombosis.

Laura M Dember - One of the best experts on this subject based on the ideXlab platform.

  • effect of dipyridamole plus aspirin on hemodialysis Graft patency
    The New England Journal of Medicine, 2009
    Co-Authors: Bradley S Dixon, Laura M Dember, Michael Allon, Gerald J Beck, Miguel A Vazquez, Arthur Greenberg, James A Delmez, Jonathan Himmelfarb, Jennifer J Gassman, Tom Greene
    Abstract:

    Background Arteriovenous Graft stenosis leading to thrombosis is a major cause of complications in patients undergoing hemodialysis. Procedural interventions may restore patency but are costly. Although there is no proven pharmacologic therapy, dipyridamole may be promising because of its known vascular antiproliferative activity. Methods We conducted a randomized, double-blind, placebo-controlled trial of extended-release dipyridamole, at a dose of 200 mg, and aspirin, at a dose of 25 mg, given twice daily after the placement of a new Arteriovenous Graft until the primary outcome, loss of primary unassisted patency (i.e., patency without thrombosis or requirement for intervention), was reached. Secondary outcomes were cumulative Graft failure and death. Primary and secondary outcomes were analyzed with the use of a Cox proportional-hazards regression with adjustment for prespecified covariates. Results At 13 centers in the United States, 649 patients were randomly assigned to receive dipyridamole plus as...

  • randomized controlled trial of prophylactic repair of hemodialysis Arteriovenous Graft stenosis
    Kidney International, 2004
    Co-Authors: Laura M Dember, Erika F Holmberg, James S Kaufman
    Abstract:

    Randomized controlled trial of prophylactic repair of hemodialysis Arteriovenous Graft stenosis. Background Previous nonrandomized studies suggest that prophylactic repair of hemodialyisis Arteriovenous (AV) Graft stenosis reduces thrombosis rates and increases cumulative Graft survival. The present study is a randomized trial comparing prophylactic repair of AV Graft stenosis with repair at the time of thrombosis. Methods Sixty-four patients with elevated static venous pressure measured in an upper extremity AV Graft were randomized to Intervention or Observation. Monthly static venous pressure/systolic blood pressure ratios (SVPR) were determined for all patients throughout the duration of study participation. Patients in the Intervention group underwent angiography and repair of identified stenoses if the monthly SVPR was elevated (≥0.4). Patients in the Observation group underwent stenosis repair only in the event of access thrombosis or clinical evidence of access dysfunction. The primary end point was access abandonment. Results Access abandonment occurred in 14 patients in the Intervention group and 14 patients in the Observation group during the 3.5-year study period. Time to access abandonment did not differ significantly between the treatment groups (hazard ratio for randomization to Intervention 1.75, 95% CI 0.80–3.82, P = 0.16). The proportion of patients with a thrombotic event was greater in the Observation group (72%) than in the Intervention group (44%) ( P = 0.04), but overall thrombosis rates were similar in the groups. Conclusion Compared with a strategy of observation and repair of accesses only in the event of thrombosis, prospective static venous pressure monitoring with prophylactic stenosis repair did not prolong Graft survival.

  • value of static venous pressure for predicting Arteriovenous Graft thrombosis
    Kidney International, 2002
    Co-Authors: Laura M Dember, Erika F Holmberg, James S Kaufman
    Abstract:

    Value of static venous pressure for predicting Arteriovenous Graft thrombosis Background Static venous pressure elevation has been shown to have both high sensitivity and high specificity for hemodialysis Arteriovenous (AV) Graft venous anastomosis stenosis. However, it is not known how well static venous pressure elevation predicts subsequent AV Graft thrombosis. Methods Monthly static venous pressure measurements were made during two consecutive dialysis sessions in all patients with a functioning upper extremity AV Graft in two hemodialysis units during a 16-month period. Static venous pressure was normalized to systolic blood pressure and corrected for the height difference between the AV Graft and the dialysis machine pressure transducer to yield the static venous pressure ratio (SVPR). Results Fifty-four patients (38%) had a thrombotic event during the study period and thus were labeled as clotters. Among the clotters, SVPR just prior to thrombosis was 0.51 ± 0.16 (mean ± SD), and mean time to thrombosis following an elevated SVPR (≥0.4) was 118 ± 106 days. Receiver operating characteristic (ROC) curves were generated using the sensitivities and specificities of a range of SVPR values for access thrombosis within one, two, three and four months. The areas under the curve (AUCs) for the ROC curves ranged from 0.557 to 0.638, reflecting the absence of SVPR values with both high sensitivity and high specificity for access thrombosis. An increase in SVPR over time was not a better predictor of access thrombosis than absolute SVPR. Conclusion Static venous pressure measurement is not an optimal screening test for identifying AV Grafts at risk for thrombosis.

Erika F Holmberg - One of the best experts on this subject based on the ideXlab platform.

  • randomized controlled trial of prophylactic repair of hemodialysis Arteriovenous Graft stenosis
    Kidney International, 2004
    Co-Authors: Laura M Dember, Erika F Holmberg, James S Kaufman
    Abstract:

    Randomized controlled trial of prophylactic repair of hemodialysis Arteriovenous Graft stenosis. Background Previous nonrandomized studies suggest that prophylactic repair of hemodialyisis Arteriovenous (AV) Graft stenosis reduces thrombosis rates and increases cumulative Graft survival. The present study is a randomized trial comparing prophylactic repair of AV Graft stenosis with repair at the time of thrombosis. Methods Sixty-four patients with elevated static venous pressure measured in an upper extremity AV Graft were randomized to Intervention or Observation. Monthly static venous pressure/systolic blood pressure ratios (SVPR) were determined for all patients throughout the duration of study participation. Patients in the Intervention group underwent angiography and repair of identified stenoses if the monthly SVPR was elevated (≥0.4). Patients in the Observation group underwent stenosis repair only in the event of access thrombosis or clinical evidence of access dysfunction. The primary end point was access abandonment. Results Access abandonment occurred in 14 patients in the Intervention group and 14 patients in the Observation group during the 3.5-year study period. Time to access abandonment did not differ significantly between the treatment groups (hazard ratio for randomization to Intervention 1.75, 95% CI 0.80–3.82, P = 0.16). The proportion of patients with a thrombotic event was greater in the Observation group (72%) than in the Intervention group (44%) ( P = 0.04), but overall thrombosis rates were similar in the groups. Conclusion Compared with a strategy of observation and repair of accesses only in the event of thrombosis, prospective static venous pressure monitoring with prophylactic stenosis repair did not prolong Graft survival.

  • value of static venous pressure for predicting Arteriovenous Graft thrombosis
    Kidney International, 2002
    Co-Authors: Laura M Dember, Erika F Holmberg, James S Kaufman
    Abstract:

    Value of static venous pressure for predicting Arteriovenous Graft thrombosis Background Static venous pressure elevation has been shown to have both high sensitivity and high specificity for hemodialysis Arteriovenous (AV) Graft venous anastomosis stenosis. However, it is not known how well static venous pressure elevation predicts subsequent AV Graft thrombosis. Methods Monthly static venous pressure measurements were made during two consecutive dialysis sessions in all patients with a functioning upper extremity AV Graft in two hemodialysis units during a 16-month period. Static venous pressure was normalized to systolic blood pressure and corrected for the height difference between the AV Graft and the dialysis machine pressure transducer to yield the static venous pressure ratio (SVPR). Results Fifty-four patients (38%) had a thrombotic event during the study period and thus were labeled as clotters. Among the clotters, SVPR just prior to thrombosis was 0.51 ± 0.16 (mean ± SD), and mean time to thrombosis following an elevated SVPR (≥0.4) was 118 ± 106 days. Receiver operating characteristic (ROC) curves were generated using the sensitivities and specificities of a range of SVPR values for access thrombosis within one, two, three and four months. The areas under the curve (AUCs) for the ROC curves ranged from 0.557 to 0.638, reflecting the absence of SVPR values with both high sensitivity and high specificity for access thrombosis. An increase in SVPR over time was not a better predictor of access thrombosis than absolute SVPR. Conclusion Static venous pressure measurement is not an optimal screening test for identifying AV Grafts at risk for thrombosis.

Arif Asif - One of the best experts on this subject based on the ideXlab platform.

  • Arteriovenous Graft Peri-anastomotic Outflow Stenosis
    Dialysis Access Cases, 2017
    Co-Authors: Tushar J. Vachharajani, Arif Asif
    Abstract:

    Arteriovenous Graft (AVG) is a conduit created between a native artery and vein using a synthetic material to provide an easy access for hemodialysis. AVG access is used when native veins are unsuitable to create an Arteriovenous fistula, which remains the preferred vascular access. Eventually all AVGs become dysfunctional due to the development of stenosis within the conduit leading to increased resistance, reduction in blood flow, and thrombosis. The Graft-vein peri-anastomotic region is the most common site for the stenosis to develop. Timely diagnosis and intervention is needed to prevent the catastrophic thrombosis of an AVG.

  • The stent Graft for stenosis: let's appraise before we praise
    Nature Reviews Nephrology, 2010
    Co-Authors: Loay Salman, Arif Asif
    Abstract:

    A recent randomized clinical trial concluded that implantation of a stent Graft plus angioplasty was superior to angioplasty alone for the treatment of stenosis at the venous anastomosis of an Arteriovenous Graft. However, concerns regarding the reliability of the results of this trial suggest that additional investigations are necessary.

  • utility of static pressure ratio recording during angioplasty of Arteriovenous Graft stenosis
    Seminars in Dialysis, 2006
    Co-Authors: Arif Asif, Donna Merrill, Anatole Besarab, Florin Gadalean, Anne E Rismeyer, Gabriel Contreras, Baudouin Leclercq, Oliver Lenz, Jeffery Wallach, Joshua Wallach
    Abstract:

    Intra-access static pressure ratio (SPR) (intra-access pressure/mean arterial pressure) can be measured during angioplasty (PTA) to assess the functional importance of an Arteriovenous Graft (AVG) stenosis. We used SPR in 70 patients with AVGs who underwent 98 angioplasty procedures. SPR was measured during angioplasty by placing a catheter tip at mid-access. Inflow stenosis (IF) = stenosis proximal to the tip of the catheter. Outflow stenosis (OF) = stenosis distal to the tip of the catheter up to the superior vena cava-atrial junction. Post PTA, access flow (Qa) was assessed within 2 weeks. Complete data sets for both SPR and Qa were available in 83 procedures. Using a normal SPR ratio of 0.3-0.4 at mid-Graft, three patterns of SPR were noted. In 63 of 83 (76%) cases SPR was elevated prior to PTA (0.71 +/- 0.13 SD). PTA reduced SPR toward normal range (0.44 +/- 0.12) in 53 cases (84%). In the remaining 10 (16%), SPR decreased to a low value (0.22 +/- 0.03) and normalized (0.40 +/- .0.11) only after PTA of a coexisting inflow stenosis. In 12 of 83 (14%) procedures, the initial SPR was low (0.18 +/- 0.04) and increased toward normal (0.3 +/- 0.08) following IF stenosis PTA in seven (58%) cases. For the remaining five (42%) cases SPR increased to a high value (0.70 +/- 0.21) and decreased toward normal range (0.33 +/- 0.07) only after OF stenosis angioplasty. In 8 of 83 (10%) procedures, initial SPR was normal (0.33 +/- 0.02). Angiography revealed coexisting IF and OF stenoses. SPR remained within the normal range after PTA of these lesions (0.33 +/- 0.02). Qa increased significantly in 74 of 83 (89%) procedures (before = 572 +/- 201, after = 1109 +/- 368 ml/min; p < 0.001). SPR measurements can assist in hemodynamic assessment of an AVG during angioplasty procedure.