Outcomes of Arteriovenous Grafts Following Simultaneous Thrombectomy and Stent Graft Placement Across the Venous Anastomosis George M. Nassar,* Dima Suki,† Edward Rhee,‡ Abdul Jabbar Khan,‡ Binh Nguyen,‡ and Katafan Achkar§ *Dialysis Access Management Centers, Nephrology Dialysis and Transplantation Associates, The Kidney Institute & Houston Methodist Hospital, Weill Cornell University, Houston, Texas, †Department of Neurosurgery, M. D. Anderson Cancer Center, Houston, Texas, ‡Dialysis Access Management Centers, Nephrology Dialysis and Transplantation Associates, The Kidney Institute, Houston, Texas, and §Hamad Medical Corporation, Heart Hospital, P.O. Box 3050, Doha, Qatar
ABSTRACT Arteriovenous grafts (AVGs) suffer from high thrombosis rates. It is not known whether placement of stent grafts at the venous anastomosis (VA) of thrombosed AVGs would impact future thrombosis. This is a retrospective study evaluating a group of AVGs that underwent endovascular thrombectomy with placement of a stent graft at their VA. The study period was a minimum of 1 year or until kidney transplantation or death. Primary and secondary AVG patency rates were obtained using Kaplan– Meier survival estimates. Demographic parameters were analyzed using Cox multivariate analysis. The effect of early vs. late first thrombosis was also studied. Sixty-six
patients were included in the study. Of these, 53 (80%) experienced ≥1 thrombotic event during the study period. Thrombosis led to AVG loss in 26 (39%). The primary patency was 47%, 35%, and 21% at 3, 6, and 12 months, respectively. The assisted primary patency was 50%, 38%, and 25% at 3, 6, and 12 months, respectively. The secondary patency rate was 85%, 76%, and 72% at 3, 6, and 12 months, respectively. Thus, poor primary patency rates were observed despite stent graft placement at the VA. In addition, early thrombosis following stent graft placement was associated with worse AVG outcomes.
The advantages of early and easy cannulation of the arteriovenous graft (AVG), compared with the arteriovenous fistula (AVF), are offset by higher thrombosis rates. Stenosis of the venous anastomosis (VA) is the most frequently reported lesion at the time of AVG thrombosis (1,2). Measures to eliminate or minimize recurrence of VA stenosis may potentially decrease rates of AVG thrombosis. Placement of a stent across the VA is one measure that has been used to prevent or delay recurrence of stenosis. In a previous randomized study, bare metal stents, placed across the VA of AVGs, at the time of angioplasty, did not decrease future AVG stenosis or thrombosis events (3). Recently, stent grafts have been introduced, and in one randomized study, treatment of VA stenosis by angio-
plasty and simultaneous placement of a stent graft across the VA gave superior outcomes to angioplasty alone (4). However, in this study, the AVGs did not present with thrombosis at the time of stent graft placement. Thus, it is not known whether placement of stent grafts at the VA of thrombosed AVGs, at the time of thrombectomy, would influence patency rates. In this retrospective study, we evaluated the patency rates of AVGs when stent grafts were electively placed across their VA, at the time of endovascular thrombectomy. Methods The database of our two outpatient access management centers was screened for a 3-year period starting in December 2008 and ending in November 2011. All patients who had endovascular AVG thrombectomy with simultaneous stent graft placement at their VA were identified. Only patients who had an electively placed stent graft were included in the study. The placement of stent graft was entirely at the discretion of the interventionalist at the time of thrombectomy. The indications for elective stent
Address correspondence to: George M. Nassar, M.D., Clinical Associate Professor of Medicine, Houston Methodist Hospital and Weill Cornell University, The Kidney Institute, 1415 La Concha Lane, Houston, Texas 77054, or e-mail: [email protected]. Seminars in Dialysis—Vol 27, No 6 (November–December) 2014 pp. 639–644 DOI: 10.1111/sdi.12254 © 2014 Wiley Periodicals, Inc. 639
640
Nassar et al.
graft placement were recurrent thrombosis, elastic recoil, or the presence of totally occlusive VA stenosis. The elastic recoil of the VA was defined as ≥ 30% stenosis that occurred despite full effacement of the angioplasty balloon. It was an anatomic observation, but in all cases, it was not functionally associated with poor AVG flow or failure of endovascular thrombectomy. The totally occlusive stenosis was defined as the inability of a 0.035” guidewire to cross the VA without significant guidewire manipulation, and in addition showed ≥90% waist on the angioplasty balloon during inflation. Patients whose stent grafts were placed to manage procedure complications or to treat long (≥10 cm) venous outflow strictures were excluded. All study patients had a minimum of 1 year of follow-up, or until they died or were transplanted. The AVG events of interest included angioplasty, thrombectomy, infection, and AVG loss.
bosis event, was also performed. The Kaplan–Meier method was used in this analysis with stratification of time to first thrombosis event (≤90 days vs. >90 days). A p-value ≤0.05 was considered significant. All tests were two-tailed. The IBM SPSS software version 21, as well as the NCSS software version 9.0.7, was used in the analysis. Results Patient Population A total of 66 patients were found to be eligible for the study (Table 1). Their mean age was 60 (31– 85) years. Thirty-one (47%) were females and 35 (53%) were males. Forty-seven (71%) were Black, 13 (20%) were Hispanic, and 6 (9%) were Caucasian. Diabetes mellitus was present in 37 (56%). Historic Events
Definitions In this manuscript, primary patency was defined as the interval of time from stent graft placement until any intervention designed to maintain or reestablish the patency of the AVG, be it successful or unsuccessful. Assisted Primary patency was defined as the interval of time from stent graft placement until access thrombosis. Secondary patency was defined as the interval of time from stent graft placement until the AVG is permanently abandoned due to thrombosis or loss of functionality for reasons other than patency, such as vascular steal, aneurysm, or infection. The AVG circuit includes the body of the graft, its arterial and venous anastomoses, its peripheral venous outflow tract, and the ipsilateral central veins. Statistics Frequencies and descriptive statistics were obtained for the various demographic and clinical variables under study. The outcomes of interest were loss of primary patency, loss of assisted primary patency, and loss of secondary patency. Kaplan–Meier survival estimates for AVG patency results were obtained. The median times to different events and the 95% confidence intervals for the medians were calculated. Univariate Cox model analyses of factors potentially associated with each of the outcomes (namely patient age, gender, diabetes mellitus status, race, number of thrombotic events before stent placement) were performed. Hazard ratios and their 95% confidence intervals (CI) were obtained. Factors significant at a level of 0.30 or less were then included in a multivariate Cox model analysis. An analysis of the effect of time from stent graft placement to the first thrombosis event, on the development of a second throm-
Of the 66 patients, 49 (74.2%) had previous events. The preceding event was thrombosis in 46 (69.7%), and angioplasty in 3 (4.5%). The median time from the most recent event to stent graft placement was 22 days (1–421 days). The median time from the most recent thrombotic event to stent placement was 17 days (1–810 days). Graft Location and Characteristics The AVGs had the following anatomic locations: 15 (23%) were a forearm loop, 28 (43%) were an upper arm curvilinear, 18 (27%) were an upper arm loop or C-shaped, and 5 (8%) were a thigh loop. The age of the AVGs was not available due to the retrospective nature of the study. At the time of stent graft placement, 51 (77%) had other associated lesions in their entire AVG circuit. An associated AVG stenosis was present in 36 (55%) with 28 (42%) in the body of the AVG, and 8 (13%) in the juxta-arterial anastomosis segment. An associated
TABLE 1. Patient characteristics Characteristic Age: median (range) Sex Male Female Race African American Hispanic Caucasian Diabetes mellitus Previous thrombosis Location of AVG Forearm Upper arm Thigh AVG, arteriovenous graft.
N 60 (31–85) 35 (53%) 31 (47%) 47 13 6 37 46
(71%) (20%) (9%) (56%) (70%)
15 (23%) 46 (70%) 4 (6%)
641
STENTS AND ARTERIOVENOUS GRAFT OUTCOMES
arterial anastomosis stenosis was seen in 9 (14%), a venous outflow tract stenosis in 12 (18%), and a central vein stenosis in 20 (30%). One or more pseudoaneurysms ( 3 months
B
Assisted Primary Patency
Fig. 3. Kaplan–Meier Chart for time to second thrombotic (T) event stratified by early (≤3 months) or late (>3 months) first thrombotic event following stent graft placement. Early T events are associated with shorter duration to a second T event (p = 0.01).
when AVG thrombosis occurred early (
ABSTRACT Arteriovenous grafts (AVGs) suffer from high thrombosis rates. It is not known whether placement of stent grafts at the venous anastomosis (VA) of thrombosed AVGs would impact future thrombosis. This is a retrospective study evaluating a group of AVGs that underwent endovascular thrombectomy with placement of a stent graft at their VA. The study period was a minimum of 1 year or until kidney transplantation or death. Primary and secondary AVG patency rates were obtained using Kaplan– Meier survival estimates. Demographic parameters were analyzed using Cox multivariate analysis. The effect of early vs. late first thrombosis was also studied. Sixty-six
patients were included in the study. Of these, 53 (80%) experienced ≥1 thrombotic event during the study period. Thrombosis led to AVG loss in 26 (39%). The primary patency was 47%, 35%, and 21% at 3, 6, and 12 months, respectively. The assisted primary patency was 50%, 38%, and 25% at 3, 6, and 12 months, respectively. The secondary patency rate was 85%, 76%, and 72% at 3, 6, and 12 months, respectively. Thus, poor primary patency rates were observed despite stent graft placement at the VA. In addition, early thrombosis following stent graft placement was associated with worse AVG outcomes.
The advantages of early and easy cannulation of the arteriovenous graft (AVG), compared with the arteriovenous fistula (AVF), are offset by higher thrombosis rates. Stenosis of the venous anastomosis (VA) is the most frequently reported lesion at the time of AVG thrombosis (1,2). Measures to eliminate or minimize recurrence of VA stenosis may potentially decrease rates of AVG thrombosis. Placement of a stent across the VA is one measure that has been used to prevent or delay recurrence of stenosis. In a previous randomized study, bare metal stents, placed across the VA of AVGs, at the time of angioplasty, did not decrease future AVG stenosis or thrombosis events (3). Recently, stent grafts have been introduced, and in one randomized study, treatment of VA stenosis by angio-
plasty and simultaneous placement of a stent graft across the VA gave superior outcomes to angioplasty alone (4). However, in this study, the AVGs did not present with thrombosis at the time of stent graft placement. Thus, it is not known whether placement of stent grafts at the VA of thrombosed AVGs, at the time of thrombectomy, would influence patency rates. In this retrospective study, we evaluated the patency rates of AVGs when stent grafts were electively placed across their VA, at the time of endovascular thrombectomy. Methods The database of our two outpatient access management centers was screened for a 3-year period starting in December 2008 and ending in November 2011. All patients who had endovascular AVG thrombectomy with simultaneous stent graft placement at their VA were identified. Only patients who had an electively placed stent graft were included in the study. The placement of stent graft was entirely at the discretion of the interventionalist at the time of thrombectomy. The indications for elective stent
Address correspondence to: George M. Nassar, M.D., Clinical Associate Professor of Medicine, Houston Methodist Hospital and Weill Cornell University, The Kidney Institute, 1415 La Concha Lane, Houston, Texas 77054, or e-mail: [email protected]. Seminars in Dialysis—Vol 27, No 6 (November–December) 2014 pp. 639–644 DOI: 10.1111/sdi.12254 © 2014 Wiley Periodicals, Inc. 639
640
Nassar et al.
graft placement were recurrent thrombosis, elastic recoil, or the presence of totally occlusive VA stenosis. The elastic recoil of the VA was defined as ≥ 30% stenosis that occurred despite full effacement of the angioplasty balloon. It was an anatomic observation, but in all cases, it was not functionally associated with poor AVG flow or failure of endovascular thrombectomy. The totally occlusive stenosis was defined as the inability of a 0.035” guidewire to cross the VA without significant guidewire manipulation, and in addition showed ≥90% waist on the angioplasty balloon during inflation. Patients whose stent grafts were placed to manage procedure complications or to treat long (≥10 cm) venous outflow strictures were excluded. All study patients had a minimum of 1 year of follow-up, or until they died or were transplanted. The AVG events of interest included angioplasty, thrombectomy, infection, and AVG loss.
bosis event, was also performed. The Kaplan–Meier method was used in this analysis with stratification of time to first thrombosis event (≤90 days vs. >90 days). A p-value ≤0.05 was considered significant. All tests were two-tailed. The IBM SPSS software version 21, as well as the NCSS software version 9.0.7, was used in the analysis. Results Patient Population A total of 66 patients were found to be eligible for the study (Table 1). Their mean age was 60 (31– 85) years. Thirty-one (47%) were females and 35 (53%) were males. Forty-seven (71%) were Black, 13 (20%) were Hispanic, and 6 (9%) were Caucasian. Diabetes mellitus was present in 37 (56%). Historic Events
Definitions In this manuscript, primary patency was defined as the interval of time from stent graft placement until any intervention designed to maintain or reestablish the patency of the AVG, be it successful or unsuccessful. Assisted Primary patency was defined as the interval of time from stent graft placement until access thrombosis. Secondary patency was defined as the interval of time from stent graft placement until the AVG is permanently abandoned due to thrombosis or loss of functionality for reasons other than patency, such as vascular steal, aneurysm, or infection. The AVG circuit includes the body of the graft, its arterial and venous anastomoses, its peripheral venous outflow tract, and the ipsilateral central veins. Statistics Frequencies and descriptive statistics were obtained for the various demographic and clinical variables under study. The outcomes of interest were loss of primary patency, loss of assisted primary patency, and loss of secondary patency. Kaplan–Meier survival estimates for AVG patency results were obtained. The median times to different events and the 95% confidence intervals for the medians were calculated. Univariate Cox model analyses of factors potentially associated with each of the outcomes (namely patient age, gender, diabetes mellitus status, race, number of thrombotic events before stent placement) were performed. Hazard ratios and their 95% confidence intervals (CI) were obtained. Factors significant at a level of 0.30 or less were then included in a multivariate Cox model analysis. An analysis of the effect of time from stent graft placement to the first thrombosis event, on the development of a second throm-
Of the 66 patients, 49 (74.2%) had previous events. The preceding event was thrombosis in 46 (69.7%), and angioplasty in 3 (4.5%). The median time from the most recent event to stent graft placement was 22 days (1–421 days). The median time from the most recent thrombotic event to stent placement was 17 days (1–810 days). Graft Location and Characteristics The AVGs had the following anatomic locations: 15 (23%) were a forearm loop, 28 (43%) were an upper arm curvilinear, 18 (27%) were an upper arm loop or C-shaped, and 5 (8%) were a thigh loop. The age of the AVGs was not available due to the retrospective nature of the study. At the time of stent graft placement, 51 (77%) had other associated lesions in their entire AVG circuit. An associated AVG stenosis was present in 36 (55%) with 28 (42%) in the body of the AVG, and 8 (13%) in the juxta-arterial anastomosis segment. An associated
TABLE 1. Patient characteristics Characteristic Age: median (range) Sex Male Female Race African American Hispanic Caucasian Diabetes mellitus Previous thrombosis Location of AVG Forearm Upper arm Thigh AVG, arteriovenous graft.
N 60 (31–85) 35 (53%) 31 (47%) 47 13 6 37 46
(71%) (20%) (9%) (56%) (70%)
15 (23%) 46 (70%) 4 (6%)
641
STENTS AND ARTERIOVENOUS GRAFT OUTCOMES
arterial anastomosis stenosis was seen in 9 (14%), a venous outflow tract stenosis in 12 (18%), and a central vein stenosis in 20 (30%). One or more pseudoaneurysms ( 3 months
B
Assisted Primary Patency
Fig. 3. Kaplan–Meier Chart for time to second thrombotic (T) event stratified by early (≤3 months) or late (>3 months) first thrombotic event following stent graft placement. Early T events are associated with shorter duration to a second T event (p = 0.01).
when AVG thrombosis occurred early (
