Endovascular Management of Transplant Renal Artery Stenosis
Endovascular Management of Transplant Renal Artery Stenosis
In this study we analyze the different types of endovascular interventions (EVIs) in de novo transplant renal artery stenosis (TRAS) and its anatomical subtypes to examine any variation in recovery of allograft function, blood pressure control, EVI patency and allograft survival with respect to EVI type (DES: drug-eluting stent, BMS: bare-metal stent, PTA: percutaneous transluminal angioplasty). Forty-five patients underwent a total of 50 primary EVIs (DES: 18, BMS: 26, PTA: 6). Patients were stratified according to medical co-morbidities, graft characteristics, biopsy results, clinical presentation and TRAS anatomic subtypes (anastomotic: 26, postanastomotic: 17, bend-kink: 2). There was significant improvement in allograft function and mean arterial blood pressure (MAP) control across all interventions (pre-EVI-creatinine [CR]: 2.8 ± 1.4, post-EVI-Cr: 2.1 ± 0.7, p < 0.001; pre-EVI-MAP: 117 ± 16, post-EVI-MAP: 112 ± 17, p = 0.03) with no significant difference among EVI types. There was no significant difference in allograft survival with respect to EVI type. Patency was significantly higher in EVIs performed with DES and BMS compared to PTA (p = 0.001). In the postanastomotic TRAS subtype, patency rates were significantly higher in DES compared to BMS (p = 0.012) in vessels of comparable reference diameter (≤5 mm).
Transplant renal artery stenosis (TRAS) is associated with allograft dysfunction, refractory hypertension and inferior allograft survival in the absence of prompt intervention. There is significant variability in the reported incidence of TRAS (1–25%) likely secondary to institutional variation of screening protocols, thresholds for intervention and baseline patient demographics. The management of TRAS is more widely agreed upon with endovascular intervention (EVI) playing a significant role in preserving graft function and prolonging graft survival.
Serial innovations in the field of endovascular surgery have created an ever-increasing variety of options in the treatment of TRAS. Initially, percutaneous transluminal angioplasty (PTA) was used in the endovascular management of TRAS with many studies demonstrating it to be effective at restoring allograft perfusion and improving allograft function. However, a relatively high recurrence rate of TRAS has been reported following PTA with incidences of restenosis cited between 20% and 40%. Despite this, the use of primary PTA in the treatment of TRAS remains somewhat prevalent with studies as recent as 2011 recommending PTA as a primary EVI modality with stents reserved for instances of restenosis and more recently published studies in 2014 using solely PTA in up to 30% of cases.
The use of bare-metal stents (BMSs) in the endovascular management of TRAS has been shown in several studies to confer the same short-term revascularization benefit of PTA with several studies citing a lower incidence of restenosis (10–20%). However, studies comparing BMS and PTA in TRAS are lacking.
More recently, drug-eluting stents (DESs) have been reported to be a feasible and safe option in both de novo and restenosis TRAS. Interest in using DES in the endovascular management of TRAS is derived from numerous prospective studies citing their lower rates of restenosis in the treatment of coronary artery disease (CAD) as well as similarities in vessel diameter of the coronary and renal arteries. However, direct extrapolation of these findings to justify the routine use of DES in the endovascular management of TRAS is confounded by factors such as large variation in vessel diameter, lesion location and etiology of stenosis.
The pathophysiology of TRAS is complex with stenotic lesions often being comprised of varying degrees of anastomotic/postsurgical, immune-mediated and atherosclerotic components. A multitude of studies have made the importance of avoiding the management of TRAS as a single entity abundantly clear. Accordingly, these studies have employed different metrics and grading systems as a means to classify TRAS to better aid in its diagnosis and management. Recently, Willicombe et al classified TRAS according to its anatomical features into anastomotic (TRAS-A), postanastomotic (TRAS-P) and bend-kink (TRAS-B) subtypes and demonstrated an association of alloimmune and cardiovascular risk factors with TRAS-P. The concept of subdividing TRAS into anastomotic and postanastomotic subtypes has also been described in prior studies.
Differences in TRAS subtype and identification of their associated risk factors have played an important role in identifying specific groups of patients at risk of developing TRAS as well as in predicting their prognosis. The potential role of tailoring management according to specific subtypes of TRAS has been suggested but not extensively studied. We report our experience with the different EVIs (DES, BMS, PTA) in de novo TRAS and the effect of any variation of TRAS subtype on the outcomes of functional allograft improvement, blood pressure (BP) control, EVI patency and allograft survival.
Abstract and Introduction
Abstract
In this study we analyze the different types of endovascular interventions (EVIs) in de novo transplant renal artery stenosis (TRAS) and its anatomical subtypes to examine any variation in recovery of allograft function, blood pressure control, EVI patency and allograft survival with respect to EVI type (DES: drug-eluting stent, BMS: bare-metal stent, PTA: percutaneous transluminal angioplasty). Forty-five patients underwent a total of 50 primary EVIs (DES: 18, BMS: 26, PTA: 6). Patients were stratified according to medical co-morbidities, graft characteristics, biopsy results, clinical presentation and TRAS anatomic subtypes (anastomotic: 26, postanastomotic: 17, bend-kink: 2). There was significant improvement in allograft function and mean arterial blood pressure (MAP) control across all interventions (pre-EVI-creatinine [CR]: 2.8 ± 1.4, post-EVI-Cr: 2.1 ± 0.7, p < 0.001; pre-EVI-MAP: 117 ± 16, post-EVI-MAP: 112 ± 17, p = 0.03) with no significant difference among EVI types. There was no significant difference in allograft survival with respect to EVI type. Patency was significantly higher in EVIs performed with DES and BMS compared to PTA (p = 0.001). In the postanastomotic TRAS subtype, patency rates were significantly higher in DES compared to BMS (p = 0.012) in vessels of comparable reference diameter (≤5 mm).
Introduction
Transplant renal artery stenosis (TRAS) is associated with allograft dysfunction, refractory hypertension and inferior allograft survival in the absence of prompt intervention. There is significant variability in the reported incidence of TRAS (1–25%) likely secondary to institutional variation of screening protocols, thresholds for intervention and baseline patient demographics. The management of TRAS is more widely agreed upon with endovascular intervention (EVI) playing a significant role in preserving graft function and prolonging graft survival.
Serial innovations in the field of endovascular surgery have created an ever-increasing variety of options in the treatment of TRAS. Initially, percutaneous transluminal angioplasty (PTA) was used in the endovascular management of TRAS with many studies demonstrating it to be effective at restoring allograft perfusion and improving allograft function. However, a relatively high recurrence rate of TRAS has been reported following PTA with incidences of restenosis cited between 20% and 40%. Despite this, the use of primary PTA in the treatment of TRAS remains somewhat prevalent with studies as recent as 2011 recommending PTA as a primary EVI modality with stents reserved for instances of restenosis and more recently published studies in 2014 using solely PTA in up to 30% of cases.
The use of bare-metal stents (BMSs) in the endovascular management of TRAS has been shown in several studies to confer the same short-term revascularization benefit of PTA with several studies citing a lower incidence of restenosis (10–20%). However, studies comparing BMS and PTA in TRAS are lacking.
More recently, drug-eluting stents (DESs) have been reported to be a feasible and safe option in both de novo and restenosis TRAS. Interest in using DES in the endovascular management of TRAS is derived from numerous prospective studies citing their lower rates of restenosis in the treatment of coronary artery disease (CAD) as well as similarities in vessel diameter of the coronary and renal arteries. However, direct extrapolation of these findings to justify the routine use of DES in the endovascular management of TRAS is confounded by factors such as large variation in vessel diameter, lesion location and etiology of stenosis.
The pathophysiology of TRAS is complex with stenotic lesions often being comprised of varying degrees of anastomotic/postsurgical, immune-mediated and atherosclerotic components. A multitude of studies have made the importance of avoiding the management of TRAS as a single entity abundantly clear. Accordingly, these studies have employed different metrics and grading systems as a means to classify TRAS to better aid in its diagnosis and management. Recently, Willicombe et al classified TRAS according to its anatomical features into anastomotic (TRAS-A), postanastomotic (TRAS-P) and bend-kink (TRAS-B) subtypes and demonstrated an association of alloimmune and cardiovascular risk factors with TRAS-P. The concept of subdividing TRAS into anastomotic and postanastomotic subtypes has also been described in prior studies.
Differences in TRAS subtype and identification of their associated risk factors have played an important role in identifying specific groups of patients at risk of developing TRAS as well as in predicting their prognosis. The potential role of tailoring management according to specific subtypes of TRAS has been suggested but not extensively studied. We report our experience with the different EVIs (DES, BMS, PTA) in de novo TRAS and the effect of any variation of TRAS subtype on the outcomes of functional allograft improvement, blood pressure (BP) control, EVI patency and allograft survival.
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