Stenting of a renal artery stenosis achieves better relief of the obstructive lesion than balloon angioplasty

Interventions for renal artery stenosis: Appraisal of novel physiological insights and procedural techniques to improve clinical outcome

Randomized clinical trials failed to show additional benefit of renal artery stenting on top of medical therapy. Instead of writing an obituary on renal artery stenting, we try to explain these disappointing results. A transstenotic pressure gradient is needed to reduce renal perfusion and to activate the renin-angiotensin-aldosterone system. In only a minority of patients included in trials, a transstenotic pressure gradient is measured and reported. Like the coronary circulation, integration of physiological lesion assessment will allow to avoid stenting of non-significant lesions and select those patients that are most likely to benefit from renal artery stenting. Renal artery interventions are associated with peri-procedural complications. Contemporary techniques, including radial artery access, no-touch technique to engage the renal ostium and the use of embolic protection devices, will minimize procedural risk. Combining optimal patient selection and meticulous technique might lead to a netto clinical benefit when renal artery stenting is added to optimal medical therapy.

Kidney Intrinsic Mechanisms as Novel Targets in Renovascular Hypertension

Almost a hundred years have passed since obstruction of the renal artery has been recognized to raise blood pressure. By now chronic renovascular disease (RVD) due to renal artery stenosis is recognized as a major source of renovascular hypertension and renal disease. In some patients, RVD unaccompanied by noteworthy renal dysfunction or blood pressure elevation may be incidentally identified during peripheral angiography. Nevertheless, in others, RVD might present as a progressive disease associated with diffuse atherosclerosis, leading to loss of renal function, renovascular hypertension, hemodynamic compromise, and a magnified risk for cardiovascular morbidity and mortality. Atherosclerotic RVD leads to renal atrophy, inflammation, and hypoxia but represents a potentially treatable cause of chronic renal failure because until severe fibrosis sets in the ischemic kidney, it retains a robust potential for vascular and tubular regeneration. This remarkable recovery capacity of the kidney begs for early diagnosis and treatment. However, accumulating evidence from both animal studies and randomized clinical trials has convincingly established the inadequate efficacy of renal artery revascularization to fully restore renal function or blood pressure control and has illuminated the potential of therapies targeted to the ischemic renal parenchyma to instigate renal regeneration. Some of the injurious mechanisms identified as potential therapeutic targets included oxidative stress, microvascular disease, inflammation, mitochondrial injury, and cellular senescence. This review recapitulates the intrinsic mechanisms that orchestrate renal damage and recovery in RVD and can be harnessed to introduce remedial opportunities.

Advancements in Treatment Strategies for Chronic Mesenteric Ischemia: A Comprehensive Review

Chronic mesenteric ischemia (CMI) arises from the inability to achieve adequate intestinal blood flow after meals, leading to an imbalance between oxygen and metabolite supply and demand. The true incidence of CMI remains uncertain. However, the occurrence of mesenteric artery occlusive disease (MAOD) is relatively common among the elderly population. Delays in diagnosing CMI can often be attributed to several factors, including the variability in patient symptoms and the range of potential causes for chronic abdominal pain with weight loss. Mikkelson pioneered the introduction of a surgical treatment for occlusive lesions of the superior mesenteric artery (SMA) in 1957. The inaugural performance of endovascular revascularization (ER) for visceral vessels took place in 1980. The literature has documented two types of endovascular revascularization (ER) methods: percutaneous transluminal angioplasty (PTA) and primary stenting (PMAS). Despite the limited quality of available evidence, the consensus among experts is strongly in favor of PMAS over PTA alone for the treatment of atherosclerotic mesenteric artery stenosis. There are several key areas of focus for chronic mesenteric ischemia (CMI) treatment. Randomized controlled trials comparing different stent types, such as covered stents versus bare metal stents, are needed to evaluate efficacy, patency rates, and long-term outcomes in CMI patients.

When and How Should We Revascularize Patients With Atherosclerotic Renal Artery Stenosis?

Atherosclerotic renal artery stenosis is the leading cause of secondary hypertension and may lead to resistant (refractory) hypertension, progressive decline in renal function, and cardiac destabilization syndromes (pulmonary edema, recurrent heart failure, or acute coronary syndromes) despite guideline-directed medical therapy. Although randomized controlled trials comparing medical therapy with medical therapy and renal artery stenting have failed to show a benefit for renal artery stenting, according to comparative effectiveness reviews by the Agency for Healthcare Research and Quality, the trials may not have enrolled patients with the most severe atherosclerotic renal artery stenosis, who would be more likely to benefit from renal stenting. Because of limitations of conventional angiography, it is critical that the hemodynamic severity of moderately severe (50% to 70%) atherosclerotic renal artery stenosis lesions be confirmed on hemodynamic measurement. The authors review techniques to optimize patient selection, to minimize procedural complications, and to facilitate durable patency of renal stenting. The authors also review the current American College of Cardiology and American Heart Association guidelines and the Society for Cardiovascular Angiography and Interventions appropriate use criteria as they relate to renal stenting.

European guidelines on chronic mesenteric ischaemia - joint United European Gastroenterology, European Association for Gastroenterology, Endoscopy and Nutrition, European Society of Gastrointestinal and Abdominal Radiology, Netherlands Association of Hepatogastroenterologists, Hellenic Society of Gastroenterology, Cardiovascular and Interventional Radiological Society of Europe, and Dutch Mesenteric Ischemia Study group clinical guidelines on the diagnosis and treatment of patients with chronic mesenteric ischaemia

Chronic mesenteric ischaemia is a severe and incapacitating disease, causing complaints of post-prandial pain, fear of eating and weight loss. Even though chronic mesenteric ischaemia may progress to acute mesenteric ischaemia, chronic mesenteric ischaemia remains an underappreciated and undertreated disease entity. Probable explanations are the lack of knowledge and awareness among physicians and the lack of a gold standard diagnostic test. The underappreciation of this disease results in diagnostic delays, underdiagnosis and undertreating of patients with chronic mesenteric ischaemia, potentially resulting in fatal acute mesenteric ischaemia. This guideline provides a comprehensive overview and repository of the current evidence and multidisciplinary expert agreement on pertinent issues regarding diagnosis and treatment, and provides guidance in the multidisciplinary field of chronic mesenteric ischaemia.

Use of shockwave intravascular lithotripsy for the treatment of calcified renal artery stenosis in a symptomatic subject

Aim: The use of shockwave lithotripsy for the treatment of heavily calcified atherosclerotic plaques before stenting showed great results in terms of feasibility and safety with favorable initial success. Evidence suggests that it is a useful tool to treat calcified lesions in peripheral and coronary arteries. Here, we describe the case of a patient with calcified renal artery stenosis successfully treated with the shockwave lithotripsy system. Case Report: We present a 76-year-old man with a known significant atherosclerotic renal artery stenosis and refractory hypertension. The patient received an angioplasty of the right renal artery in the first session and he was admitted for a second session to intervene in the left renal artery. The lesion was successfully treated with the lithotripsy system. Final angiography demonstrated an excellent position of the stent and good wall apposition. Conclusion: Our clinical case demonstrates that lithotripsy is safe and effective also for the treatment of the renal artery.

The Localized Hemodynamics of Drug-Eluting Stents Are Not Improved by the Presence of Magnetic Struts

The feasibility of implementing magnetic struts into drug-eluting stents (DESs) to mitigate the adverse hemodynamics which precipitate stent thrombosis is examined. These adverse hemodynamics include platelet-activating high wall shear stresses (WSS) and endothelial dysfunction-inducing low wall shear stresses. By magnetizing the stent struts, two forces are induced on the surrounding blood: (1) magnetization forces which reorient red blood cells to align with the magnetic field and (2) Lorentz forces which oppose the motion of the conducting fluid. The aim of this study was to investigate whether these forces can be used to locally alter blood flow in a manner that alleviates the thrombogenicity of stented vessels. Two-dimensional steady-state computational fluid dynamics (CFD) simulations were used to numerically model blood flow over a single magnetic drug-eluting stent strut with a square cross section. The effects of magnet orientation and magnetic flux density on the hemodynamics of the stented vessel were elucidated in vessels transporting oxygenated and deoxygenated blood. The simulations are compared in terms of the size of separated flow regions. The results indicate that unrealistically strong magnets would be required to achieve even modest hemodynamic improvements and that the magnetic strut concept is ill-suited to mitigate stent thrombosis.

Percutaneous Endovascular Therapy of Renal Artery Stenosis: Technical and Clinical Developments in the past Decade

Renal artery stenosis may initiate or exacerbate arterial hypertension and/or renal insufficiency. During the last decade, technical improvements of diagnostic and interventional endovascular tools have led to more widespread use of endoluminal renal artery revascularization and broader indications for this type of therapy. Since the first renal artery angioplasties performed by Felix Mahler and Andreas Grüntzig in 1978, numerous single-center studies have documented the benefits of percutaneous renal revascularization. In the early 1990s, stent implantation was added to the interventionist's armamentarium for treating renal artery stenosis due to atherosclerosis or fibromuscular dysplasia. The metaanalysis of 3 randomized studies comparing balloon angioplasty with best medical therapy found intervention to be beneficial for blood pressure control but not for preservation of renal function. Despite the absence of randomized studies, there is mounting evidence that stenting of hemodynamically relevant atherosclerotic renal artery stenosis has a positive impact on blood pressure control and renal function. This article summarizes the technical improvements in these endovascular tools during the last decade and gives an overview concerning their clinical impact on renal artery revascularization.

[Management of atherosclerotic renal-artery stenosis in 2016]

Endovascular revascularization as treatment of atherosclerotic renal-artery stenosis (aRAS) is controversial since 3 large and multicentric randomised trials (CORAL, ASTRAL, STAR) failed to prove the superiority of percutaneous transluminal renal-artery stenting (PTRAS) over medical treatment only (MT). However, considering the multiple bias of these trials, among which questionable inclusion criterias, these results must be extrapolated in clinical practice with caution. New pathophysiological data have been helping to understand why restoring blood flow does not necessarily lead to kidney function improvement. Today, the diagnostic approach must in one hand confirm the artery stenosis and on the other hand assess its severity and impact on the kidney. Therapeutic options still lie on the American guidelines published in 2006, since no study data can be reasonably used in everyday practice. However, particular sub-groups of patients who could benefit from revascularisation have been identified through recent cohort studies. Further prospective studies are needed in order to confirm the superiority of PTRAS in these populations. Meanwhile, multidisciplinary approach should be promoted, in order to provide the best treatment for each patient.

Technological Advances in the Design of Catheters and Devices Used in Renal Artery Interventions: Impact on Complications

Purpose:

To analyze the impact of technical improvements in stent devices and guiding catheters (e.g., reduced device diameter, increased flexibility) on the complication rates associated with percutaneous renal artery interventions.

Methods:

During a 5-year period (1997–2001), 268 consecutive patients (178 men; mean age 67±9 years) had 370 atherosclerotic renal artery stenoses (RAS) ≥70% treated with angioplasty/stenting in 320 procedures. The guiding catheter technique was used routinely until 2000; in 2001, a guiding sheath was used in 29% of cases. From 1997 to 2000, sealing devices were frequently used for sheath removal; during the last year, the sheaths were removed using the Femostop device.

Results:

In 320 interventions, 32 (10%) complications occurred, with a decreasing frequency during the last 2 years (1996/97: 13% [7/53]; 1998: 16% [9/57]; 1999: 15% [11/74]; 2000: 4% [3/70]; 2001: 3% [2/66]). There were 21 (6.6%) local complications, including 4 cases requiring permanent hemodialysis after the intervention and 11 (3.4%) access site complications. No procedure-related death occurred. During the study period, the average sheath diameter was reduced from 8.15±0.76 F to 6.15±0.63 F (p<0.05). Mean procedural time was reduced from 42±13 minutes to 23±11 minutes (p<0.05). The initial heparin dose was reduced from 10,000 to 5000 units.

Conclusions:

In parallel with the use of more flexible catheters and premounted stents of lower profile, the complication rate of renal angioplasty/stenting of atherosclerotic RAS has been reduced significantly during a 5-year period.

Successful Wallstent Implantation for Extensive Iatrogenic Renal Artery Dissection in a Patient with Fibromuscular Dysplasia

Purpose:

To describe a case of renal artery stenosis with fibromuscular dysplasia (FMD) and extensive iatrogenic dissection treated with Wallstent implantation.

Methods and Results:

An 83-year-old woman with a history of coronary artery disease and hypertension presented at another facility with exertional angina and poorly controlled hypertension. Renal arteriography uncovered a critical right renal artery stenosis with severe FMD. However, angioplasty resulted in extensive dissection of the renal artery, for which the patient was referred to our institution. The renal artery was recanalized via the left brachial approach with restoration of flow using a Wallstent and a Palmaz stent. The patient's blood pressure was controllable after this procedure, and follow-up duplex imaging with flow velocities at 6 months showed patent right renal artery stents.

Conclusions:

Owing to its length and flexibility, the Wallstent endoprosthesis was a useful treatment modality in this case of extensive renal artery dissection.

Stents in the Treatment of Renal Artery Stenosis: Long-Term Follow-up

Purpose:

To evaluate the role of percutaneous stenting in the treatment of renal arterial lesions after failure of balloon angioplasty.

Methods:

Two hundred ten patients (139 males; mean age 67.7 ± 9.9 years, range 27 to 87) had 259 balloon-expandable stents (165 Palmaz and 94 Renal Bridge stents) implanted in 244 renal artery stenoses (171 ostial and 73 nonostial lesions). The patients were suffering from intractable hypertension (n = 210) and/or renal dysfunction (n = 48). The majority of the lesions (n = 234) were atheromatous in origin. Stents were implanted for suboptimal balloon dilation (n = 182, 75%), restenotic lesions (n = 27, 11%), or dissection (n = 9, 4%); 26 (11%) ostial lesions were stented primarily. Mean lesion length was 11.9 ± 4.4 mm (range 5 to 30) and mean percent stenosis was 81.9% ± 8.25% (range 70 to 100).

Results:

Immediate technical success was 99% (241 of 244). Three (1.2%) major complications included one intraprocedural stent thrombosis, one arterial perforation manifesting as a perirenal hematoma 24 hours after the procedure, and one renal arterial rupture. Follow-up over a mean 25.4 ± 22.8 months (range 1 to 96) in 185 eligible patients (209 arteries) found 24 cases of restenosis (11.4%). Primary and secondary patencies for all lesions at 60 months were 79% and 98%, respectively, with no significant differences between ostial and nonostial lesions or stent types. Hypertension was reversed in 35 (19%), improved in 112 (61%), and remained unchanged in 37 (20%). Renal function was improved in 29% (14 of 48), unchanged in 67% (32 of 48), and worse in 4% (2 of 48).

Conclusions:

Renal artery stenting is safe, effective, and may be an alternative to surgery, particularly in ostial lesions. Our experience shows reduction in the restenosis rate compared to conventional angioplasty. All ostial stenoses should be stented.

The Impact of Blood Rheology on Drug Transport in Stented Arteries: Steady Simulations

BACKGROUND AND METHODS

It is important to ensure that blood flow is modelled accurately in numerical studies of arteries featuring drug-eluting stents due to the significant proportion of drug transport from the stent into the arterial wall which is flow-mediated. Modelling blood is complicated, however, by variations in blood rheological behaviour between individuals, blood's complex near-wall behaviour, and the large number of rheological models which have been proposed. In this study, a series of steady-state computational fluid dynamics analyses were performed in which the traditional Newtonian model was compared against a range of non-Newtonian models. The impact of these rheological models was elucidated through comparisons of haemodynamic flow details and drug transport behaviour at various blood flow rates.

RESULTS

Recirculation lengths were found to reduce by as much as 24% with the inclusion of a non-Newtonian rheological model. Another model possessing the viscosity and density of blood plasma was also implemented to account for near-wall red blood cell losses and yielded recirculation length increases of up to 59%. However, the deviation from the average drug concentration in the tissue obtained with the Newtonian model was observed to be less than 5% in all cases except one. Despite the small sensitivity to the effects of viscosity variations, the spatial distribution of drug matter in the tissue was found to be significantly affected by rheological model selection.

CONCLUSIONS/SIGNIFICANCE

These results may be used to guide blood rheological model selection in future numerical studies. The clinical significance of these results is that they convey that the magnitude of drug uptake in stent-based drug delivery is relatively insensitive to individual variations in blood rheology. Furthermore, the finding that flow separation regions formed downstream of the stent struts diminish drug uptake may be of interest to device designers.

Where and when device therapy may be useful in the management of drug-resistant hypertension

Device therapy for the treatment of uncontrolled and resistant hypertension has evolved significantly over the past several decades. Both renal artery disease and sympathetic hyperactivity have been linked to resistant hypertension. This manuscript will review the current evidence base supporting device therapy (e.g., renal artery revascularization, sympathetic nervous system modulation) for resistant hypertension.

Technical discussion of diagnostic angiography and intervention of atherosclerotic renal artery stenosis

Renal artery stenting remains an important adjuvant treatment for true-resistant hypertension, although recent disappointing randomized trials highlight the importance of careful patient selection. Safe and successful renal interventions begin with critical core knowledge regarding renal artery anatomy and understanding the often hostile nature of the parent vessel (pararenal aorta). Armed with fundamental knowledge about anatomy and renal ostial disease pathology, it becomes easier to understand the advantages of less traumatic access techniques and how low-profile contemporary flexible stents have enhanced outcomes. In addition to suggested techniques based on detailed understanding of the vessel architecture and pathology, we will review the current available US Food and Drug Administration-approved balloon-expandable on-label renal stents and discuss the role of intravascular ultrasound for definition of lesion severity, stent sizing, and stent apposition. The durability of renal stenting will also be discussed, as will the velocity criteria for duplex surveillance. Lastly, the current empirical data related to renal embolic protection is provided, along with insight into technical issues in this domain.

SCAI expert consensus statement for renal artery stenting appropriate use

The pathophysiology of atherosclerotic renal artery stenosis (RAS) includes activation of the renin-angiotensin-aldosterone axis with resultant renovascular hypertension. Renal artery stenting has emerged as the primary revascularization strategy in most patients with hemodynamically significant atherosclerotic RAS. Despite the frequency with which hemodynamically significant RAS is observed and high rates of technical success of renal artery stenting, there remains considerable debate among experts regarding the role of medical therapy versus revascularization for renovascular hypertension. Modern, prospective, multicenter registries continue to demonstrate improvement in systolic and diastolic blood pressure with excellent safety profiles in patients with RAS. Modern randomized, controlled clinical trials of optimal medical therapy versus renal stenting particularly designed to demonstrate preservation in renal function after renal artery stenting have demonstrated limited benefit. However, these trials frequently excluded patients that may benefit from renal artery stenting. This document was developed to guide physicians in the modern practical application of renal stenting, to highlight the current limitations in the peer-reviewed literature, to suggest best-practices in the performance of renal stenting and to identify opportunities to advance the field.

Management of Renal Arterial Disease

Severe atherosclerotic renal artery stenosis can manifest as treatment-resistant hypertension, ischemic nephropathy and/or cardiac disturbance syndromes of recurrent flash pulmonary edema and refractory angina. Renal artery revascularization can dramatically impact patient outcome. However, patient selection for revascularization can be challenging. Renal artery stenting is most commonly used for renal revascularization and is a safe procedure when performed in carefully selected patients. This review addresses the pathophysiology of renal artery stenosis and the data supporting revascularization in such patients.

Current views on the management of atherosclerotic renovascular disease

Atherosclerotic renovascular disease (ARVD) is a common condition in both elderly patients and those with other vascular disease. No published randomized controlled trial has demonstrated an overall benefit of revascularization on any clinical or biochemical end-point, and optimal medical therapy in this condition is not clearly defined. In this review we consider the epidemiology of ARVD and discuss the evidence for current medical treatment. We also address the literature on revascularization, consider settings in which an interventional approach may still be considered, and touch upon on-going areas of research.

Secondary arterial hypertension: improvements in diagnosis and management in the last 10 years

The diagnosis and management of secondary hypertension has improved in the last decade as a result of the advances in the acknowledgment of some physiopathologic mechanisms and mainly by the development of new diagnostic methods. Furthermore, the treatment of some types of secondary hypertension may be solved by noninvasive techniques. Hypertension of renal and renovascular origin, coarctation of the aorta, primary hyperaldosteronism, and adrenal medullary tumors are analyzed. The main results of some relevant studies on diagnostic and treatment of those diseases are presented. Also, some experimental methods are mentioned, taking into account the possibility of clinical use in the near future.

Atherosclerotic renal artery stenosis: review of pathophysiology, clinical trial evidence, and management strategies

Renal artery stenosis is prevalent and commonly encountered by cardiovascular specialists. Recently published randomized studies have provoked tremendous controversies in the treatment strategy with regard to renal artery stenting. However, these studies are inconclusive because of major study limitations. As such, cardiovascular specialists are uncertain of the indications or utility of renal revascularization, with differing opinions on management by nephrologists and cardiologists. A greater understanding of this disease process, especially with regard to its functional significance and consequence and treatment strategies based on well-designed clinical trials, is sorely needed. Our review focuses on atherosclerotic renal artery stenosis, with an emphasis on indications for revascularization and review of current trial data.

Dramatic improvement of rapidly progressing acute renal failure and severe hypertension after bilateral renal artery stenting

In this case report, we describe an 83-year-old man with bilateral renal artery stenosis who had rapidly progressing acute renal failure and severe hypertension. These conditions improved dramatically after bilateral renal artery stenting. Renal artery stenosis can cause renal failure, hypertension, and heart failure, leading to a poorer life prognosis. If renal artery stenosis is found as a cause of acute renal failure, severe hypertension, or heart failure, it is useful to perform revascularization as soon as possible. Revascularization by stenting has a high success rate and is expected to improve the condition remarkably.

Clinical efficacy of percutaneous renal revascularization with stent placement in hypertension among patients with atherosclerotic renovascular diseases

AIM

The aim was to assess the effect of renal angioplasty with stent on systolic, diastolic, and mean arterial blood pressure (MAP) in awake and sleep time with ambulatory blood pressure (ABP) monitoring (Holter monitoring).

MATERIALS AND METHODS

Patients with angiographically proven atherosclerotic renal artery stenosis (RAS) were referred to the Angiography Department of Imam Hospital for intervention during a 1-year period from June 2008 to December 2009. Primary stent placement was attempted by a single operator in 27 severe RAS cases although 1 case was omitted from the study because of technical failure. Pre- and postprocedure creatinine levels, ejection fraction (EF), history of diabetes mellitus (DM), and ABP were obtained. Twenty-six (17 men, 9 women; average age, 62.6 years; age range, 90-21 years) consecutive patients participated in the study.

RESULTS

All patients had severe hypertension resistant to multiple medications; 10 patients had impaired renal function (serum creatinine level greater than 130 µmol/L). A total of 3 (11.5%) patients had congestive heart failure, and 10 (37.7%) were diabetic. Hypertension was cured in 1 (4%) patient, had improved in 23 (88.4%) patients, and had failed to respond to treatment in 2 (7.6%). Serum creatinine decreased significantly from 1.46 ± 0.89 to 1.35 ± 0.61 mg/dL (P<0.05).

CONCLUSION

Percutaneous transluminal angioplasty for atheromatous RAS rarely cures hypertension, but improved blood pressure control is often achieved.

One year clinical outcomes of renal artery stenting: the results of ODORI Registry

The safety, efficacy and long term clinical benefits of renal artery revascularization by stenting are still a matter of debate. The aim of our study was to define the safety and efficacy of renal artery stenting with the Tsunami peripheral stent (Terumo Corporation, Tokyo, Japan). The ODORI was a prospective, multicentre registry which enrolled 251 consecutive patients, (276 renal arteries) in 36 centres across Europe. The primary endpoint was acute procedural success defined as <30% residual stenosis after stent placement. Secondary endpoints included major adverse events, blood pressure control, serum creatinine level, and target lesion revascularization (TLR) at 6 and 12 months. Patients were 70 +/- 10 years old, 59% were male, 33% had diabetes, and 96% hypertension. The main indications for renal stent implantation were hypertension in 83% and renal salvage in 39%. Direct stent implantation was performed in 76% of the cases. Acute success rate was 100% with residual stenosis of 2.5 +/- 5.4%. Systolic/diastolic blood pressure decreased from a mean of 171/89 at baseline to 142/78 mmHg at 6 months (p < 0.0001 vs. baseline), and 141/80 mmHg at 12 months (p < 0.0001 vs. baseline). Mean serum creatinine concentration did not change significantly in the total population. However, there was significant improvement in the highest tercile (from 283 micromol/l at baseline to 205 and 209 micromol/l at 6 and 12 months respectively). At 12-months, rates of restenosis and TLR were 6.6 and 0.8% respectively. The 12 month cumulative rate of all major clinical adverse events was 6.4% while the rate of device or procedure related events was 2.4%. In hypertensive patients with atherosclerotic renal artery stenosis Tsunami peripheral balloon-expandable stent provides a safe revascularization strategy, with a potential beneficial impact on hypertension control and renal function in the highest risk patients.

Critical review of indications for renal artery stenting: do randomized trials give the answer?

Significant renal artery stenosis (RAS) is a well accepted cause of deterioration of arterial hypertension and of renal insufficiency. Just recently, more interest has been focused on the impact of RAS on structural heart disease and patient survival. Technical improvements of diagnostic and interventional endovascular tools have lead to a more widespread use of endoluminal renal artery revascularization and extension of the indications for this type of therapy during the past 2 decades. Since the first renal artery angioplasties performed by Felix Mahler and Andreas Grüntzig, numerous single centre studies have reported the beneficial effect of percutaneous transluminal renal angioplasty, and since the early 1990's stenting of renal artery stenosis caused either by atherosclerosis or fibromuscular dysplasia. However, none of the so far published or presented randomized controlled trials (RCT) could prove a beneficial outcome of RAS revascularization compared with medical management. As a result of these negative trials including the recently presented ASTRAL trial, referrals to endovascular renal artery revascularization went down and moreover, reimbursement of these procedures became a matter of debate. This article summarizes the background and the limitations of the so far published and still ongoing controlled trials. Moreover, we discuss why well-designed registries might give important insight on the impact of endovascular revascularization of hemodynamically relevant atherosclerotic RAS.

Diagnosis and management of atherosclerotic renal artery stenosis: improving patient selection and outcomes

Renal artery stenosis (RAS) is common among patients with atherosclerosis, and is found in 20-30% of individuals who undergo diagnostic cardiac catheterization. Renal artery duplex ultrasonography is the diagnostic procedure of choice for screening outpatients for RAS. Percutaneous renal artery stent placement is the preferred method of revascularization for hemodynamically significant RAS, and is favored over balloon angioplasty alone. Stent placement carries a class I recommendation for atherosclerotic RAS according to ACC and AHA guidelines. Discordance exists between the very high (>95%) procedural success rate and the moderate (60-70%) clinical response rate after renal stent placement, which is likely to be a result of poor selection of patients, inadequate angiographic assessment of lesion severity, and the presence of renal parencyhmal disease. Physiologic lesion assessment using translesional pressure gradients, and measurements of biomarkers (e.g. brain natriuretic peptide), or both, could enhance the selection of patients and improve clinical response rates. Long-term patency rates for renal stenting are excellent, with 5-year secondary patency rates greater than 90%. This Review will outline the clinical problem of atherosclerotic RAS and its diagnosis, and will critically assess treatment options and strategies to improve patients' outcomes.

Clinical and angiographic long-term outcomes of vertebral artery–subclavian artery transposition to treat symptomatic stenosis of vertebral artery origin

Object

Although angioplasty and stent placement for vertebral artery (VA)–origin stenosis have been performed using endovascular techniques, a high likelihood of restenosis has been observed in the long term. Therefore, the authors assessed the long-term clinical and angiographic outcomes in patients after VA–subclavian artery (SA) transposition.

Methods

Thirty-six patients (31 men, 5 women; mean age 64.3 years, range 46–76 years) underwent clinical evaluation (modified Rankin Scale [mRS]) and cervical angiographic evaluation preoperatively and within 1 month of and 6 months after VA-SA transposition undertaken to treat symptomatic stenosis of VA origin.

Results

Postoperative neurological deficits due to intraoperative brain ischemia did not occur, and MR imaging demonstrated no new postoperative ischemic lesions in any of the patients. One patient died of acute myocardial infarction 2 months after surgery and another developed a left thalamic hemorrhage (mRS score of 5) at 42 months postsurgery. None of the remaining 34 patients experienced further ischemic events, and the mRS score in all of these patients remained unchanged during a mean follow-up period of 54 months. The degree of VA-origin stenosis (preoperative mean 84%) was reduced to ≤ 30% after surgery (mean 2%). Long-term follow-up angiography in 29 patients (81%) revealed the absence of restenosis, defined as > 50% luminal narrowing, in all of them.

Conclusions

The clinical and angiographic long-term outcomes demonstrated here suggest that VA-SA transposition will be useful in patients with symptomatic stenosis of VA origin.

Catheter-based therapy for atherosclerotic renal artery stenosis

The prevalence of atherosclerotic renal artery stenosis (RAS) is more common than was previously thought, particularly in patients with known coronary, cerebrovascular, or peripheral vascular atherosclerosis. Clinical subsets in which RAS is more common include patients with uncontrolled hypertension, renal insufficiency, and/or sudden onset ("flash") pulmonary edema. Renal artery atherosclerosis progresses over time and is associated with loss of renal function regardless of medical therapy. Patients with symptomatic (hypertension, renal insufficiency, or flash pulmonary edema) and hemodynamically significant RAS are potential candidates for revascularization. The current standard of care is stent placement for aorto-ostial atherosclerotic lesions. Procedure success rates are very high (> or =95%), with infrequent major complication rates. Five-year primary patency rates are 80% to 85%, and secondary patency rates exceed 90%. The key element in managing patients with RAS is selecting those most likely to benefit, that is, those with blood pressure control, preservation or improvement of renal function, and control of flash pulmonary edema from renal revascularization. This article will highlight the anatomical features, physiologic parameters, and biomarkers that may be helpful in optimally selecting patients for renal artery revascularization.

Management of atherosclerotic renovascular disease: the effect of renal artery stenting on renal function and blood pressure

In the last few years, renal artery stenting has gradually evolved into one of the most important therapeutic modalities in the management of atherosclerotic renovascular disease. Stenting is nowadays preferred by a steadily increasing number of physicians, not only because of its significant contribution to blood pressure control, but also because of its documented ability to maintain, and even improve, renal function. At the same time, procedure-related morbidity and mortality rates are extremely low, while recurrent stenosis rates have been repeatedly reported to be minimal. Percutaneous transluminal renal angioplasty (PTRA) and stenting are nowadays considered by many physicians to be the treatment of choice for atherosclerotic renovascular disease.

Treatment of instent restenosis following stent-supported renal artery angioplasty

OBJECTIVES

We prospectively studied the long-term outcome of endovascular treatment of instent renal artery stenosis (IRAS).

BACKGROUND

Restenosis is a considerable drawback of stent-supported angioplasty of renal artery stenosis especially in small vessel diameters. The appropriate treatment strategy is not yet defined.

PATIENTS AND METHODS

During a 10-year period 56 consecutive patients (65 lesions) with their first IRAS were included in a prospective follow-up program (mean follow-up 53 +/- 25 months, range 6-102). Primary endpoint of the study was the reoccurence of IRAS (>or= 70%) after primarily successful treatment of the first IRAS determined by duplex ultrasound.

RESULTS

Primary success rate was 100%, no major complication occurred. Nineteen lesions were treated with plain balloon angioplasty (group 1, 30%), 42 lesions with stent-in-stent placement (group 2, 65%) using various bare metal balloon expandable stents, and 4 lesions with drug-eluting stent angioplasty (group 3, 6%). During follow-up, overall 21 lesions (32%) developed reoccurence of IRAS: n = 7/19 in group 1 (37%), n = 14/42 in group 2 (33%), and n = 0/4 in group 3 (0%; P = 0.573). Reoccurence of IRAS was more likely to occur in smaller vessel diameters than in larger ones [3-4mm: 4/7 (57%); 5 mm: 11/26 (42%); 6 mm: 5/25 (20%); 7 mm: 1/7 (14%), P = 0.088]. Multivariable analysis found bilateral IRAS and IRAS of both renal arteries of the same side in case of multiple ipsilateral renal arteries as independent predictors for reoccurence of IRAS.

CONCLUSION

Treatment of IRAS is feasible and safe. The data demonstrate a nonsignificant trend towards lower restenosis with restenting of IRAS versus balloon angioplasty of IRAS. Individual factors influence the likelihood of reoccurence of IRAS.

Treatment of reoccurring instent restenosis following reintervention after stent-supported renal artery angioplasty

BACKGROUND

Reoccurrence of restenosis following angioplasty of renal instent restenosis is a considerable drawback of stent-supported angioplasty of renal artery stenosis especially in small vessel diameters. We therefore prospectively studied the long-term outcome of different techniques of endovascular treatment of reoccurrence of instent renal artery restenosis after primarily successful reangioplasty focusing on the impact of covered and drug eluting stents, respectively.

PATIENTS AND METHODS

The study included 31 consecutive patients (33 lesions) presenting with their at least second instent restenosis following renal artery stenting who were included in a prospective follow-up program (mean follow-up 36+/-25 months, range 1-85). Primary endpoint of the study was the reoccurrence rate of instent stenosis after primarily successful treatment of instent restenosis determined by duplex ultrasound.

RESULTS

Primary success rate was 100%, no major complication occurred. Seven lesions were treated with balloon angioplasty (21%, group 1), 7 lesions with stent-in-stent placement (21%, group 2), 6 lesions with placement of a covered stent (18%, group 3), 3 lesions with a cutting balloon (9%, group 4), and 10 lesions with placement of a drug eluting stent (31%, group 5). During follow-up, overall 12 lesions (36%) developed reoccurrence of instent restenosis: n=5 in group 1 (reoccurrence rate 71%), n=3 in group 2 (43%), n=1 in group3 (17%), 3 in group 4 (100%), and n=0 in group 5 (0%). Treatment with a cutting balloon was the only significant predictor of restenosis (hazard ratio 32.3 (95% CI, 3.3-315.0); P<0.001).

CONCLUSION

Treatment of at least second renal artery instent restenosis is feasible and safe. Balloon angioplasty and the implantation of a bare metal stent, a covered stent, or a drug eluting stent seemed to offer favorable long-term patency, whereas cutting balloon angioplasty resulted in a very high rate of restenoses and should therefore be discouraged for this indication.

Factors Influencing the Need for Target Vessel Revascularization After Renal Artery Stenting

PURPOSE

To provide additional insight into factors that may be associated with the need for target vessel revascularization (TVR) following de novo renal artery stenting during long-term follow-up.

METHODS

A retrospective chart and database review was conducted to analyze the progress of all patients with de novo symptomatic renal artery stenosis who underwent stent-supported angioplasty under the auspices of the Single Operator, Single Center, Renal Stent Retrospective Study (SOCRATES). The records review identified 782 patients who were enrolled in the study between 1993 and 2004; after excluding 34 (4.5%) patients (lost to follow-up or inadequate data), 748 consecutive patients (412 women; mean age 70.7+/-9.7 years, range 37-92) were suitable for longitudinal analysis. The need for TVR was based on strict clinical criteria (> or =20% rise in serum creatinine, worsening hypertension, and/or recurrent flash pulmonary edema), and all patients underwent multidisciplinary evaluation before stenting and during follow-up.

RESULTS

Follow-up spanned a mean 45.8+/-26.5 months. TVR was needed in 88 (10.03%) of 877 arteries and was best predicted by patient age < or =67 years (OR 2.91, p=0.0001), stent diameter < or =5.0 mm (OR 2.31, p=0.001), solitary functioning kidney (OR 2.01, p=0.048), history of lower extremity peripheral artery disease (OR 1.87, p=0.008), and antecedent history of stroke (OR 1.73, p=0.026).

CONCLUSION

Renal artery stenting appears to be durable, with only 10% of stented arteries requiring TVR during clinically-based long-term follow-up. Arteries with a final stent diameter < or =5.0 mm were more than twice as likely to need TVR, as were patients with a solitary kidney. The authors acknowledge that clinical recurrence is not a surrogate for ultrasound surveillance after renal artery stenting, so prospective controlled trials will be needed to determine risk factors for restenosis.

Coronary-like revascularization for atherosclerotic renal artery stenosis--results in 181 consecutive patients

AIMS

The aim of this study was to document the early outcome of coronary-like revascularization for atherosclerotic renal artery stenosis (ARAS).

METHODS AND RESULTS

A total of 181 consecutive patient, 102 men, mean age 66.1 (+/- 9.2) years and 79 females, mean age 68.4 (+/- 9.2) years and 198 lesions were treated between February 1999 and May 2004 for ARAS and retrospectively analyzed. At least one major cardiovascular risk factor was present in 179 (98.9%) patients. Pre-dilatation ARAS was 81.3+/-9.6%, 27 ARAS were 50-70% and no ARAS was <50%. 135 (68.2%) of the ARAS lesions were ostial and 63 (31.8%) were non-ostial. In 17 (9.4%) patients bilateral ARAS were present. Technical success defined as residual stenosis < or =30% was achieved in 178 (98.3%) of patients and 195 (98.5%) of lesions. In one patient (0.5%) the target ARAS could not be crossed, in two (1.1%) patients residual stenosis was >30%. No major adverse cardiac or cerebral effects were observed. In 3.9% of patients minor local complications of the access site occurred; 4 (2.2%) inguinal hematoma, 3 (1.7%) pseudoaneurysm were documented. Serum creatinine concentrations and systolic and diastolic blood pressure before and after the intervention were not statistically different.

CONCLUSIONS

Coronary-like approach to ARAS revascularization is technically feasible and associated with a very low complication rate.