Catheter-Based Therapy for Atherosclerotic Renal Artery Stenosis

The Implications of Acute Anatomic Injury After Percutaneous Renal Intervention

PURPOSE

Percutaneous renal artery revascularization for hypertension and renal dysfunction remains common. The frequency, cause, and outcomes of anatomic injury associated with renal intervention are poorly delineated. This study aims to determine the frequency of acute anatomic renal injury after renal artery interventions, identify factors associated with anatomic renal injury, and determine whether anatomic renal injury related to renal intervention is associated with late adverse clinical events.

METHODS

A retrospective analysis of patients undergoing renal artery interventions for atherosclerotic renal artery disease between 2002 and 2022 was performed. Acute anatomic renal injury encompassed renal artery dissection, renal artery perforation, acute occlusion, renal parenchymal infarction, and renal parenchymal perforation. Freedom from renal-related morbidity (increase in persistent creatinine >20% of baseline, progression to hemodialysis, death from renal-related causes) and patient survival were measured.

RESULTS

A total of 968 patients underwent 1309 renal artery interventions: 47% for hypertension, 25% for hypertension associated with chronic renal dysfunction, and 28% for chronic renal dysfunction. An acute anatomic renal injury occurred in 5.9% of the patients. The occurrence of an anatomic injury was associated with a significant decrement in freedom from renal-related morbidity (79±2% vs 55±8%, no-injury vs injury group, mean±standard error of the mean; p=0.003) and markedly decreased survival at 5 year follow-up (78±3% vs 48±8%; p=0.002). No factor was identified that predicted anatomic injury. In those patients with anatomic injury, perforation was associated with decreased survival, while estimated glomerular filtration rate <60, resistive index >0.8, and dissection were associated with a lack of retained renal benefit.

CONCLUSION

Acute anatomic renal injury occurs in approximately 6% of patients undergoing percutaneous renal artery intervention and is a negative predictor of survival and is associated with subsequent renal failure, need for dialysis, and death from renal-related causes.

CLINICAL IMPACT

Acute anatomic renal injury occurs in approximately 5% of patients undergoing percutaneous renal artery intervention. Modern endovascular interventions allow for the control and remediation of injuries in the majority of cases with an overall low mortality and morbidity. There is a significant early occlusion of renal arteries following the injury within 1 month. In the long term, the occurrence of injury is a negative predictor of survival and is associated with subsequent renal failure, the need for dialysis, and death from renal-related causes.

Defining Hemodynamic Significance of Renal Artery Stenosis: Insights From a Porcine Model of Graded Renal Artery Stenosis

RATIONALE AND OBJECTIVES

To investigate the renal pressure-flow relationship and its relation to renin release, because the renal perfusion pressure below which renal flow starts to decline and renin secretion is upregulated is unclear.

MATERIALS AND METHODS

A porcine model of graded unilateral renal artery stenosis was created. The severity of the stenosis was expressed as the ratio between distal renal pressure (Pd) and aortic pressure (Pa). Pd and renal flow velocity were continuously measured using a combined pressure-flow wire (Combowire®). Hemodynamic measurements and blood sampling for renin, angiotensin and aldosterone were performed in baseline conditions and during progressive balloon inflation in the renal artery leading to Pd decrease per 5% increment. Resistive index (RI) was computed as (1 - (End Diastolic V/Peak Systolic V))*100.

RESULTS

For a 5% decrease in renal perfusion pressure (95% of aortic pressure or 5% decrease compared to Pa), peak systolic velocity started to decrease. A significant decrease in average peak flow velocity was observed when distal renal perfusion pressure decreased by 25% and was associated with activation of ipsilateral renin secretion. The RI decreased already for minimal changes in Pd/Pa ratio.

CONCLUSION

In an animal model of unilateral graded renal artery stenosis, a 25% decrease in perfusion pressure results in a significant decrease in distal renal flow, causing upregulation of renin secretion.

Renal artery stenosis

Renal artery stenosis is the most common secondary cause of hypertension and predominantly caused by atherosclerosis. In suspected patients, a non-invasive diagnosis with ultrasound is preferred. Asymptomatic, incidentally found RAS does not require revascularization. In symptomatic patients requiring revascularization, renal artery stenting is the preferred therapy. Selecting appropriate patients for revascularization requires careful consideration of lesion severity and is optimized with a multidisciplinary team. All patients with atherosclerotic RAS should be treated with guideline-directed medical therapy, including hypertension control, diabetes control, statins, antiplatelet therapy, smoking cessation and encouraging activity.

Is stenting for atherosclerotic renal stenosis an effective technique?

INTRODUCTION

One of the treatments for renal artery stenosis is endovascular intervention, but its effectiveness is controversial. The present study aims to analyze the experience of a working group in the endovascular treatment of selected patients with severe obstructive atherosclerotic lesions of the renal arteries, and to characterize early and late results.

METHODS

This is a retrospective study of symptomatic patients with atherosclerotic renal artery stenosis who underwent endoluminal therapy between May 12, 1999 and March 12, 2015 at two institutions. Statistical analysis was performed using the PASW Statistics program.

RESULTS

A total of 99 patients were treated, mean age 66 years and 76.8% male. The mean degree of stenosis measured by renal Doppler echocardiography was 83% and 64.6% were ostial lesions. Mean preoperative creatinine level was higher than the postoperative mean: 1.3 vs. 1.2 mg/dl (p=0.014). The number of antihypertensive drugs in the preoperative period was higher than in the postoperative period: 2.0 vs. 1.3 (p=0.001). The mean follow-up was 40 months (0-164). The mean peak systolic velocity over time in the postoperative period was 77 cm/s (40-250). The restenosis rate was 8%, and 30-day mortality was 0%.

CONCLUSIONS

The results demonstrated that the endovascular technique has a beneficial effect on blood pressure and renal function in selected patients, and is a safe technique associated with a high rate of technical success and few complications.

Functional Assessment of Intermediate Vascular Disease

Interventional treatment in various vascular beds has advanced tremendously. However, there are several problems to be considered. We searched the literature and tried to analyze major parts of it. One is safety and applicability of coronary proven methods in other vascular beds. An unresolved problem is the functional assessment of intermediate lesions, as far as various target organs have quite different circulation from the coronary one and the functional tests should be modified in order to be applicable and meaningful. In the majority of the acute vascular syndromes, the culprit lesion is of intermediate size on visual assessment. On the other hand, a procedurally successfully managed high-degree stenosis is not always followed by clinical and prognostic benefit. In vascular beds, where collateral network naturally exists, the readings from the functional assessment are complicated and thus the decision for interventional treatment is even more difficult. Here come into help the functional assessment and imaging with IVUS, OCT, high-resolution MRI, and contrast enhanced CT or SPECT. The focus of the current review is on the functional assessment of intermediate stenosis in other vascular beds, unlike the coronary arteries.

Recurrent Pleural Effusion as a Result of Bilateral Renal Artery Stenosis. Does Renal Revascularization Help?

Renal artery stenosis (RAS) is the leading cause of secondary hypertension. Renal artery stenosis can result in various cardiopulmonary complications mostly through activation of neurohormonal pathways that result in fluid overload and systemic hypertension. We herein describe a 72-year-old man with recurrent rapidly accumulating transudative pleural effusion in a patient with severe bilateral RAS. Patient pleural effusion resolved following stent placement with revascularization of the left renal artery despite absence of improvement of renal function. Patient renal function continued to decline and ultimately treated with fixed hemodialysis.

Attenuation of Renal Functional Decline Following Angioplasty and Stenting in Atherosclerotic Renovascular Disease

BACKGROUND

To date, renal revascularization has not been shown to be advantageous when compared to optimized medical treatment in patients with atheromatous renovascular disease (ARVD). This study aims to investigate the effect of revascularization in patients with pre-intervention worsening renal function and in those with stable renal function.

PATIENTS AND METHODS

In this single-centre observational study, patients who were diagnosed with at least 60% angiographic stenosis unilaterally or bilaterally between January 1996 and October 2008 and who were followed-up until February 2011 were retrospectively analysed. Evolution of renal function was determined from the slope of reciprocal of serum creatinine (RCr-slope) before and after diagnostic angiography or revascularization; this required 5 or more creatinine measurements before and at least another 5 measurements post-procedure. Patients were divided into 2 groups: one comprising patients with negative RCr-slope before the procedure and a second group of patients with prior positive RCr-slope. A stepwise, adjusted logistic regression was used to determine the OR of revascularization on attenuation of RCr-slope.

RESULTS

Data for 52 patients were analysed. Median age was 64 (58-72) and median follow-up was 15 (8-34) months. Only patients with a negative RCr-slope (-0.0078 (95% CI -0.0174, -0.0033) dl/mg/month) who underwent revascularization manifested an improved RCr-slope during follow-up (+0.0013 (95% CI -0.0002, 0.0039) dl/mg/month, p < 0.001). This finding remained statistically significant even after the adjustment for proteinuria and bilateral arterial disease.

CONCLUSION

Revascularization may be indicated for patients with ARVD and progressively worsening renal function. This patient subgroup should ideally be evaluated in future randomized controlled trials.

Renal Artery Stenosis: Optimal Therapy and Indications for Revascularization

Atherosclerotic renal artery stenosis (ARAS) is associated with increased cardiovascular risk and overall mortality. Manifestations of ARAS include resistant or malignant hypertension, progressive deterioration of renal function, and cardiac dysfunction syndromes of flash pulmonary edema and angina. Diagnosis rests upon non-invasive studies such as duplex ultrasonography and is confirmed using invasive renal arteriography. Regardless of the severity of ARAS, management of this entity has been a topic of contentious debate. For over two decades, the use of percutaneous revascularization to treat ARAS has been studied with various clinical trials. Though case series seem to demonstrate favorable clinical response to revascularization, the overwhelming majority of randomized clinical trials have not mirrored a robust outcome. In these trials, poor correlation is noted between the reduction of stenosis and the improvement of renovascular hypertension and glomerular filtration rate, and decrease in cardiovascular outcomes and mortality. With dichotomizing results, the explanation for these discrepant findings has been attributed to improper trial design and inappropriate patient selection. An overview of the treatment options available will be provided, with a focus on the methodology and design of clinical trials investigating the efficacy of percutaneous revascularization. Emphasis is placed on appropriate patient selection criteria, which may necessitate the use of hemodynamic lesion assessment and clinical correlation based on individualized care. When clinical equipoise exists between optimal medical therapy and revascularization, the current paradigm supports ongoing medical therapy as the treatment of choice. However, renal artery stenting remains a viable therapeutic option for those who continue to have clinical syndromes consistent with renal hypoperfusion while adequately treated with optimal medical therapy. Despite observational studies suggesting clinical benefit for this specific patient population, there remains a paucity of randomized clinical trial data. Further trials targeting the patients who are inadequately treated with optimal medical therapy need to be undertaken to confirm the efficacy of revascularization.

Emergent unilateral renal artery stenting for treatment of flash pulmonary edema: fact or fiction?

Flash pulmonary edema is characteristically sudden in onset with rapid resolution once appropriate therapy has been instituted (Messerli et al., 2011). Acute increase of left ventricular (LV) end diastolic pressure is the usual cause of sudden decompensated cardiac failure in this patient population. Presence of bilateral renal artery stenosis or unilateral stenosis in combination with a single functional kidney in the susceptible cohort is usually blamed for this condition. We describe a patient who presented with flash pulmonary edema in the setting of normal coronary arteries. Our case is distinct as our patient developed flash pulmonary edema secondary to unilateral renal artery stenosis in the presence of bilateral functioning kidneys. Percutaneous stent implantation in the affected renal artery resulted in rapid resolution of pulmonary edema.

Kissing stenting of aorto-ostial lesions in juxtaposed renal arteries

Percutaneous angioplasty with or without stenting has become an established procedure for treatment of renal artery stenosis for control of hypertension or progressive renal dysfunction. Anatomic variation of renal arteries is common with dual blood supply of unilateral kidney noted in almost 25% of the general population. Renal angioplasty of these anatomic variants of renal arteries is challenging. We present an unusual case of juxtaposed renal arteries with aorto-ostial lesion where direct kissing stenting was done with excellent technical and clinical outcome.

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.

Clinical outcomes and effectiveness of renal artery stenting in patients with critical atherosclerotic renal artery stenosis: does it improve blood pressure control and renal function assessed by estimated glomerular filtration rate?

Introduction

Atherosclerotic renal artery stenosis (ARAS) is associated with uncontrolled hypertension and chronic renal failure.

Aim

To evaluate the influence of gender and presence of chronic renal failure on the outcomes of percutaneous transluminal renal artery stenting (PTRAS) due to atherosclerosis.

Material and methods

A total of 28 ARAS patients underwent PTRAS and 36 stents were placed. Basal characteristics, laboratory data and blood pressure of patients were recorded. The differences between genders and improvement/deterioration of renal functions and blood pressure were analyzed. The predictors of outcomes were determined.

Results

Baseline characteristics were similar between men and women. Significant improvement of systolic and diastolic blood pressure control was achieved after PTRAS (153.04 ±17.07 mm Hg vs. 124.75 ±11.40 mm Hg, p = 0.001 and 92.50 ±10.76 mm Hg vs. 77.54 ±8.23 mm Hg, p < 0.001, respectively). Although mean estimated glomerular filtration rate (eGFR) and creatinine levels did not significantly improve at the 6-month follow-up visit compared to baseline values, of the 28 patients 13 (46.4%) patients had improvement of renal functions.

Conclusions

Our results suggest that PTRAS is a safe procedure and may offer blood pressure control but beneficial effects of PTRAS on renal function may be anticipated in a selected group of patients, especially those with a low eGFR.

Renal artery stenosis in patients with resistant hypertension

The aim of the study was to assess the significance of renal translesional pressure gradients in predicting improvement in resistant hypertension after stenting for moderate renal artery stenosis (RAS). In 37 patients with RAS and resistant hypertension subjected to renal stenting, translesional pressure gradients both at rest and hyperemic were measured using a pressure guidewire. Twenty-four-hour ambulatory blood pressure measurements were performed in all patients on admission and 3 months after the intervention. Angioplasty was successful in all patients, with reduction of artery diameter stenosis from 60 ± 12% to 10 ± 6% (p <0.0001). At 3 months, with maintained hypotensive agents (4.0 ± 1.4 vs 4.0 ± 1.6), significant reductions in systolic blood pressure (SBP) and diastolic blood pressure were noted (-5 and -2 mm Hg, respectively). In multivariate analysis, the mean baseline gradient (MBG) was the only independent predictor of improvement in SBP (regression coefficient 0.292; standard error 0.11; p value 0.014). In the receiver operating characteristic curve analysis, MBG had a larger area under the curve than other parameters, and the MBG >22 mm Hg had the highest sensitivity, specificity, and accuracy (50%, 95%, and 0.74%, respectively) in predicting hypertension improvement after stenting. In patients with MBG >22 mm Hg, SBP decreased by 12 versus 3 mm Hg (p <0.01) in patients with MBG ≤22 mm Hg, whereas diastolic blood pressure in both groups decreased by 3 versus 1 mm Hg, respectively (NS). In conclusion, MBG value of >22 mm Hg provides the highest accuracy in predicting hypertension improvement after stenting for moderate RAS in patients with resistant hypertension.

Renal artery stenosis - an update

Renal artery stenosis (RAS) is a common form of peripheral arterial disease. The most common cause of RAS is atherosclerosis. It is predominantly unilateral. The pathophysiologic mechanism stems from renal underperfusion resulting in the activation of the renin- angiotensin-aldosterone pathway. Even though the majority of patients with RAS are asymptomatic, it can clinically present with hypertension, nephropathy and congestive heart failure. This progressive disease can lead to resistant hypertension and end stage kidney failure. Screening patients for RAS with either Doppler ultrasonography, computed tomographic angiography, or magnetic resonance angiography is preferred. Adequate blood pressure control, goal-directed lipid-lowering therapy, smoking cessation, and other preventive measures form the foundation of management of patients with RAS. Catheter-based percutaneous revascularization with angioplasty and stenting showed modest clinical benefit for patients in small retrospective studies, but data from randomized clinical trials failed to confirm these beneficial results. The current ongoing Cardiovascular Outcomes in Renal Atherosclerotic Lesions (CORAL) trial may provide more concrete data regarding the role of stenting in RAS. Surgical revascularization is considered only if catheter-based revascularization is unsuitable or unsuccessful. The American College of Cardiology/American Heart Association guidelines on evaluation and management of patients with RAS provide the framework for determining individualized assessment and treatment plans for patients with RAS.

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 and renal artery stenting: an evolving therapeutic option

Atherosclerotic renal artery stenosis is a common clinical problem for which the optimal therapeutic strategy remains to be defined. However, renal artery stenting procedures have significantly increased as one approach to treat this clinical problem. Despite improvements in device design and technical performance of the procedure, the benefits and results of randomized clinical trials of renal artery stenting as a therapy remain confusing. Understanding the epidemiology, pathophysiology and natural history of renal artery stenosis are central to improving the outcomes of renal artery stenting. Developing both noninvasive and invasive predictive tools to better identify which patient will respond to renal revascularization will also be beneficial. In this article, we will present an overview of atherosclerotic renal artery disease. The results of renal artery stenting will be discussed and from this, the available noninvasive and invasive tools available to assess the clinical and hemodynamic significance of renal artery stenosis will be presented.

Arterial interventions for renovascular hypertension

Renovascular hypertension is a major cause of secondary hypertension. It affects relatively younger patients. The unifying pathology is renal artery stenosis. The most common cause is atherosclerosis accounting for about 90% of cases with fibromuscular dysplasia being the second most common cause. Both of these are amenable to percutaneous interventional therapy. With the advent of new medical therapies, the control of blood pressure has improved significantly. In well-selected patients, renal arterial intervention has a good outcome. The intervention includes renal angioplasty and stenting. In this article, the authors review the role of percutaneous intervention and the techniques involved with renal angioplasty and stenting for the treatment of renovascular hypertension.

Common secondary causes of resistant hypertension and rational for treatment

Resistant hypertension is defined as uncontrolled blood pressure despite the use of three antihypertensive drugs, including a diuretic, in optimal doses. Treatment resistance can be attributed to poor adherence to antihypertensive drugs, excessive salt intake, physician inertia, inappropriate or inadequate medication, and secondary hypertension. Drug-induced hypertension, obstructive sleep apnoea, primary aldosteronism, and chronic kidney disease represent the most common secondary causes of resistant hypertension. Several drugs can induce or exacerbate pre-existing hypertension, with non-steroidal anti-inflammatory drugs being the most common due to their wide use. Obstructive sleep apnoea and primary aldosteronism are frequently encountered in patients with resistant hypertension and require expert management. Hypertension is commonly found in patients with chronic kidney disease and is frequently resistant to treatment, while the management of renovascular hypertension remains controversial. A step-by-step approach of patients with resistant hypertension is proposed at the end of this review paper.

Cardiac benefits of renal artery stenting

AIMS

The aims of this study were to evaluate the effects of renal stenting on cardiac function using echocardiographic parameters, and to clarify whether changes in clinical and echocardiographic variables after renal stenting differ between atherosclerotic renal artery stenosis (ARAS) patients with and without cardiac symptoms.

METHODS AND RESULTS

A total of 61 patients who underwent renal stenting and echocardiography were included in the study. Left ventricular (LV) filling pressure and LV relaxation were evaluated with tissue Doppler imaging. The ratio of the peak early diastolic mitral inflow velocity to the peak early mitral annular velocity (E/e' ratio) and the e'-velocity were measured to assess diastolic function. LV ejection fraction remained unchanged, but the E/e' ratio (P<0.001) and the e'-velocity (P=0.004) improved after renal stenting. In particular, the E/e' ratio improved from 13.7±5.6 to 11.9±4.0 (P=0.002) within 24 hours after renal stenting and remained low at 11.2±3.8 after a mean follow-up period of 7±4 months (P=0.001). Patients with cardiac symptoms showed significantly better change in E/e' ratio (P=0.002) and E-velocity (P=0.005) compared to those without cardiac symptoms. Cardiac symptoms also significantly improved after renal stenting (New York Heart Association functional class: 2.5±0.6 at baseline to 1.4±0.6 at follow-up; P<0.001).

CONCLUSIONS

Renal stenting improved echocardiographic parameters that reflect LV diastolic function, and yielded a higher benefit for E/e' ratio and E-velocity in patients with cardiac symptoms than in those without cardiac symptoms.

Renovascular disease, microcirculation, and the progression of renal injury: role of angiogenesis

Emerging evidence supports the pivotal role of renal microvascular disease as a determinant of tubulo-interstitial and glomerular fibrosis in chronic kidney disease. An intact microcirculation is vital to restore blood flow to the injured tissues, which is a crucial step to achieve a successful repair response. The purpose of this review is to discuss the impact and mechanisms of the functional and structural changes of the renal microvascular network, as well as the role of these changes in the progression and irreversibility of renal injury. Damage of the renal microcirculation and deterioration of the angiogenic response may constitute early steps in the complex pathways involved in progressive renal injury. There is limited but provocative evidence that stimulation of vascular proliferation and repair may stabilize renal function and slow the progression of renal disease. The feasibility of novel potential therapeutic interventions for stabilizing the renal microvasculature is also discussed. Targeted interventions to enhance endogenous renoprotective mechanisms focused on the microcirculation, such as cell-based therapy or the use of angiogenic cytokines have shown promising results in some experimental and clinical settings.

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.

Renal microvascular disease determines the responses to revascularization in experimental renovascular disease

BACKGROUND

Percutaneous transluminal renal angioplasty (PTRA) is the most frequent therapeutic approach to resolving renal artery stenosis (RAS). However, renal function recovers in only 30% of the cases. The causes of these poor outcomes are still unknown. We hypothesized that preserving the renal microcirculation distal to RAS will improve the responses to PTRA.

METHODS AND RESULTS

RAS was induced in 28 pigs. In 14, vascular endothelial growth factor (VEGF)-165 0.05 microg/kg was infused intrarenally (RAS+VEGF). Single-kidney function was assessed in all pigs in vivo using ultrafast CT after 6 weeks. Observation of half of the RAS and RAS+VEGF pigs was completed. The other half underwent PTRA and repeated VEGF, and CT studies were repeated 4 weeks later. Pigs were then euthanized, the stenotic kidney removed, renal microvascular (MV) architecture reconstructed ex vivo using 3D micro-CT, and renal fibrosis quantified. The degree of RAS and hypertension were similar in RAS and RAS+VEGF. Renal function and MV density were decreased in RAS but improved in RAS+VEGF. PTRA largely resolved RAS, but the improvements of hypertension and renal function were greater in RAS+VEGF+PTRA than in RAS+PTRA, accompanied by a 34% increase in MV density and decreased fibrosis.

CONCLUSIONS

Preservation of the MV architecture and function in the stenotic kidney improved the responses to PTRA, indicating that renal MV integrity plays a role in determining the responses to PTRA. This study indicates that damage and early loss of renal MV is an important determinant of the progression of renal injury in RAS and instigates often irreversible damage.

Timing and selection for renal revascularization in an era of negative trials: what to do?

Management of atherosclerotic renal artery stenosis has become more complex with advances in both medical therapy and endovascular procedures. Results from recent trials fail to demonstrate major benefits of endovascular stenting in addition to optimal medical therapy. The general applicability of these results to many patients is limited by short-term follow-up and selection biases in recruitment. Many patients at highest risk were excluded from these studies and some were included with trivial lesions. Identification of patients with hemodynamically significant lesions remains a challenge and has led to more stringent criteria for Doppler ultrasound, measurement of translesional gradients and quantitative angiography. Although many patients can now be managed with medical therapy, it should be recognized that long-term reduction in antihypertensive drug requirements and recovery of kidney function are limited to those undergoing renal revascularization. As with any major vascular lesion, follow-up for disease stability and/or progression is essential. The ambiguity of present trial data may lead some to overlook selected subgroups that would benefit from restoring renal blood supply through revascularization. Further studies to more precisely identify kidneys that can recover function and/or are beyond meaningful recovery are essential. Considering the comorbid risks for the atherosclerotic population, it will remain imperative for clinicians to consider the hazards, costs and benefits carefully for each patient to determine the role and timing for both medical therapy and revascularization.

Limitations of angiography for the assessment of renal artery stenosis and treatment implications

Renovascular hypertension due to atherosclerotic renal artery stenosis is the most common cause of secondary hypertension. Percutaneous catheter-based renal artery revascularization has been increasingly utilized for the treatment of renal artery stenosis. Renal artery stenting has a high technical success rate, but the rate of improvement in hypertension is somewhat less than expected with this technique. Misinterpretation of angiographic images may play a role in these unfavorable clinical results. We present a case in which the diagnosis of severe renal artery stenosis was not apparent by angiography. Intravascular ultrasound and translesional pressure gradient measurements during arteriography can help to determine the precise severity of stenosis and may augment the clinical results of percutaneous renal artery stent placement.

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.

Evaluation and approach to treatment of renal artery stenosis in patients with diabetic nephropathy

Patients with diabetes mellitus are at increased risk for developing peripheral vascular disease and renal artery stenosis (RAS). Furthermore, in diabetic patients the progression of renal atherosclerotic disease toward critical stenosis or occlusion occurs more frequently than in their nondiabetic counterparts. Consequently, clinicians must carry a high level of suspicion for detecting RAS in diabetic patients, particularly those with established coronary and/or peripheral atherosclerotic disease and compromised renal function. In this group of patients early detection of this condition, preferably with a noninvasive diagnostic test, is very important to plan revascularization therapy. In nondiabetic patients, several studies have demonstrated that catheter-based revascularization therapy may arrest or revert renal dysfunction in patients with RAS. Although still the subject of debate, a recent study has shown that in diabetic patients with RAS and impaired renal function, revascularization therapy with endovascular stents has a positive impact in the progression of renal dysfunction.

Renovascular hypertension: an update

Renovascular hypertension, the most common remediable cause of elevated blood pressure, is a controversial topic, but most authorities agree on several principles. The absolute risk of renovascular hypertension for a specific patient can be estimated using only clinical information, thereby sparing many patients further expensive and potentially dangerous evaluations. Patients with a high absolute risk of renovascular hypertension should have angiography only if they are willing to undergo revascularization if warranted. A screening test (captopril renography, Doppler ultrasonography, magnetic resonance angiography, or computed tomography) is recommended for those with an intermediate absolute risk. Angioplasty should be offered to patients with fibromuscular dysplasia. Whether intensive medical therapy (including an angiotensin-converting enzyme inhibitor or angiotensin II receptor blocker) for atherosclerotic renovascular hypertension is improved by angioplasty plus stent placement may be answered by ongoing studies, the largest of which may be the National Institutes of Health-funded Cardiovascular Outcomes in Renal Atherosclerotic Lesions (CORAL) trial.