Renovascular hypertension: anatomic and renal function changes during drug therapy

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.

A new threshold for kidney asymmetry improves association with abnormal renal-aortic ratio for diagnosis of renal artery stenosis

BACKGROUND

Renal artery stenosis (RAS) reflects more widespread atherosclerosis deposition and is associated with high morbidity and mortality. According to the guidelines, a discrepancy in the size of the kidneys of over 15 mm found in an ultrasound should initiate the RAS diagnostic algorithm. This study aims to find the optimal threshold for renal asymmetry that better reflects the frequency of a significantly abnormal renal-aortic ratio (RAR), justifying further RAS diagnostic workup, than the currently used cut-off of 15 mm difference in renal diameters.

METHODS

The analysis included 1175 patients (mean age: 52 years, IQR: 38-66, men/women: 597/578) who underwent Doppler ultrasonography screening of renal arteries with recorded kidney size and RAR calculation. Ultrasound features of RAS were defined as a RAR greater than 3.5 or signs of renal artery occlusion. Receiver operating characteristic (ROC) curves were created and analyzed for absolute differences in kidney size and abnormal RAR. We calculated the area under the curve (AUC) and optimal cut-off values for sensitivity and specificity analysis.

RESULTS

The final analysis included 169 patients with a significant difference in renal dimension. RAS features were met in 61 patients. According to ROC curve analysis, the optimal index of renal asymmetry was 12 mm. The sensitivity and specificity for this method were 82.0% and 83.3%, respectively, and AUC was 86.3%.

CONCLUSION

Changing the definition of a significant difference in kidney size from 15 mm to 12 mm increases sensitivity and specificity for abnormal RAR and this finding may accelerate the diagnosis of RAS.

Ultrasonographic Assessment of Atherosclerotic Renal Artery Stenosis in Elderly Patients with Chronic Kidney Disease: An Italian Cohort Study

Although atherosclerotic renal artery stenosis (ARAS) is strictly associated with high cardiovascular risk and mortality, it often may remain unrecognized being clinically silent and frequently masked by co-morbidities especially in elderly patients with coexisting chronic kidney disease (CKD). The present observational study was conducted in elderly CKD-patients with atherosclerosis on other arterial beds. The aims were assessment of (1) ARAS prevalence; (2) best predictor(s) of ARAS, using duplex ultrasound; and (3) cardiovascular and renal outcomes at one-year follow-up. The cohort was represented by 607 consecutive in-patients. Inclusion criteria were age ≥65 years; CKD stages 2−5 not on dialysis; single or multiple atherosclerotic plaque on epiaortic vessels, abdominal aorta, aortic arch, coronary arteries, peripheral arteries that had been previously ascertained by one or more procedures. Duplex ultrasound was used to detect ARAS. Multiple regression analysis and ROS curve were performed to identify the predictors of ARAS. ARAS was found in 53 (44%) out of 120 patients who met the inclusion criteria. In univariate analysis, GFR (b = −0.021; p = 0.02); hemoglobin (b = −0.233; p = 0.02); BMI (b = 0.134; p = 0.036) and atherosclerosis of abdominal aorta and/or peripheral vessels (b = 1.025; p < 0.001) were associated with ARAS. In multivariable analysis, abdominal aorta and/or peripheral atherosclerosis was a significant (p = 0.002) predictor of ARAS. The area under the ROC curve was 0.655 (C.I. = 0.532−0.777; p = 0.019). ARAS is common in older CKD patients with extra-renal atherosclerosis, with the highest prevalence in those with aortic and peripheral atherosclerosis. ARAS may pass by unnoticed in everyday clinical practice.

Reversible Ischemic Nephropathy in a Deceased Donor Renal Transplant Recipient With BK Nephropathy

Atherosclerotic renal artery stenosis is one of the risk factors for cardiovascular death and can lead to the ischemic nephropathy. In this report, we describe the successful management of ischemic nephropathy that developed in a kidney transplant recipient with graft artery stenosis. The 52-year-old male patient had diabetes and hypertension and was a nonsmoker with hypothyroidism on replacement therapy. He had a history of recurrent urinary tract infection due to vesicoureteric reflux before starting hemodialysis in July 2009. In November 2020, he received a deceased donor renal allograft and showed slow graft function. He received thymoglobulin as induction and steroid, tacrolimus, and mycophenolate mofetil as maintenance therapy. He was discharged with nadir creatinine around 130 μmol/L. His diabetes was controlled by intensive insulin regimen. Later, he presented with graft dysfunction with partially controlled hypertension and suspected graft artery stenosis by Doppler ultrasonography but no evidence of obstruction. His tacrolimus level was adequate, and his echocardiography was unremarkable. He received empirical pulse steroid. A graft biopsy showed severe acute tubular necrosis, suspicious T-cell-mediated rejection, and negative C4d and positive SV40 stain, suggesting BK nephropathy. His BK viremia (500 copies/mL) and viruria (885 billion copies/mL) improved after immunosuppression minimization, although he remained dependent on dialysis. A repeated Doppler ultrasonogram showed flattening of the systolic wave. Computed tomographic angiography revealed diffusely attenuated graft arteries. The patient received graft artery angioplasty and stenting of the 2 arteries. The patient showed good response, with same-day urine production and Doppler showing good systolic wave. His graft function started to improve, and he was discharged with stable graft function. His immunosuppressive regimen was subsequently tailored to steroid and low-dose tacrolimus. In conclusion, we found that ischemic nephropathy could be reversed if properly managed, even in presence of other comorbidities.

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.

Atherosclerotic renovascular disease - epidemiology, treatment and current challenges

The neutral results of recent large randomized controlled trials comparing renal revascularization with optimal medical therapy in patients with atherosclerotic renovascular disease (ARVD) have cast doubt on the role of revascularization in the management of unselected patients with this condition. However, these studies have strengthened the evidence base for the role of contemporary intensive medical vascular protection therapy and aggressive risk factor control in improving clinical outcomes in ARVD. Patients presenting with ‘high-risk’ clinical features such as uncontrolled hypertension, rapidly declining renal function or flash pulmonary oedema are underrepresented in these studies; hence these results may not be applicable to all patients with ARVD. In this ‘high-risk’ subgroup, conservative management may not be sufficient in preventing adverse events, and indeed, observational evidence suggests that this specific patient subgroup may gain benefit from timely renal revascularization. Current challenges include the development of novel diagnostic techniques to establish haemodynamic significance of a stenosis, patient risk stratification and prediction of post-revascularization outcomes to ultimately facilitate patient selection for revascularization. In this paper we describe the epidemiology of this condition and discuss treatment recommendations for this condition in light of the results of recent randomized controlled trials while highlighting important clinical unmet needs and challenges faced by clinicians managing this condition.

Endovascular Management of Atherosclerotic Renal Artery Stenosis: Post-Cardiovascular Outcomes in Renal Atherosclerotic Lesions Era Winner or False Alarm?

Renal artery stenosis (RAS) is frequently associated with severe comorbidities such as reduced renal perfusion, hypertension, and end-stage renal failure. In approximately 90% of patients, renal artery atherosclerosis is the main cause for RAS, and it is associated with an increased risk for fatal and non-fatal cardiovascular and renal complications. Endovascular management of atherosclerotic RAS (ARAS) has been recently evaluated by several randomized controlled trials that failed to demonstrate benefit of stenting. Furthermore, the Cardiovascular Outcomes in Renal Atherosclerotic Lesions study did not demonstrate any benefit over the revascularization approach. In this review, we summarized the available data from retrospective, prospective and randomized trials on ARAS to provide clinicians with sufficient data in order to produce useful conclusions for everyday clinical practice.

Concomitant coronary and renal revascularization improves left ventricular hypertrophy more than coronary stenting alone in patients with ischemic heart and renal disease

Percutaneous transluminal renal artery stenting (PTRAS) has been proved to have no more benefit than medication alone in treating atherosclerotic renal artery stenosis (ARAS). Whether PTRAS could improve left ventricular hypertrophy (LVH) and reduce adverse events when based on percutaneous coronary intervention (PCI) for patients with coronary artery disease (CAD) and ARAS is still unclear. A retrospective study was conducted, which explored the effect of concomitant PCI and PTRAS versus PCI alone for patients with CAD and ARAS complicated by heart failure with preserved ejection fraction (HFpEF). A total of 228 patients meeting inclusion criteria were divided into two groups: (1) the HFpEF-I group, with PCI and PTRAS; (2) the HFpEF-II group, with PCI alone. Both groups had a two-year follow-up. The left ventricular mass index (LVMI) and other clinical characteristics were compared between groups. During the follow-up period, a substantial decrease in systolic blood pressure (SBP) was observed in the HFpEF-I group, but not in the HFpEF-II group. There was marked decrease in LVMI in both groups, but the HFpEF-I group showed a greater decrease than the HFpEF-II group. Regression analysis demonstrated that PTRAS was significantly associated with LVMI reduction and fewer adverse events after adjusting for other factors. In HFpEF patients with both CAD and ARAS, concomitant PCI and PTRAS can improve LVH and decrease the incidence of adverse events more than PCI alone. This study highlights the beneficial effect of ARAS revascularization, as a new and more aggressive revascularization strategy for such high-risk patients.

Renovascular Hypertension

Hypertension constitutes a major health problem and the challenge is to identify patients having ‘surgically’ curable renal vascular disease among the majority with so-called essential hypertension. The best of unsatisfactory diagnostic tests are renography and plasma renin activity both before and during angiotensin II blockade. The necessity of better screening tests has increased because of the recent advances in surgical techniques and especially percutaneous transluminal renal angioplasty. The latter has definitely become the method of choice for correction of suspected hemodynamically significant artery stenoses whenever technically feasible. With improved angioplasty techniques the risk of treating renal artery stenosis without hemodynamic and clinical importance (so-called cosmetic repair) has increased. Unfortunately randomized trials including surgery versus angioplasty are not available. It should be kept in mind that only after correction of the stenosis is achieved and the blood pressure has become normal, can the diagnosis of renovascular hypertension be made with certainty.

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.

Progress in the treatment of atherosclerotic renovascular disease: the conceptual journey and the unanswered questions

Over the past decades, management of atherosclerotic renovascular disease (ARVD) has undergone significant progress, in parallel with increased knowledge about the complex pathophysiology of this condition. Modern multi-targeted medical management of atherosclerosis has driven a change in both the natural history and the clinical outcomes of ARVD. Progression to total renal artery occlusion is a much less common occurrence and while early studies have reported that up to 41% of patients reached renal end-points over a mean follow-up of 44 months, the latest randomized controlled trials have shown that progressive renal impairment occurs in 16-22% of patients, with <8% of patients reaching end-stage kidney disease (ESKD) over a similar time-frame. However, the results of the latest large ARVD trials investigating the effect of renal stenting upon clinical outcomes have been influenced by selection bias as high-risk patients with clinically significant renal artery stenosis (RAS) have largely been excluded from these studies. Although the neutral results of these trials have shown uncertainty about the role of revascularization in the management of patients with ARVD, there is evidence that revascularization can optimize outcomes in selected patients with a high-risk clinical phenotype. Future challenges lie in identifying important subgroups of patients with critical RAS and viable kidneys, while continuing to develop strategies to protect the renal parenchyma and hence improve clinical outcomes.

Endovascular versus medical therapy for atherosclerotic renovascular disease

The diagnosis of renal artery stenosis (RAS) has become increasingly common in part due to greater awareness of ischemic renal disease and increased use of diagnostic techniques. Over 90 % of RAS cases are caused by atherosclerotic renovascular disease (ARVD). Patients with ARVD are at high risk for fatal and nonfatal cardiovascular and renal events. The mortality rate in patients with ARVD is high, especially with other cardiovascular or renal comorbidities. Recent clinical studies have provided substantial evidence concerning medical therapy and endovascular interventional therapeutic approaches for ARVD. Despite previous randomized clinical trials, the optimal therapy for ARVD remained uncertain until the results of the Cardiovascular Outcomes in Renal Atherosclerotic Lesions (CORAL) trial were released recently. CORAL demonstrated that optimal medical therapy was equally effective to endovascular therapy in the treatment of ARVD. Clinicians can now practice with more evidence-based medicine to treat ARVD and potentially decrease mortality in patients with ARVD using optimal medical therapy.

Renal artery stenting may not be appropriate for patients with atherosclerotic renal artery stenosis

INTRODUCTION

This study compared aortorenal bypass to renal artery stenting to determine the most efficacious and financially sound method for treating patients with atherosclerotic renal artery stenosis (RAS).

METHODS

A decision analysis using direct and indirect costs, and value of statistical life (VSL) was completed. Direct costs were obtained using the Nationwide Inpatient Sample (NIS), indirect costs from the National Institute of Diabetes and Digestive and Kidney Diseases, and VSL from the Department of Transportation. A variance-based sensitivity analysis was completed to assess the accuracy of the decision analysis.

RESULTS

Aortorenal bypass has a 95% five-year patency, a 98% 30-day survival, a 26% rate of overall complications, and a 70% five-year dialysis-free survival. Renal artery stenting has a 56% five-year patency, a 99% 30-day survival, a 40% rate of complications, and a 65% five-year dialysis-free survival. Renal artery stenting has an overall cost of $305,370 and aortorenal bypass has an overall cost of $103,453 per patient. After accounting for VSL, renal artery stenting has a negative value of -$182,270 and aortorenal bypass has a value of $415,881.

CONCLUSIONS

Lower five-year patency and higher rate of complications from renal artery stenting that ultimately lead to significantly lower five-year dialysis-free survival.

Safety and efficacy of carbon dioxide and intravascular ultrasound-guided stenting for renal artery stenosis in patients with chronic renal insufficiency

We evaluated the feasibility, safety, and mid-term outcomes of renal artery stenting using carbon dioxide (CO₂) digital subtraction angiography and intravascular ultrasound (IVUS) for patients with renal insufficiency and significant atherosclerotic renal artery stenosis (RAS). Eighteen consecutive patients with chronic renal insufficiency underwent renal artery stenting under the guidance of CO₂ angiography and IVUS without contrast media. Renal function and blood pressure were assessed pre- and postintervention. A total of 27 de novo RAS in 18 patients (15 males; mean age: 72 ± 9 years) with renal insufficiency were treated by renal artery stenting with the combined use of the CO₂ angiography and IVUS without any procedural complications. Although the mean serum creatinine concentration preprocedure and 6 months after treatment did not change (2.7 ± 1.0-2.4 ± 1.1 mg/dL), blood pressure significantly decreased 6 months after stenting (158 ± 10-147 ± 11 mm Hg, P < .01).

Renal artery stenosis: epidemiology and treatment

Renal artery stenosis (RAS) is a frequently encountered problem in clinical practice. The disease encompasses a broad spectrum of pathophysiologies and is associated with three major clinical syndromes: ischemic nephropathy, hypertension, and destabilizing cardiac syndromes. The two most common etiologies are fibromuscular dysplasia and atherosclerotic renal artery disease with atherosclerotic disease accounting for the vast majority of cases. Atherosclerotic renovascular disease has considerable overlap with atherosclerotic disease elsewhere and is associated with a poor prognosis. A wide range of diagnostic modalities and treatment approaches for RAS are available to clinicians, and with the advent of endovascular interventions, selecting the best course for a given patient has only grown more challenging. Several clinical trials have demonstrated some benefit with revascularization but not to the extent that many had hoped for or expected. Furthermore, much of the existing data is only marginally useful given significant flaws in study design and inherent bias. There remains a need for further identification of subgroups and appropriate indications in hopes of maximizing outcomes and avoiding unnecessary procedures in patients who would not benefit from treatment. In recent decades, the study of RAS has expanded and evolved rapidly. In this review, we will attempt to summarize the amassed body of literature with a focus on the epidemiology of RAS including prevalence, overlap with other atherosclerotic disease, and prognosis. We will also outline existing diagnostic and treatment approaches available to clinicians as well as summarize the findings of several major clinical trials. Finally, we will offer our perspective on future directions in the field.

Measurement of renal dimensions in vivo: A critical appraisal

Kidney volume is regarded as the most precise indicator of kidney size. However, volume assessment is not widely used clinically because its measurement is difficult due to the complex kidney shape. Apart from the conventional methods of measurement of renal dimensions from X-rays, ultrasound scan, computed tomography scan and magnetic resonance imaging have evolved as the three best modalities for this purpose currently. Assessment of kidney size should also be made individually since many factors like body mass index, height, gender, age, position of kidneys, sex, stenoses and number of renal arteries influence the measurements. In this paper, we have critically analysed the advantages and disadvantages of the various methods of renal morphometry, by reviewing the literature spanning over the period of 1976 - 2009.

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.

Atherosclerotic renal artery stenosis--diagnosis and treatment

Renal artery stenosis (RAS) is characterized by a heterogeneous group of pathophysiologic entities, of which fibromuscular dysplasia and atherosclerotic RAS (ARAS) are the most common. Whether and which patients should undergo revascularization for ARAS is controversial. The general consensus is that all patients with ARAS should receive intensive medical treatment. The latest randomized clinical trials have increased confusion regarding recommendations for revascularization for ARAS. Although revascularization is not indicated in all patients with ARAS, experts agree that it should be considered in some patients, especially those with unstable angina, unexplained pulmonary edema, and hemodynamically significant ARAS with either worsening renal function or with difficult to control hypertension. A search of the literature was performed using PubMed and entering the search terms renal artery stenosis, atherosclerotic renal artery stenosis, and renal artery stenosis AND hypertension to retrieve the most recent publications on diagnosis and treatment of ARAS. In this review, we analyze the pathways related to hypertension in ARAS, the optimal invasive and noninvasive modalities for evaluating the renal arteries, and the available therapies for ARAS and assess future tools and algorithms that may prove useful in evaluating patients for renal revascularization therapy.

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.

Prevalence and predictors of renal artery stenosis in hypertensive patients undergoing elective coronary procedures

This study explored the prevalence and predictors of renal artery stenosis in a cohort of 525 hypertensive patients referred for elective coronary procedures. Patients underwent coronary and renal arteriography. The study defined renal artery stenosis as > or =60% luminal obstruction (physiologic or hemodynamic significance was not tested). Patients were classified into groups of those with normal renal arteries, those with insignificant renal artery stenosis, and individuals with significant renal artery stenosis. The mean age was 52.6+/-8.5 years, and 403 (76.8%) were males. Significant renal artery stenosis was found in 3.6%. It correlated significantly with hypertension duration (P=.005), history of cerebrovascular stroke (P=.01), history of angioplasty to >1 coronary vessel (P=.003), and 3-vessel coronary disease (P=.0003). Multivariate regression analysis identified 2-vessel and 3-vessel coronary artery disease as independent predictors of renal artery stenosis, with odds ratios of 4.9 and 12.1, respectively. It was concluded that invasive screening for renal artery stenosis was probably warranted only in hypertensive patients with multivessel coronary disease referred for elective coronary procedures.

Serum Creatinine Stabilization Following Renal Artery Stenting

The impact of renal artery stenting on renal function in a subgroup of consecutive de novo patients with atherosclerotic renal artery stenosis from the single operator, single center, retrospective renal stent trial is defined. Patients with inadequate preprocedure and/or follow-up renal function studies were excluded. Abnormal baseline serum creatinine (sCr) was defined as ≥1.5 mg/dL. Follow-up sCr was improved, unchanged, or worsened if the variance from baseline decreased by >20%, stayed within 20%, or increased >20%, respectively. For the total cohort (194 patients), renal function stabilized or improved in 72% of patients. Plotting 1/sCr demonstrated a decline in renal function before the procedure that stabilized following renal artery stenting. Bilateral renal artery stenting predicted normal follow-up sCr, and baseline sCr >2.1 mg/dL was associated with improvement in sCr long-term. In conclusion, renal artery stenting results in overall stabilization of renal function, and bilateral renal artery stenting seems to have added benefit.

Treatment of renovascular hypertension by transluminal angioplasty--13 years experience in a single centre

OBJECTIVE

The study is a follow-up on treatment of renovascular hypertension (RVH) with percutaneous transluminal renal angioplasty (PTRA).

METHODS

Patients were screened on the basis of clinical criteria of increased probability of RVH with renography and in selected cases with renal vein renin measurements. A positive work-up suggesting a functionally important renal artery stenosis led to renal angiography and PTRA if stenosis was confirmed; in 59%, an intravascular stent was inserted.

RESULTS

Outcome of treatment was classified as follows - group I: normotensive without medication; group II: with improved control of blood pressure; group III: unchanged blood pressure control. Grouping was performed immediately after treatment, at 1 month, 6 months and at the latest follow-up. One hundred-and-twenty-two patients (124 atherosclerotic and 12 fibromuscular lesions) were treated during 13 years. Immediately after PTRA the patients were grouped as follows - I: 31%, II: 59%, III: 10%. At 1 month, I: 13%, II: 72%, III: 15%; at 6 months, I: 11%, II: 74%, III: 15%, and at the latest follow-up, I: 11%, II: 78%, III: 11%. There were few significant complications, and renal function remained on average stable.

CONCLUSION

PTRA is an effective treatment of RVH in patients selected by signs of a flow-restricting stenosis. Twelve percent were normotensive after angioplasty and a further 77% had better controlled hypertension. Few complications were seen and renal function was on average unchanged as measured by serum creatinine.

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.

Renal Artery Stenosis and Cardiovascular Risk

Atherosclerotic renal artery stenosis is the most common disease of the renal arteries and may lead to ischemic renal disease and hypertension. A close relationship exists between renal and cardiovascular disease, as they often occur concomitantly, and abnormalities in either system can cause disease and determine clinical outcome in the other. Renovascular disease is gaining recognition as a potentially important risk factor for cardiovascular morbidity and mortality. This article explores the association between atherosclerotic renal artery stenosis and the cardiovascular system.

Factors affecting long-term survival following renal artery stenting

INTRODUCTION

This study defines clinical variables at the time of renal artery stenting that may be predictors of long-term all-cause mortality.

METHODS

The data are derived from the single operator, single center, renal stent retrospective study (SOCRATES) and includes a review of 748 (336 men, 412 women) consecutive symptomatic patients with de novo atherosclerotic renal artery stenosis treated over an 11-year period. All patients had clinical indications for renal revascularization, including, but not limited to; suboptimal control of hypertension, chronic kidney disease, and cardiac disturbance syndromes. Clinical variables at the time of the index procedure were evaluated as predictors of all-cause mortality using multivariate analysis. Mortality data were derived from hospital records and formal queries of the State Department of Health and Human Services, Health and Vital Statistics Division database.

RESULTS

In-hospital, 30-day and 6-month mortality rates were 0.5, 2.0, and 6.3%, respectively. Overall patient survival at years 1, 5, and 10 was 91.2, 66.6, and 40.9%, respectively. Comorbid conditions, including chronic obstructive pulmonary disease and congestive heart failure, were independently associated with increased mortality. There were incremental changes in mortality in patients with baseline azotemia, [preprocedure serum creatinine (sCr) 1.5-2.09 mg/dL hazard ratio 1.52; sCr >2.5 mg/dL hazard ratio 3.39]. Therapy with lipid lowering agents offered a survival advantage (hazard ratio 0.69, P = 0.0.049); however, this study was not designed to evaluate a "protective effect" of lipid lowering medications.

CONCLUSIONS

Patients with chronic obstructive pulmonary disease and congestive heart failure undergoing renal artery stent revascularization have a poor long-term prognosis. Baseline azotemia is the strongest independent predictor of all cause mortality, with more than 70% of patients with marked azotemia (sCr >2.5) dead at 5 years.

Progression of atherosclerotic renovascular disease: a prospective population-based study

OBJECTIVE

Previous reports from select hypertensive patients suggest that atherosclerotic renovascular disease (RVD) is rapidly progressive and associated with a decline in kidney size and kidney function. This prospective, population-based study estimates the incidence of new RVD and progression of established RVD among elderly, free-living participants in the Cardiovascular Health Study (CHS).

METHOD

The CHS is a multicenter, longitudinal cohort study of cardiovascular risk factors, morbidity, and mortality among men and women aged >65 years old. From 1995 through 1996, 834 participants underwent renal duplex sonography (RDS) to define the presence or absence of significant RVD. Between 2002 and 2005, a second RDS study was performed in 119 participants (mean study interval, 8.0 +/- 0.8 years). Significant RVD was defined as hemodynamically significant stenosis (renal artery peak systolic velocity [RA-PSV] exceeding 1.8 m/s) or renal artery occlusion. Prevalent RVD was significant RVD at the first RDS, and incident disease was defined as new significant RVD at the second RDS. Significant change of RVD was defined as a change in RA-PSV of greater than two times the standard deviation of expected change over time, regardless of hemodynamic significance or progression to renal artery occlusion.

RESULTS

The second RDS study cohort included 119 CHS participants with 235 kidneys (35% men; mean age, 82.8 +/- 3.4). On follow-up, no prevalent RVD (n = 13 kidneys; 6.0%) progressed to occlusion. Twenty-nine kidneys without RVD at the first RDS demonstrated significant change in PSV at the second RDS; including nine kidneys with new significant RVD (8 new stenoses; 1 new occlusion). Controlling for within-subject correlation, the overall estimated change in RVD among all 235 kidneys was 14.0% (95% confidence interval [CI], 9.2% to 21.4%), with progression to significant RVD in 4.0% (95% CI, 1.9% to 8.2%). Longitudinal increase in diastolic blood pressure and decrease in renal length were significantly associated with progression to new (ie, incident) significant RVD but not prevalent RVD.

CONCLUSIONS

This is the first prospective, population-based estimate of incident RVD and progression of prevalent RVD among free-living elderly Americans. In contrast to previous reports among select hypertensive patients, CHS participants with a low rate of clinical hypertension demonstrated a significant change of RVD in only 14.0% of kidneys on follow-up of 8 years (annualized rate, 1.3% per year). Progression to significant RVD was observed in only 4.0% (annualized rate, 0.5% per year), and no prevalent RVD progressed to occlusion.

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.

Clinical insights into the diagnosis and management of atherosclerotic renal artery disease

Atherosclerotic renovascular disease (ARVD) is an increasingly common contributor to hypertension and renal failure. However, not all patients with an identified obstructive atherosclerotic renal artery stenosis will have clinical improvement, even after successful percutaneous intervention. As such, there remains extensive controversy regarding optimal diagnostic and treatment strategies. Part of this controversy is the result of a paucity of well-designed prospective, randomized clinical trials, but the complex nature of the disorder and the heterogeneity of patients presenting with possible ARVD make simple diagnostic and treatment paradigms difficult to develop. This narrative review describes the latest observations concerning the prevalence, pathogenesis, natural history, diagnostic studies, and treatment options for suspected ARVD. Hopefully, this knowledge will improve the ability of clinicians to weigh risks and benefits and determine the best strategy in individual patients.

Coronary bypass procedures in patients with renal artery stenosis

BACKGROUND AND AIM OF THE STUDY

We present our experience on patients with renal artery stenosis undergoing myocardial revascularization procedures.

METHODS

Eighteen patients with varying degrees of renal artery stenosis were operated for coronary artery bypass grafting between 1996 and 2003. The overall incidence was 0.15%. There were nine male and nine female patients with a mean age of 62 +/- 8.2 (40-72 years). Four had bilateral and eight had significant unilateral (>50%) renal artery stenoses. Preoperatively, three patients had renal arterial intervention (stenting), and one patient was on hemodialysis. The mean preoperative creatinine value was 2.6 +/- 2.7 mg/dL (range 0.7 to 9.3). The patients were followed medically: two patients underwent off-pump coronary bypass grafting and the others were operated on-pump.

RESULTS

There was only one mortality and two patients required hemodialysis postoperatively. The postoperative mean creatinine values were 3.4 +/- 4.9 mg/dL (range 1.0 to 12.5). No electrolyte imbalances were noted except that one case revealed a transient metabolic acidosis. Five patients required inotropic support with dopamine and two needed diuretic infusions. Only five patients demonstrated a refractory hyper tensive period postoperatively.

CONCLUSIONS

The concomitant correction of renal artery stenosis with CABG is usually not necessary, but the principles for renovascular diseases must be kept in mind and individually oriented strategies must be planned.

Renal duplex parameters, blood pressure, and renal function in elderly people

BACKGROUND

Changes in renal artery and renal parenchyma perfusion are believed to correlate with severity of hypertension and worsened renal function, but population-based studies of these associations are not available. This study examines relationships between parameters derived from renal duplex sonography (RDS), blood pressure (BP), and excretory renal function in a population-based cohort of elderly Americans.

METHODS

Through an ancillary study to the Cardiovascular Health Study, 758 participants (37% men; mean age, 77 years) underwent RDS in which flow velocities and frequency shifts were determined from spectral analysis of Doppler-shifted signals obtained from the renal artery and parenchyma. Associations of these duplex parameters with BP and inverse serum creatinine were examined by using multivariate regression techniques.

RESULTS

Main renal artery peak systolic flow velocity (PSV) showed independent associations with BP, with an SD increase in PSV (0.53 m/s) associated with a 3.3-mm Hg increase in systolic BP (SBP) and a 2.4-mm Hg decrease in diastolic BP (DBP). An SD decrease in end-diastolic frequency shift (EDF; 131 kHz) was associated with a 6.0-mm Hg increase in SBP, a 4.2-mm Hg decrease in DBP, and a significant 3.7% decrease in inverse serum creatinine.

CONCLUSION

Increases in renal artery PSV and decreases in parenchymal EDF are associated with increased SBP and decreased DBP. Moreover, decreased parenchymal EDF showed significant associations with impaired excretory renal function. These results suggest that renal duplex parameters are associated with renal parenchymal changes caused by hypertension and progressive renal dysfunction in elderly people.

Atherosclerotic renovascular disease in chronic heart failure: should we intervene?

Renal artery stenosis (RAS) is most commonly caused by atherosclerosis, which is also the most common cause of chronic heart failure (CHF). One-third of patients with CHF are reported to have significant renovascular disease. The presence of RAS confers a worse outcome in studies of hypertension and coronary disease, though data are lacking for patients with CHF. As the kidney is intricately involved in the fluid retention that occurs in CHF, an adverse effect of RAS on outcome would be expected. Presentations of RAS in CHF include flash pulmonary oedema, hypertension, worsening of CHF, and worsening renal function. RAS commonly progresses and may cause worsening of renal function in patients with CHF and previously stable renal function. A variety of investigations that can safely and accurately identify RAS in CHF are available, although none is recommended in current guidelines for the management of CHF. Treatment for RAS, whether for hypertension, for renal dysfunction, or for pulmonary oedema, is at the discretion of the physician due to the lack of adequate randomized controlled trials demonstrating the efficacy and safety of intervention. As it is not clear how RAS should be managed in CHF, screening cannot be advocated. Currently, a multicentre randomized outcome trial, which includes a cohort of patients with RAS and CHF, is in progress to provide answers in this area of uncertainty.

Diagnosis and treatment of renovascular hypertension: a cost-benefit analysis

OBJECTIVE

We sought to evaluate and compare the relative cost-benefit of Doppler sonography, MR angiography, and captopril-enhanced renal scintigraphy as techniques for predicting a patient's clinical response to renal angioplasty.

MATERIALS AND METHODS

Estimations of positive and negative predictive values of baseline and captopril-enhanced renal scintigraphy and Doppler sonography examinations for predicting a favorable outcome after renal angioplasty were based on a previously published prospective study involving 74 patients who underwent this treatment. For gadolinium-enhanced MR angiography, predictive values were calculated from a subpopulation of 57 of these 74 subjects. The value of different combined strategies with these techniques for predicting clinical success after angioplasty was evaluated in this population. The costs of investigation and treatment per improved patient were calculated for each imaging technique and for combined strategies in a hypothetic 1,000-patient population with a 30% prevalence of renal artery stenosis, relying on the diagnostic performance reported in the literature for each technique in detecting renal artery stenosis.

RESULTS

The costs for each improved patient were $12,579 for patients selected on the basis of a positive finding on Doppler sonography (false-negative results = 12/1,000) and $10,149 for patients selected with criteria combining a positive finding on Doppler sonography with a bilateral resistive index of less than 0.75 (false-negative results = 32/1,000). Patient selection based on a positive finding on MR angiography cost $18,119 (false-negative results = 0), whereas the cost of patient selection based on a positive finding on renal scintigraphy was $12,939 (false-negative results = 29/1,000).

CONCLUSION

Doppler sonography is more cost-efficient but less sensitive than MR angiography for identifying patients with renovascular hypertension. MR angiography should be favored in hypertensive patients who are resistant to medical therapy to avoid false-negative examinations.

Renal fibromuscular dysplasia in elderly persons

Renal artery stenosis (RAS) is a significant cause of secondary hypertension, the progression of which can lead to renal insufficiency, uncontrolled hypertension, and even end-stage renal disease. The 2 most common forms of RAS are atherosclerotic renovascular disease and fibromuscular dysplasia (FMD). Atherosclerosis accounts for 90% of all cases of RAS and generally affects an elderly population. Conversely, FMD accounts for approximately 10% of all RAS cases and is described as affecting a younger population. Four cases of FMD in individuals older than 70 years are presented, in a period of 1 year at 1 facility. This case series calls into question the previously reported low prevalence of FMD in elderly persons. It is conceivable that renal artery investigation might be denied an elderly patient thought to have atherosclerotic disease. Because conventional angioplasty is considered the treatment of choice for patients with FMD because of the high response rate for uncontrolled hypertension, the prevalence of FMD in the elderly population should be reevaluated to detect and treat this population accordingly.

Ultrasound measured renal length versus low dose CT volume in predicting single kidney glomerular filtration rate

Ultrasound measured renal length and CT measured renal volume are potential surrogate markers for single kidney glomerular filtration rate (SKGFR). The aims of this study are to determine: (1) the repeatability of ultrasound measured length and low radiation dose spiral CT measured volume; (2) the relationship between renal length and volume; and (3) whether length and/or volume is a predictor of SKGFR. 69 patients with suspected renal artery stenosis underwent ultrasound renal length measurement, CT evaluation of renal volume and assessment of SKGFR. 40 patients had ultrasound measurement of length and CT evaluation of volume performed twice on two separate visits. 25 patients also had ultrasound measured renal parenchymal thickness and area. The region of interest was drawn around the kidneys and a threshold set to subtract renal peripelvic fat and renal pelvis. The volume from each slice was summed to obtain the total volume for each kidney. The limits of agreement for ultrasound measured renal length were -1.6 cm to 1.52 cm and that for CT renal volume were -33 ml to 32 ml. There was significant correlation between ultrasound measured length and CT volume (r=0.74, p<0.01). Volume was a better predictor of SKGFR (r(2)=0.57) than length (r(2)=0.48). The combined parameters of ultrasound measured length, area and parenchymal thickness were a better predictor of volume (r(2)=0.81) and SKGFR (r(2)=0.58) than ultrasound measured length on its own. The low dose CT technique was reasonably reproducible and renal volume measurements correlate better with SKGFR than length. Ultrasound predictions of renal volume and SKGFR can be improved by incorporating cross-sectional area and parenchymal thickness. Further investigation is required to refine our low dose CT technique.