Guidelines for the reporting of renal artery revascularization in clinical trials. American Heart Association

Restenosis after stenting of atherosclerotic renal artery stenosis: Is there a rationale for the use of drug-eluting stents?

Percutaneous stent-angioplasty has become an accepted therapy for the treatment of atherosclerotic renal artery stenosis (RAS) because of higher acute and long-term success rates compared with balloon angioplasty alone. Restenosis rates after successful renal stent placement vary from 6 to 20% and depend mainly on the definition of restenosis and the vessel diameter of the renal artery or stent. We recommend that restenosis should be defined as >70%. The safety and efficacy of drug-eluting stents for the treatment of RAS is poorly defined. The currently partially published GREAT study (Palmaz Genesis peripheral stainless steel balloon expandable stent: comparing a sirolimus-coated vs. a bare stent in REnal Artery Treatment) examined the effect of a sirolimus-coated stent on restenosis rate in 102 patients and found a relative risk reduction of angiographic binary in-stent restenosis by 50% (7% versus 14%, P = ns). Given the lack of outcome data, the considerable expenses associated with drug-eluting stents, morbidity, and cost associated with prolonged dual antithrombotic therapy, the use of drug-eluting stents in RAS should be restricted to clinical trials. This is a review on restenosis rate following renal stenting, its definition, and the potential use for implantation of a drug-eluting stent in RAS, which so far for this indication is not yet commercially available.

The performance of renal duplex ultrasonography for the detection of hemodynamically significant renal artery stenosis

OBJECTIVES

The value of renal duplex ultrasonography for the detection of angiographical renal artery stenosis (RAS) has been demonstrated in many clinical studies. None of the published studies, however, have adequately scrutinized the performance of this modality for the detection of hemodynamically significant RAS. The purpose of this study is to investigate the correlation and accuracy between renal duplex parameters and translesional pressure gradient (TLPG).

METHODS

A total of 60 patients, with 75 stenotic lesions in the renal arteries determined by angiography, underwent duplex ultrasonography before angiography and the measurement of TLPG using a 0.014'' pressure wire in the single setting of angiography were prospectively included. Peak systolic velocity (PSV) in the renal artery and a ratio of PSV in the renal artery to the aorta (RAR) were examined as duplex ultrasonography parameters. Angiographical stenosis was evaluated by percent diameter stenosis (%DS) derived from quantitative angiographic analysis.

RESULTS

The correlation with TLPG proved to be stronger in the following order, PSV (r = 0.743, P < 0.001), %DS (r = 0.701, P < 0.001), and RAR (r = 0.572, P < 0.001). The best performing parameter for TLPG of 20 mm Hg was revealed to be PSV, as the areas under the receiver operator characteristics curves using %DS, PSV, and RAR were 0.888, 0.939, and 0.834, respectively. A PSV cutoff value of 219 cm/sec provided the best predictive value with a sensitivity of 89%, a specificity of 89%, and an accuracy of 89%. The positive predictive value was 83% and the negative predictive value was 93%.

CONCLUSIONS

The measurement of PSV is not only noninvasive but also highly accurate in detecting patients who have hemodynamically significant RAS. The authors emphasize that an enthusiastic application of renal duplex ultrasonography, particularly the measurement of PSV, is warranted.

Restenosis in gold-coated renal artery stents

BACKGROUND

Gold coating improves stent visibility under fluoroscopy. This is particularly valuable for precise stent placement during renal artery stenting (RAS). There is conflicting evidence regarding restenosis with gold-coated stents. To evaluate the effect of gold coating on restenosis after renal stenting, we reviewed the results of all patients undergoing RAS in our practice.

METHODS

A retrospective cohort study of all patients undergoing RAS between June 2000 and September 2003 was performed. During this time, both gold-coated and stainless steel stents were used. Restenosis (>60% diameter) was determined by serial follow-up duplex exams (peak systolic velocity >180 cm/s and renal-aortic ratio >3.5). Restenosis rates were determined by using the Kaplan-Meier life-table method. Variables potentially affecting restenosis were evaluated with the log-rank test and Cox proportional hazards modeling.

RESULTS

RAS was performed in 97 arteries (78 patients). Gold-coated (NIRoyal) stents were placed in 59 arteries (48 patients). Stainless steel stents (Corinthian, Genesis, and Herculink) were placed in 38 arteries (34 patients). Patient demographics, indication for treatment, technical success, and complications did not differ between gold and stainless steel stent groups. Mean follow-up was 15 months for gold-coated stents and 18 months for stainless steel stents (NS). By life-table method, 1-year and 2-year freedom from restenosis rates were 84% and 78% in arteries treated with stainless steel stents versus 69% and 39% in those treated with gold-coated stents (P = .012, log-rank test). By multivariate analysis, only the use of gold-coated stents (P = .018; hazard ratio [HR], 3.3; 95% confidence interval [CI], 1.2 to 8.7) and bilateral disease (P = .046; HR, 2.3; 95% CI, 1.02 to 5.2) predicted restenosis. Stent diameter, patient demographics, and indication for RAS had no effect on restenosis by univariate analysis. According to American Heart Association criteria, 87% of patients in the stainless steel group had improved blood pressure at 1 year, compared with 77% in the gold-coated stent group (Kaplan-Meier; P = .042, log-rank test). There were no significant differences in the effect of RAS on serum creatinine levels between the two groups.

CONCLUSION

Gold-coated renal stents had a substantially higher rate of restenosis than stainless steel stents in our series. These findings have led us to abandon the use of gold-coated stents for RAS. Patients who have received gold-coated stents for the treatment of atherosclerotic renal artery stenosis should be followed closely for evidence of restenosis.

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.

High-Spatial-Resolution MR Angiography of Renal Arteries with Integrated Parallel Acquisitions: Comparison with Digital Subtraction Angiography and US

PURPOSE

To retrospectively compare three-dimensional gadolinium-enhanced magnetic resonance (MR) angiography, performed with an integrated parallel acquisition technique for high isotropic spatial resolution, with selective digital subtraction angiography (DSA) and intravascular ultrasonography (US) for accuracy of diameter and area measurements in renal artery stenosis.

MATERIALS AND METHODS

The study was approved by the institutional review board, and consent was obtained from all patients. Forty-five patients (17 women, 28 men; mean age, 62.2 years) were evaluated for suspected renal artery stenosis. Three-dimensional gadolinium-enhanced MR angiograms were acquired with isotropic spatial resolution of 0.8 x 0.8 x 0.9 mm in 23-second breath-hold with an integrated parallel acquisition technique. In-plane diameter of stenosis was measured along vessel axis, and perpendicular diameter and area of stenosis were assessed in cross sections orthogonal to vessel axis, on multiplanar reformations. Interobserver agreement between two radiologists in measurements of in-plane and perpendicular diameters of stenosis and perpendicular area of stenosis was assessed with mean percentage of difference. In a subset of patients, degree of stenosis at MR angiography was compared with that at DSA (n = 20) and intravascular US (n = 11) by using Bland-Altman plots and correlation analyses.

RESULTS

Mean percentage of difference in stenosis measurement was reduced from 39.3% +/- 78.4 (standard deviation) with use of in-plane views to 12.6% +/- 9.5 with use of cross-sectional views (P < .05). Interobserver agreement for stenosis grading based on perpendicular area of stenosis was significantly better than that for stenosis grading based on in-plane diameter of stenosis (mean percentage of difference, 15.2% +/- 24.2 vs 54.9% +/- 186.9; P < .001). Measurements of perpendicular area of stenosis on MR angiograms correlated well with those on intravascular US images (r(2) = 0.90).

CONCLUSION

Evaluation of cross-sectional images reconstructed from high-spatial-resolution three-dimensional gadolinium-enhanced MR renal angiographic data increases the accuracy of the technique and decreases interobserver variability.

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 Gruntzig 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 meta-analysis 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.

Elevated Brain Natriuretic Peptide Predicts Blood Pressure Response After Stent Revascularization in Patients With Renal Artery Stenosis

Background— A significant number (20% to 40%) of hypertensive patients with renal artery stenosis will not have blood pressure improvement after successful percutaneous revascularization. Identifying a group of patients with refractory hypertension and renal artery stenosis who are likely to respond to renal stent placement would be beneficial.

Methods and Results— Brain natriuretic peptide (BNP) was measured in 27 patients with refractory hypertension and significant renal artery stenosis before and after successful renal artery stent placement. This neuropeptide was elevated (median, 187 pg/mL; 25th to 75th percentiles, 89 to 306 pg/mL) before stent placement and fell within 24 hours of the successful stent procedure (96 pg/mL; 25th to 75th percentiles, 61 to 182 pg/mL; P =0.002), remaining low (85 pg/mL; 25th to 75th percentiles, 43 to 171 pg/mL) at follow-up. Clinical improvement in hypertension was observed in the patients with a baseline BNP >80 pg/mL (n=22) in 17 patients (77%) compared with 0% of the patients with a baseline BNP ≤80 pg/mL (n=5) ( P =0.001). After correction for glomerular filtration rate, BNP was strongly correlated with improvement in hypertension.

Conclusions— BNP is increased in patients with severe renal artery stenosis and decreases after successful stent revascularization. In addition, an elevated baseline BNP level of >80 pg/mL appears to be a good predictor of a blood pressure response after successful stent revascularization.

Outcomes of renal artery angioplasty and stenting using low-profile systems

OBJECTIVE

Renal artery percutaneous transluminal angioplasty (RPTA) and stenting (RAS) are accepted therapies for selected patients with renovascular hypertension and chronic renal insufficiency. We evaluated the outcomes and complications of RAS performed by vascular surgeons at our institution with modern low-profile systems.

METHOD

We retrospectively analyzed all RPTA and RAS procedures attempted with the use of low-profile systems from June 2000 to September 2003. Eighty-two patients (96 arteries) with atherosclerotic renal artery stenosis were treated. Indication for treatment was hypertension in 44 (54%) and chronic renal insufficiency in 38 (46%). Technical success, complication rates, clinical success for control of hypertension or renal insufficiency, restenosis, and survival were reviewed with a mean follow-up of 1 year.

RESULTS

Ninety-three arteries were treated with stents, three with RPTA only. Primary technical success was 95%, with 98% overall technical success. Major complications occurred in 6.1% and minor complications in 1.2%. Hypertension was improved in 81% at 1 year. Renal function was improved in 23%, stable in 53%, and worse in 24% at 1 year. Restenosis was seen by routine duplex surveillance in 25% at 1 year. Restenosis associated with clinical deterioration and confirmed by angiogram was seen in 10%. The overall 3-year survival was 83%.

CONCLUSION

RPTA/RAS can be performed with low-profile systems with excellent technical success, low complication rates, and clinical outcomes that compare favorably with prior reports.

The profile of cardiac patients with renal artery stenosis

OBJECTIVES

We examined the prevalence and severity of renal artery stenosis (RAS) in patients undergoing cardiac catheterization who were deemed at risk for RAS based on clinical or laboratory criteria for study entry, but who had not previously been suspected of having RAS.

BACKGROUND

The diagnosis of atherosclerotic RAS remains problematic because its clinical manifestations are nonspecific.

METHODS

Consecutive patients undergoing non-emergent cardiac catheterization at a single institution during a 12-month period were evaluated using standardized clinical, laboratory, and angiographic criteria. Patients exhibiting at least one of four predefined selection criteria (severe hypertension, unexplained renal dysfunction, acute pulmonary edema with hypertension, or severe atherosclerosis) were prospectively registered and underwent coincident diagnostic renal angiography.

RESULTS

Renal angiography was performed in 851 patients and was diagnostic in 837. Angiographically evident renal atherosclerosis was present in 39% of the population, with RAS > or =50% in 120 (14.3%) and severe stenosis (> or =70%) in 61 (7.3%). Severe stenosis was present in 48 (7%) patients with severe atherosclerosis, 38 (16%) with renal dysfunction, 25 (9%) with hypertension, and 2 (22%) with acute pulmonary edema with hypertension. The prevalence was higher in those exhibiting multiple selection criteria. In a multivariate model, severe RAS was associated with age, female gender, reduced creatinine clearance, increased systolic blood pressure, and peripheral or carotid artery disease.

CONCLUSIONS

In a population at risk of, but not previously suspected of having RAS, severe RAS is associated with simple and readily determined clinical and laboratory patient characteristics. These data facilitate focused application of diagnostic renal angiography.

Stent-Supported Angioplasty of Severe Atherosclerotic Renal Artery Stenosis Preserves Renal Function and Improves Blood Pressure Control:Long-term Results From a Prospective Registry of 456 Lesions

PURPOSE

To report a prospective study evaluating the long-term impact of stent-supported angioplasty on renal function and blood pressure control.

METHODS

In a 6-year period, 456 hemodynamically significant de novo renal artery stenoses > or =70% were treated in 340 consecutive hypertensive patients (223 men; mean age 66+/-10 years, range 44-84) with or without impaired renal function. Baseline data on serum creatinine (sCr), intrarenal resistance index, ambulatory 24-hour blood pressure monitoring, and documentation of the number and dose of antihypertensive drugs were compared to values obtained during follow-up. The primary endpoint was a 10% decrease in sCr; the glomerular filtration rate and changes in blood pressure control were additional outcome measures.

RESULTS

During a mean follow-up of 34+/-20 months, sCr decreased significantly from 1.45+/-0.87 to 1.39+/-0.73 mg/dL (p=0.048). In 34% of the patients, sCr decreased >10%, 39% were unchanged, and 27% had an increase >10%. Glomerular filtration rate increased from 59+/-26 to 62+/-26 mL/min/1.73 m(2) (p=0.6). Systolic, diastolic, and mean blood pressure measurements significantly improved immediately after the intervention (132/72/93 versus 144/79/102 mmHg at baseline, p<0.0001) and remained improved during follow-up (p<0.0001). Blood pressure control was improved in 46%, unchanged in 43%, and deteriorated in 11%. Baseline sCr, bilateral intervention, percent diameter stenosis, and 3-vessel coronary disease were independent predictors of improved renal function during follow-up; the number of antihypertensive drugs taken before the intervention predicted improved blood pressure control.

CONCLUSIONS

Stent-supported angioplasty of renal artery stenoses preserves renal function and improves blood pressure control in a broader spectrum of patients than previously thought.

Predictors of Improved Renal Function After Percutaneous Stent-Supported Angioplasty of Severe Atherosclerotic Ostial Renal Artery Stenosis

BACKGROUND

Percutaneous stent-supported angioplasty is a treatment option for atherosclerotic ostial renal artery stenosis. Improvement of renal function by such intervention, however, is controversial and thought to be limited to specific subsets, such as nondiabetic patients and bilateral stenoses. In this prospective study, we investigated predictors for improvement of renal function and blood pressure after renal artery stent placement.

METHODS AND RESULTS

The study included 215 consecutive patients with ostial renal artery stenosis of > or =70% diameter stenosis undergoing stent-supported angioplasty. The primary end point was decrease in serum creatinine concentration at 1 year; the secondary end point, decrease in average mean arterial blood pressure assessed by 24-hour monitoring. One-year follow-up was complete in 191 surviving patients. In 52% (99/191) of the patients, serum creatinine concentration decreased during 1-year follow-up. Median serum creatinine concentration dropped significantly from 1.21 mg/dL (quartiles: 0.92, 1.60 mg/dL) at baseline to 1.10 mg/dL (quartiles: 0.88, 1.50 mg/dL) at 1 year (P=0.047). On average, mean arterial blood pressure decreased significantly, from 102+/-12 mm Hg (mean+/-SD) at baseline to 92+/-10 mm Hg at 1 year (P<0.001). Significant independent predictors of improved renal function were baseline serum creatinine (odds ratio [95% CI], 2.58 [1.35 to 4.94], P=0.004) and left ventricular function (OR 1.51 [1.04 to 2.21], P=0.032). Female sex, high baseline mean blood pressure, and normal renal parenchymal thickness were independent predictors for decreased mean blood pressure.

CONCLUSIONS

Stent-supported angioplasty for severe ostial renal artery stenosis improves renal function and blood pressure in a broader spectrum of patients than previously thought.

Percutaneous Therapy for Renal Artery Fibromuscular Dysplasia

Fibromuscular dysplasia (FMD) accounts for 10% of cases of renal artery stenosis. This study evaluates the anatomic and functional outcomes of endovascular therapy for symptomatic renal artery FMD at an academic medical center. A retrospective analysis of records from patients who underwent percutaneous transluminal renal artery angioplasty (PTRA) found 14 patients (all female) who underwent 19 interventions on 18 renal artery segments. Significant cardiovascular comorbidities were few in this patient population. The PTRA technical success rate was 95%. There were no periprocedural mortalities. Primary patency rates were 81%, 69%, 69%, and 69% at 2, 4, 6, and 8 years. Assisted primary patency rates were 87%, 87%, 87%, and 87% at 2, 4, 6, and 8 years. The restenosis rate was 25% at 8 years. Clinical benefit (improved or cured hypertension) was seen in 79% of patients overall; 65% of patients maintained this benefit at 8 years by life-table analysis. Percutaneous endovascular intervention for clinically symptomatic FMD of the renal arteries is technically successful, safe, and durable. Most patients demonstrate immediate clinical benefit and retain durable functional outcomes.

Managing renal arterial disease and hypertension

Treating patients with renovascular disease is complex, particularly as imaging and medical techniques become more effective. Atherosclerotic renal artery disease is present in 7% of the general population above age 65 and in 20 to 45% of patients with coronary disease or aortoiliac disease. Most patients are treated medically, but when progressive hypertension, renal insufficiency, or circulatory congestion develops, revascularization should be considered. Endovascular procedures with arterial stents are now widely employed. These procedures sometimes offer major benefits in blood pressure control and stabilization of renal function. Stent procedures continue to entail hazards, including atheroemboli, arterial dissections, and thrombosis, in addition to restenosis rates of 14 to 20%. Small, randomized trials to date demonstrate no survival benefit to either endovascular or surgical revascularization as compared with medical management. Recognizing renal artery disease and directing revascularization procedures to those with the most benefit remains a premier challenge for the clinician.