Stent placement for treatment of renal artery stenosis guided by intravascular ultrasound

Issues related to renal artery angioplasty and stenting

Renal artery stenosis may play a significant role in the pathogenesis of secondary hypertension, renal dysfunction, and flash pulmonary edema. Currently correction of renal arterial inflow stenosis is reserved for resistant hypertension patients who have failed maximal medical therapy, have worsening renal function and/or unexplained proximal congestive failure. With the recent advances in minimally invasive percutaneous stent placement techniques, open surgical revascularization has been largely replaced by renal artery stenting. The potential benefit of revascularization seemed intuitive; however, the initial enthusiasm and rise in the number of percutaneous interventions have been tempered by many subsequent negative randomized clinical trials that failed to prove the proposed benefits of the percutaneous intervention. The negative randomized trial results have fallen under scrutiny due to trial design concerns and inconsistent outcomes of these studies compared to pivotal trials undertaken under US Food and Drug Administration scrutiny. Treatment of atherosclerotic renal artery occlusive disease has become one of the most debatable topics in the field of vascular disease. The results from recent randomized clinical trials of renal artery stenting have basically limited the utilization of the procedure in many centers, but not every clinical scenario was covered in those trials. There are potential areas for improvement focusing mainly on procedural details and patient selection with respect to catheter based treatment of atherosclerotic renal artery stenosis. We believe, limiting patient selection, enrollment criteria and outcomes measured functioned to reduce the benefit of renal artery stenosis stenting by not enrolling patients likely to benefit. Future studies incorporating potential procedural improvements and that include patients more likely to benefit from renal stenting than were included in ASTRAL and CORAL are needed to more carefully examine specific patient subgroups so that “the baby is not thrown out with the bath water.” We also discuss several other concerns related to renal artery stenting which include diagnostic, procedure, indication, and reimbursement issues.

Issues related to renal artery angioplasty and stenting

Renal artery stenosis may play a significant role in the pathogenesis of secondary hypertension, renal dysfunction, and flash pulmonary edema. Currently correction of renal arterial inflow stenosis is reserved for resistant hypertension patients who have failed maximal medical therapy, have worsening renal function and/or unexplained proximal congestive failure. With the recent advances in minimally invasive percutaneous stent placement techniques, open surgical revascularization has been largely replaced by renal artery stenting. The potential benefit of revascularization seemed intuitive; however, the initial enthusiasm and rise in the number of percutaneous interventions have been tempered by many subsequent negative randomized clinical trials that failed to prove the proposed benefits of the percutaneous intervention. The negative randomized trial results have fallen under scrutiny due to trial design concerns and inconsistent outcomes of these studies compared to pivotal trials undertaken under US Food and Drug Administration scrutiny. Treatment of atherosclerotic renal artery occlusive disease has become one of the most debatable topics in the field of vascular disease. The results from recent randomized clinical trials of renal artery stenting have basically limited the utilization of the procedure in many centers, but not every clinical scenario was covered in those trials. There are potential areas for improvement focusing mainly on procedural details and patient selection with respect to catheter based treatment of atherosclerotic renal artery stenosis. We believe, limiting patient selection, enrollment criteria and outcomes measured functioned to reduce the benefit of renal artery stenosis stenting by not enrolling patients likely to benefit. Future studies incorporating potential procedural improvements and that include patients more likely to benefit from renal stenting than were included in ASTRAL and CORAL are needed to more carefully examine specific patient subgroups so that "the baby is not thrown out with the bath water." We also discuss several other concerns related to renal artery stenting which include diagnostic, procedure, indication, and reimbursement issues.

Renal Artery Stenosis: When to Revascularize in 2017

Atherosclerotic renal artery stenosis is the leading cause of secondary hypertension; it can also cause progressive renal insufficiency and cardiovascular complications such as refractory heart failure and flash pulmonary edema. Medical therapy including risk factor modification, renin-angiotensin-aldosterone system antagonists, lipid lowering agents, and antiplatelet therapy is the first line of treatment in all patients. Patients with uncontrolled renovascular hypertension despite optimal medical therapy, ischemic nephropathy, and cardiac destabilization syndromes who have severe renal artery stenosis are likely to benefit from renal artery revascularization. Screening for renal artery stenosis can be done with Doppler ultrasonography, computed tomographic angiography and magnetic resonance angiography. Invasive physiologic measurements are useful to confirm the severity of renal hypoperfusion and therefore improve the selection patients likely to respond to renal artery revascularization. Primary patency exceeds 80% at 5 years and surveillance for in-stent restenosis can be done with periodic clinical, laboratory, and imaging follow-up.

Response of Renal and Femoropopliteal Arteries to Palmaz Stent Implantation Assessed with Intravascular Ultrasound

Purpose:

To establish the processes responsible for late lumen loss in renal and femoropopliteal Palmaz stents using intravascular ultrasound (IVUS).

Methods:

The first 7 consecutive patients treated with stents for renal (n = 4) and femoropopliteal (n = 3) arterial occlusive disease were studied with IVUS immediately after angiographically successful stent placement (< 10% residual stenosis) and periodically during follow-up. Images of both stent edges and the most stenotic site inside the stent at follow-up were matched to the same cross sections captured immediately after stent placement for quantitative analysis.

Results:

Late lumen loss in renal artery stents at 5 to 34 months was considerably less than in femoropopliteal stents (17% versus 62%, respectively). In the renal location, late lumen loss (3.0 ± 1.3 mm2) was due to neointimal hyperplasia, whereas stent area remained unchanged (3% decrease). Late lumen loss (7.4 ± 8.2 mm2) in femoropopliteal stents was due to neointimal hyperplasia and stent area reduction (26%). Overall, in both types of arteries, neointimal development and stent area reduction were larger at the most stenotic site than at the stent edges.

Conclusions:

These data suggest that there may be differences between renal and femoropopliteal arteries in the extent of hyperplastic response to stents.

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

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

Percutaneous transluminal renal angioplasty remarkably improved severe hypertension and renal function in a patient with renal artery stenosis and postrenal kidney failure

A 69-year-old man was admitted to our hospital with severe hypertension and rapidly worsening renal function. He presented with a 10-year history of chronic renal failure caused by bilateral ureteral obstruction due to retroperitoneal fibrosis. Magnetic resonance angiography and Doppler ultrasonography suggested severe right renal artery stenosis (RAS). Renal angiography revealed 99% stenosis at the ostium of the right renal artery. We performed percutaneous transluminal renal angioplasty (PTRA) with the support of intravascular ultrasound to decrease the amount of contrast agent needed. In addition, to prevent distal atheroembolism, a distal protection device was used. The procedure was completed without any adverse effects. After PTRA, renal function and blood pressure improved remarkably and remained stable for one year. PTRA for RAS remains controversial, especially in patients with renal insufficiency. Use of new devices should be considered to decrease catheterization-related adverse effects.

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.

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.

Shrinkage of the distal renal artery 1 year after stent placement as evidenced with serial intravascular ultrasound

The objective of this study was to determine the quantitative intravascular ultrasound (IVUS) and angiographic changes that occur during 1 year follow-up after renal artery stent placement, given that restenosis continues to be a limitation of renal artery stent placement. 38 consecutive patients with symptomatic renal artery stenosis treated with Palmaz stent placement were studied prospectively. IVUS and angiography were performed at the time of stent placement and at 1 year follow-up. At follow-up, angiographic restenosis was seen in 14% of patients. The lumen area in the stent, seen with IVUS, was significantly decreased from 24+/-5.6 mm(2) to 17+/-5.6 mm(2) (p<0.001) solely due to plaque accumulation. The distal main renal artery showed a significant decrease in lumen area owing to a significant vessel area decrease from 39+/-14.0 mm(2) to 29+/-9.3 mm(2) (p<0.001) without plaque accumulation. Angiographic analysis confirmed this reduction in luminal diameter and showed that the distal renal artery diameter at follow-up was significantly smaller than before stent placement (86+/-23.0% vs 104+/-23.9% of the contralateral renal artery diameter; p=0.003). Besides plaque accumulation in the stent, unexplained shrinkage of the distal main renal artery was evidenced with IVUS and angiography 1 year following stent placement.

Functional effects of renal artery stent placement on treated and contralateral kidneys

BACKGROUND

This study examined the effects of stent placement for renal artery stenosis on the function of treated and contralateral kidneys.

METHODS

Eighteen patients who underwent stent placement for unilateral renal artery stenosis presenting with hypertension and/or renal failure were studied before angiography and stent placement and at their one-year follow-up. Renal vein blood samples were taken at both sides, at each side simultaneously with a sample from the aorta, to measure the plasma renin concentration and the concentrations of 131I-hippuran and 125I-thalamate during constant systemic infusion of these radiochemicals. This allowed an assessment of the single-kidney contributions to the total renin secretion, effective renal plasma flow (131I-hippuran clearance) and glomerular filtration rate (125I-thalamate clearance).

RESULTS

At the one-year follow-up, the vein-to-artery renin ratio at the treated side had decreased to normal, from 1.65 +/- 0.131 to 1.23 +/- 0.076 (mean +/- SEM; P = 0.011), indicating an improved renal blood flow. Contralaterally it rose from 1.09 +/- 0.042 to 1.17 +/- 0.029 (P = 0.055) at follow-up. The extraction ratio of 131I-hippuran improved at the treated side (0.48 +/- 0.049 to 0.62 +/- 0.034; P = 0.003) and contralaterally (0.67 +/- 0.033 to 0.73 +/- 0.026; P = 0.043). The extraction ratio of 125I-thalamate, which equals filtration fraction, improved at both sides (0.12 +/- 0.014 to 0.17 +/- 0.012 at the treated side, P = 0.001; 0.18 +/- 0.013 to 0.22 +/- 0.011 contralaterally, P = 0.002). Two-kidney effective renal blood flow and glomerular filtration rate remained unchanged.

CONCLUSION

Renal artery stenting was capable of causing improvement of glomerular filtration rate of the treated kidney, although the overall glomerular filtration rate did not change.

Predictors for clinical success at one year following renal artery stent placement

PURPOSE

To determine pretreatment variables that may predict 1-year clinical outcome of stent placement for renal artery stenosis.

METHODS

In a prospective study, 40 consecutive patients (29 men; mean age 60 +/- 9.1 years) with angiographically proven atherosclerotic renal artery stenosis were treated with stent placement because of drug resistant hypertension (n=14), renal function impairment (n=14), or both (n=12). Clinical success at 1 year was defined as a decrease of diastolic blood pressure > or = 10 mmHg or a decrease in serum creatinine > or = 20%, depending on the indication for treatment. Regression analysis was performed using anatomical parameters from angiography and intravascular ultrasound, estimates of renal blood flow from renal scintigraphy, and single-kidney renal function measurements.

RESULTS

Patients treated for hypertension had better outcome than those treated for renal function impairment, with clinical success rates of 85% and 35%, respectively. Preserved renal function, with low serum creatinine and high 2-kidney glomerular filtration rate at baseline, was associated with clinical success in the entire patient group at follow-up (p=0.02 and p=0.03, respectively). An elevated vein-to-artery renin ratio on the affected side was borderline predictive (p=0.06). In patients treated for renal impairment, lateralization to the affected kidney (affected kidney-to-2-kidney count ratio < or = 0.45) on the scintigram emerged as a significant predictor for clinical success, with an odds ratio of 15 (p=0.048).

CONCLUSIONS

Clinical success of renal artery stent placement is better for the treatment of hypertension than for preserving renal function. In patients with renal function impairment, lateralization to the affected kidney on the scintigram appears to be a predictor of clinical success.

Intravascular ultrasound-guided renal artery stenting

PURPOSE

To evaluate the clinical outcomes of patients undergoing renal artery stenting with intravascular ultrasound (IVUS) guidance and compare measurements between IVUS and angiography.

METHODS

One hundred thirty-one patients (71 women; mean age 71 +/- 8 years) underwent IVUS-guided Palmaz stent implantation in 153 stenotic renal arteries at a single center. The indications for stenting were uncontrolled hypertension (102, 77.9%), renal insufficiency (10, 7.6%), and both conditions (19, 14.5%). The majority of lesions were ostial (114, 74.5%); the remainder occupied the proximal renal artery (39, 25.5%). The mean lesion length and diameter stenosis were 6.5 +/- 3.0 mm and 74% +/- 10%, respectively, as measured by angiography. Data were recorded in a prespecified database; angiographic and IVUS images were analyzed at dedicated core laboratories and compared.

RESULTS

Angiographic success was achieved in all patients, but IVUS indicated the need for additional intervention in 36 (23.5%) cases. There was strong correlation between the angiographic and IVUS measurements of lesion length (r = 0.60, p < 0.0001) and pre-/postprocedural minimal luminal diameter (r = 0.72 and 0.63, respectively; p < 0.0001). The mean contrast volume was 74 +/- 18 mL per case. In-hospital renal failure occurred in 8 (6.1%) patients; 2 (1.5%) required transient hemodialysis. At a mean 15-month follow-up, patients were treated with fewer antihypertensive medications (p = 0.05), and systolic and diastolic arterial blood pressures had decreased (p = 0.001); no significant change was noted in serum creatinine.

CONCLUSIONS

IVUS-guided stenting facilitates safe renal artery revascularization. IVUS imaging may complement angiography in certain cases, which should be studied further in prospective studies with iodinated or noniodinated contrast agents.

Stent placement for renal arterial stenosis: where do we stand? A meta-analysis

PURPOSE

To perform a meta-analysis of renal arterial stent placement in comparison with renal percutaneous transluminal angioplasty (PTA) in patients with renal arterial stenosis.

MATERIALS AND METHODS

Studies dealing with renal arterial stent placement (14 articles; 678 patients) and renal PTA (10 articles; 644 patients) published up to August 1998 were selected. A random-effects model was used to pool the data.

RESULTS

Renal arterial stent placement proved highly successful, with an initial adequate performance in 98% and major complications in 11%. The overall cure rate for hypertension was 20%, whereas hypertension was improved in 49%. Renal function improved in 30% and stabilized in 38% of patients. The restenosis rate at follow-up of 6-29 months was 17%. Stent placement had a higher technical success rate and a lower restenosis rate than did renal PTA (98% vs 77% and 17% vs 26%, respectively; P <.001). The complication rate was not different between the two treatments. The cure rate for hypertension was higher and the improvement rate for renal function was lower after stent placement than after renal PTA (20% vs 10% and 30% vs 38%, respectively; P <.001).

CONCLUSION

Renal arterial stent placement is technically superior and clinically comparable to renal PTA alone.

Response of renal and femoropopliteal arteries to Palmaz stent implantation assessed with intravascular ultrasound

PURPOSE

To establish the processes responsible for late lumen loss in renal and femoropopliteal Palmaz stents using intravascular ultrasound (IVUS).

METHODS

The first 7 consecutive patients treated with stents for renal (n = 4) and femoropopliteal (n = 3) arterial occlusive disease were studied with IVUS immediately after angiographically successful stent placement (< 10% residual stenosis) and periodically during follow-up. Images of both stent edges and the most stenotic site inside the stent at followup were matched to the same cross sections captured immediately after stent placement for quantitative analysis.

RESULTS

Late lumen loss in renal artery stents at 5 to 34 months was considerably less than in femoropopliteal stents (17% versus 62%, respectively). In the renal location, late lumen loss (3.0 +/- 1.3 mm2) was due to neointimal hyperplasia, whereas stent area remained unchanged (3% decrease). Late lumen loss (7.4 +/- 8.2 mm2) in femoropopliteal stents was due to neointimal hyperplasia and stent area reduction (26%). Overall, in both types of arteries, neointimal development and stent area reduction were larger at the most stenotic site than at the stent edges.

CONCLUSIONS

These data suggest that there may be differences between renal and femoropopliteal arteries in the extent of hyperplastic response to stents.