Percutaneous renal artery stent placement for hypertension and azotemia: pilot study

[Ischemic renal disease and renal artery stenosis]

Severe renal artery stenosis may cause renovascular hypertension; in case of bilateral narrowing or in a stenotic solitary or transplant kidney, renal insufficiency (ischemic renal disease) or rarely pulmonary flash edema may occur. In most cases arteriosclerotic disease is the underlying cause; less prevalent are the various manifestations of fibromuscular disease. Renal artery stenosis may be treated by revasularization, using either percutaneous (balloon angioplasty, stenting) or rarely open surgical procedures, both with excellent primary patency rates. However, randomized trials of renal artery angioplasty or stenting in patients with arteriosclerotic lesions have failed to demonstrate a longer-term benefit with regard to hypertension control and renal dysfunction over medical management alone. Careful patient selection is essential to maximize the potential benefit (e.g., in patients with refractory hypertension, progressive renal failure or recurrent pulmonary flash edema).

Embolic protection: Limitations of current technology and novel concepts

Distal embolic event is one of the major limitations of coronary and non-coronary vascular interventions. Balloon and filter-based Embolic Protection Devices (EPDs) are a new class of interventional devices, used to prevent consequential morbidity and mortality of the distal embolic events. Data from first generation EPD supply proof of concept and show approximately 40% reduction in mortality and morbidity, when EPDs are used during saphenous vein grafts (SVGs) interventions. Current limitations of all first generation EPD technology taper their penetration. With breakthroughs in embolic protection technology, it is estimated that, in the near future, EPDs will be used with stenting in all high-risk lesions (SVGs, carotid arteries and acute coronary syndromes), become the standard of care and even be used in low risk cases.

Cost-effectiveness analysis of treatment of renal-artery stenoses by medication, angioplasty, stenting and surgery

This study analysed the cost-effectiveness of four different treatment modalities (medical therapy, PTA with and without stent, and surgery) for the therapy of renal-artery stenoses in hypertensive patients in Germany. A computerised, predictive decision-analytic model, based on economic input data and the cost of medical care in Germany, and the results of published data from prospective clinical trials, was developed. The economic analysis was performed from the perspective of a third-party payer. The base-case analysis showed that the primary end-point (major vascular bleeding, stroke, dialysis, or repeat arterial revascularisation) was reached at 36 months by 82.4% of the patients in the medical treatment group, 81.4% in the angioplasty group, 52.9% in the surgical group and 27.7% in the stent group. The average reimbursed treatment cost per patient after 3 years was € 9121 (medication), € 17 164 (surgery), € 14 670 (PTA), and € 8437 (stent). This resulted in a cost-effectiveness ratio of € 51 752 (medical treatment), € 36 454 (surgery), € 78 766 (PTA), and € 11 663 (stent) per event-free patient at 3 years. The accelerated cost-development after balloon dilatation was caused by higher rates of restenosis compared with primary stent implantation. The analysis of published prospective clinical data and current economic variables for renovascular interventions leads to the conclusion that a strategy using primary stent implantation is more cost-effective than stand-alone balloon dilatation. Both medical therapy and surgery offer a better cost-effectiveness ratio than PTA treatment alone.

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

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

Renal artery stenting in solitary functioning kidneys: Technical and clinical results

OBJECTIVE

To evaluate the clinical and technical results of renal artery stenting for the treatment of renovascular hypertension and renal failure in patients with solitary functioning kidney.

MATERIALS AND METHODS

Fifteen patients with solitary functioning kidney underwent renal artery stenting and were followed up for 12-60 months. Before the procedures, systolic and diastolic blood pressures and serum creatinine levels were measured and the number of antihypertensive drugs was recorded and followed up after stenting. In case of restenosis, either in-stent percutaneous transluminal renal angioplasty or stent-in-stent placement was performed.

RESULTS

Primary technical success rate was 100%. One lesion was nonostial while 14 were ostial. Primary patency rates were 100% for 6 months, 92.3% for 12 months, and 69.2% for 24 months. The secondary patency rate at 24 months was 100%. The differences between the baseline and postprocedural values of systolic blood pressures, diastolic blood pressures and the number of antihypertensive drug were statistically significant (P < 0.05), except the values of serum creatinine. Hypertension was cured in 1 (6.7%) patient, improved in 4 (26.6%) and stabilized in 10 (66.7%) patients. Renal function improved in 9 (60%), stabilized in 4 (26.6%), and deteriorated in 2 (13.4%) patients. Minor complication rate was 13.4% and major complication rate was 13.4%.

CONCLUSION

Revascularization of renal artery stenosis using stent in solitary functioning kidneys is a safe and efficient procedure with high primary technical results, low restenosis rates and acceptable complication rates. It has an improving and controlling effect on blood pressure and renal functions.

Revascularisation of renal artery stenosis caused by fibromuscular dysplasia: effects on blood pressure during 7-year follow-up are influenced by duration of hypertension and branch artery stenosis

Fibromuscular dysplasia (FMD) mainly affects renal arteries. Percutaneous transluminal renal angioplasty (PTRA) and surgery are effective treatments, but long-time follow-up is lacking. Retrospective follow-up for 7.0+/-4.7 years of 69 consecutive patients (age 44+/-13 years) treated for hypertension due to FMD, 59 patients underwent PTRA and eight patients surgery. In two patients no PTRA was performed. Technical success was achieved in 56 (95%) patients undergoing PTRA and all eight undergoing surgery. After successful PTRA, both systolic and diastolic blood pressures (SBP and DBP) had decreased at discharge (from 174+/-33/100+/-13 to 138+/-19/80+/-15 mmHg; P<0.0001), and remained lower at 1 month, 1 year, and last follow-up after 7.0+/-4.7 years (140+/-25/83+/-12 mmHg; P<0.0001). Serum-creatinine had decreased both at 1 year (from 84+/-28 to 75+/-13 micromol/l; P=0.0030) and last follow-up (75+/-16 micromol/l; P=0.0017). The number of antihypertensive drugs decreased (from 2.3+/-1.2 before PTRA to 1.4+/-1.3 at discharge and at 1 month; P<0.0001, and 1.6+/-1.5 at last follow-up; P=0.0011). SBP decreased more after PTRA among patients with FMD only in the main renal artery than in those with branch artery involvement (43+/-29 vs 20+/-41 mmHg; P=0.0198). Beneficial effects on BP, creatinine and antihypertensive drugs also occurred after surgery. Patients on antihypertensive drugs at last follow-up had longer hypertension duration before PTRA than those without (5.9+/-7.7 vs 1.8+/-4.1 years; P=0.0349). Cure was achieved in 16 (24%), improvement in another 26(39%), and benefit in 42(63%). In conclusion, renal artery FMD, PTRA and surgery have beneficial long-term effects, negatively affected by hypertension duration and branch artery involvement.

Guidelines for the Reporting of Renal Artery Revascularization in Clinical Trials

Although the treatment of atherosclerotic renal artery stenosis with use of percutaneous angioplasty, stent placement, and surgical revascularization has gained widespread use, there exist few prospective randomized controlled trials (RCTs) comparing these techniques to each other or against the standard of medical management alone. To facilitate this process as well as help answer many important questions regarding the appropriate application of renal revascularization, well-designed and rigorously conducted trials are needed. These trials must have clearly defined goals and must be sufficiently sized and performed so as to withstand intensive outcomes assessment. Toward this end, this document provides guidelines and definitions for the design, conduct, evaluation, and reporting of renal artery revascularization RCTs. In addition, areas of critically necessary renal artery revascularization investigation are identified. It is hoped that this information will be valuable to the investigator wishing to conduct research in this important area.

Guidelines for the reporting of renal artery revascularization in clinical trials

Although the treatment of atherosclerotic renal artery stenosis with use of percutaneous angioplasty, stent placement, and surgical revascularization has gained widespread use, there exist few prospective randomized controlled trials (RCTs) comparing these techniques to each other or against the standard of medical management alone. To facilitate this process as well as help answer many important questions regarding the appropriate application of renal revascularization, well-designed and rigorously conducted trials are needed. These trials must have clearly defined goals and must be sufficiently sized and performed so as to withstand intensive outcomes assessment. Toward this end, this document provides guidelines and definitions for the design, conduct, evaluation, and reporting of renal artery revascularization RCTs. In addition, areas of critically necessary renal artery revascularization investigation are identified. It is hoped that this information will be valuable to the investigator wishing to conduct research in this important area.

Effect of renal artery stenting on renal function and size in patients with atherosclerotic renovascular disease

BACKGROUND

Renal artery stenting is widely performed, but little is known about its effectiveness in preserving renal function and size in patients with renovascular disease and chronic renal insufficiency. We studied the effect of renal artery stenting on renal function and size in patients with obstructive renovascular disease and chronic renal insufficiency.

METHODS AND RESULTS

Stent deployment was performed in patients with chronic renal insufficiency (creatinine >1.5 mg. dL(-1)) and global renovascular obstruction (bilateral renal artery stenosis or unilateral stenosis in the presence of a solitary or single functional kidney). The effect of renal artery stenting on renal function was assessed by comparing the slopes of the regression lines derived from the reciprocal of serum creatinine versus time plotted before and after stent deployment. Renal size was assessed by serial ultrasound of pole-to-pole kidney length. Stenting was successful in all 61 vessels in 33 patients. Twenty-five patients had complete follow-up (mean 20+/-11 months). Before stent deployment, all patients exhibited a negative slope, indicating progressive renal insufficiency. After stent deployment, the slopes were positive in 18 and less negative in 7 patients. Thus, the mean slope increased from -0.0079 to 0.0043 dL. mg(-1). mo(-1) (P:<0.001). Ultrasonography on 41 kidneys revealed preservation of size, with the kidney length measuring 10.4+/-1.4 cm at baseline and 10.4+/-1.1 cm at last follow-up (P:=NS). Patient survival at 20+/-11 months was 90%.

CONCLUSIONS

In patients with chronic renal insufficiency and global obstructive atherosclerotic renovascular disease, renal artery stenting improves or stabilizes renal function and preserves kidney size.

Outpatient percutaneous transluminal renal artery angioplasty: a Canadian experience

PURPOSE

The authors performed a retrospective study of their experience and complication rate while performing outpatient percutaneous transluminal renal artery angioplasty (PTRA) during a 5-year period.

MATERIALS AND METHODS

From July 1992 to July 1997, 87 PTRAs were performed. Of these, 62 PTRA procedures were performed on 53 outpatients. In total, 66 arteries were dilated in 62 PTRA sessions using standard, established techniques. During the same period, only 25 PTRAs were performed on inpatients. Angioplasties were performed on those patients with demonstrated renal artery stenosis and poorly controlled hypertension and/or renal failure. Patients chosen for PTRA were picked by a team that included a vascular surgeon, a nephrologist, and a radiologist. Patients who were deemed suitable for an outpatient procedure were recommended by a nephrologist. Radiological input was sought at that time. Specific guidelines were used to select these patients who were otherwise healthy, well-orientated, and able to respond to an emergency situation. None of the subjects had significant risk factors. All were accompanied by an adult for the first 24 hours and all lived no more than an hour's travel time from a hospital. All were stable on discharge and were seen within 24 hours by a nephrologist.

RESULTS

The technical success rate, defined as a residual stenosis on imaging of less than 30% and/or by a pressure gradient of less than 10 mm Hg across the stenosis, was 85%. The early complication rate was 5.6%, including two patients who developed a localized hematoma. In all, four patients were admitted to the hospital rather than being discharged to home after an average of 4.2 hours of observation. The late complication rate was 3% and involved two patients. One patient, who reported pain after balloon deflation, was readmitted 6 hours after discharge with hypotension, and a diagnosis of renal artery rupture was confirmed with computed tomography. Another patient developed peripheral atheroemboli 20 days after the procedure.

CONCLUSION

Outpatient PTRA can be performed on selected patients. In this study, late complications occurred in only 3% of patients. Early complications were readily recognized in 5.6% of patients, and these patients were admitted for observation after the procedure.

Renal artery angioplasty and stent placement: predictors of a favorable outcome

BACKGROUND

Renal artery stenosis is a common disorder and is an established cause of hypertension and renal insufficiency. Although treatment with renal artery stents has been shown to improve blood pressure and renal function for some patients, the patient population most likely to benefit is unknown. The current study was designed to determine which factors are predictive of improved blood pressure and renal function when patients with renal artery stenosis are treated with renal artery angioplasty and stent placement.

METHODS

In a prospective evaluation 127 consecutively enrolled patients with renal artery stenosis in 171 vessels were treated with angioplasty and intravascular stents. Blood pressure and serum creatinine concentration were measured before stent placement and during the follow-up period.

RESULTS

The mean length of the follow-up period was 15 +/- 14 months. Mean systolic blood pressure improved among patients with hypertension (from 177 +/- 26 mm Hg before stent placement to 151 +/- 24 mm Hg 6 months after stent placement (P <.001). The greatest improvement occurred among those with the highest baseline systolic blood pressure. This beneficial effect on blood pressure was sustained for 3 years. Sex, age, diastolic blood pressure, number of vessels into which stents were placed, serum creatinine concentration, presence of bilateral disease, race, and severity of stenosis were not predictive of improved blood pressure. Mean creatinine concentration was not significantly changed for the group as a whole. A significant decrease in serum creatinine concentration occurred among 43% of patients with baseline renal insufficiency. None of the examined variables was predictive of improvement.

CONCLUSIONS

Renal artery angioplasty and stent placement produced a significantly greater reduction in systolic blood pressure among patients with the highest baseline systolic blood pressure. Other examined variables were not predictive of a significant improvement in blood pressure. No examined variable was predictive of improved renal function. We concluded that management of renal artery stenosis with renal artery angioplasty and stent placement is most likely to result in significant improvement in systolic blood pressure among patients with the highest baseline systolic blood pressure.

Duplex ultrasonography in assessing restenosis of renal artery stents

PURPOSE

To determine the accuracy and optimal threshold values of duplex ultrasonography (US) in assessing restenosis of renal artery stents.

METHODS

Twenty-four consecutive patients with 33 renal arteries that had previously been treated with placement of a Palmaz stent underwent duplex US prior to intraarterial digital subtraction angiography (DSA), which was the reference standard. Diagnostic accuracy of in-stent peak systolic velocity (PSV) and reno-aortic ratio (RAR = PSV renal stent/PSV aorta) in detecting > 50% in-stent restenosis were evaluated by the receiver operating characteristic curve. Sensitivity and specificity were determined using the optimal threshold values, and using published threshold values: RAR > 3.5 and in-stent PSV > 180 cm/sec.

RESULTS

Six examinations were technically inadequate. Nine stents had residual or restenosis > 50% at DSA. The two duplex parameters were equally accurate since areas under the curves were similar (0.943). With optimal threshold values of 226 cm/sec for PSV and 2.7 for RAR, sensitivities and specificities were 100% and 90%, and 100% and 84%, respectively. Using the published duplex criteria resulted in sensitivities and specificities of 100% and 74% for PSV, and 50% and 89% for RAR.

CONCLUSION

Duplex US is a sensitive modality for detecting in-stent restenosis if laboratory-specific threshold values are used.

Renal artery stenosis treated with stent deployment: indications, technique, and outcome for 108 patients

From January 1993 to May 1996, 108 patients (64 men, 44 women; mean age, 72 years; age range, 37 to 87 years) underwent 125 percutaneous transluminal angioplasties and stent implantations primarily for atherosclerotic lesions of the renal artery. Sixty-four patients underwent treatment for renovascular hypertension (two antihypertensive medications or more), 32 patients underwent treatment for a combination of hypertension and renal failure (serum creatinine level >/=1.6 mg/dL), and a small group of six patients (5%) without hypertension or diminished renal function underwent treatment to prevent the progression to renal artery occlusion and kidney loss. Thirty-three patients (31%) had renovascular hypertension that was classified as severe on three or more medications, 31 patients (29%) had renovascular hypertension that was classified as moderate on two medications, and 38 patients (35%) had renovascular hypertension that was classified in the mild group on a single antihypertensive agent. Stenotic lesions were located at the ostium of the renal artery in 82 cases (65%) and were ostial-adjacent (<5 mm from renal ostium) in the other 43 cases (34%). A total of 125 stents were deployed in 125 arteries (procedural success 97.6%). Renovascular hypertension either was cured or was improved in 73 patients (68%), with 14 patients (13%) considered cured (normotensive on no medications). The conditions of 29 patients (27%) were unchanged, and 6 patients (5%) had worsening hypertension after surgery. We were unable to demonstrate a statistically significant improvement in serum creatinine levels after renal artery balloon angioplasty/stenting. Complications occurred in a total of nine cases (7.2%), six of which were related to technical problems. One patient had worsening renal insufficiency caused by contrast agent, and another patient had a perinephric hematoma develop that necessitated evacuation. There were four postoperative deaths (30-day mortality). Two of these deaths were caused by postoperative myocardial infarction. The other two patients had progressive renal failure develop that necessitated dialysis. These patients later died of the disease process despite supportive care. Follow-up renal artery duplex scan studies and angiograms were available on 96 patients (76%). The mean peak systolic renal/aortic ratio on duplex scanning was 2.2. Life-table analysis yielded a 74% primary patency rate and an 85% secondary patency rate at 36 months. This retrospective analysis showed the effectiveness of combining percutaneous transluminal angioplasty with stent deployment for significant renal artery stenosis to treat renovascular hypertension.

Ostial renal artery stent placement for atherosclerotic renal artery stenosis in patients with coronary artery disease

To test the utility of endoprosthetic treatment for ostial renal artery stenosis, and to examine blood pressure and its treatment, serum creatinine, and restenosis rate, 44 ostial renal stent placements were performed in 30 patients with concomitant coronary artery disease, arterial hypertension, and the indication for angiotensin converting enzyme (ACE) therapy. There was a marked decrease in systolic and diastolic blood pressure (163+/-30 to 145+/-17 and 93+/-18 to 83+/-10 mm Hg; P < 0.008) with a decrease in number of medication (3.2+/-0.9 to 2.8+/-1.0; P = 0.005). In 5 out of 8 patients not receiving an ACE inhibitor, this drug could be added. Serum creatinine changed from 1.46+/-0.7 mg/dl to 1.39+/-0.58 mg/dl (P = ns). Three patients showed restenosis (12.5%). Ostial stenting lowers blood pressure, decreases antihypertensive drugs and increases medication flexibility.

Infected renal artery pseudoaneurysm and mycotic aortic aneurysm after percutaneous transluminal renal artery angioplasty and stent placement in a patient with a solitary kidney

Endovascular infections after percutaneous transluminal renal angioplasty with stenting (PTRAS) are rarely reported. Because strict longitudinal follow-up of patients undergoing PTRAS is lacking, the true incidence of such complications remains obscure. We report the first case of a patient with an infected renal artery pseudoaneurysm and de novo mycotic aortic aneurysm after PTRAS. This case serves to illustrate several important points, including (1) the retrieval of renal function in patients with renal artery occlusion, (2) the pathogenesis of infection after PTRAS, (3) the diagnosis and management of endovascular infection after percutaneous vascular intervention, and (4) recommendations for periprocedural antibiotic prophylaxis during PTRAS.

Renal artery stent placement for the management of ischemic nephropathy

PURPOSE

To evaluate the angiographic and clinical results of percutaneously implanted renal artery endoprostheses (stents) for the treatment of patients with ischemic nephropathy.

MATERIALS AND METHODS

During a 52-month period, 45 patients with azotemia (serum creatinine > or = 1.5 mg/dL) and atheromatous renal artery stenosis untreatable by, or recurrent after, balloon angioplasty were treated by percutaneous placement of Palmaz stents. Stent implantation was unilateral in 32 cases and bilateral in 11 cases. Clinical results were determined by measurements of serum creatinine and follow-up angiography. Clinical benefit was defined as stabilization or improvement in serum creatinine level. Angiographic patency was defined as less than 50% diameter recurrent arterial stenosis.

RESULTS

Stent placement was technically successful in 51 of 54 (94%) renal arteries. Technical failures were stent misdeployment requiring percutaneous stent retrieval (n = 2) and inadvertent placement distal to the desired position (n = 1). Complications included acute stent thrombosis (n = 1) and early initiation of hemodialysis (within 30 days; n = 1). There were two periprocedural deaths. With use of life-table analysis, clinical benefit was seen in 78% of patients at 6 months (n = 36), 72% at 1 year (n = 24), 62% at 2 years (n = 12), and 54% at 3 years (n = 3). In patients with clinical benefit, average creatinine level was reduced from 2.21 mg/dL +/- 0.91 before treatment to 2.05 mg/dL +/- 1.05 after treatment (P = .018). Lower initial serum creatinine level was associated with a better chance of clinical benefit (P = .05). No other variables affected outcome, including patient age, sex, diabetes, implanted stent diameter, unilateral versus bilateral stent placement, or ostial versus nonostial stent positioning. Conventional catheter angiography or spiral computed tomographic (CT) angiography performed in 19 patients (28 stents) at a mean interval of 12.5 months demonstrated primary patency in 75%. Maintained stent patency appeared to correlate with renal functional benefit.

CONCLUSIONS

Percutaneous renal artery stent placement for angioplasty failures or restenoses provides clinical benefit in most patients with ischemic nephropathy.

Renovascular hypertension

Renovascular hypertension is the most common cause of secondary hypertension. Interest in identifying patients with renal artery stenosis has been stimulated recently by advances in three areas. First, is the realization that not only can renal artery stenosis cause renovascular hypertension, but it can also lead to progressive renal failure (ischemic nephropathy) caused by progression of disease, usually atherosclerotic in nature. Second, advances in percutaneous transluminal renal angioplasty and, especially, the recent use of renal stents has led to a less invasive management of these patients as compared with traditional renal revascularization. Finally, the development of newer less invasive diagnostic techniques, both for the identification of patients with renal artery stenosis and to follow patients with known renal artery stenosis, has simplified the diagnostic aspect of the disease.