Protected renal stenting with the PercuSurge GuardWire device: a pilot study

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.

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 Grüntzig 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 metaanalysis 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.

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.

Technological Advances in the Design of Catheters and Devices Used in Renal Artery Interventions: Impact on Complications

Purpose:

To analyze the impact of technical improvements in stent devices and guiding catheters (e.g., reduced device diameter, increased flexibility) on the complication rates associated with percutaneous renal artery interventions.

Methods:

During a 5-year period (1997–2001), 268 consecutive patients (178 men; mean age 67±9 years) had 370 atherosclerotic renal artery stenoses (RAS) ≥70% treated with angioplasty/stenting in 320 procedures. The guiding catheter technique was used routinely until 2000; in 2001, a guiding sheath was used in 29% of cases. From 1997 to 2000, sealing devices were frequently used for sheath removal; during the last year, the sheaths were removed using the Femostop device.

Results:

In 320 interventions, 32 (10%) complications occurred, with a decreasing frequency during the last 2 years (1996/97: 13% [7/53]; 1998: 16% [9/57]; 1999: 15% [11/74]; 2000: 4% [3/70]; 2001: 3% [2/66]). There were 21 (6.6%) local complications, including 4 cases requiring permanent hemodialysis after the intervention and 11 (3.4%) access site complications. No procedure-related death occurred. During the study period, the average sheath diameter was reduced from 8.15±0.76 F to 6.15±0.63 F (p<0.05). Mean procedural time was reduced from 42±13 minutes to 23±11 minutes (p<0.05). The initial heparin dose was reduced from 10,000 to 5000 units.

Conclusions:

In parallel with the use of more flexible catheters and premounted stents of lower profile, the complication rate of renal angioplasty/stenting of atherosclerotic RAS has been reduced significantly during a 5-year period.

Clinical effectiveness of secondary interventions for restenosis after renal artery stenting

OBJECTIVE

Secondary interventions for renal artery restenosis (RAS) after renal artery stenting are common, despite limited data about their effectiveness. This study was designed to evaluate the outcomes of endovascular treatment of recurrent RAS.

METHODS

We conducted a retrospective review of patients who underwent renal artery stenting between 2001 and 2011 at Dartmouth-Hitchcock Medical Center. Patients who required secondary interventions were compared with control patients who underwent only primary interventions for RAS. Multivariate regression models were used to identify factors associated with successful outcomes, as measured by changes in blood pressure, estimated glomerular filtration rate, and number of antihypertensive medications required.

RESULTS

Sixty-five secondary (57 patients) renal interventions were undertaken for recurrent RAS associated with progressive hypertension or renal dysfunction and compared with outcomes after 216 primary (180 patients) renal artery stenting procedures. Patients undergoing primary vs secondary interventions did not differ significantly in the number of preoperative antihypertensive medications used, comorbid conditions, or blood pressure. All primary and secondary interventions were performed with stents and showed no difference in procedural complications. At a mean follow-up of 23 months (range, 1-128 months), similar improvements in renal function and blood pressure were found between patients undergoing primary and secondary interventions, and there was no difference in rates of restenosis or survival between cohorts. Regression models showed that the use of embolic protection devices was associated with improved renal function after primary (odds ratio [OR], 2.0; 95% confidence interval [CI], 1.1-3.8; P < .05) and secondary (OR, 4.7; 95% CI, 1.7-12.5; P < .05) interventions, whereas statin therapy was associated with improved renal (OR, 2.0; 95% CI, 1.3-3.2; P < .05) and blood pressure response (OR, 4.1; 95% CI, 1.1-14.9; P < .05) after secondary interventions.

CONCLUSIONS

Patients undergoing secondary interventions for recurrent RAS have outcomes that are comparable with those for primary interventions. These data suggest that repeated endovascular procedures for RAS can be undertaken with similar expectations for clinical improvement and may be further improved by routine use of embolic protection devices and statin therapy.

Percutaneous revascularization for ischemic nephropathy: the past, present, and future

Occlusion of the renal arteries can threaten the viability of the kidney when severe, in addition to accelerating hypertension and circulatory congestion. Renal artery stenting procedures have evolved from a treatment mainly for renovascular hypertension to a maneuver capable of recovering threatened renal function in patients with “ischemic nephropathy” and improving management of congestive heart failure. Improved catheter design and techniques have reduced, but not eliminated hazards associated with renovascular stenting. Expanded use of endovascular stent grafts to treat abdominal aortic aneurysms has introduced a new indication for renal artery stenting to protect the renal circulation when grafts cross the origins of the renal arteries. Although controversial, prospective randomized trials to evaluate the added benefit of revascularization to current medical therapy for atherosclerotic renal artery stenosis until now have failed to identify major benefits regarding either renal function or blood pressure control. These studies have been limited by selection bias and have been harshly criticized. While studies of tissue oxygenation using blood oxygen level dependent (BOLD) MR establish that kidneys can adapt to reduced blood flow to some degree, more severe occlusive disease leads to cortical hypoxia associated with microvascular rarefication, inflammatory injury and fibrosis. Current research is directed toward identifying pathways of irreversible kidney injury due to vascular occlusion and to increase the potential for renal repair after restoring renal artery patency. The role of nephrologists likely will focus upon recognizing the limits of renal adaptation to vascular disease and identifying kidneys truly at risk for ischemic injury at a time point when renal revascularization can still be of benefit to recovering kidney function.

Clinical outcomes in patients with renal artery stenosis treated with stent placement with embolic protection compared with those treated with stent alone

PURPOSE

To compare the clinical outcomes in patients with chronic renal insufficiency (CRI) and renal artery stenosis (RAS) following renal artery (RA) stent placement with and without embolic protection device (EPD) usage.

MATERIALS AND METHODS

Eighteen patients who had RA stent placement with EPD were matched to control patients (RA stent only). Blood pressure, number of hypertensive medications, and estimated glomerular filtration rate (eGFR) at 3 months before the procedure and after 12 months were determined. An increase of ≥ 20% in eGFR at 12 months from baseline was defined as "improvement," decrease of ≥ 20% as "deterioration," and an eGFR change between those values as "stabilization" at 12 months.

RESULTS

At 12 months, stage 4 patients treated with EPD had significantly higher eGFR than controls (P = .01). There was no statistical difference in blood pressure outcomes between the 2 groups.

CONCLUSIONS

Patients with stage 4 CRI did significantly better with EPD than those treated without it.

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.

Renal artery stenosis: optimizing diagnosis and treatment

Renal artery stenosis (RAS) is the most commonly caused by atherosclerosis, with fibromuscular dysplasia being the most frequent among other less common etiologies. A high index of suspicion based on clinical features is essential for diagnosis. Revascularization strategies are currently a topic of discussion and debate. When revascularization is deemed appropriate, atherosclerotic RAS is most often treated with stent placement, whereas patients with fibromuscular dysplasia are usually treated with balloon angioplasty. Ongoing randomized trials should help to better define the optimal management of RAS.

Predictors of embolization during protected renal artery angioplasty and stenting: Role of antiplatelet therapy

OBJECTIVE

The objective of this study was to identify the predictors of distal embolization (DE) during protected renal artery angioplasty and stenting.

BACKGROUND

DE may contribute to worsening renal function after renal artery stenting. The factors associated with DE, rates of platelet-rich emboli, and treatments that may prevent DE during renal stenting have not been evaluated.

METHODS

The current study evaluated patients randomized to receive an embolic protection device (EPD) in the RESIST trial. Forty-two patients were identified for inclusion in this study. These patients were further randomized to abciximab (N = 22) or placebo (N = 20). Modification in Diet in Renal Disease glomerular filtration rate (GFR) was used as the primary measure of renal function. Creatinine was measured by a modified Jaffe reaction using the IDMS-traceable assay. The primary endpoint was capture of platelet rich emboli in the angioguard basket.

RESULTS

DE occurred in 15/42 (35%) of the patients and platelet rich DE in 10 (24%) of the patients who received an EPD. Of the angiographic characteristics only lesion length was significantly higher in patients with DE (16 +/- 7 mm vs. 10 +/- 5 mm, P = 0.04). Preprocedural abciximab reduced DE from 42 to 8% (P = 0.02). The rate of platelet rich emboli was 50% with neither abciximab nor a thienopyridine, 36% with thienopyridine only, 15% abciximab only, and 0% in patients who received both a thienopyridine and abciximab. Only Abciximab use was associated with improved renal function at 1-month, thienopyridine was not. Angiographic characteristics including percent stenosis, minimal luminal diameter (MLD), reference diameter, change in MLD, contrast volume, and procedure time were not predictors of DE during renal stenting.

CONCLUSION

Capture of DE and specifically platelet DE are common during protected renal stenting using a filter-type EPD. Abciximab use, and potentially combined thienopyridine and abciximab use, decreased the rate of platelet rich DE; however, only abciximab improved renal function at 1-month.

The uncertain value of renal artery interventions: where are we now?

Improved technology for detection of and endovascular procedures for renal artery stenosis due to atherosclerosis has been associated with increases in renal artery intervention. Hypertension with accelerated target organ injury, reduced kidney function, and episodic circulatory congestion in patients with renovascular disease predict reduced patient survival. Recent studies indicate that activation of pressor mechanisms depends upon hemodynamic gradients that are often overrated by visual estimates. Although activation of the renin-angiotensin system initiates renovascular hypertension, additional mechanisms perpetuate vascular remodeling and kidney injury that may not depend upon large vessel occlusion. Major advances in medical therapy have led to initiation of at least 4 major prospective trials comparing optimal medical therapy with or without stenting. Up to now, outcome data fail to support broad application of renal revascularization, including results from a recent large, prospective trial from the United Kingdom, despite small groups of patients that experience major clinical benefit. The ambiguity of these results partly reflect poor characterization of the severity of vascular lesions and competing risks within the population related to aging and pre-existing disease. Many patients currently undergoing renal artery interventions derive little net benefit and some are exposed to significant complications, including atheroembolic disease. Determining the appropriate role for renal artery interventions will depend on developing better methods for judging the role of large vessel occlusive disease regarding tissue oxygenation, activation of profibrotic pathways, and irreversible injury in the post-stenotic kidney.

Utilization of excimer laser debulking for critical lesions unsuitable for standard renal angioplasty

BACKGROUND

The energy emitted by ultraviolet laser is avidly absorbed in atherosclerotic plaques. Conceptually, it could be applied for debulking of selected atherosclerotic renal artery stenoses. We describe early experience with revascularization of critical renal artery lesions deemed unsuitable for standard renal angioplasty. Institutional Review Board permission to conduct the data analysis was obtained.

METHODS

Among 130 percutaneous renal artery interventions with balloon angioplasty and adjunct stenting, there were 12 (9%) patients who underwent laser debulking prior to stenting. These patients presented with critical (95+/-3.5% stenoses) lesions (11 de novo, 1 stent restenosis) deemed unsuitable for standard renal angioplasty because of marked eccentricity and presence of thrombus. Indications for intervention included preservation of kidney function, treatment of uncontrolled hypertension, management of congestive heart failure, and treatment of unstable angina. Blood pressure and estimated glomerular filtration rate (eGFR) were measured pre- and 3 weeks post-intervention.

RESULTS

A baseline angiographic stenosis of 95+/-3.5% was reduced to 50+/-13% with laser debulking. There were no laser-induced complications. Post-stenting the angiographic residual stenosis was 0%. The mean gradient across the lesions was reduced from baseline 85+/-40 to 0 mmHg. A normal post-intervention antegrade renal flow was observed in all patients. Baseline mean systolic BP of 178+/-20 mmHg decreased to 132+/-12 mmHg (P<0.0001) and mean diastolic pressure of 85+/-16 mmHg reduced to 71+/-9 mmHg (P = 0.01). A pre-intervention mean eGFR of 47.7+/-19 ml/min/1.73 m(2) increased to 56+/-20.4 ml/min/1.73 m(2) (P = 0.05) post-procedure. The interventions were not associated with major renal or cardiac adverse events. During follow-up one patient developed transient contrast-induced nephropathy.

CONCLUSIONS

Debulking of select renal artery stenoses with laser angioplasty followed by adjunct stenting is feasible. Further prospective, randomized studies will be required to explore the role of debulking and laser angioplasty in renal artery revascularization.

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.

Current role of emboli protection devices in percutaneous coronary and vascular interventions

After the observation that distal embolization is a frequent complication of coronary and vascular interventions, mechanical emboli protection devices (EPD) have been developed and tested in different vascular territories. The most frequently used device type incorporates a guidewire with a filter that is placed distal to the target lesion, unfolded, and then retrieved at the end of the procedure. Alternative approaches are based on transient flow obstruction using proximal or distal balloon occlusion. The procedure is then performed under flow reversal or flow arrest and the blood column is evacuated prior to restoration of flow. The efficacy of EPD in reducing major adverse cardiac events among patients undergoing percutaneous intervention of aortocoronary bypass grafts has been demonstrated in a randomized trial. In the acute myocardial infarction setting, EPD failed to improve outcomes. Although randomized data in carotid artery stenting are lacking, a broad, but not unanimous, consensus supports the use of these devices. While a small randomized trial showed disappointing results of emboli protection in renal stenting, no data are available for lower extremity interventions.

The role of percutaneous revascularization for renal artery stenosis

Renal artery stenosis (RAS) is usually caused by atherosclerosis or fibromuscular dysplasia. RAS leads to activation of the renin-angiotensin-aldosterone system and may result in hypertension, ischemic nephropathy, left ventricular hypertrophy and congestive heart failure. Management options include medical therapy and revascularization procedures. Recent studies have shown angiotensin receptor blockers (ARB) and angiotensin converting enzyme inhibitors (ACE-I) to be highly effective in treating the hypertension associated with RAS and in reducing cardiovascular events; however, they do not correct the underlying RAS and loss of renal mass may continue. Renal artery angioplasty was first performed by Gruntzig in 1978. The routine use of stents has increased technical success rates compared with angioplasty, and surgery is now only rarely performed. Although numerous case series claimed benefit in terms of blood pressure control, no adequately powered randomized, controlled, prospective study of renal artery interventions has reported their effect on cardiovascular morbidity or mortality. The CORAL trial, an ongoing study of renal artery stent placement and optimal medical therapy (OMT) funded by the National Institutes of Health, is the first study to attempt to do so. Until the CORAL trial results are in, physicians will continue to be faced with difficult choices when determining the optimal management for RAS patients and deciding which, if any, patients should be offered revascularization.

Endovascular management of atherosclerotic renovascular disease: early results following primary intervention

OBJECTIVE

This retrospective review examines periprocedural morbidity and early functional responses to primary renal artery angioplasty and stenting (RA-PTAS) for patients with atherosclerotic renovascular disease (RVD).

METHODS

Consecutive patients undergoing primary RA-PTAS for hemodynamically significant atherosclerotic RVD with hypertension and/or ischemic nephropathy were identified from a prospectively maintained registry. Hypertension responses were determined based on pre- and post-intervention blood pressure measurements and medication requirements. Estimated glomerular filtration rate (eGFR) was used to determine renal function responses. Both hypertension and renal function responses were assessed at least three weeks after RA-PTAS. Stepwise multivariable regression analysis was used to examine associations between blood pressure and renal function responses to RA-PTAS and select clinical variables.

RESULTS

One-hundred ten primary RA-PTAS were performed on 99 patients with atherosclerotic RVD with a mean angiographic diameter-reducing stenosis of 79.2 +/- 12.9%. All patients had hypertension (mean of 3.4 +/- 1.3 antihypertensive agents). Mean pre-intervention eGFR was 49.9 +/- 22.7 mL/min/1.73 m(2), and 74 patients had a pre-intervention eGFR < 60 mL/min/1.73 m(2). The technical success rate for RA-PTAS was 94.5%. The periprocedural complication rate was 5.5%; there were no periprocedural deaths. Statistically significant decreases in mean systolic blood pressure (161.3 +/- 25.2 vs. 148.5 +/- 25.2 post-intervention, P < .0001), diastolic blood pressure (78.6 +/- 13.3 versus 72.5 +/- 13.5 post-intervention, P < .0001), and number of antihypertensive agents (3.3 +/- 1.2 versus 3.1+/- 1.3 post-intervention, P = .009) were observed. Assessed categorically, hypertension response to RA-PTAS was cured in 1.1%, improved in 20.5%, and unchanged in 78.4%. Categorical eGFR response to RA-PTAS was improved in 27.7%, unchanged in 65.1%, and worsened in 7.2%. Multivariable stepwise regression revealed associations between pre- and post-intervention systolic blood pressure (P < .0001), diastolic blood pressure (P < .0001), and eGFR (P < .0001), as well as a trend toward improved diastolic blood pressure response among patients managed with staged bilateral intervention (P = .0589).

CONCLUSION

Primary RA-PTAS for atherosclerotic RVD was associated with low peri-procedural morbidity and mortality but only modest early improvements in blood pressure and renal function. Results from ongoing prospective trials are needed to assess the long term outcomes associated with RA-PTAS and clarify its role in the management of atherosclerotic RVD.

Embolic Protection and Platelet Inhibition During Renal Artery Stenting

Background— Preservation of renal function is an important objective of renal artery stent procedures. Although atheroembolization can cause renal dysfunction during renal stent procedures, whether adjunctive use of embolic protection devices or glycoprotein IIb/IIIa inhibitors improves renal function is unknown.

Methods and Results— One hundred patients undergoing renal artery stenting at 7 centers were randomly assigned to an open-label embolic protection device, Angioguard, or double-blind use of a platelet glycoprotein IIb/IIIa inhibitor, abciximab, in a 2×2 factorial design. The main effects of treatments and their interaction were assessed on percentage change in Modification in Diet in Renal Disease–derived glomerular filtration rate from baseline to 1 month using centrally analyzed creatinine. Filter devices were analyzed for the presence of platelet-rich thrombus. With stenting alone, stenting and embolic protection, and stenting with abciximab alone, glomerular filtration rate declined ( P <0.05), but with combination therapy, it did not decline and was superior to the other allocations in the 2×2 design ( P <0.01). The main effects of treatment demonstrated no overall improvement in glomerular filtration rate; although abciximab was superior to placebo (0±27% versus −10±20%; P <0.05), embolic protection was not (−1±28% versus −10±20%; P =0.08). An interaction was observed between abciximab and embolic protection ( P <0.05), favoring combination treatment. Abciximab reduced the occurrence of platelet-rich emboli in the filters from 42% to 7% ( P <0.01).

Conclusions— Renal artery stenting alone, stenting with embolic protection, and stenting with abciximab were associated with a decline in glomerular filtration rate. An unanticipated interaction between Angioguard and abciximab was seen, with combination therapy better than no treatment or either treatment alone.

Renal artery stenting with two simultaneous protection devices

PURPOSE

To describe a new technique for distal protection during stenting of a bifurcated renal artery using two simultaneous filter devices.

CASE REPORT

A 70-year-old patient underwent angiography of a single functional kidney. Severe proximal, nonostial narrowing of an early bifurcated renal artery was found. Two AngioGuard filter protection devices were placed, one in each branch. A balloon mounted stent was advanced over both wires simultaneously till they reached divergence point, expanded fully, and the protection devices were retrieved. No complications were observed and the final result was good.

CONCLUSION

The concomitant use of two protection devices is feasible in a particular anatomy context.

Atheroembolism during percutaneous renal artery revascularization

INTRODUCTION

Atheroembolization during renal artery angioplasty and stenting (RA-PTAS) has been postulated as a cause for the inferior renal function results observed when compared with those with surgical revascularization. To further characterize procedure-associated atheroembolism, we analyzed recovered atheroembolic debris and clinical data from patients undergoing RA-PTAS with distal embolic protection (DEP).

METHODS

RA-PTAS procedures were performed with DEP using a commercially available temporary balloon occlusion and aspiration catheter system between July 2005 and December 2006. Following RA-PTAS but prior to deflation of the distal occlusion balloon, the static column of blood proximal to the balloon was aspirated and submitted for embolic particle analysis. Angiograms, demographics, and laboratory data were reviewed. Glomerular filtration rate (eGFR) was estimated before RA-PTAS and at 4 to 8 weeks postintervention using the abbreviated Modification of Diet in Renal Disease formula. Associations between clinical factors, captured particle counts, and changes in renal function were examined using univariate techniques and multiple linear regression.

RESULTS

Twenty-eight RA-PTAS procedures were performed with DEP. Mean total number of embolic particles counted per procedure was 2033 +/- 1553 for particles 20-60 microm and 265 +/- 132 for particles >60 microm. Significant positive associations with quantity of captured particles 20 to 60 microm were observed for African American race (P = .002), predilation (P = .005), and stent diameter (P < .001); a significant negative association was observed for preoperative aspirin use (P =.016). Quantity of captured particles >60 microm was positively associated with ratio of stent to renal artery diameter (P =.009). Change in eGFR was positively associated with preoperative aspirin use (P = .006) and preoperative eGFR (P < .001), while a negative association was observed for captured particle counts >60 microm (P = .015).

CONCLUSION

These results demonstrate the liberation of thousands of atheroembolic particles during RA-PTAS. Clinical, anatomic, and device-related factors may be predictive of procedural embolization, and increasing captured particle counts >60 microm were associated with inferior renal function results. Further investigation is warranted to establish relationships between atheroembolism, end organ functional impairment, and clinical responses.

Renal artery stenosis

Fibromuscular dysplasia (FMD) and aortoarteritis are the most frequent causes of secondary hypertension induced by renal artery stenosis (RAS). Revascularization of this disease entity usually cures arterial hypertension. Demographic evolution leads to an increasing incidence of atherosclerotic RAS, one of the major causes of end-stage renal failure. Furthermore, atherosclerotic RAS leads to deterioration of primary hypertension, progression of atherosclerosis manifestation such as occlusive and aneurysmatic peripheral artery disease, and chronic or acute organ damage such as left ventricular hypertrophy and recurrent flash pulmonary edema. Despite the lack of sufficiently powered randomized controlled trials, each hemodynamically relevant RAS (eg, > or = 70%) should be considered for stent angioplasty in patients without end-stage ischemic nephropathy or limited life expectancy due to concomitant disease (eg, cancer). Drug-eluting stents will probably reduce the overall low in-stent restenosis rate of 10% to 20%. Interventions in patients with dialysis-dependent end-stage nephropathy are left to appropriate clinical study protocols.

Endovascular Treatment of Peripheral Vascular Disease

An estimated 10 million people in the U.S. have symptomatic peripheral arterial disease (PAD); 20 to 30 million have asymptomatic PAD. The prevalence of intermittent claudication increases with age, affecting >5% of patients over 70. The incidence of claudication doubles or triples in patients with diabetes. As people grow older, symptoms from peripheral vascular disease increasingly limit daily activity. Until recently, vascular surgical procedures were the only alternative to medical therapy in such patients. Today, advances in minimally invasive percutaneous interventions have made endovascular procedures the primary modality for revascularization in most patients. Compared with open surgical procedures, endovascular interventions offer comparable or superior long-term rates of success with very low rates for morbidity and mortality. Furthermore, most of these interventions are performed on an outpatient basis, reducing hospital stays considerably. In this monograph we discuss current endovascular interventions for treating occlusive PAD, aneurysmal arterial disease, and increasingly common venous occlusive diseases.

Distal protection in cardiovascular medicine: current status

Iatrogenic and spontaneous downstream microembolization of atheromatous material is increasingly recognized as a source of cardiovascular morbidity and mortality. Devising ways of reducing this distal embolization using a variety of mechanical means--distal protection--is currently under intense and diverse investigation. This review therefore summarizes the present status of distal protection. It examines the problem of distal embolization, describes the available distal protection devices, reviews those areas of cardiovascular medicine where distal protection devices are being investigated, and discusses potential future developments.

Renal angioplasty and stenting: long-term results and the potential role of protection devices

Renal angioplasty and stenting have become the first treatments to be proposed to patients presenting with renal artery stenosis. The immediate technical success rate is high, with a low complication rate and good long-term patency. In most reports, renal stenting has been proven to improve blood pressure. However, despite good immediate- and long-term results, postprocedural deterioration of renal function is a concern, and may occur after renal artery angioplasty and stenting in 20 to 40% of patients, which limits the immediate benefits of this technique. Of the causes of this deterioration in renal function, atheroembolism seems to play an important role. Contrary to earlier beliefs that atheroembolization is not an issue during percutaneous catheter interventions, there is now mounting evidence that distal atherosclerotic debris commonly embolizes from lesions in many vascular territories during percutaneous interventions. Atheroembolism seems to be the root cause of many procedural complications wherever atherosclerotic lesions are treated. Distal embolization was first demonstrated in saphenous vein grafts and now, clinical data are proving that similar embolization and distal-organ complications also occur during catheter treatment in certain native coronary lesions, carotid stenting and renal artery stenting, demonstrating the role and efficacy of protection devices to reduce the incidence of end-organ complications. The same protection devices (protection balloon and filters) utilized for coronary or carotid procedures may be used to protect the kidney from atheroembolism. In this review, the authors discuss recently published data concerning the techniques and results of renal angioplasty and stenting procedures performed under protection, and evaluate the benefits of this technique on renal function and its role in the future. Indications for this technique need to be discussed.

Distal embolic protection during renal artery angioplasty and stenting

BACKGROUND

Percutaneous renal artery angioplasty and/or stenting (RA-PTAS) is increasingly being used as an alternative to surgery for renal artery revascularization. Unfortunately, renal function responses after RA-PTAS appear to be inferior to those observed after surgical revascularization both in terms of improving and preventing deterioration of renal function postintervention. Atheroembolism during RA-PTAS has been postulated as a potential cause for the disparate results. Strategies to limit the occurrence of atheroembolism, such as the use of distal embolic protection (DEP) systems, may result in improved outcomes after RA-PTAS.

METHODS

All RA-PTAS procedures performed with DEP (using a commercially available temporary balloon occlusion and aspiration catheter) between October 2003 and July 2005 were reviewed. Glomerular filtration rate (eGFR) was estimated preintervention and 4 to 6 weeks postintervention using the abbreviated Modification of Diet in Renal Disease formula. Renal function and hypertension response rates as well as procedural data were classified and reported according to American Heart Association guidelines. Renal function improvement and deterioration were defined as a 20% increase and decrease in eGFR, respectively, compared with preoperative values. Continuous and categoric data were analyzed using paired t tests and repeated measures linear models.

RESULTS

DEP was used in 32 RA-PTAS procedures in 15 women and 11 men with a mean age of 71 years. All patients were hypertensive, 24 (92%) had renal insufficiency, and the mean preintervention degree of renal artery stenosis was 79%. Immediate technical success was achieved in 100% of RA-PTAS cases. Mean pre- and postintervention serum creatinine and eGFR values were 1.9 vs 1.6 mg/dL (P < .001) and 37 vs 43 mL/min/1.73 m(2) (P < .001), respectively. Renal function was defined as improved after 17 (53%) of 32 procedures and worsened in none (0%).

CONCLUSIONS

RA-PTAS using DEP resulted in 4- to 6-week postintervention renal function results approximating those of surgical revascularization. These data suggest that DEP use may prevent renal function harm during RA-PTAS as a result of atheroembolism and warrant further investigation.

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.

Delicate Percutaneous Renal Artery Stenting Minimizes Postoperative Renal Injury and Protects Kidney in Patients With Severe Atherosclerotic Renal Artery Stenosis and Impaired Renal Function

Percutaneous transluminal renal artery stenting (PTRAS) is associated with declining renal function in a non-negligible portion of patients and is inflicted by different mechanisms, including atheroembolism. This study investigated whether delicate PTRAS to reduce atheroembolism might minimize postoperative renal injury and better preserve renal function. Patients undergoing PTRAS performed by experienced interventional cardiologists, applying coronary intervention concepts, techniques, devices and delicacy principles whenever possible, were prospectively studied. A total of 34 patients (29 M/5 F) with impaired renal function (group A, creatinine 2.4 +/- 0.1 mg/dL) and another 20 patients (16 M/4 F) with normal serum creatinine (group B, baseline creatinine 1.2 +/- 0.0 mg/dL) were studied. PTRAS was successfully performed in all but one group A patient. During a 6-month follow-up, systolic and diastolic blood pressure (130 +/- 2 versus 148 +/- 4 mmHg, P = 0.001 and 70 +/- 2 versus 78 +/- 3 mmHg, P = 0.006) and serum creatinine (2.1 +/- 0.1 versus 2.4 +/- 0.1 mg/dL, P < 0.001) were all significantly lowered in group A patients. Using a 20% change cut-off value, renal function improved in eight (24%), remained unchanged in 24 patients (73%), and deteriorated in only one patient (3%). The corresponding alterations in blood pressure and renal function were insignificant in group B patients. Patients with bilateral involvement (eleven patients) also had significantly lowered serum creatinine on follow-up. In conclusion, delicately practiced PTRAS can reduce the rate of postprocedural renal deterioration in patients with impaired renal function, and should be adopted in every renal intervention.

Divergent outcomes after percutaneous therapy for symptomatic renal artery stenosis

OBJECTIVE

Percutaneous intervention for symptomatic renal artery atherosclerosis is rapidly replacing surgery in many centers. This study evaluated the anatomic and functional outcomes of endovascular therapy for atherosclerotic renal artery stenosis on a combined vascular surgery and interventional radiology service at an academic medical center.

METHODS

This was a retrospective analysis of patients who underwent renal artery angioplasty with or without stenting between January 1990 and June 2002. Indications included hypertension (86%) and rising serum creatinine concentration (55%). One hundred forty-six patients (80 women; average age, 71 years [range, 44-89 years]) underwent 183 attempted interventions (64 to treat bilateral stenosis). Forty-five percent of patients had significant bilateral disease: 27% had greater than 50% bilateral stenosis, and the remainder had nonfunctioning, absent, or occluded vessels.

RESULTS

Of 183 planned interventions, technical success (<30% residual stenosis) was achieved in 179 vessels (98%) with placement of 137 stents (75%). Thirty-day mortality was 0.7%. The major morbidity rate was 4%, and the procedure-related complication rate was 18%. Five-year cumulative patient mortality was 25%. Primary patency, assisted primary patency, and recurrent stenosis rates were 82% +/- 9%, 100% +/- 0%, and 30% +/- 7%, respectively, at 5 years. Within 3 months of the procedure, 52% of patients who received treatment of hypertension demonstrated clinical benefit (hypertension improved or cured), which was maintained in 68% of patients at 5 years. Serum creatinine concentration was lowered or stabilized in 87% of patients within 3 months of the procedure, but this benefit, including freedom from dialysis, was maintained in only 45% of patients at 5 years.

CONCLUSIONS

Endovascular intervention for symptomatic atherosclerotic renal artery stenosis is technically successful. There were excellent patency and low recurrent stenosis rates. There is immediate clinical benefit for most patients, but divergent long-term functional outcomes. Endovascular interventions modestly enhance the care of the patient with hypertension, but poorly preserve long-term renal function in the patient with chronic renal impairment.

Percutaneous coronary intervention: historical perspectives, current status, and future directions

In the twenty-six years since Gruntzig introduced a simple balloon angioplasty technique, percutaneous coronary intervention has undergone extraordinary growth and has now surpassed bypass surgery in frequency of performance. Several critical breakthrough technologies account for this remarkable progress: intracoronary stents have increased success rates and reduced restenosis, adjunctive antiplatelet therapy has reduced periprocedural complications, and restenosis after stent placement has been effectively treated with local radiation. Most recently, drug-eluting stents coated with cell-cycle inhibitors have shown great promise for further reducing restenosis, possibly to negligible levels.

Evaluation of the percusurge guardwire plus temporary occlusion and aspiration system during primary angioplasty in acute myocardial infarction

Thirty patients with acute myocardial infarction (AMI) underwent primary angioplasty under distal protection of PercuSurge GuardWire Plus Temporary Occlusion and Aspiration System. Before angioplasty, protection of the distal circulation was achieved with the system, followed by balloon angioplasty and/or stenting and debris aspiration. Technical device success was 100%. Distal occlusion was well tolerated in all patients. Mean total distal occlusion time was 7.3 +/- 5.4 min. Macroscopically visible debris was aspirated from 29 cases (96.7%). Postprocedural Thrombolysis in Myocardial Infarction flow grade 3 was achieved in all cases (100%, vs. 16.7% at baseline). Myocardial blush flow grade 3 was achieved in 26 cases (86.7%). Regression of ST segment elevation >/= 50% was shown in 23 cases (76.7%). No patient developed angiographic evidence of no-reflow or distal embolization. Both angiographic and procedural success were 100%. The system is feasible, safe, and effective for distal protection against embolism during primary angioplasty in AMI.

Current issues in the diagnosis and management of patients with renal artery stenosis: a cardiologic perspective

Renal artery stenosis most often is caused by atherosclerosis. Although patients with renal artery stenosis can be managed conservatively, renal revascularization may be indicated, particularly in patients with refractory hypertension on a multidrug regimen and patients with declining renal function. Duplex ultrasonography of the renal arteries and magnetic resonance angiography are currently the most efficient noninvasive methods for the evaluation of renal artery stenosis. Selective digital subtraction renal arteriography remains the gold standard for the definitive diagnosis. In selected patients undergoing coronary studies and angiography immediately after the coronary procedure can be efficient. Atherosclerotic renal artery lesions, which commonly affect the renal artery ostium, can be treated safely and effectively with balloon-expandable stents. Successful angioplasty commonly results in improved control of hypertension, but an overall benefit on renal function and/or patient survival has not been shown. Generally the risk/benefit ratio of renal artery stenting seems favorable, but further randomized studies are needed for evidence-based decision making. All patients with atherosclerotic renal artery stenosis should receive rigorous secondary prevention measures including platelet inhibitors, statins, and beta-blockers.

Renal angioplasty and stenting with distal protection of the main renal artery in ischemic nephropathy: early experience

PURPOSE

We present a retrospective review of a single tertiary hospital experience in renal artery stent revascularization with distal protection in patients with ischemic nephropathy. The objectives of the study included preliminary assessment of the effect of distal protection on procedure-related acute deterioration in renal function and on renal salvage.

MATERIAL AND METHODS

All patients had significant atherosclerotic main renal artery stenosis, documented at preprocedural imaging, and a degree of chronic renal impairment before revascularization. Forty-six renal arteries were treated in 37 patients with preprocedural renal impairment, which was mild in 10 patients, moderate in 19 patients, and severe in 8 patients. Median patient age was 72 years (range, 59-85 years). All patients underwent primary stenting of renal artery ostial stenoses with adjuvant use of a filter device (Angioguard guide wire system; Cordis Corp, Division of Johnson & Johnson, Miami, Fla) in the distal main renal artery. The filter baskets were recaptured for pathologic analysis.

RESULTS

Overall, in 95% of patients, including all patients with preprocedural mild or moderate renal impairment, renal function was stabilized or improved after revascularization. In 5% of patients decline in renal function was unchanged. No patients had acute postprocedural deterioration. Mean follow-up was 12.5 months (range, 2-28 months). These results are better than in most reports in the literature and also better than in a historical group of similar patients with ischemic nephropathy who underwent stent revascularization without distal protection at the same institution. The improved results are thought to be due to prevention of cholesterol atheroembolization during the procedure by the distal filter baskets. Sixty-five percent of the distal protection baskets contained embolic material, including fresh thrombus, chronic thrombus, atheromatous fragments, and cholesterol clefts.

CONCLUSION

A distal protection device may significantly improve results during stent revascularization. There are a number of unique demands on a renal protection device, and the ideal device has not yet been developed.

Renal angioplasty and stenting under protection: The way for the future?

The purpose of this study was to evaluate the feasibility and safety of renal artery angioplasty and stenting utilizing a distal protection device to reduce the risk of intraprocedural artery embolism and avoid deterioration of the renal function. Fifty-six hypertensive patients (32 men; mean age, 66 +/- 11.8 years; range, 22-87) with atherosclerotic renal artery stenosis (8 bilateral) underwent angioplasty and stenting with distal protection in 65 renal arteries (58 ostial lesions). Five patients had a solitary kidney, 18 a renal insufficiency. The lesion was crossed either with a GuardWire temporary occlusion balloon (n = 38), which was inflated to provide parenchyma protection or with a filter (EPI Filter; n = 26), or with Angioguard (n = 1), which allows a continuous flow. Generated debris was aspirated and analyzed. Blood pressure and serum creatinine levels were followed. Immediate technical success was 100%. All lesions except one were stented, either directly (43 ostial lesions) or after predilatation (22 ostial lesions). Visible debris were aspirated with the PercuSurge in all patients or removed with filters in 80% of the patients. Mean particle number and diameter were 98.1 +/- 60.0 per procedure (range, 13-208) and 201.0 +/- 76.0 microm (range, 38-6,206), respectively. Mean renal artery occlusion time was 6.55 +/- 2.46 min (range, 2.29-13.21) with the PercuSurge device. Mean time in situ (filters) was 4.25 +/- 1.12 min. Mean follow-up was 22.6 +/- 17.6 months (range, 1-47). Systolic and diastolic blood pressure declined from 169.0 +/- 15.2 and 104.0 +/- 13.0 mm Hg, respectively, to 149.7 +/- 12.4 and 92.7 +/- 6.7 mm Hg after the procedure. The mean creatinine level remains constant during the follow-up. At 6-month follow-up (45 patients), renal function did not deteriorate in any patient, whereas 8 patients with baseline renal insufficiency improved after the procedure. At 3 years (19 patients), renal function deteriorated only in 1 patient with renal insufficiency and in 1 patient treated for bilateral renal stenosis, one side without protection. These preliminary results suggest the feasibility and safety of distal protection during renal interventions to protect against atheroembolism and to avoid renal function deterioration. This technique's beneficial effects should be evaluated by randomized studies.

Export aspiration catheter thrombosuction before actual angioplasty in primary coronary intervention for acute myocardial infarction

Primary percutaneous coronary intervention (PCI) for acute myocardial infarction (AMI) in lesions with a large thrombus load increases the procedural complication rate. We describe a thrombus reduction technique in this setting using the Export aspiration catheter (EAC) for primary thrombosuction before actual angioplasty. The EAC is a component of the GuardWire Plus system (PercuSurge, Sunnyvale, CA), which was originally developed for emboli containment in saphenous vein graft and peripheral vessel interventions. Primary EAC thrombosuction was performed successfully in 12 patients undergoing primary PCI, and gross thrombi were obtained from 9 patients (75%). After definitive treatment with balloon angioplasty and/or stenting, TIMI 3 flow was restored in all target vessels. There was no angiographic evidence of distal branch loss or vessel injury. No major procedural or in-hospital complication occurred in any patients. This primary EAC thrombosuction technique may offer a new, potentially effective method for thrombus burden reduction in treating AMI patients.