Atheroemboli during renal artery angioplasty: An ex vivo 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.

Atherosclerotic renovascular disease: a clinical practice document by the European Renal Best Practice (ERBP) board of the European Renal Association (ERA) and the Working Group Hypertension and the Kidney of the European Society of Hypertension (ESH)

Atherosclerotic renovascular disease (ARVD) is the most common type of renal artery stenosis. It represents a common health problem with clinical presentations relevant to many medical specialties and carries a high risk for future cardiovascular and renal events, as well as overall mortality. The available evidence regarding the management of ARVD is conflicting. Randomized controlled trials failed to demonstrate superiority of percutaneous transluminal renal artery angioplasty (PTRA) with or without stenting in addition to standard medical therapy compared with medical therapy alone in lowering blood pressure levels or preventing adverse renal and cardiovascular outcomes in patients with ARVD, but they carried several limitations and met important criticism. Observational studies showed that PTRA is associated with future cardiorenal benefits in patients presenting with high-risk ARVD phenotypes (i.e. flash pulmonary oedema, resistant hypertension or rapid loss of kidney function). This clinical practice document, prepared by experts from the European Renal Best Practice (ERBP) board of the European Renal Association (ERA) and from the Working Group on Hypertension and the Kidney of the European Society of Hypertension (ESH), summarizes current knowledge in epidemiology, pathophysiology and diagnostic assessment of ARVD and presents, following a systematic literature review, key evidence relevant to treatment, with an aim to support clinicians in decision making and everyday management of patients with this condition.

Cholesterol crystal embolism-related cerebral infarction: Magnetic resonance imaging and clinical characteristics

BACKGROUND AND AIMS

Cholesterol crystal embolism-related cerebral infarction (CCE-CI) is frequently misdiagnosed due to the lack of specific symptoms. To aid in differential diagnosis, this study comprehensively characterized the magnetic resonance imaging (MRI) and clinical manifestations of CCE-CI and compared these features to those of atherothrombotic cerebral infarction (ACI).

METHODS

This single-center, retrospective, observational study was conducted at Kitasato University Hospital, Kanagawa, Japan. We identified 37 clinically or histopathologically confirmed CCE-CI cases and 110 ACI cases treated from January 2006 to May 2020. Groups were compared for mean age, sex ratio, clinical presentations, imaging manifestations, precipitating factors, comorbid conditions, medications, and smoking history.

RESULTS

Of 37 eligible patients with CCE-CI, 10 (27.0%) received brain MRI, of which 8 (21.6%) exhibited high-intensity signals indicative of brain lesions on diffusion-weighted imaging (DWI). However, two patients with DWI lesions exhibited no detectable neurological abnormalities. Patients with CCE-CI frequently demonstrated bilateral DWI lesions involving the bilateral anterior and posterior circulation, a pattern absent in ACI (50% vs. 0%, p < 0.001). Compared to patients with ACI, CCE-CI patients also demonstrated significantly lower estimated glomerular filtration rate (p < 0.001) as well as more frequent eosinophilia (p = 0.006), atherosclerotic plaques ≥4-mm thick in the ascending aorta or proximal arch (p = 0.001), and aortic aneurysm (p < 0.001).

CONCLUSIONS

Patients with CCE-CI develop multiple DWI lesions across several vascular territories, even in the absence of neurological symptoms. Comorbid aortic aneurysm may increase CCE-CI risk. These findings could help in the differential diagnosis of CCE-CI.

[Update on cholesterol crystal embolism]

Cholesterol crystal embolism is a systemic pathology associated with diffuse atherosclerosis. Pathophysiology corresponds to tissue necro-inflammation secondary to arteriolar occlusion associated with microembolism from atherosclerotic plaques of large diameter arteries. The clinical presentation is heterogeneous and polymorphic. Multiple organs may be the targets, but preferential damage is skin, kidneys and digestive system. It is a serious pathology, underdiagnosed, with a poor prognosis. The risk factors for developing the disease remain the same risk factors as atheroma. The factors favouring migration of microembolism remain mainly vascular interventional procedures; easy to diagnose, they oppose spontaneous embolic migrations or secondary to the introduction of antithrombotic treatment, whose diagnosis is more difficult and the prognosis more severe. The diagnosis of the disease remains mostly a diagnosis of elimination and often refers to a bundle of clinical, biological, morphological and histologic arguments. The treatment is poorly codified and the subject of few publications. It will favour both symptomatic treatment (and mainly that of pain) and complications (high blood pressure, renal insufficiency). The aetiological support remains less consensual. The treatment of atherosclerotic plaques consists, of course, in the correction of classical cardiovascular risk factors, the introduction of a statin. It will be discussed in the implementation of surgery or angioplasty to exclude potentially responsible atherosclerotic lesions. Eviction of antithrombotic therapy should be considered in terms of the benefit-risk balance, but often in favour of maintaining it. Finally, other treatments may be proposed in a case-by-case basis, such as oral or intravenous corticosteroid therapy, colchicine or LDL aphaeresis.

Assessment of aortic wall thrombus predicts outcomes of endovascular repair of complex aortic aneurysms using fenestrated and branched endografts

OBJECTIVE

The goal of this study was to investigate the correlation between atherothrombotic aortic wall thrombus (AWT) and clinical outcomes in patients treated by fenestrated-branched endovascular aortic repair (F-BEVAR) and present a new classification system for assessment of AWT burden.

METHODS

The clinical data of 301 patients treated for pararenal and thoracoabdominal aortic aneurysms (TAAAs) by F-BEVAR was reviewed. The study excluded 89 patients with extent I to III TAAA because of extensive laminated thrombus within the aneurysm sac. Computed tomography angiograms were analyzed in all patients to determine the location, extent, and severity of atherothrombotic AWT. The aorta was divided into three segments: ascending and arch (A), thoracic (B) and renal-mesenteric (C). Volumetric measurements (cm³) of AWT were performed using TeraRecon software (TeraRecon Inc, Foster City, Calif). These volumes were used to create an AWT index by dividing the AWT volume from the total aortic volume. A classification system was proposed using objective assessment of the number of affected segments, thrombus type, thickness, area, and circumference. Clinical outcomes included 30-day mortality, neurologic and gastrointestinal complications, renal events (Risk, Injury, Failure, Loss of kidney function, End-stage renal disease [RIFLE]), and solid organ infarction.

RESULTS

The study included 212 patients, 169 men (80%) and 43 women (20%), with a mean age of 76 ± 7 years. A total of 700 renal-mesenteric arteries were incorporated (3.1 ± 1 vessels/patient). AWT was classified as mild in 98 patients (46%) and was considered moderate or severe in 114 (54%). There was one death (0.5%) at 30 days. Solid organ infarction was present in 50 patients (24%), and acute kidney injury occurred in 45 patients (21%) by RIFLE criteria. An association with higher AWT indices was found for time to resume enteral diet (P = .0004) and decline in renal function (P = .0003). Patients with acute kidney injury 2 by RIFLE criterion had significantly higher (P = .002) AWT index scores in segment B. Spinal cord injury occurred in three patients (1.4%) and stroke in four (1.9%), but were not associated with the AWT index. Severity of AWT using the new proposed classification system correlated with the AWT index in all three segments (P < .001). Any of the end points occurred in 35% of the patients with mild and in 53% of those with moderate or severe AWT (P = .016).

CONCLUSIONS

AWT predicts solid organ infarction, renal function deterioration, and longer time to resume enteral diet after F-BEVAR of pararenal and type IV TAAAs. Evaluation of AWT should be part of preoperative planning and decision making for selection of the ideal method of treatment in these patients.

Renal Function after Endovascular Aortic Aneurysm Repair: A Single-Center Experience with Transrenal versus Infrarenal Fixation

Purpose:

To describe the short-term consequences of endovascular aortic aneurysm repair (EVAR) on renal function after infrarenal (IR) versus transrenal (TR) stent-graft fixation.

Methods:

Between December 1996 and January 2006, 369 consecutive patients were treated with EVAR. All patients had an AneuRx or a Talent stent-graft implanted using IR (AneuRx) or transrenal (Talent) fixation. Post-EVAR, a standardized follow-up scheme included computed tomography (CT) scanning and serum creatinine measurements at 2 days, 3 months, and 12 months. Postoperative renal dysfunction was defined as a >20% decrease in serum creatinine clearance compared to baseline, the presence of new-onset dialysis, or both. Of the 369 patients, 309 (291 men; mean age 71±7 years, range 63–82) had complete 1-year follow-up and were included in this study. An IR stent-graft was placed in 190 patients, and a TR stent-graft was placed in the remaining 119 patients.

Results:

At discharge, renal dysfunction occurred in 3.7% of the patients in the IR group versus 5.9% in the TR group (p=NS) and rose significantly to 13.7% in the IR group (p=0.001) and 15.1% in the TR group (p=0.02) at the 1-year follow-up. However, no significant difference was noted between the IR and TR groups at either time point. At the 1-year follow-up, at least 50% of renal dysfunction was caused by obstructions of (accessory) renal arteries and renal infarctions. During the follow-up interval, 3 (0.97%) of 309 patients underwent new-onset dialysis.

Conclusion:

Both infrarenal and transrenal fixation techniques in EVAR will lead to a significant rise in renal dysfunction during the first year. A few patients with dysfunction will require dialysis.

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 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.

Current views on the management of atherosclerotic renovascular disease

Atherosclerotic renovascular disease (ARVD) is a common condition in both elderly patients and those with other vascular disease. No published randomized controlled trial has demonstrated an overall benefit of revascularization on any clinical or biochemical end-point, and optimal medical therapy in this condition is not clearly defined. In this review we consider the epidemiology of ARVD and discuss the evidence for current medical treatment. We also address the literature on revascularization, consider settings in which an interventional approach may still be considered, and touch upon on-going areas of research.

Renal intervention to treat hypertension

Renal artery intervention to treat hypertension is one of the frontiers of ongoing research in combating this epidemic. This article focuses on recent data regarding PTRS and catheter-based renal sympathetic denervation. Despite progress in this field large multicenter, randomized trials that compare these treatment modalities with medical therapy for hypertension are lacking.

Renovascular hypertension and ischemic nephropathy

Renovascular disease remains among the most prevalent and important causes of secondary hypertension and renal dysfunction. Many lesions reduce perfusion pressure including fibromuscular diseases and renal infarction, but most are caused by atherosclerotic disease. Epidemiologic studies establish a strong association between atherosclerotic renal-artery stenosis (ARAS) and cardiovascular risk. Hypertension develops in patients with renovascular disease from a complex set of pressor signals, including activation of the renin-angiotensin system (RAS), recruitment of oxidative stress pathways, and sympathoadrenergic activation. Although the kidney maintains function over a broad range of autoregulation, sustained reduction in renal perfusion leads to disturbed microvascular function, vascular rarefaction, and ultimately development of interstitial fibrosis. Advances in antihypertensive drug therapy and intensive risk factor management including smoking cessation and statin therapy can provide excellent blood pressure control for many individuals. Despite extensive observational experience with renal revascularization in patients with renovascular hypertension, recent prospective randomized trials fail to establish compelling benefits either with endovascular stents or with surgery when added to effective medical therapy. These trials are limited and exclude many patients most likely to benefit from revascularization. Meaningful recovery of kidney function after revascularization is limited once fibrosis is established. Recent experimental studies indicate that mechanisms allowing repair and regeneration of parenchymal kidney tissue may lead to improved outcomes in the future. Until additional staging tools become available, clinicians will be forced to individualize therapy carefully to optimize the potential benefits regarding both blood pressure and renal function for such patients.

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.

Atherosclerotic Renovascular Hypertension : Lessons from Recent Clinical Studies

Atherosclerotic renovascular hypertension is a form of secondary hypertension due to renal artery stenosis. After the introduction of medical therapy such as with statins and angiotensin blocking agents, it has been considered a very slowly progressive disease. In the 1990s, surgical methods were compared to radiological intervention and showed no additional benefits. Recent clinical data also demonstrate that in cases of relatively stable atherosclerotic renovascular disease, medical therapy is as effective as other interventions with regard to patient outcomes. In this paper the recent clinical outcomes are reviewed.

Current approaches to renovascular hypertension

This article examines the status regarding prevalence, mechanisms, clinical manifestations and management of renovascular hypertension at this point in time. It should be viewed as a work in progress. As with most complex conditions, clinicians must integrate the results of published literature studies while considering each patient's specific features and comorbid disease risks. Beyond identifying renovascular disease as a cause of secondary hypertension, one must manage renal artery stenosis (RAS) itself as an atherosclerotic vascular complication. This disease warrants follow-up regarding progression and potential for ischemic tissue injury. These elements often determine the role and timing for revascularization. In this respect, atherosclerotic renal artery stenosis is analogous to progressive carotid or aortic aneurysmal disease.

Embolic protection device use in renal artery stent placement

PURPOSE

The purpose of the present study was to report safety, efficacy, and renal function outcomes with use of the GuardWire embolic protection device (EPD) in renal artery stent placement for patients with renal artery stenosis (RAS) and chronic renal insufficiency (CRI).

MATERIALS AND METHODS

This was a retrospective study of all patients with RAS and CRI treated concomitantly with a GuardWire EPD and renal artery stents from December 2002 through June 2006. Renal function was determined by calculating the estimated glomerular filtration rate (eGFR) according to the Modification of Diet in Renal Disease formula, and subjects were divided into Kidney Disease Outcomes and Quality Initiative (K-DOQI) classes based on baseline eGFR. After revascularization, an improvement from baseline of at least one K-DOQI class was defined as improvement, unchanged K-DOQI class as stabilization, and worsening of at least one K-DOQI class as deterioration.

RESULTS

There were 63 patients (54% men) with a mean age of 75.2 years +/- 7.7. The mean baseline serum creatinine level and eGFR were 1.87 mg/dL +/- 0.6 (range, 1-3.8 mg/dL) and 36.63 mL/min per 1.73 m(2) +/- 11.42 (range, 13.85-59.99 mL/min per 1.73 m(2)), respectively, and at the last clinical follow-up, the respective measurements were 1.96 mg/dL +/- 0.72 and 38.75 mL/min per 1.73 m(2) +/- 13.25 (P = not significant). Over a mean follow-up period of 16 months +/- 12, 14 patients (25%) showed improvement, 33 (58%) had stable renal function, and 10 (18%) showed deterioration. There was one GuardWire-related dissection, which was successfully treated with a stent.

CONCLUSIONS

The GuardWire EPD, used during renal artery stent placement, is safe and was associated with stabilization or improvement in kidney function in 83% of patients with RAS and CRI.

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.

Renal artery revascularization: collaborative approaches for specialists

Endovascular revascularization for atherosclerotic renal artery stenosis (RAS) is the revascularization strategy of choice for patients with hemodynamically and clinically significant renal artery stenosis. Surgical revascularization is reserved for failed endovascular therapy or concomitant abdominal aortic surgery. Endovascular renal artery stenting is associated with excellent technical success, low complication rates, and acceptable long-term patency. This technique has been proven to be beneficial for preserving kidney function and stabilizing or improving blood pressure control in selected patients. Nevertheless, deterioration in kidney function after the procedure in 10% to 20% of cases may limit the immediate benefits of this technique. Atheroembolism appears to play an important role in the cause of kidney dysfunction after renal revascularization. Renal revascularization with a distal embolic protection device is a promising strategy in reducing the risk of atheroembolism and deterioration in kidney function.

Embolic protection devices in patients with renal artery stenosis with chronic renal insufficiency: a clinical study

PURPOSE

To present clinical outcomes with the use of embolic protection devices (EPDs) and renal artery stents in patients with chronic renal insufficiency (CRI) and renal artery stenosis (RAS).

MATERIALS AND METHODS

A retrospective study was conducted in 23 patients with RAS and CRI who were treated with renal artery stent placement with an EPD. Follow-up data were obtained through medical records.

RESULTS

In 23 patients (18 men; 78%) with an average age of 69.4 years +/- 11 (range, 46-86 y), 32 renal arteries were treated for worsening renal function (n = 17; 74%) or uncontrolled hypertension and worsening renal function (n = 6; 26%). Nine FilterWire EZ devices were used in eight patients (35%) and 17 SpideRX devices were used in 15 patients (65%). The average follow-up was 8 months +/- 5. After the stent procedure, the mean systolic blood pressure decreased significantly (P < .05) whereas the diastolic pressure remained unchanged. There was a significant increase in the mean estimated glomerular filtration rate from 32.9 mL/min +/- 12.9 at baseline to 41.3 mL/min +/- 13.7 at last follow-up (P < .05). In 96% of patients, there was improvement or stabilization of kidney function. In six of the 17 SpideRX devices (35%), macroscopically evident embolic material was observed in the device after stent placement. There were two minor and two major complications.

CONCLUSIONS

Renal artery stent placement combined with the use of a SpideRX or FilterWire EZ device is associated with an good clinical outcome with a reasonable safety profile.

Serum Creatinine Stabilization Following Renal Artery Stenting

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

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.

Catheter-based therapy for atherosclerotic renal artery stenosis

The prevalence of atherosclerotic renal artery stenosis (RAS) is more common than was previously thought, particularly in patients with known coronary, cerebrovascular, or peripheral vascular atherosclerosis. Clinical subsets in which RAS is more common include patients with uncontrolled hypertension, renal insufficiency, and/or sudden onset ("flash") pulmonary edema. Renal artery atherosclerosis progresses over time and is associated with loss of renal function regardless of medical therapy. Patients with symptomatic (hypertension, renal insufficiency, or flash pulmonary edema) and hemodynamically significant RAS are potential candidates for revascularization. The current standard of care is stent placement for aorto-ostial atherosclerotic lesions. Procedure success rates are very high (> or =95%), with infrequent major complication rates. Five-year primary patency rates are 80% to 85%, and secondary patency rates exceed 90%. The key element in managing patients with RAS is selecting those most likely to benefit, that is, those with blood pressure control, preservation or improvement of renal function, and control of flash pulmonary edema from renal revascularization. This article will highlight the anatomical features, physiologic parameters, and biomarkers that may be helpful in optimally selecting patients for renal artery revascularization.

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.

The management of renal artery atherosclerosis for renal salvage: Does stenting help?

OBJECTIVE

The use of endovascular techniques to treat renal artery stenosis (RAS) has increased in recent years but remains controversial. The purpose of this study was to review the outcomes and durability of percutaneous transluminal angioplasty and stenting (PTA/S) for patients with RAS and decreasing renal function.

METHODS

Between 1999 and 2004, 125 consecutive patients underwent angiography and intervention for renal salvage and formed the basis of this study. Inclusion criteria for this study included serum creatinine greater than 1.5 mg/dL, ischemic nephropathy, and high-grade RAS perfusing a single functioning kidney. Patients undergoing PTA/S for renovascular hypertension or fibromuscular dysplasia or in conjunction with endovascular stent grafting for aneurysm repair were excluded. The original angiographic imaging was evaluated for lesion grade and parenchymal kidney size. All medical records and noninvasive testing were reviewed. Preoperative and postoperative patient data were standardized and analyzed by using chi(2) tests for nominal values and t tests for continuous variables. The Modification of Diet in Renal Disease equation was used to estimate glomerular filtration rate (GFR), and univariate analysis was performed.

RESULTS

Preoperative variables included the presence of coronary artery disease (93%), diabetes (44%), tobacco use (48%), and hypercholesterolemia (70%). RAS was suspected on the basis of preoperative duplex imaging or magnetic resonance angiography. Aortography and PTA/S were performed in 125 patients (mean age, 71 years; 59% male) with a mean baseline creatinine level of 2.2 mg/dL. There were two mortalities (1.6%) in the 30-day postoperative period, but there was no case of acute renal loss. Blood pressure decreased after PTA/S (151/79 mm Hg before vs 139/72 mm Hg after 1 month; P < .03). For all patients, the estimated GFR went from 33 +/- 12 mL . min(-1) . 1.73 m(-2) (mean +/- SD) to 37 +/- 19 mL . min(-1) . 1.73 m(-2) at 6 months (P = .10). Sixty-seven percent of treated patients had improvement (>10% increase in GFR) or stabilization of renal function. A rapid decline in GFR before intervention was correlated with improvement after PTA/S. Responders after PTA/S had a 27% decrease in GFR before intervention (44 +/- 13 mL . min(-1) . 1.73 m(-2) to 32 +/- 13 mL . min(-1) . 1.73 m(-2); P < .001) with a negative to positive slope change in GFR values. Ten patients underwent reintervention for in-stent restenosis. Cases without improvement in GFR after PTA/S were associated with eventual dialysis need (P = .01; mean follow-up, 19 months). Survival at 3 years was 76%, and dialysis-free survival was 63% as estimated by Kaplan-Meier analyses.

CONCLUSIONS

Renal artery stenoses causing renal dysfunction can be safely treated via endovascular means. Rapidly decreasing renal function is associated with the response to renal artery angioplasty/stenting and helps identify patients for renal salvage.

Atherosclerotic process, renovascular disease and outcomes from bench to bedside

PURPOSE OF REVIEW

Atherosclerotic renal artery stenosis has become an important cause of secondary hypertension and renal dysfunction in the aging population. Its presence increases cardiovascular morbidity and mortality independent of other atherosclerotic risk factors. Therefore, novel renoprotective strategies are needed to decrease the impact of this disease.

RECENT FINDINGS

Although medical therapy can be effective in patients with atherosclerotic renal artery stenosis and mild renal dysfunction, revascularization is desirable for patients with target-organ injury. Technical developments (such as drug-eluting or low-profile stents and distal protection devices) have increased the safety and effectiveness of renal revascularization, but in a significant proportion of patients renal function is not fully restored. Recent experimental evidence suggests that atherosclerotic renal artery stenosis is associated with the activation of intrarenal fibrogenic and inflammatory pathways, oxidative stress, and microvascular remodeling, and blocking these mechanisms can improve renal hemodynamics and function.

SUMMARY

Despite significant advances in revascularization techniques, it remains unclear why the kidney affected by atherosclerotic renal artery stenosis often does not improve or even progressively deteriorates. In addition to the restoration of blood flow, targeted interventions to attenuate injurious intrarenal mechanisms should probably become part of a comprehensive management plan to preserve the ischemic kidney.

Revascularization in atherosclerotic renovascular disease: Problems beyond the obstruction

The main goal in the treatment of obstructive atherosclerotic renovascular disease (ARVD) is to preserve or recover renal function. The ARVD kidney continues to deteriorate in 20-40% of cases despite restoration of blood flow. Holden et al. report that renal function stabilized or improved in up to 97% of patients with the use of a distal embolic protection device.

Renal artery stent revascularization with embolic protection in patients with ischemic nephropathy

A prospective analysis of renal artery stent revascularization with distal embolic protection in a high-risk patient population with ischemic nephropathy is presented. A total of 63 patients (median age 70.2 years, range 54-86 years) had significant atherosclerotic stenosis of 83 renal arteries documented on pre-procedural imaging. All patients had baseline chronic renal insufficiency with a documented deterioration in renal function in the 6 months before revascularization. The endovascular technique used in all patients involved primary passage of an embolic filter into the distal main renal artery followed by primary stent deployment with a balloon expandable stainless steel stent. The filter baskets were recaptured and contents submitted for pathological analysis. At 6 months post-intervention, 97% of patients demonstrated stabilization or improvement in renal function. Only 3% of patients had an inexorable decline in renal function, unchanged by the intervention. After a mean follow up of 16.0 months (6-27), 94% of patients demonstrated stabilization or improvement in renal function. One patient suffered an acute post-procedural deterioration in renal function. In total, 60% of the filter baskets contained embolic material. This study confirms the technical feasibility of renal artery stent deployment with adjuvant embolic protection. The excellent results for renal preservation at 6 months post-intervention also suggest that a distal embolic protection device may improve the impact of percutaneous renal revascularization on progressive deterioration in renal function. The postulated mechanism is through the prevention of atheromatous embolization and the embolic yield from the distal filters supports this hypothesis. Patients most likely to receive the greatest benefit are those with mild baseline chronic renal insufficiency and a recent decline in renal function.

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.