William R. Colyer

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.

Utility of a 0.014" pressure-sensing guidewire to assess renal artery translesional systolic pressure gradients.

Renal ischemia due to renal artery stenosis (RAS) is an important cause of secondary hypertension and renal insufficiency. Several methods are available to diagnose RAS; however, the identification of clinically significant lesions remains problematic. We measured the translesional systolic pressure gradient (TSPG) with a 4 Fr catheter and a 0.014″ pressure‐sensing guidewire and compared these data to angiographic findings. The TSPG obtained by pressure‐sensing guidewire correlated more strongly with angiographic minimal lumen diameter (r2 = 0.801) than those obtained by 4 Fr catheter (r2 = 0.360). The relationship of TSPG with percent stenosis was not strong, regardless of the method used (r2 = 0.228 with pressure‐sensing guidewire, 0.358 with 4 Fr catheter). Using a 0.014″ pressure‐sensing guidewire is effective for assessing TSPG and provides a more reliable indication of stenosis significance than use of a 4 Fr catheter. Cathet Cardiovasc Intervent 2003;59:372–377.

Common femoral artery access techniques: a review.

The increasing burden of coronary artery disease has resulted in more percutaneous coronary artery interventions. The common femoral artery remains the most widely accepted site for percutaneous coronary artery access. Local access site, vascular complications remain a considerable source of morbidity during common femoral arterial puncture. This has prompted angiographers, over the years, to define various reliable landmarks and techniques to access the common femoral artery, in an attempt to minimize and avoid complications. In this discourse, we discuss the various techniques of obtaining common femoral arterial access, with their relative benefits and disadvantages. The literature supporting the various palpatory or radiographic landmark-guided methods is reviewed. There are limited data on the superiority of any individual method.

Cardiovascular Morbidity and Mortality and Renal Artery Stenosis

Renal artery stenosis (RAS) is a common manifestation of atherosclerosis and is associated with many other atherosclerotic conditions. Cardiovascular morbidity and mortality is increased among patients with RAS. This increase is likely due in part to the associated disease states; however, RAS itself may also contribute. Current strategies to limit cardiovascular morbidity and mortality in RAS include various pharmacologic interventions targeting both RAS atherosclerosis in general. Additionally, revascularization has been advocated; however, clear data are lacking. Ongoing clinical trials such as the Cardiovascular Outcomes in Renal Atherosclerotic Lesions (CORAL) trial will ultimately help to determine the best strategies to limit the morbidity and mortality associated with 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 abcizimab (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.

Management of Renal Artery Stenosis: 2010

Opinion statementRenal artery stenosis (RAS) is a relatively common manifestation of atherosclerosis, although in a small percentage of cases it is due to fibromuscular dysplasia and less frequently may have other etiologies. RAS may be treated by revascularization, using either percutaneous or open surgical techniques. Currently, technical success with percutaneous revascularization utilizing angioplasty and stenting is achieved in 95% or more of cases in which it is attempted. Despite this, at least one third of patients undergoing renal artery stenting do not receive any measurable benefit. Furthermore, randomized trials of stenting for RAS have failed to demonstrate a benefit over medical management alone. Thus, the clinician is faced with a challenge when determining how to manage an individual patient with RAS. In the current era, all patients with RAS should receive “optimal medical therapy.” This approach should use medicines to control blood pressure, and specifically utilize agents proven to reduce cardiovascular morbidity and mortality. Other components of “optimal medical therapy” include the use of anti-platelet drugs such as aspirin and statins to minimize progression of atherosclerosis. In addition to these strategies, consideration should be given to revascularization therapy. When deciding to revascularize RAS, the patient should have an appropriate clinical indication, in addition to a significant anatomic stenosis. Importantly, stents should not be placed due to the “oculostenotic reflex.” Specifically, patients who continue to have uncontrolled blood pressure or worsening renal function despite an aggressive approach with medical therapy may be particularly good candidates for renal artery stenting. Despite the lack of benefit in randomized trials to date, there is likely still a role for renal artery stenting in RAS; however, careful patient selection is essential to maximize the potential benefit.

Intraaortic balloon pump insertion after percutaneous revascularization in patients with severe peripheral vascular disease.

Severe aortoiliac peripheral vascular disease (PVD) is considered a contraindication for the placement of an intraaortic balloon pump (IABP) because of a high risk of limb ischemia. Recent advances in percutaneous transluminal angioplasty (PTA) and stenting have altered the treatment of iliac stenoses such that the results of PTA with stenting compare favorably with surgery. We reviewed our experience with placement of IABP between July 1994 and February 1996. Of 64 patients receiving IABP, 17 had known or suspected peripheral vascular disease. Severe iliac or distal aortic stenoses were present in 9. These 9 patients underwent PTA with or without stenting prior to 10 IABP insertions. Limb ischemia occurred in 10% of PVD patients treated with percutaneous revascularization, compared to 11% in patients without PVD. No patient had a serious vascular complication or required vascular surgery. We conclude that percutaneous revascularization in patients with severe aortoiliac PVD, for whom this IABP insertion had previously been considered contraindicated, results in a low rate of limb ischemia.

Complete versus partial distal embolic protection during renal artery stenting

The aim of this study was to evaluate whether complete embolic protection is superior to partial embolic protection for preservation of kidney function during renal artery angioplasty and stenting.

Determinants of renal function in patients with renal artery stenosis.

Renal artery stenosis (RAS) is an important cause of renal failure; however, the factors associated with loss of kidney function in patients with RAS are poorly described, as are the predictors of an improvement in kidney function after stenting. One hundred patients at seven centers undergoing renal stenting were randomly assigned to an embolic protection device or double-blind use of a platelet glycoprotein IIb/IIIa inhibitor. The glomerular filtration rate (GFR) was measured using the creatinine-derived modified Modification of Diet in Renal Disease (MDRD) equation, cystatin C, and iohexol clearance. In univariate and multivariate models, baseline MDRD and cystatin C GFR were associated with congestive heart failure (CHF) (p = 0.01), lesion length (p = 0.01), and percent stenosis (–0.27, p = 0.01). In multivariate models, MDRD-estimated GFR 1 month after stenting was associated with bilateral stenosis (p < 0.05) and lesion length (p < 0.05), whereas with cystatin C the multivariate model included angiotensin receptor blocker (ARB) (p < 0.05) and minimal luminal diameter (MLD) (p < 0.05). The improvement in GFR from baseline to 1 month, measured as percent change, was related to baseline MDRD (p = 0.009) and cystatin C (p = 0.03) GFR. For MDRD GFR combined treatment with abciximab and Angioguard® embolic protection (p = 0.02) remained significant in multivariate analysis as did CHF, which was also significant with cystatin C (p = 0.05). In conclusion, CHF and lesion characteristics (MLD, percent stenosis and lesion length) are determinants of renal function in patients with RAS. In contrast, the acute improvement in renal function after revascularization is most strongly influenced by baseline GFR, and to a lesser degree CHF and combined procedural treatment with abciximab and embolic protection but not lesion characteristics. Clinical Trial Registration – URL:http://www.clinicaltrials.gov. Unique identifier: NCT00234585

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.