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Vascular and Interventional Radiology |
1 From the Department of Radiology, General Infirmary at Leeds, West Yorkshire, England. From the 2000 RSNA scientific assembly. Received July 23, 2001; revision requested September 11; final revision received June 11, 2002; accepted July 1. Address correspondence to K.S.G., Department of Radiology, Pinderfields General Hospital, Aberford Rd, Wakefield, West Yorkshire WF1 4DG, England (e-mail: kanwargill@doctors.org.uk).
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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MATERIALS AND METHODS: Primary stent placement was performed in 100 consecutive patients with atherosclerotic RAS. Indications for treatment were resistant hypertension (n = 25), impaired renal function, (n = 50), and both (n = 25). Immediate technical results were evaluated with angiography. Clinical outcomes were assessed with serial systolic and diastolic blood pressure and serum creatinine values obtained from retrospective review of case notes. Results obtained every 6 months after the procedure were compared with those obtained at the time of the procedure with the paired t test. Radiologic reports were evaluated for immediate and case notes for delayed complications.
RESULTS: Technical success was achieved in 120 (95.2%) of 126 RAS in 95 patients. Mean follow-up was 25 months (median, 24 months; range, 1–66 months). Resistant hypertension was cured in two (4.2%) of 48 patients, had improved in 38 (79.1%), and had failed to respond to treatment in eight (16.7%). Mean systolic and diastolic blood pressures were significantly lower at 6, 12, 18, 24, and 30 months (P < .01) than before the procedure. Among 65 patients treated for renal impairment, renal function improved in 20 (30.8%), stabilized in 25 (41.7%), and continued to deteriorate in 20 (30.8%). The mean serum creatinine level did not show significant change with time for this group. In the improved subgroup, it was significantly higher at 6, 12, 18, 24, 36, and 42 months (P < .05) than prior to the procedure. Procedure-related complications occurred in 18 (18%) cases: Ten were minor and self-limiting and eight were major and included two procedure-related deaths.
CONCLUSION: In atherosclerotic RAS, primary stent deployment has a high technical success rate, producing clinical benefits in the majority of patients when performed for resistant hypertension and recovery of renal function.
© RSNA, 2003
Index terms: Interventional procedures, complications, 961.1268 • Renal arteries, stenosis or obstruction, 961.721, 961.723 • Renal arteries, transluminal angioplasty, 961.1282, 961.1286 • Stents and prostheses, 961.1268, 961.1286
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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Atherosclerotic renovascular disease is the underlying cause in as many as 20% of all patients older than 60 years currently receiving renal replacement therapy (3,4). Absolute numbers are likely to increase as life expectancy increases. Severe RAS is a progressive condition. Between 12% and 15% of stenoses, which reduce luminal diameter by more than 65%, progress to occlusion within 1 year. As many as 40% of patients have a marked deterioration in renal function within the same period if it is managed medically (5–7). Revascularization may stabilize or retard the progression of renal impairment. Since average life expectancy of a patient starting hemodialysis because of renovascular disease is 2 years (8), valuable improvements may be made, both in the quality and the quantity of life, by delaying dialysis.
In recent years, endovascular treatment has largely replaced surgical intervention in the management of RAS. While effectiveness of both approaches is similar, endovascular procedures have lower complication rates, lower costs, and shorter patient recovery times (9,10). They allow treatment in a number of patients who are deemed unfit for surgery because of unacceptable general anesthetic risk.
In atherosclerotic RAS, and particularly in the high proportion that are ostial lesions (starting within 3 mm of the aortic wall), primary renal arterial stent placement is being increasingly favored because success of percutaneous angioplasty (PTA) is limited with the elastic recoil (11–14). The purpose of our retrospective study was to assess the technical success rates and long-term clinical outcomes of primary renal arterial stent placement in atherosclerotic RAS.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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Twenty-five patients had severe hypertension resistant to multiple medications, 50 patients had impaired renal function (serum creatinine level greater than 130 µmol/L), and the remaining 25 patients had resistant hypertension accompanied by impaired renal function. The 75 patients with impaired renal function included four patients with angiotensin converting enzyme inhibitor–induced renal impairment and four with flash pulmonary edema clinically considered to be renal in origin. Predictably, there was a heavy burden of coexisting atherosclerotic disease. Forty-seven (47%) patients had symptomatic coronary artery disease, 36 had intermittent claudication, 25 had cerebrovascular disease, 25 had congestive heart failure, and 23 were diabetic.
There were a total of 141 (75 left and 66 right) RAS. Of these, 126 were graded as severe (>50% reduction in luminal diameter) and 15 were graded as mild to moderate (<50% reduction in luminal diameter). One hundred two (81%) of the 126 stenoses graded as severe were in fact greater than 85%.
Primary stent placement was attempted by a single operator (R.C.F.) in 126 severe RAS (64 left and 62 right) in 100 patients. There were 98 stenoses (78%) involving the ostium (within 3 mm of the aortic wall) of the renal artery and 28 that were nonostial. Twenty-nine patients (29%) had severe stenosis in a single functioning kidney (the contralateral kidney was congenitally absent, had been removed, or had occluded arterial circulation). Twenty-six (26%) patients had severe bilateral RAS.
Technique
The femoral approach was used in all cases except one in which brachial arterial access was necessary because of aortoiliac occlusion. Standard technique involved placement of an 8-F introducer sheath into the femoral artery and negotiation of the stenosis by using a wire (Tad II; Mallinckrodt, St Louis, Mo). Balloon-mounted (Medtronic AVE, Santa Rosa, Calif) or Palmaz (Johnson & Johnson, Warren, NJ) stents were positioned coaxially through an 8-F guiding catheter, with its tip in the renal ostium. Ten to 15 mL of contrast material (Iopramide [150 mg of iodine per milliliter]; Schering Health Care, Burgen Hill, Sussex, United Kingdom) was hand injected into the guiding catheter by using a side-arm adaptor (Tuohy-Borst; Wilham Cook Europe, Bjaeverskov, Denmark) to obtain fine adjustment of the stent position before deployment. In ostial lesions, stents were deliberately deployed so that they projected 1 mm into the aortic lumen. Optimal final stent diameter was determined by measuring the caliber of a normal segment of the same renal artery. Stenoses were not routinely predilated but this was necessary with some manually crimped Palmaz stents and a single premounted stent.
The immediate technical result was evaluated (R.C.F.) with angiography. Technical success was defined as a residual stenosis of less than 10%. All patients received 5,000 units of heparin that was administered intraarterially during the procedure and antiplatelet therapy (aspirin, 75–300 mg daily) for an indefinite period after the procedure, unless it was specifically contraindicated. No patients formally received anticoagulation therapy following this procedure. Intraarterial angiographic follow-up was not performed routinely in this high-risk patient group. Clinical follow-up was used to guide management. If patients showed clinical evidence of relapse following initial favorable outcome, angiography was performed.
In patients who were reluctant to undergo angiography, duplex ultrasonography (US) was used initially. If the duplex US examination was technically inadequate or suggestive of restenosis (interlobar artery Doppler waveforms demonstrated abnormal acceleration times [>70 msec] or "tardus parvus" appearance), then the requirement for angiography with further therapy was explained to the patient, and consent was obtained. Restenosis was diagnosed angiographically (R.C.F. in all cases) if the vessel diameter was reduced by 50% or more.
Pre- and postprocedure creatinine levels, systolic and diastolic blood pressure recordings, and survival times were obtained by review of the case notes by one author (K.S.G.). Since this was performed as a part of ongoing follow-up by the clinical team responsible for the patient treatment, our review board did not require its approval or informed consent. All patients were examined once within 2 weeks of the procedure and those reported in this study, every 3 months thereafter. Postprocedure results were analyzed every 6 months.
In most patients, blood pressure and serum creatinine values were also available for as many as 12 months prior to the procedure. Criteria used to classify clinical outcome are as specified by the Standards Practice Committee of the Society of Cardiovascular and Interventional Radiology (15). Renal impairment was classified as improved if serum creatinine level decreased by 20% or more and stable if it was within 20% of the preprocedure level. Renal impairment with an increase of more than 20% was classified as a failure. Hypertension was classified as cured if all antihypertension medication was stopped and diastolic blood pressure returned to less than 90 mm Hg. Criteria for improvement were either diastolic blood pressure less than 90 mm Hg without increased medication dose or between 90 and 110 mm Hg with a decrease greater than 15 mm Hg and no increase in medication dose. All other possibilities constituted a failure.
Complications were evaluated (R.C.F. and K.S.G.) by reviewing the radiology reports for immediate procedural complications and the case notes for delayed procedure-related and clinical complications.
Statistical Analysis
Systolic and diastolic blood pressure and serum creatinine values were obtained at intervals after the procedure (Table 1) and were compared with those obtained at the time of the procedure (time 0) by using the paired t test for means. Hence, the P value given in Tables 1 and 2 refers to the probability that the mean value obtained at intervals after the procedure differs by chance alone from that obtained at the time of the procedure. Data are for the number of patients for whom blood pressure or creatinine values were available at intervals after the procedure and at the time of the procedure.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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Resistant hypertension.—Forty-eight of 50 patients with resistant hypertension had technically successful procedures. Hypertension was cured in two (4.2%) patients, had improved in 38 (79.1%), and had failed to respond to treatment in eight (16.7%). Mean systolic and diastolic blood pressures for all patients who underwent stent placement for resistant hypertension (including nonresponders) are shown in Table 1.
Renal impairment.—The procedure was successful in 70 of 75 patients. However, five patients died within 3 months of the procedure. Since only one early result was available in these five cases, they have not been included in the following analysis. Renal impairment improved in 20 (30.8%) of the remaining 65 patients, stabilized in 25 (41.7%), and failed to respond to treatment in 20 (30.8%). Although there was a downward trend in the mean serum creatinine level for the group as a whole (improved, stabilized, and nonresponders), this did not reach a significant level (Table 3). However, some important subgroup changes were noted.
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Of 26 patients with a stenosis in a single functioning kidney, four had died within 3 months of the procedure. Among the remaining 22 patients, stenosis had improved in nine (41%), was stable in six (27%), and failed to respond to treatment in seven (32%). Twenty-five of 29 patients with bilateral renal arterial stent placement for renal impairment were available for follow-up. Renal impairment had improved in nine (36%) patients, remained stable in 10 (40%), and failed to respond to treatment in six (24%). There was no significant difference in response rates to stent placement between these two subgroups nor when these subgroups were compared with all patients treated for renal impairment.
Complications
Procedure-related complications occurred in 18 (18%) of the 100 cases. Of these, 10 were minor and self-limiting and eight were more serious. The minor complications were in six patients with moderate to large groin hematomas that did not require any treatment. There were two cases of transient guide wire–induced lobar branch renal arterial occlusion due to spasm, one case of non–flow-limiting intimal dissection, and one case in which serum creatinine levels had deteriorated after the procedure but recovered spontaneously and completely within 1 week.
The major complications included one femoral artery false aneurysm that was successfully treated with US-guided compression and one that required surgical repair. One patient required hemodialysis for a week before recovery of the procedure-related acute on chronic renal failure. In two patients, removal of balloon-mounted stents was necessary because of partial deployment while attempt was made to cross the stenosis without prior angioplasty. Their removal caused trauma to the femoral artery at the puncture site, which required surgical repair, but in both cases, predilatation allowed successful stent deployment. Surgical retrieval of a stent from the renal artery was required in one case in which distal migration of the stent following deployment suggested a high potential risk of occlusion of renal circulation if left in position. This patient underwent surgical revascularization at the time of stent retrieval.
There were two procedure-related deaths. In one case, a 73-year-old woman with severe generalized atherosclerotic disease had end-stage renal failure at presentation. She was not a candidate for renal replacement therapy because of severe cardiac comorbidity. A prolonged but not successful attempt was made to cross a critically severe stenosis in her one functioning kidney. Unfortunately, she had massive lower limb cholesterol embolization following the procedure and died 24 hours later. In the second case, renal arterial stent placement was successful, but in achieving hemostasis at the groin, thrombosis of the patient’s aortofemoral prosthetic graft had occurred. Emergency surgery was required. Death ensued 19 days following postoperative sepsis.
Angiographic Follow-up and Patency Rates
Ninety-five patients underwent successful stent insertion. A total of 29 patients either failed to show any clinical benefit (n = 15) or died (n = 14) within 6 months of the procedure. Hence, there were 66 patients eligible for stent patency follow-up.
Follow-up angiography was performed in 27 (41%) of 66 patients. Average time to first follow-up angiography was 11.1 months (range, 0–36 months; median, 12 months). Restenosis was seen in 23 (66%) of 35 arteries assessed in the 27 patients. This included three patients with bilateral restenoses. Causes of the 23 restenoses were neointimal hyperplasia in 14 (61%), stent migration in five (22%), and true stent restenosis in the remaining four (17%) renal arteries.
Balloon angioplasty was successful in 11 patients. Further stent insertion was required in the remaining nine patients. In all cases, residual stenosis was less than 10% at the end of the secondary procedure.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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A total of 81% of the patients treated for resistant hypertension benefitted from the procedure. The mean systolic and diastolic blood pressure values for the group show a statistically significant decrease at all time intervals up to 30 months after the procedure, beyond which numbers are too small to be statistically valid. These results are comparable to the reported 59%–86% of patients benefitting following PTA (12,13,21,22) and 64%–78% benefitting following stent placement.
In a recent randomized controlled trial in which blood pressure outcome in PTA versus that in medical treatment for atherosclerotic RAS was evaluated, Plouin et al (28) concluded that investigators in previous reports of PTA had overestimated its beneficial effect in uncontrolled hypertension because mean blood pressures were no different in the two groups compared at 6 months. However, while all patients in the control group were still receiving antihypertensive medication, 26% in the angioplasty group no longer received medication. Blood pressure was also controlled with fewer medications in the patients who underwent angioplasty compared with that in the control group. The authors accepted that their results had limited validity owing to small numbers of patients and a high (30%) number of eligible patients who declined inclusion into the study. The study was further limited by the exclusion of patients with a baseline diastolic blood pressure greater then 110 mm Hg. Undoubtedly, a controlled trial of medical treatment versus stent placement is required, but there is high expectation based on our study findings that stent placement will have results superior to those of PTA.
Renovascular renal impairment is known to be progressive, with markedly reduced life expectancy in patients who become dependent on dialysis. Therefore, any stabilization of renal impairment represents a beneficial outcome, particularly if it is maintained 1 year or more. On this basis, 68% of patients treated for renal impairment benefitted from primary stent placement in this study. The two patients who were undergoing dialysis at the time of stent placement and no longer remained dependent on dialysis at 42 and 18 months demonstrate the true potential reversibility of the disease and the long-term durability of the procedure. Reported results about the response of renal impairment secondary to RAS treated with PTA show considerable variation. The most consistent results are those of Martin et al (11), Tegtmeyer et al (14), and Pattison et al (29), who recorded improvement in 43%, 45%, and 40% of patients, respectively. These results are generally inferior, and at best, equal to those reported in this study. The largest series (26) of outcome in surgery reported stabilization or improvement of renal function in 89% of 161 patients, while smaller series reported values of 81% and 70% (25,27).
Our findings agree with those of Kim et al (23) and Shannon et al (30), suggesting that endovascular revascularization is a safe and effective means of salvaging renal function when RAS is present in one functioning kidney or in bilateral RAS. It would appear to be no more effective in these subgroups than in the remaining patients, with a benefit in 68% of single and in 78% of bilateral RAS patients in this study. These percentages compare with the 70% in the studies of Kim et al and Shannon et al.
Atherosclerotic RAS is one manifestation of a widespread systemic condition. In common with other reports of endovascular treatment of atherosclerotic RAS, we found that the majority of patients in our study had clinically evident cardiac, cerebral, and peripheral vascular disease. Wollenweber et al (6) reported 5-year survival of 66% for 112 patients with atherosclerotic RAS compared with 92% survival for a comparable age-matched healthy cohort. A quarter of the patients in our study died of causes not related to the procedure during follow-up, with a mean survival time of 6 months after stent placement. This has major implications for monitoring the medium to long-term effectiveness of revascularization. We have concentrated on clinical outcome measures. This may be considered a weakness of the study because "clinically silent" restenosis has occasionally been described (27). Nonetheless, we believe that any potential reintervention should be dictated by clinical relapse in this high-risk group.
The apparent restenosis rate in this study, with imaging prompted by a clinical deterioration after initial favorable response, was 17%. We accept that there is a possibility of missing restenoses with this approach, but our value is in the middle of the range of 11%–25% reported when routine angiography follow-up has been performed in patients with stents (17–20). In such a high-risk group, we suggest that evidence of clinical relapse coupled initially with noninvasive investigation is an appropriate follow-up algorithm.
An overall complication rate of 18% (including 10% minor complications) compares with rates of 13%–24% in other stent series (17,20,31,32). A 2% procedure-related mortality, while of concern to us, is comparable with the 3% mortality experienced by other authors (20,31,32). Surgery for RAS, whether of the traditional aortorenal bypass type or the more recently favored hepatorenal and splenorenal bypasses, continues to have higher complication rates, regardless of patient selection (9,25,26). Surgery-related death rates have ranged from 2% (26) to 21% (9).
The major difficulty remains prediction which patients will benefit from revascularization. Three criteria have previously been described as possible adverse predictors of recoverable renal function (33). Renal length of less than 8 cm, the presence of diffuse glomerular hyalinization at renal biopsy, and diffuse sclerosis of the intrarenal arteries at angiography have all been associated with poor recovery of renal function. Unfortunately, not one of these criteria has proved consistently useful, and all have individually been shown to be present in cases that have responded well to revascularization (33). It would be ideal to select poor-benefit patients to avoid inappropriate risk. However, in the absence of sensitive and specific features, we preferred not to deny patients the chance of benefit. This is particularly so since, in our experience, one of these predictors has been present in the absence of the other two in most cases where there was concern regarding potential benefit of the procedure.
In conclusion, findings of this study indicate that primary stent placement in atherosclerotic RAS is beneficial in the majority of patients for both improved blood pressure control and recovery of renal function. It is the treatment of choice on the basis of reported superior technical success and clinical response rates when compared with PTA. It has comparable technical and clinical success but lower complication rates and reduced patient morbidity when compared with those reported for renal arterial bypass grafting.
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FOOTNOTES |
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Author contributions: Guarantors of integrity of entire study, K.S.G., R.C.F.; study concepts and design, R.C.F.; literature research, K.S.G.; clinical studies, R.C.F.; data acquisition and analysis/interpretation, K.S.G.; statistical analysis, K.S.G.; manuscript preparation, definition of intellectual content, editing, revision/review, and final version approval, K.S.G., R.C.F.
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REFERENCES |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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