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Renal Artery Stenting for Renal Artery Stenosis: Interventional Approach and Initial Clinical Results
ORIGINAL ARTICLE
Original Article
Renal Artery Stenting for Renal Artery Stenosis: Interventional Approach and Initial Clinical Results Grayson G. Geary, MBBS, FRACP∗ , David L. Ross, MBBS, FRACP and A. Robert Denniss, MD, FRACP Department of Cardiology, Westmead Hospital, Westmead, Sydney, Australia Available online 25 August 2004
Background. Significant renal artery stenosis is being increasingly diagnosed and interventional cardiologists are taking on the unfamiliar role of deploying renal stents. We describe our technique for renal artery stenting using techniques and equipment similar to that used in coronary stenting and present early results. Methods. Thirty-two patients with significant renal artery stenosis (diameter stenosis 60–95%) and difficult to control hypertension or renal impairment were referred for renal stenting. Renal DTPA scans were performed before intervention. All the procedures were attempted from the femoral artery approach using guides, low profile wires and balloon catheters similar to those used for coronary work. The lowest profile renal or coronary stents were deployed using a monorail technique. Results. Atherosclerosis was the cause of the renal artery stenosis in 31 patients. Stents were successfully deployed in 30 of these patients (97%). One patient required a second procedure from the brachial artery approach. An additional patient with fibromuscular dysplasia underwent angioplasty only. Angiographic diameter stenosis was reduced from a mean of 79 to 1%. Translesional mean pressure gradients were reduced from 22 to 1 mmHg. There were no major procedural or in-hospital complications. Anti-hypertensive drugs were reduced from a mean of 3 prior to stenting to 0.7 at discharge. Renal DTPA scans were a poor predictor of severity of stenosis. Renal DTPA scans suggested functionally significant renal artery stenosis in only 48% of patients but the clinical responses suggested that this was an underestimate. Conclusions. Stenting of renal arteries using coronary like techniques and equipment results in a high rate of procedural success and good early clinical outcomes. (Heart Lung and Circulation 2004;13:274–279) © 2004 Australasian Society of Cardiac and Thoracic Surgeons and the Cardiac Society of Australia and New Zealand. Published by Elsevier Inc. All rights reserved. Keywords. Renal artery stenting; Hypertension; Renal insufficiency
Introduction
R
enal artery stenosis (RAS) is a recognised cause of hypertension and chronic renal insufficiency. In recent years it has become apparent that RAS is more common than previously thought and increased numbers of patients are being considered for renal artery stenting. Renal angiography is the gold standard for detection of RAS. More patients with difficult to control hypertension are being investigated with angiography and found to have significant RAS. Unsuspected RAS is found in a significant percentage of patients with coronary artery disease1–3 and peripheral vascular disease.4 when screened by renal angiography. Serial angiography shows that RAS tends to be progressive.3 Some of these patients may benefit from renal artery stenting for treatment of difficult to control hypertension or to prevent deterioration of renal function.
∗
Corresponding author. Tel.: +61 2 98312120; fax: +61 2 98316903. E-mail address: [email protected] (G.G. Geary).
Increasing numbers of renal artery stenting procedures are now performed by interventional cardiologists driven by their considerable experience in coronary stenting. Previously, renal artery angioplasty with or without stenting was performed by interventional radiologists utilizing different techniques and equipment. In this article we describe our technique and initial results for renal artery stenting. These techniques are similar to those utilised for ostial stenting of a coronary artery or saphenous vein graft. We stress the use of low profile equipment, monorail approach and avoidance of intubating the lesion with the guide catheter.
Methods Patient Selection All of the patients referred for renal artery stenting had difficult to control hypertension. Some (28%) also had chronic renal impairment (serum creatinine > 130 mol/L) and one patient had recurrent pulmonary oedema. Aortograms and sometimes selective renal angiograms were
© 2004 Australasian Society of Cardiac and Thoracic Surgeons and the Cardiac Society of Australia and New Zealand. Published by Elsevier Inc. All rights reserved.
1443-9506/04/$30.00 doi:10.1016/j.hlc.2004.06.006
performed separately prior to the interventional procedure. Renal DTPA scans and review by a nephrologist were recommended for all patients. Other tests such as renal dopplers, renal ultrasounds or CT angiograms were left to the discretion of the referring doctor. Angiotensin converting enzyme inhibitors and angiotensin-2 antagonists were stopped 2 days prior to admission. Electrolytes and serum creatinine were checked on admission. All antihypertensive drugs were stopped on the day of renal stenting. Prehydration and N-acetylcysteine were given if the patient had renal impairment. All patients were on aspirin and clopidogrel prior to stenting. Informed consent was obtained from the patients.
Technical Aspects in the Catheter Laboratory All renal artery stenting was attempted from the femoral artery approach. Initially 8F sheaths and guides were used but more recently 7F systems have been employed as the stents have become lower profile. The use of a long sheath (Brite-tip, Cordis) is particularly useful for tortuous iliac anatomy or extensive distal aortic atheroma to facilitate catheter manipulation and minimise dislodgement of atheromatous material. Contrast injections through these long sheaths can also be used initially to locate and landmark the renal arteries. It is important to use non-ionic contrast and minimise the amount of contrast, particularly in patients with renal insufficiency. GUIDING CATHETERS. We use short 50 cm 7F guiding catheters (Veripath, Guidant) which come in varying shapes. These include a renal double curve, hockey stick and LIMA designs. The LIMA guide is usually best for right renal artery engagement and for left renal artery engagement if there is an inferiorly directed takeoff. Renal artery stenosis is usually ostial or very proximal in the vessel. Care needs to taken to avoid catheters diving into the artery and wedging in the lesion. An assistant is very useful for controlling the guide while the other operator advances the wire. The advantage of using a long sheath is that it can be moved over the guide catheter to alter the shape of the guide tip and minimise the risk of deep engagement (particularly with the LIMA guides). SELECTIVE ANGIOGRAPHY. Baseline angiography is done in the AP view in both wide angle (to see the intrarenal arteries) and magnified views of the lesion. The lesions are often eccentric. Cranial or caudal views are often useful to better estimate the severity of stenosis. The renal arteries run posteriorly and occasionally LAO or RAO angulation will profile the lesion better.
GUIDE WIRES. We use 0.014 wires for all cases. Ironcore or Spartacore wires (Guidant) were used for the majority of the cases and were particularly useful since they have soft 3–4 cm tips and are very steerable like coronary wires. However, the shaft is stiff proximal to the short soft tip segment. This is important since this stiff section allows the relatively high profile renal stents (compared to coronary stents) to track through what is essentially a right angle from the guide into the renal artery. The wires come in 130, 190, and 300 cm lengths.
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PRE-DILATATION. We routinely pre-dilate the stenosis to ensure that the relatively high profile renal stents will pass through the stenosis easily. Coronary monorail balloon catheters were used for pre-dilatation rather than higher profile peripheral angioplasty balloons. They can be passed over the short length wire. A slightly undersized balloon is chosen for the pre-dilatation to minimise the chance of dissection.
We have mainly used renal stents which are loaded on short (80 cm) monorail catheter systems. The lowest profile renal stents currently available are the Herculink Plus (Guidant) and Corinthian IQ (Cordis). The Palmaz-Genesis stent (Cordis) is a new low profile stent currently available in over-the-wire form only but will be available in monorail in the future. The Bridge X3 (Medtronic) is an alternative but is also available in an over-the-wire system only. We have also deployed coronary stents in smaller ≤5 mm diameter renal arteries. With ostial lesions it is important to deploy the stent with the proximal segment protruding 1–2 mm inside the aorta. This ensures the lesion is covered by the stent. The stent has a tendency to move slightly forward into the renal artery when being deployed so caution must be exercised to ensure that the proximal end of the stent remains just inside the aorta.
STENT DEPLOYMENT.
PRESSURE MEASUREMENT. We are currently studying the usefulness of measuring the mean pressure gradient across the renal artery stenosis. This is best done using over-thewire balloon and stent systems. The long exchange length wire is advanced across the stenosis and an over-the-wire coronary angioplasty balloon catheter advanced over the wire to a point distal to the stenosis. The wire is removed and simultaneous pressure measurements are then made between the guide and balloon catheter. The systolic pressure in the small lumen of the coronary balloon catheters tends to be damped and the diastolic pressure is higher than that obtained with a larger lumen catheter but the mean pressure will be accurate. Following stent deployment simultaneous pressures are again measured. An alternate system is to use a pressure wire (Radi, Medtronic) which gives excellent pressure traces but is a relatively soft wire and not ideal for stent placement. It usually needs to be exchanged for a regular guide wire prior to intervention.
Post-Procedure Blood pressures were monitored carefully and antihypertensive drugs reinstituted at the discretion of the patient’s cardiologist or nephrologist. Renal function was checked prior to discharge usually one or two days poststenting. Patients were discharged on clopidogrel 75 mg daily for 1 month and long-term aspirin. Arrangements were made for early follow up of renal function and review of blood pressure and anti-hypertensive medications.
Statistical Analysis Data are summarised using either means and standard deviation for normally distributed variables or median
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Heart Lung and Circulation 2004;13:274–279
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Geary et al. Renal artery stenting for renal artery stenosis
and interquartile range (IQR) for slewed distributions. The Pearson correlation coefficient (r) was used to quantify the degree of association between continuous variables.
Results From October 1999 to December 2002, a total of 35 procedures were attempted on 32 patients. There were 14 males and 18 females. Ages ranged from 19 to 79. There was one failure. Another patient had bilateral stenting done as separate procedures. One patient failed an initial femoral approach and was done later from the left brachial artery. The stenoses were considered to be atherosclerotic in 31 patients and due to fibromuscular dysplasia in one patient. All patients had hypertension. Nine had chronic renal impairment (serum creatinine > 130 mol/L). One had recurrent pulmonary oedema.
Comorbidities In the 31 patients with atherosclerotic renal disease comorbidities included significant coronary artery disease in 21 (68%), peripheral vascular disease in 13 (42%), cerebrovascular disease in 10 (32%) and diabetes in eight (26%).
Procedural Success Thirty-four of the 35 patient procedures were ultimately successful (97%). There was one failure due to inability to cross a renal artery stenosis with a wire. This patient had five renal arteries, of which four had significant stenoses, and we were not able to cross the most severe stenosis in a small artery. There was one other initial procedural failure via a femoral artery approach in a patient with an inferiorly directed left renal artery take-off with a very eccentric proximal stenosis. This patient was later successfully stented via a left brachial artery approach. Stents were deployed in all patients with atheromatous disease as the cause of their stenosis. Balloon angioplasty
Heart Lung and Circulation 2004;13:274–279
only was performed in the one young patient (19 years) with fibromuscular dysplasia. Usually only one stent was deployed in each renal artery but three patients had two stents deployed per artery. Three patients required bilateral renal artery stenting. Six coronary stents were deployed in relatively small renal arteries of 4–5 mm diameter and one 2.5 mm stent was used through the side holes of another stent in a side branch of a bifurcation lesion. Fig. 1 shows an example of a severe left renal artery stenosis pre- and post-stenting.
Procedural and Peri-Procedural Complications There were no procedural complications. One patient developed back pain 2 days after stenting of uncertain aetiology despite extensive investigations. Two patients represented a week after discharge, one with anaemia due to bleeding from a previously unrecognised gastric ulcer and another patient with a urinary infection, dehydration and a rise in serum creatinine to 200 mol/L compared to 104 mol/L immediately post-procedure. This returned to baseline after treatment of infection and rehydration.
Severity of Stenosis The angiographic diameter stenosis pre-procedure ranged from 60 to 95%. The angiographic severity was reduced from a mean of 79 ± 11% prior to procedure to 1 ± 3% post-procedure. The mean translesional gradient was measured in 25/34 procedures. The mean translesional gradient was reduced from 22 ± 23 mmHg to 1 ± 2 mmHg post-procedure. Fig. 2 shows an example of pressure recordings pre- and post-procedure
Correlation Between Angiographic Severity of Stenoses and the Mean Pressure Gradients Fig. 3 shows the relationship between the angiographic severity of stenosis and the mean pressure gradient in
Figure 1. (A) Selective left renal angiogram showing a severe ostial stenosis (arrow). (B) Post-stent deployment.
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Figure 2. Translesional pressure gradients pre (A) and post (B) stent deployment showing an initial 20 mmHg mean pressure gradient which is abolished after stent deployment.
the 25 procedures where both were measured. There is a tendency for the pressure gradient to be higher with increasing severity of stenosis but the correlation is poor (r = 0.56).
DTPA Scans Scans were obtained in 31 of the 32 patients prior to their procedures. The scans suggested functionally significant renal artery stenosis in 13 patients (42%). Two further scans were equivocal and at least raised the suspicion of RAS. Combining these with the positive scans, 48% of the scans suggested possible significant renal artery stenosis. Sixteen scans showed no evidence of functionally significant stenosis. Captopril challenge at the time of the DTPA scans was done in six of the 31 patients. Three scans were positive, one equivocal and two negative. Twenty-four patients had both DTPA scans performed and mean pressure gradients recorded. There were wide variations in the pressure gradients. Where the scans were suggestive of functionally significant RAS the median pressure gradient was 18 mmHg (IQR 10, 22). With a negative scan the median pressure gradient was 10 mmHg (IQR 6, 42). These differences are not statistically difference (P = 0.4).
Anti-Hypertensive Drugs
Figure 3. Relationship between angiographic severity of renal artery stenosis and the mean translesional pressure gradient.
Thirty patients with atherosclerotic RAS had successful procedures. All patients were discharged on less antihypertensive medications including 12 patients (40%) who were discharged on no drugs. The mean number of antihypertensive drugs prior to procedure was 3.0 ± 0.9 and 0.7 ± 0.7 at discharge. There was a median decrease of two drugs. The one patient with RAS due to fibromuscular dysplasia was on two drugs prior to angioplasty and none on discharge.
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Renal Function Mean serum creatinine prior to procedure was 113 ± 41 mol/L (range 56–220) and 108 ± 41 mol/L at discharge (ns).
Discussion In recent years physicians and cardiologists have adopted a lower threshold for investigating patients to exclude significant RAS. These patients usually have difficult to control hypertension and sometimes renal impairment. Overall, there are increasing numbers of patients requiring renal artery intervention. In many centres this is done by interventional cardiologists. Screening for RAS at the time of coronary angiography has become more common and detects significant angiographic RAS in 6–15% of cases.1–3 Renal artery stenosis has a strong association with other vascular disease.4 We recently showed that significant RAS (angiographic stenosis > 50%) occurs in 13% of patients with coronary artery disease compared to only 1% if no significant coronary disease.2 Hence, patients with hypertension or renal insufficiency who have significant coronary disease should be considered for screening for RAS particularly if other vascular risk factors are present. We do not advocate routine “drive by renal angiography” for all patients having coronary angiography. Renal angiography should be regarded as the gold standard for detection of significant RAS. Renal DTPA scans are often used as a screening test but have low sensitivity for the detection of functionally significant RAS and should not be relied on.5 Our experience confirms this conclusion. Use of captopril challenge at the time of the DTPA scan has been reported to increase sensitivity. A review of nine studies6 indicated that the sensitivity averaged 84% with a range of 71–94% An improvement in diagnostic accuracy has also been questioned.7 Nonetheless, referring physicians, cardiologists and nephrologists are reluctant to stop ACE inhibitors or angiotensin-2 antagonists prior to the DTPA scan. Captopril scans were ordered in only six out of 31 scans (19%) in our series. Other possible screening tests include CT angiography and magnetic resonance angiography. These techniques are improving and will probably be used more in the future. Balloon angioplasty alone for RAS has proven disappointing.8–10 This appears due to suboptimal initial results at the time of angioplasty and subsequent high restenosis rates. Routine stenting gives better initial results and lower restenosis rates.11,12 This has translated to improved long-term clinical results with better blood pressure control and stabilisation of renal function.13,14 However, there are no randomised trials directly comparing renal artery stenting with medical therapy. Our early results are encouraging but long-term follow up will be required to confirm the clinical benefit. Indications for renal artery stenting remain controversial particularly because of the lack of evidence to prove stenting is better than medical therapy. Despite this, it would seem reasonable to advise renal artery stenting for
Heart Lung and Circulation 2004;13:274–279
failure of medical therapy in patients with significant unilateral or bilateral RAS who have difficult to control hypertension (particularly if short duration), deteriorating renal function (especially if made worse with ACE inhibitors) and flash pulmonary oedema. Our technique for renal artery stenting is relatively straightforward and uses equipment familiar to interventional cardiologists. Radiologists have traditionally used an over-the-wire approach with neuroradiological type guiding catheters, large 0.035 wires, peripheral balloons and often intubate the artery past the lesion with the guide. In contrast, our technique can be an entirely monorail approach if desired. We use guides which are shorter than used for coronary angiography but otherwise have similar shapes. The wires are almost identical to coronary wires and have the same feel and torque control. Predilatation with low profile coronary balloons is useful. Renal stents are bulkier than coronary stents but are becoming lower profile and can be deployed through 7F guide catheters and over 0.014 wires. Coronary stents are another option for smaller renal arteries. There is some concern about whether they are rigid enough to prevent deformity at the aorto-ostial origin. We have not seen any problem in this regard so far but more information is required. The poor correlation between angiographic severity of stenosis and the pressure gradient is intriguing. Another study demonstrated that the pressure gradients also varied widely in lesions with 20–70% stenoses.15 The reasons for this are uncertain and require further investigation. Cardiologists perform the majority of endovascular interventions because of the sheer prevalence of coronary artery disease compared to other vascular beds. The coronary environment is testing because of the technical demands of small, mobile vessels and the dire consequences of procedural complications. The extension of these skills and experience to other vascular beds is logical and should help develop improved techniques and outcomes. The early results of cardiological involvement in renal arterial stenting are encouraging. We would like to thank Karen Blyth for her assistance with the statistical analysis.
References 1. Harding M, Smith L, Himmelstein K, Harrison K, Phillips H, Schwab S, et al. Renal artery stenosis: prevalence and associated risk factors in patients undergoing routine cardiac catheterisation. J Am Soc Nephrol 1992;2:1608–16. 2. Geary G, Tanous D, Ross D. Incidence of renal artery stenosis in 2111 patients undergoing coronary angiography: a model of predictive risk of renal artery stenosis. J Am Coll Cardiol 2003;2(Suppl A):7A (abstract). 3. Crowley J, Santos R, Peter R, Puma J, Schwab S, Phillips H, et al. Progression of renal artery stenosis in patients undergoing cardiac catheterisation. Am Heart J 1998;136:913–8. 4. Choudhri A, Cleland J, Rowlands P, Tran T, McCarty M, Al-Kutoubi M, et al. Unsuspected renal artery stenosis in peripheral artery disease. Br Med J 1990;301:1197–8.
5. Canzanello VJ, Textor SC. Noninvasive diagnosis of renovascular disease. Mayo Clin Proc 1994;69:1172–81. 6. Prigent A. The diagnosis of renovascular hypertension: the role of captopril renal scintigraphy and related issues. Eur J Nucl Med 1993;20:625–44. 7. Jaarsveld B, Krijnen P, Derkx F, Oei Y, Postma C, Schalekamp M, et al. The place of renal scintigraphy in the diagnosis of renal artery stenosis. Fifteen years of clinical experience. Arch Intern Med 1997;157:1226–34. 8. Sos T, Pickering T, Sniderman K, Saddekni S, Case D, Silane M, et al. Percutaneous transluminal renal angioplasty in renovascular hypertension due to atheroma or fibromuscular dysplasia. N Engl J Med 1983;309:274–9. 9. Plouin P, Darne B, Chatellier G, Pannier I, Battaglia C, Raynaud A, et al. Restenosis after a first percutaneous transluminal renal angioplasty. Hypertension 1993;21:89–96. 10. Jaarsveld B, Krijnen P, Pieterman H, Frans H, Derkx M, Deinum J, et al. The effect of balloon angioplasty on hypertension in atherosclerotic renal-artery stenosis. N Engl J Med 2000;342:1007–14.
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11. Blum U, Krumme B, Flugel P, Gabelmann A, Lehnert T, Buitrago-Tellez M, et al. Treatment of ostial renal-artery stenosis with vascular endoprosthesis after unsuccessful balloon angioplasty. N Engl J Med 1997;336:459–65. 12. White C, Ramee S, Collins T, Jenkins S, Escobar A, Shaw D, et al. Renal artery stent placement: utility in lesions difficult to treat with balloon angioplasty. J Am Coll Cardiol 1997;30:1445–50. 13. Dorros G, Jaff M, Mathiak L, Dorros I, Lowe A, Murphy K, et al. Four year follow-up of Palmaz-Schatz stent revascularization as treatment for atherosclerotic renal artery stenosis. Circulation 1998;98:642–7. 14. Watson P, Hadjipetrou P, Cox S, Piemonte T, Eisenhauer A. Effect of renal artery stenting on renal function and size in patients with atherosclerotic renovascular disease. Circulation 2000;102:1671–7. 15. Lederman R, Chetcuti S, Grossman P, Esteban J, Luciano A, Werns W, et al. All stenoses are not equal: angiographic renal artery stenosis severity does not predict trans-lesional pressure gradient. J Am Coll Cardiol 2001;98(Suppl A):30 (abstract).
ORIGINAL ARTICLE
Heart Lung and Circulation 2004;13:274–279
Original Article
Renal Artery Stenting for Renal Artery Stenosis: Interventional Approach and Initial Clinical Results Grayson G. Geary, MBBS, FRACP∗ , David L. Ross, MBBS, FRACP and A. Robert Denniss, MD, FRACP Department of Cardiology, Westmead Hospital, Westmead, Sydney, Australia Available online 25 August 2004
Background. Significant renal artery stenosis is being increasingly diagnosed and interventional cardiologists are taking on the unfamiliar role of deploying renal stents. We describe our technique for renal artery stenting using techniques and equipment similar to that used in coronary stenting and present early results. Methods. Thirty-two patients with significant renal artery stenosis (diameter stenosis 60–95%) and difficult to control hypertension or renal impairment were referred for renal stenting. Renal DTPA scans were performed before intervention. All the procedures were attempted from the femoral artery approach using guides, low profile wires and balloon catheters similar to those used for coronary work. The lowest profile renal or coronary stents were deployed using a monorail technique. Results. Atherosclerosis was the cause of the renal artery stenosis in 31 patients. Stents were successfully deployed in 30 of these patients (97%). One patient required a second procedure from the brachial artery approach. An additional patient with fibromuscular dysplasia underwent angioplasty only. Angiographic diameter stenosis was reduced from a mean of 79 to 1%. Translesional mean pressure gradients were reduced from 22 to 1 mmHg. There were no major procedural or in-hospital complications. Anti-hypertensive drugs were reduced from a mean of 3 prior to stenting to 0.7 at discharge. Renal DTPA scans were a poor predictor of severity of stenosis. Renal DTPA scans suggested functionally significant renal artery stenosis in only 48% of patients but the clinical responses suggested that this was an underestimate. Conclusions. Stenting of renal arteries using coronary like techniques and equipment results in a high rate of procedural success and good early clinical outcomes. (Heart Lung and Circulation 2004;13:274–279) © 2004 Australasian Society of Cardiac and Thoracic Surgeons and the Cardiac Society of Australia and New Zealand. Published by Elsevier Inc. All rights reserved. Keywords. Renal artery stenting; Hypertension; Renal insufficiency
Introduction
R
enal artery stenosis (RAS) is a recognised cause of hypertension and chronic renal insufficiency. In recent years it has become apparent that RAS is more common than previously thought and increased numbers of patients are being considered for renal artery stenting. Renal angiography is the gold standard for detection of RAS. More patients with difficult to control hypertension are being investigated with angiography and found to have significant RAS. Unsuspected RAS is found in a significant percentage of patients with coronary artery disease1–3 and peripheral vascular disease.4 when screened by renal angiography. Serial angiography shows that RAS tends to be progressive.3 Some of these patients may benefit from renal artery stenting for treatment of difficult to control hypertension or to prevent deterioration of renal function.
∗
Corresponding author. Tel.: +61 2 98312120; fax: +61 2 98316903. E-mail address: [email protected] (G.G. Geary).
Increasing numbers of renal artery stenting procedures are now performed by interventional cardiologists driven by their considerable experience in coronary stenting. Previously, renal artery angioplasty with or without stenting was performed by interventional radiologists utilizing different techniques and equipment. In this article we describe our technique and initial results for renal artery stenting. These techniques are similar to those utilised for ostial stenting of a coronary artery or saphenous vein graft. We stress the use of low profile equipment, monorail approach and avoidance of intubating the lesion with the guide catheter.
Methods Patient Selection All of the patients referred for renal artery stenting had difficult to control hypertension. Some (28%) also had chronic renal impairment (serum creatinine > 130 mol/L) and one patient had recurrent pulmonary oedema. Aortograms and sometimes selective renal angiograms were
© 2004 Australasian Society of Cardiac and Thoracic Surgeons and the Cardiac Society of Australia and New Zealand. Published by Elsevier Inc. All rights reserved.
1443-9506/04/$30.00 doi:10.1016/j.hlc.2004.06.006
performed separately prior to the interventional procedure. Renal DTPA scans and review by a nephrologist were recommended for all patients. Other tests such as renal dopplers, renal ultrasounds or CT angiograms were left to the discretion of the referring doctor. Angiotensin converting enzyme inhibitors and angiotensin-2 antagonists were stopped 2 days prior to admission. Electrolytes and serum creatinine were checked on admission. All antihypertensive drugs were stopped on the day of renal stenting. Prehydration and N-acetylcysteine were given if the patient had renal impairment. All patients were on aspirin and clopidogrel prior to stenting. Informed consent was obtained from the patients.
Technical Aspects in the Catheter Laboratory All renal artery stenting was attempted from the femoral artery approach. Initially 8F sheaths and guides were used but more recently 7F systems have been employed as the stents have become lower profile. The use of a long sheath (Brite-tip, Cordis) is particularly useful for tortuous iliac anatomy or extensive distal aortic atheroma to facilitate catheter manipulation and minimise dislodgement of atheromatous material. Contrast injections through these long sheaths can also be used initially to locate and landmark the renal arteries. It is important to use non-ionic contrast and minimise the amount of contrast, particularly in patients with renal insufficiency. GUIDING CATHETERS. We use short 50 cm 7F guiding catheters (Veripath, Guidant) which come in varying shapes. These include a renal double curve, hockey stick and LIMA designs. The LIMA guide is usually best for right renal artery engagement and for left renal artery engagement if there is an inferiorly directed takeoff. Renal artery stenosis is usually ostial or very proximal in the vessel. Care needs to taken to avoid catheters diving into the artery and wedging in the lesion. An assistant is very useful for controlling the guide while the other operator advances the wire. The advantage of using a long sheath is that it can be moved over the guide catheter to alter the shape of the guide tip and minimise the risk of deep engagement (particularly with the LIMA guides). SELECTIVE ANGIOGRAPHY. Baseline angiography is done in the AP view in both wide angle (to see the intrarenal arteries) and magnified views of the lesion. The lesions are often eccentric. Cranial or caudal views are often useful to better estimate the severity of stenosis. The renal arteries run posteriorly and occasionally LAO or RAO angulation will profile the lesion better.
GUIDE WIRES. We use 0.014 wires for all cases. Ironcore or Spartacore wires (Guidant) were used for the majority of the cases and were particularly useful since they have soft 3–4 cm tips and are very steerable like coronary wires. However, the shaft is stiff proximal to the short soft tip segment. This is important since this stiff section allows the relatively high profile renal stents (compared to coronary stents) to track through what is essentially a right angle from the guide into the renal artery. The wires come in 130, 190, and 300 cm lengths.
Geary et al. Renal artery stenting for renal artery stenosis
275
PRE-DILATATION. We routinely pre-dilate the stenosis to ensure that the relatively high profile renal stents will pass through the stenosis easily. Coronary monorail balloon catheters were used for pre-dilatation rather than higher profile peripheral angioplasty balloons. They can be passed over the short length wire. A slightly undersized balloon is chosen for the pre-dilatation to minimise the chance of dissection.
We have mainly used renal stents which are loaded on short (80 cm) monorail catheter systems. The lowest profile renal stents currently available are the Herculink Plus (Guidant) and Corinthian IQ (Cordis). The Palmaz-Genesis stent (Cordis) is a new low profile stent currently available in over-the-wire form only but will be available in monorail in the future. The Bridge X3 (Medtronic) is an alternative but is also available in an over-the-wire system only. We have also deployed coronary stents in smaller ≤5 mm diameter renal arteries. With ostial lesions it is important to deploy the stent with the proximal segment protruding 1–2 mm inside the aorta. This ensures the lesion is covered by the stent. The stent has a tendency to move slightly forward into the renal artery when being deployed so caution must be exercised to ensure that the proximal end of the stent remains just inside the aorta.
STENT DEPLOYMENT.
PRESSURE MEASUREMENT. We are currently studying the usefulness of measuring the mean pressure gradient across the renal artery stenosis. This is best done using over-thewire balloon and stent systems. The long exchange length wire is advanced across the stenosis and an over-the-wire coronary angioplasty balloon catheter advanced over the wire to a point distal to the stenosis. The wire is removed and simultaneous pressure measurements are then made between the guide and balloon catheter. The systolic pressure in the small lumen of the coronary balloon catheters tends to be damped and the diastolic pressure is higher than that obtained with a larger lumen catheter but the mean pressure will be accurate. Following stent deployment simultaneous pressures are again measured. An alternate system is to use a pressure wire (Radi, Medtronic) which gives excellent pressure traces but is a relatively soft wire and not ideal for stent placement. It usually needs to be exchanged for a regular guide wire prior to intervention.
Post-Procedure Blood pressures were monitored carefully and antihypertensive drugs reinstituted at the discretion of the patient’s cardiologist or nephrologist. Renal function was checked prior to discharge usually one or two days poststenting. Patients were discharged on clopidogrel 75 mg daily for 1 month and long-term aspirin. Arrangements were made for early follow up of renal function and review of blood pressure and anti-hypertensive medications.
Statistical Analysis Data are summarised using either means and standard deviation for normally distributed variables or median
ORIGINAL ARTICLE
Heart Lung and Circulation 2004;13:274–279
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Geary et al. Renal artery stenting for renal artery stenosis
and interquartile range (IQR) for slewed distributions. The Pearson correlation coefficient (r) was used to quantify the degree of association between continuous variables.
Results From October 1999 to December 2002, a total of 35 procedures were attempted on 32 patients. There were 14 males and 18 females. Ages ranged from 19 to 79. There was one failure. Another patient had bilateral stenting done as separate procedures. One patient failed an initial femoral approach and was done later from the left brachial artery. The stenoses were considered to be atherosclerotic in 31 patients and due to fibromuscular dysplasia in one patient. All patients had hypertension. Nine had chronic renal impairment (serum creatinine > 130 mol/L). One had recurrent pulmonary oedema.
Comorbidities In the 31 patients with atherosclerotic renal disease comorbidities included significant coronary artery disease in 21 (68%), peripheral vascular disease in 13 (42%), cerebrovascular disease in 10 (32%) and diabetes in eight (26%).
Procedural Success Thirty-four of the 35 patient procedures were ultimately successful (97%). There was one failure due to inability to cross a renal artery stenosis with a wire. This patient had five renal arteries, of which four had significant stenoses, and we were not able to cross the most severe stenosis in a small artery. There was one other initial procedural failure via a femoral artery approach in a patient with an inferiorly directed left renal artery take-off with a very eccentric proximal stenosis. This patient was later successfully stented via a left brachial artery approach. Stents were deployed in all patients with atheromatous disease as the cause of their stenosis. Balloon angioplasty
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only was performed in the one young patient (19 years) with fibromuscular dysplasia. Usually only one stent was deployed in each renal artery but three patients had two stents deployed per artery. Three patients required bilateral renal artery stenting. Six coronary stents were deployed in relatively small renal arteries of 4–5 mm diameter and one 2.5 mm stent was used through the side holes of another stent in a side branch of a bifurcation lesion. Fig. 1 shows an example of a severe left renal artery stenosis pre- and post-stenting.
Procedural and Peri-Procedural Complications There were no procedural complications. One patient developed back pain 2 days after stenting of uncertain aetiology despite extensive investigations. Two patients represented a week after discharge, one with anaemia due to bleeding from a previously unrecognised gastric ulcer and another patient with a urinary infection, dehydration and a rise in serum creatinine to 200 mol/L compared to 104 mol/L immediately post-procedure. This returned to baseline after treatment of infection and rehydration.
Severity of Stenosis The angiographic diameter stenosis pre-procedure ranged from 60 to 95%. The angiographic severity was reduced from a mean of 79 ± 11% prior to procedure to 1 ± 3% post-procedure. The mean translesional gradient was measured in 25/34 procedures. The mean translesional gradient was reduced from 22 ± 23 mmHg to 1 ± 2 mmHg post-procedure. Fig. 2 shows an example of pressure recordings pre- and post-procedure
Correlation Between Angiographic Severity of Stenoses and the Mean Pressure Gradients Fig. 3 shows the relationship between the angiographic severity of stenosis and the mean pressure gradient in
Figure 1. (A) Selective left renal angiogram showing a severe ostial stenosis (arrow). (B) Post-stent deployment.
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Figure 2. Translesional pressure gradients pre (A) and post (B) stent deployment showing an initial 20 mmHg mean pressure gradient which is abolished after stent deployment.
the 25 procedures where both were measured. There is a tendency for the pressure gradient to be higher with increasing severity of stenosis but the correlation is poor (r = 0.56).
DTPA Scans Scans were obtained in 31 of the 32 patients prior to their procedures. The scans suggested functionally significant renal artery stenosis in 13 patients (42%). Two further scans were equivocal and at least raised the suspicion of RAS. Combining these with the positive scans, 48% of the scans suggested possible significant renal artery stenosis. Sixteen scans showed no evidence of functionally significant stenosis. Captopril challenge at the time of the DTPA scans was done in six of the 31 patients. Three scans were positive, one equivocal and two negative. Twenty-four patients had both DTPA scans performed and mean pressure gradients recorded. There were wide variations in the pressure gradients. Where the scans were suggestive of functionally significant RAS the median pressure gradient was 18 mmHg (IQR 10, 22). With a negative scan the median pressure gradient was 10 mmHg (IQR 6, 42). These differences are not statistically difference (P = 0.4).
Anti-Hypertensive Drugs
Figure 3. Relationship between angiographic severity of renal artery stenosis and the mean translesional pressure gradient.
Thirty patients with atherosclerotic RAS had successful procedures. All patients were discharged on less antihypertensive medications including 12 patients (40%) who were discharged on no drugs. The mean number of antihypertensive drugs prior to procedure was 3.0 ± 0.9 and 0.7 ± 0.7 at discharge. There was a median decrease of two drugs. The one patient with RAS due to fibromuscular dysplasia was on two drugs prior to angioplasty and none on discharge.
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Renal Function Mean serum creatinine prior to procedure was 113 ± 41 mol/L (range 56–220) and 108 ± 41 mol/L at discharge (ns).
Discussion In recent years physicians and cardiologists have adopted a lower threshold for investigating patients to exclude significant RAS. These patients usually have difficult to control hypertension and sometimes renal impairment. Overall, there are increasing numbers of patients requiring renal artery intervention. In many centres this is done by interventional cardiologists. Screening for RAS at the time of coronary angiography has become more common and detects significant angiographic RAS in 6–15% of cases.1–3 Renal artery stenosis has a strong association with other vascular disease.4 We recently showed that significant RAS (angiographic stenosis > 50%) occurs in 13% of patients with coronary artery disease compared to only 1% if no significant coronary disease.2 Hence, patients with hypertension or renal insufficiency who have significant coronary disease should be considered for screening for RAS particularly if other vascular risk factors are present. We do not advocate routine “drive by renal angiography” for all patients having coronary angiography. Renal angiography should be regarded as the gold standard for detection of significant RAS. Renal DTPA scans are often used as a screening test but have low sensitivity for the detection of functionally significant RAS and should not be relied on.5 Our experience confirms this conclusion. Use of captopril challenge at the time of the DTPA scan has been reported to increase sensitivity. A review of nine studies6 indicated that the sensitivity averaged 84% with a range of 71–94% An improvement in diagnostic accuracy has also been questioned.7 Nonetheless, referring physicians, cardiologists and nephrologists are reluctant to stop ACE inhibitors or angiotensin-2 antagonists prior to the DTPA scan. Captopril scans were ordered in only six out of 31 scans (19%) in our series. Other possible screening tests include CT angiography and magnetic resonance angiography. These techniques are improving and will probably be used more in the future. Balloon angioplasty alone for RAS has proven disappointing.8–10 This appears due to suboptimal initial results at the time of angioplasty and subsequent high restenosis rates. Routine stenting gives better initial results and lower restenosis rates.11,12 This has translated to improved long-term clinical results with better blood pressure control and stabilisation of renal function.13,14 However, there are no randomised trials directly comparing renal artery stenting with medical therapy. Our early results are encouraging but long-term follow up will be required to confirm the clinical benefit. Indications for renal artery stenting remain controversial particularly because of the lack of evidence to prove stenting is better than medical therapy. Despite this, it would seem reasonable to advise renal artery stenting for
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failure of medical therapy in patients with significant unilateral or bilateral RAS who have difficult to control hypertension (particularly if short duration), deteriorating renal function (especially if made worse with ACE inhibitors) and flash pulmonary oedema. Our technique for renal artery stenting is relatively straightforward and uses equipment familiar to interventional cardiologists. Radiologists have traditionally used an over-the-wire approach with neuroradiological type guiding catheters, large 0.035 wires, peripheral balloons and often intubate the artery past the lesion with the guide. In contrast, our technique can be an entirely monorail approach if desired. We use guides which are shorter than used for coronary angiography but otherwise have similar shapes. The wires are almost identical to coronary wires and have the same feel and torque control. Predilatation with low profile coronary balloons is useful. Renal stents are bulkier than coronary stents but are becoming lower profile and can be deployed through 7F guide catheters and over 0.014 wires. Coronary stents are another option for smaller renal arteries. There is some concern about whether they are rigid enough to prevent deformity at the aorto-ostial origin. We have not seen any problem in this regard so far but more information is required. The poor correlation between angiographic severity of stenosis and the pressure gradient is intriguing. Another study demonstrated that the pressure gradients also varied widely in lesions with 20–70% stenoses.15 The reasons for this are uncertain and require further investigation. Cardiologists perform the majority of endovascular interventions because of the sheer prevalence of coronary artery disease compared to other vascular beds. The coronary environment is testing because of the technical demands of small, mobile vessels and the dire consequences of procedural complications. The extension of these skills and experience to other vascular beds is logical and should help develop improved techniques and outcomes. The early results of cardiological involvement in renal arterial stenting are encouraging. We would like to thank Karen Blyth for her assistance with the statistical analysis.
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