Placement of balloon-expandable intraluminal stents in iliac arteries: first 171 procedures

Impact of different hemodynamic criteria for stent placement after suboptimal iliac angioplasty. Dutch Iliac Stent Trial Study Group

PURPOSE

To investigate the consequences of different hemodynamic criteria as indications for stent placement after suboptimal iliac angioplasty.

MATERIALS AND METHODS

One hundred thirty-six patients with intermittent claudication, on the basis of atherosclerotic disease of the iliac artery, underwent angioplasty. Intraarterial systolic and mean pressures were simultaneously recorded above and below the lesion, with and without vasodilation, and before and after percutaneous angioplasty. These data were used to estimate what proportion of the study population would be eligible for stent placement according to different criteria reported in the literature. Subsequently, the authors compared peak systolic velocity (PSV) ratios during follow-up in their patients, with and without indication for stent placement according to two different criteria.

RESULTS

Applying the different thresholds reported in the literature to the patient group shows that stent placement would be indicated in anywhere from 4% to 87% of cases. No difference was observed when PSV ratios were compared in patients with a residual mean pressure gradient of > or = 5 and < or = 10 mm Hg with patients with a residual mean pressure gradient of less than 5 mm Hg.

CONCLUSIONS

Application of the various published thresholds as indications for secondary stent placement leads to a wide range in proportion of cases requiring stent placement. Lesions with a residual mean pressure gradient of > 5 and < 10 mm Hg fare as well as lesions with a residual mean pressure gradient of less than 5 mm Hg. The optimal criterion is still not clear.

Quantitative digital angiography as an adjunct to the intraoperative placement of endovascular stents in congenital heart disease

Clearly identifiable intraoperative landmarks render the placement of intraoperative stents difficult. Preoperative use of quantitative digital angiography helps the surgeon accurately insert endovascular stents intraoperatively. By using defined points of reference, we were able to carefully select the size and lengths of stents before the operation and precisely place these stents in the operating room. Furthermore, we have been able to redilate these stents using the same techniques at subsequent operations. Our results reflect the efficacy of this technique.

Diagnosis and treatment of chronic lower extremity ischemia

Chronic lower extremity ischemia is due to progressive atherosclerosis of the aorto-iliac and/or infrainguinal arteries. This disease process is of great importance as millions of patients are affected by lower extremity arterial occlusive disease. Most of these patients are asymptomatic but a growing number of them are symptomatic, with complaints ranging from mild claudication to gangrene. The increasing number of patients affected by lower extremity atherosclerosis is, in part, due to the 'graying' of the general population and to the medical improvements of the past three decades that have allowed patients with generalized atherosclerosis to survive longer. Fortunately, the diagnosis and management of peripheral arterial occlusive disease has also significantly progressed leading to improved graft patency, limb salvage rates, and quality of life for patients.

Infection of endovascular stents: an uncommon but important complication

In this review article, four cases of peripheral endovascular stent infection (including a case presented in this issue of the journal) reported in the medical literature are reported. While the actual incidence of endovascular stent infection is probably low, when it occurs it can have serious consequences. This complication may result in the death of a patient, as seen in two of the case reports. The presentation of this complication, the site of stent deployment, the treatment given and the outcome in each of these cases are discussed. Stent infection should be recognized early to avoid the high morbidity and mortality of this complication.

Primary stenting for complex atherosclerotic plaques in aortic and iliac stenoses

PURPOSE

To evaluate the efficacy of primary stenting for complex atherosclerotic plaques in aortic and iliac stenoses that are not amenable to balloon angioplasty alone.

METHODS

Nineteen patients with complex atherosclerotic plaques were treated with a Palmaz stent (n = 19), Wallstent (n = 1), Strecker stent (n = 1), or Memotherm stent (n = 1). A total of 22 stenoses presenting with complex plaque morphology including ulcerated plaques, ulcerated plaques with focal aneurysms, plaques with heavy calcification, severely eccentric plaques, plaques with overhanging edge, and plaques with spontaneous dissection were stented. The lesions were in the aorta (n = 1), common iliac artery (n = 19), or external iliac artery (n = 2).

RESULTS

Immediate angiography after stent placement revealed restoration of patency of the stented segment. Focal aneurysms and ulcerated areas were occluded in the follow-up angiographies obtained 4-12 weeks after the procedure. In one case with poor distal runoff and multiple complex lesions of the iliac artery, subacute occlusion occurred. Clinical and angiographic follow-up (3-46 months) revealed patency of all other stented segments.

CONCLUSION

Primary stenting is an effective and reliable approach for complex plaques in stenoses. Patency of the arterial segment with a smooth lumen can be created without the risk of acute complications such as distal embolization, dissection, or occlusion.

Balloon angioplasty, stenting, and role of atherectomy

Endovascular interventions for the treatment of lower-extremity atherosclerotic disease have undergone a rapid course of development during the past 30 years. Balloon angioplasty is the most widely applied of these techniques and has been shown to yield excellent results, at least in the short and intermediate terms, in appropriately selected patients. The ideal candidate is one with a focal stenotic lesion of the iliac artery; this is also the type of patient in whom placement of an endoluminal stent, whether primarily or as an adjunct to balloon angioplasty, has been shown to be most effective. The initial enthusiasm for transluminal atherectomy of lower-extremity atherosclerotic lesions has met with some disappointing long-term results. It is now used mainly in conjunction with either or both of the above modalities in a select group of patients. Clearly, more controlled studies of all these techniques are needed to better define their exact indications and limitations in treatment of lower-extremity arterial disease.

Lower-extremity arterial endovascular stenting

Intraluminal arterial stenting for the management of arterial occlusive disease of the lower extremities has evolved over the years. Most stents are used to correct inadequacies of PTA or to correct a PTA complication. These include (1) restenosis within 90 days of PTA, (2) chronic iliac occlusion, (3) acute occlusions during PTA, (4) a significant residual gradient following PTA, (5) dissections longer than the angioplasty site, and (6) a 30% or greater residual stenosis after PTA. Both the Palmaz stent and the Wallstent have performed well in the iliac artery system. Their use in the femoropopliteal system has not been as successful and should be reserved for selected cases. Long-term anticoagulation is generally required for femoropopliteal stent patency. Placement in the lower superficial femoral or popliteal artery is best avoided. Re-angioplasty or additional stenting may be used to prolong patency, although with the risk of a second intervention. Progression of arteriosclerosis is a factor to consider when choosing an endoluminal treatment versus standard bypass.

Aortoiliac stent deployment versus surgical reconstruction: analysis of outcome and cost

PURPOSE

The purpose of this study is to compare complication rate, primary patency, and cost of stent deployment with direct surgical reconstruction for the treatment of severe aortoiliac occlusive disease.

METHODS

From March 1, 1992, to May 31, 1996, 119 patients receiving treatment for aortoiliac occlusive disease were analyzed after exclusions. Sixty-five patients had stent deployment and 54 patients had surgical reconstruction. Data were evaluated within and between the groups by univariate and multivariate logistic regression, life-table, t-test, and cross tabulation with chi2 analysis.

RESULTS

There was no significant difference between the groups with regard to demographic features or presenting symptoms (all p values > 0.07). Incidence of procedure-related complications was similar (p = 0.30). However, there were more systemic complications in the surgery group (15 versus 2; RR = 5.5, p < 0.01) and more vascular complications in the stent group (16 versus 3; RR = 12, p < 0.002). Incidence and type of late complications were not appreciably different (all p values > 0.05). Cumulative primary patency rate of bypass grafts was significantly better than stented iliac arteries at 18 months (93% versus 77%), 30 months (93% versus 68%) and 42 months (93% versus 68%); p = 0.002, log rank. Multivariate analysis identified female gender (RR = 4.6, p = 0.03), ipsilateral SFA occlusion (RR = 5.6, p = 0.01), procedure-related vascular complication (RR = 9.7, p = 0.002), and hypercholesterolemia (RR = 5.0, p = 0.02) as independent predictors of bypass graft or stent thrombosis. Mean total hospital cost per limb treated did not differ significantly between surgery and stent deployment groups ($9383 versus $8626, respectively; p = 0.66, t-test).

CONCLUSIONS

Treatment of severe aortoiliac occlusive disease by surgical reconstruction or stent deployment has a similar complication rate. Mean hospital cost per limb treated is essentially equal. However, cumulative primary patency rate of bypass grafts is superior to stents. Therefore, considering the elements of cost and patency, surgical revascularization has greater value. The benchmark for cost-effective treatment of severe aortoiliac occlusive disease is direct surgical reconstruction.

Intraoperative endovascular angioplasty and stenting of iliac artery: an adjunct to femoro-popliteal bypass

BACKGROUND

With the rapid development of endovascular techniques, the management strategy of patients with multilevel atherosclerotic arterial occlusive disease is also evolving. Iliac artery stenting is a means whereby multiple bypass operations can be avoided in such patients. The early results of preoperative iliac artery stenting seem promising but the role of intraoperative iliac artery angioplasty and stenting is less clear.

STUDY DESIGN

This study was undertaken to evaluate our early results of a combined endovascular and operative approach to patients with multilevel atherosclerotic arterial occlusive disease. Between June 1995 and March 1997, primary intraoperative iliac artery balloon angioplasty and stent placement were performed on 13 affected limbs of 12 patients undergoing an infrainguinal bypass operation. Indications for operation, patient demographics, and risk factors were noted. The outcome of surgery and the patency rates of bypass graft and stent were also recorded.

RESULTS

The initial technical success of primary iliac artery angioplasty and stenting was 93%. An improvement of the ankle-brachial index by a mean value of 0.38 was attained after operation (p < 0.001). Clinical success, based on the criteria suggested by the Society for Vascular Surgery/International Society for Cardiovascular Surgery, was achieved in all patients. There was no operative or hospital mortality. Postoperative morbidity rate was 8% (n = 1). The cumulative 1-year patency rates of iliac stent and infra-inguinal bypass grafts were 100% and 85%, respectively. The limb loss rate was 7%.

CONCLUSIONS

The technique of intraoperative angioplasty and stenting can be easily mastered by an experienced and skilled vascular surgeon, using a portable C-arm fluoroscopic unit, in the operation theater. A combined endovascular and operative approach optimizes the therapeutic option to this selected group of patients.

Use of balloon-expandable stents for coarctation of the aorta: initial results and intermediate-term follow-up

OBJECTIVES

In this study we report our preliminary results and intermediate-term follow-up (up to 3.5 years) of stent implantation for coarctation of the aorta (COA).

BACKGROUND

Balloon angioplasty has gained acceptance as a modality of treatment for COA. Some patients do not respond optimally to balloon angioplasty alone. Balloon-expandable stents have been used in pulmonary arteries and large systemic arteries such as the femoroiliac vessels, with a significant improvement in vessel patency and a reduction in the pressure gradient compared with balloon angioplasty alone.

METHODS

Nine patients (>10 years old) with COA in whom balloon dilation alone was thought to be ineffective underwent stent implantation. Seven patients had a previous operation or balloon dilation, or both, to relieve their coarctation but had a significant residual/recurrent gradient.

RESULTS

At the time of stent implantation, the systolic and mean gradients decreased from a mean (+/-SEM) of 37 +/- 7 and 14 +/- 3 mm Hg to 4 +/- 1 and 2 +/- 0.6 mm Hg, respectively (p < or = 0.002). The coarctation diameter increased from a mean of 9 +/- 1 to 15 +/- 1 mm (p < 0.002). The patients have been followed for up to 42 months (mean 18, median 13) with no complications; the stents remain in position with no fracture. One patient underwent further successful dilation 3 years after stent implantation because of an exercise-induced gradient. No other intervention has been required. The systolic gradient at latest follow-up is 7 +/- 2 mm Hg. Only two (a 44-year old with diabetes and a 50-year old with long-standing hypertension) of five patients previously requiring antihypertensive treatment still remain on medications for blood pressure control.

CONCLUSIONS

The use of stents in COA is a feasible alternative to surgical repair or balloon angioplasty in selected patients with an effective gradient reduction. Intermediate-term follow-up shows excellent gradient relief, with no complications in this group of patients.

Should balloon angioplasty and stents have any role in operative intervention for lower extremity ischemia?

Balloon angioplasty has been combined with open vascular surgery to treat lower extremity ischemia due to multilevel occlusive disease. The purposes of this study were: (1) to compare staged and simultaneous approaches to determine the optimal method for combining endovascular and open techniques and; (2) to assess the role of stents in intraoperative balloon angioplasty. Among 274 patients undergoing lower extremity revascularization over 30 months, 38 (13.9%) required a combination of endovascular and open techniques; 17 were staged (endovascular followed at an interval by distal open surgery) and 21 were simultaneous (intraoperative balloon angioplasty with or without stent placement at the time of open surgery). Groups were similar with respect to demographics, lesions treated with endovascular intervention, incidence and location of stent placement, and results of surgery. Additional operating time required for intraoperative endovascular intervention was 41.0 +/- 30.7 min., fluoroscopic time was 3.9 +/- 2.4 min. and contrast administered was 58.8 +/- 28.1 ml. There was no perioperative mortality. Length of stay was longer in the staged than in the simultaneous group (p < 0.01). Cumulative combined primary patency at 1 year by life-table methods was 82 +/- 10% in the staged group and 83 +/- 9% in the simultaneous group (p = 0.79). Mean follow-up was 13 +/- 6 months. There is a role for balloon angioplasty and stent placement in operative revascularization of ischemic limbs in selected patients: patency was similar to that produced with the staged approach while the length of stay was shorter. Intraoperative balloon angioplasty is safe and effective and stents permit a measure of control in assuring an optimal intraoperative postangioplasty result.

Infection of a chronically implanted iliac artery stent

Pseudoaneurysm formation and infection at the site of iliac artery stenting are uncommon complications that occur soon after stent placement. We describe a case in which an infected pseudoaneurysm developed 22 months following stent implantation. Stent infection, although rare, has potentially disastrous implications, as made evident by a review of the literature. Prophylactic antibiotic therapy at the time of stent placement is recommended.

Evaluation of the Palmaz stent in the trachea and mainstem bronchi of normal dogs

OBJECTIVE

This study evaluates the efficacy of the Palmaz balloon expandable intraluminal stent in the trachea and mainstem bronchi of normal dogs.

STUDY DESIGN

Effects of the stent were evaluated by physical examination, thoracic radiography, respiratory tract fluoroscopy and endoscopy, tracheal diameter measurement, postmortem examination, and airway histomorphometry.

ANIMALS OR SAMPLE POPULATION

Ten normal beagle dogs.

METHODS

Stent size was estimated from thoracic radiographs in awake dogs. Group I dogs (n = 4) had two stents placed: one in the thoracic trachea (TT) plus a randomly chosen mainstem bronchus (MB). Group II dogs (n = 3) had stents placed in the MB (one stent), TT (one stent), and mid- or proximal cervical trachea (CT) (one or two stents). Three dogs were used as sham-operated controls (group III). Temperature, pulse, respiration, and cough were measured twice daily. Dogs were evaluated at 21 and 49 to 56 days after stent placement, euthanatized, and tissues were collected for histomorphometric analysis of stent integration and epithelial pathology.

RESULTS

Mean tracheal diameters of awake (10.5 +/- 1.7 mm) and anesthetized dogs before stent implantation (13.9 +/- 2.0 mm) were significantly different (P < .01). Complications associated with stent placement included acute pulmonary edema (n = 2), stent migration (n = 7), stent collapse (n = 4 CT, 2 TT, and 1 MB), and positive tracheal culture (n = 10). Group II dogs coughed more at rest, exercise, and with tracheal palpation than dogs in other groups (P < .01). Group I dogs coughed more at rest than group III dogs (P < .01). Stent integration ranged from 0 to 91.3%. Squamous metaplasia and epithelial ulceration associated with stents ranged from 0 to 57.5% and 0 to 32.7%, respectively.

CONCLUSIONS

Determination of stent size should be based on measurements taken on anesthetized dogs because use of inappropriately sized stents may promote stent migration, squamous metaplasia, and/or ulceration. Epithelialization over stent struts may occur if the stent is closely associated with tracheal epithelium.

CLINICAL RELEVANCE

Palmaz stents do not appear to be appropriate for placement in the CT of dogs; however, with technical modifications, application in the TT and MB may be feasible.

Restenosis of endovascular stents from stent compression

OBJECTIVES

We sought to determine the basis for restenosis within superficial femoral arteries (SFAs) and hemodialysis conduits treated with balloon-expandable stents.

BACKGROUND

Use of stents within coronary and peripheral vessels continues to increase exponentially. The mechanism of restenosis within stents placed at various vascular sites is not well understood. In particular, the implications of deploying a balloon-expandable stent in a compressible site are not well understood.

METHODS

After the serendipitous detection of stent deformation during intravascular ultrasound (IVUS) examination of a restenosed dialysis fistula, we evaluated a consecutive series of patients with stents placed in compressible vascular sites, including the SFA (six patients) and hemodialysis fistulae (five patients). Clinical, angiographic and IVUS examinations were performed to evaluate mechanisms of restenosis.

RESULTS

Stent compression was identified as the principal cause of restenosis in all dialysis conduits and SFAs. Stent deformity was not reliably identified by angiography; however, IVUS identified compression of two forms: eccentric deformation, implicating two-point compressive force, and complete circumferential encroachment of stent struts around the catheter, suggesting multidirectional compressive force. Despite redilation, secondary restenosis resulting from recurrent compression recurred in most sites.

CONCLUSIONS

Restenosis within balloon-expandable endovascular stents may occur as a result of stent compression, a phenomenon readily detected by IVUS, but often not by angiography. These findings have significant implications for the use of balloon-expandable stents within vascular sites subject to extrinsic compression, such as hemodialysis conduits, the adductor canal segment of the SFA and carotid arteries.

The effect of endovascular aortic stents placed across the renal arteries

OBJECTIVES

To investigate renal artery patency and renal function after deployment of aortic stents covering the orifices of renal arteries.

DESIGN

Prospective open animal study.

SETTING

Department of Experimental Surgery at a university hospital.

MATERIALS

Twenty-three pigs were used.

METHODS

Ten pigs were observed for 1 h after graft-anchoring aortic stents, Gianturco (5) and Palmaz (5), were placed so that the stents covered the renal arterial orifices. In 13 pigs, Gianturco (6) and Palmaz (7) stents without grafts were placed over the renal arteries and left in situ for 7 days. Renal function and blood flow were measured by renograms, iohexol clearance and ultrasonic blood flow meter and patency was verified by angiograms. The kidneys were microscopically examined for signs of ischaemia and microemboli.

RESULTS

One renal artery covered by a graft-anchoring Gianturco stent occluded. The remaining renal arteries remained patent without any significant decrease in renal blood flow after stent deployment. Normal renal function and histology was maintained.

CONCLUSIONS

Aortic stents placed at the level of the renal arteries do not affect renal blood flow within 1 week in this experimental model. This may prove valuable in endovascular treatment of aortic aneurysms and in other procedures involving stents.

Percutaneous transluminal stent placement in the abdominal aorta

PURPOSE

To retrospectively review and to report the results of stent placement for focal mid-abdominal aortic stenoses.

MATERIALS AND METHODS

During a 4-year period, 10 focal mid-abdominal aortic stenoses were treated with stent placement in nine patients (six women and three men; mean age, 61 years; range, 49-73 years). All of the stenoses were atherosclerotic in nature except for one at the proximal anastomosis of an aortobi-femoral graft, which may have been from fibrointimal hyperplasia. Seven of the 10 stenoses were treated with primary stent placement, whereas three were treated with stent placement after suboptimal angioplasty.

RESULTS

The technical success rate was 100%. Clinical success, defined as complete elimination or improvement of symptoms present before stent placement, was achieved in eight of the nine patients with a mean duration of follow-up of 1.6 years (range, 0.2-3.0 years).

CONCLUSION

In view of the excellent technical and clinical success, the authors believe that stent placement should be considered as an adjective therapy to angioplasty or as a primary method of treatment in properly selected patients with focal mid-abdominal aortic stenoses.

Endovascular stenting in patients with Iliac compression syndrome. Experience in three cases

The authors report their experience in the percutaneous treatment of the iliac compression syndrome in three women (20-53 years old) with acute iliofemoral deep venous thrombosis; in one case, there was an additional thrombus in the inferior caval vein. They were treated by percutaneous implantation of Palmaz stents in the left common iliac vein 1 day after surgical thrombectomy and construction of an arterial venous fistula. All patients showed marked improvement, as determined from venograms obtained immediately after stent implantation. The arteriovenous fistulae were closed 3 months later. At 6 months follow-up, the median clinical and color-coded duplex ultrasound indicates that all stents are patent and all patients are free of symptoms.

Complications of iliac artery stent deployment

PURPOSE

This study was performed to determine the primary patency, foot salvage, and complication rates associated with iliac artery stent deployment.

METHODS

From March 1992 to May 1995, 147 iliac artery stents were deployed in 98 limbs of 72 patients for disabling claudication or limb-threatening ischemia. Procedure-related and late (> 30 days) complications, as well as adjunctive maneuvers required to correct a complication, were tabulated. Stented iliac artery cumulative primary patency and foot salvage rates were calculated with life-table analysis. Factors that impacted early complications, late complications, foot salvage rates, and stented iliac artery primary patency rates were identified with stepwise logistic regression analysis.

RESULTS

A procedure-related complication occurred in 19 (19.4%) limbs. Initial technical success, however, was achieved in all but three of 98 limbs (96.9%). Stented iliac artery cumulative primary patency rates were 87.6%, 61.9%, 55.3%, and foot salvage rates were 97.7%, 85.1%, 76.1%, at 12, 18, and 24 months, respectively. External iliac artery stent deployment, superficial femoral artery occlusion before treatment, and single-vessel tibial runoff before treatment negatively affected stented iliac artery cumulative primary patency rates. Stented iliac artery primary patency rates were not significantly affected by age, smoking, coronary artery disease, diabetes, hypercholesterolemia, hypertension, presenting symptom, early complication, number of stents deployed, type of stent deployed, or stent deployment for stenosis versus occlusion.

CONCLUSIONS

Limb-threatening and life-threatening complications can be associated with iliac artery stent deployment. Stented iliac artery primary patency rates are affected by distal atherosclerotic occlusive disease and the position of the deployed stent within the iliac system. Stent reconstruction of severe iliac artery occlusive disease is feasible but should be thoughtfully selected.

Does donor iliac artery percutaneous transluminal angioplasty or stent placement influence the results of femorofemoral bypass? Analysis of 70 consecutive cases with long-term follow-up

PURPOSE

Femorofemoral bypass procedures are being performed with increasing frequency in some patients with bilateral disease in whom the "donor" iliac artery undergoes percutaneous transluminal angioplasty or stent placement. This study was undertaken to critically examine the efficacy of this approach.

METHODS

The records of 70 consecutive patients who over a 14-year period underwent elective femorofemoral bypass procedures for chronic occlusive disease, including those who did (group I; n = 26) and did not (group II; n = 44) undergo donor iliac percutaneous transluminal angioplasty or stent placement, were reviewed.

RESULTS

No significant differences were found between group I and II patients with respect to age, gender, risk factors, surgical indications, preoperative ankle-arm indices, and the performance of associated procedures. One patient (1.4%) died of a myocardial infarction; no other major cardiopulmonary complications occurred. The postoperative change in the group I donor limb ankle-brachial index ranged from -0.18 to 0.11 (mean, 0.00), revealing no significant steal. The primary graft patency rates for group I and II patients 30 days after surgery were 92% and 98%, respectively, and at 1, 3, 5, and 7 years after surgery were 87% and 81%, 79% and 73%, 79% and 59%, and 66% and 59%.

CONCLUSIONS

Donor iliac artery percutaneous transluminal angioplasty or stent placement does not compromise the results of femorofemoral bypass procedures in patients with chronic iliac artery occlusive disease.

Implantation of balloon-expandable stents for coarctation of the aorta: implantation data and short-term results

We report the immediate results and the short-term follow-up in a group of selected patients with coarctation of the aorta who underwent endovascular stent implantation. Balloon-expandable stents were implanted in 6 patients (mean age 19.8 +/- 5.1 years) with coarctation of the aorta (4 recurrent and 2 native) who underwent a total of 7 procedures (6 implantation and 1 further expansion). The systolic peak pressure gradient was decreased from 36.7 +/- 16.9 to 13.3 +/- 23.2 mm Hg (P < 0.005). There was a 66% increase in the mean coarctation diameter from 9.3 +/- 1.7 to 15.6 +/- 3.1 mm (P = 0.001) with the ratio of the coarctation to descending aorta diameter, measured at the level of the diaphragm, increasing from 0.49 +/- 0.1 to 0.81 +/- 0.2 (P < 0.005). The dilatation was successful in expanding the stent to an acceptable diameter in 5 of 6 patients. One patient underwent successful further expansion of a stent implanted 22 months previously. There were no immediate complications during balloon expansion and stent implantation. One patient suffered a femoral arterial bleed requiring surgical repair. There was one unrelated death. All patients were hypertensive (systolic blood pressure > 140 mm Hg) prior to stent implantation. At mean follow-up of 8 months, 3 patients are normotensive. There was no recurrence of coarctation, aortic dissection, or aneurysm formation in the patients in whom stent implantation was successful. These findings indicate that balloon-expandable stent implantation for coarctation of the aorta in selected patients is a safe and effective alternative approach for relieving the obstruction with a low complication rate and no recoarctation at short-term follow-up.

Percutaneous treatment of acute iliac artery injury after intraaortic balloon counterpulsation

We report on a novel approach to correcting iliac artery occlusions caused by aortic counterpulsation. Two patients who had leg ischemia after retrieval of an intraaortic balloon pump underwent angiograms that showed occlusion of the right external iliac artery because of dissection (one case) or thrombosis (one case). Percutaneous self-expandable stents were implanted in the occluded vessels, and they fully restored normal iliac patency with no complications and satisfactory midterm follow-up results. We conclude that iliac artery occlusion induced by aortic counterpulsation can be safely treated by implanting self-expandable stents in cases of acute iatrogenic dissection.

Neointimal hyperplasia in low-profile Nitinol stents, Palmaz stents, and Wallstents: a comparative experimental study

PURPOSE

To compare neointima formation following insertion of low-profile Nitinol stents, Palmaz stents, and Wallstents.

METHODS

Nitinol stents, Palmaz stents, and Wallstents similar in size were transfemorally inserted into the iliac arteries of 12 sheep. Four stents per sheep were deployed; the position of the stents was varied so that each type of stent was placed in each position (right or left, proximal or distal) with equal frequency. Stent patency was followed by angiography. Six sheep were euthanized after 1 month, and the remaining six after 6 months. Iliac arteries were removed en bloc and prepared for histological examination. Neointimal and medial thickness were measured by light microscopy, and measurements were analyzed statistically.

RESULTS

Mean neointimal thickness both over (NO) and between (NB) the stent struts was greater in Wallstents (NO = 0.341 mm, NB = 0.368 mm) than in the Nitinol (NO = 0.260 mm, NB = 0.220 mm) and Palmaz stents (NO = 0.199 mm, NB = 0. 204 mm), but differences were not significant (p > 0.05). Medial atrophy in the area between the stent struts was greater in Wallstents compared with Nitinol and Palmaz stents (p < 0.007 and p < 0.02, respectively); in the area under the stent struts there was a significant difference only between Palmaz stents and Wallstents (p < 0.02).

CONCLUSION

Under defined experimental conditions, none of the three types of stent appears to be preferable to the others regarding neointima formation in the short- to mid-term follow-up period.

Successful exclusion of a large femoropopliteal aneurysm with a covered nitinol stent

A 70-year-old woman presented with a large femoro-popliteal aneurysm. A covered nitinol stent was implanted successfully and complete exclusion of the aneurysm was achieved. At follow-up 5 months later the stent was still patent and the patient was free of symptoms. However, moderate stenosis was seen at the proximal end of the stent.

Infected iliac pseudoaneurysm after uncomplicated percutaneous balloon angioplasty and (Palmaz) stent insertion: a case report and literature review

Percutaneous balloon angioplasty and endovascular stent placement are becoming common techniques intended to reduce the need for surgical bypass procedures that may be more expensive or have higher morbidity rates. Prophylactic antibiotics are not currently used before stent placement in most centers even when implanted via the femoral route. Infectious complications have been rare. In the case presented here an infected common iliac pseudoaneurysm occurred after percutaneous balloon angioplasty and stent placement. The literature is reviewed.

Multicenter trial of the wallstent in the iliac and femoral arteries

PURPOSE

To report the results of the FDA phase II, multicenter trial of the Wallstent in the iliac and femoral arteries.

PATIENTS AND METHODS

Two hundred twenty-five patients entered the trial. Stents were placed in the iliac system in 140 patients and in the femoral system in 90 (five patients required both iliac and femoral stents). Clinical patency was measured over 2 years by means of life-table analysis with use of clinical and hemodynamic data and the Rutherford scale. Angiographic patency was measured at 6 months.

RESULTS

In the iliac system the primary clinical patency was 81% at 1 year and was 71% at 2 years. The secondary clinical patency was 91% and 86%, respectively. The 6-month angiographic patency was 93%. In the femoral system the primary clinical patency was 61% at 1 year and 49% at 2 years. The secondary patency was 84% and 72%, respectively. The 6-month angiographic patency was 80%.

CONCLUSIONS

The results are similar to those with the Palmaz stent in the iliac system and with angioplasty alone in the iliac and femoral systems.

Long-term follow-up of the Palmaz stent for iliac occlusive disease

BACKGROUND

Thirty-eight limbs with iliac occlusive disease were treated with Palmaz stents from 1987 through 1991.

METHODS

Indications for stent utilization included dissection induced by percutaneous transluminal balloon angioplasty (PTA) (10), restenosis after PTA (nine), post-PTA residual stenosis (nine), multiple stenoses or occlusion (five), and unfavorable location (five).

RESULTS

The ankle/brachial pressure index increased from 0.53 +/- 0.27 to 0.8 +/- 0.26 after stent deployment. The intraluminal pressure gradient decreased from 31.9 +/- 16.3 to 0.9 +/- 2.2 mm Hg after stent deployment. Complications included pseudoaneurysm (one), arteriovenous fistula (one), iliac perforation (one), groin hematoma (two), and occlusion (two). Follow-up arteriogram showed stenosis proximal or distal (n = 4) or within the stents (n = 4). These were treated with PTA or stents. Two patients required an aortobifemoral graft. Nine patients have died. Life table analysis showed a 1-, 3-, and 5-year primary and secondary cumulative patency of 87% +/- 5.9%, 74% +/- 8.2%, and 63% +/- 10% and 91% +/- 5.1%, 91% +/- 5.6%, and 86% +/- 7.6%, respectively.

CONCLUSIONS

Palmaz stents, often required to salvage a PTA failure, appear to maintain overall patency at a high level. However, intimal hyperplasia and the progression of atherosclerotic disease may result in a need for additional procedures to obtain this favorable outcome.

Hydrophilic surface modification of metallic endoluminal stents

PURPOSE

Stainless steel endovascular stents are inherently thrombogenic so that thrombus accumulates on these devices, leading to acute vessel occlusion. A potential solution to this problem is stent surface modification with hydrophilic polymers, which might limit platelet adhesion and reactivity.

METHODS

N-vinylpyrrolidone (NVP) and potassium sulfopropyl acrylate (KSPA) hydrophilic monomers were gamma graft polymerized onto 1 cm2 stainless steel slabs and 4 mm Palmaz stainless steel stents. Surface characteristics of modified and plain stainless steel stents were then investigated with contact angle and x-ray photoelectron spectroscopy measurements, and in vitro and in vivo platelet reactivity was assessed as 111Indium platelet accumulation expressed as counts/min/cm2.

RESULTS

Surface modification of stainless steel slabs and stents with both NVP and KSPA hydrophilic polymers significantly reduced in vitro platelet adhesion (plain = 2249 +/- 723 counts/min/cm2, NVP = 428 +/- 156 counts/min/cm2, KSPA = 958 +/- 223 counts/min/cm2) and in vivo platelet accumulation after 1 hour of blood flow exposure (plain = 1407 +/- 796 counts/min/cm2, NVP = 426 +/- 175 counts/min/cm2, KSPA = 399 +/- 124 counts/min/cm2. In addition, platelet accumulation on modified stents indexed to plain stents was lowest in KSPA-modified stents (NVP = 79.3% +/- 31.7% of plain, KSPA = 51.2% +/- 36.2% of plain). Surface analysis confirmed surface grafting with both monomers, and SEM documented smoothing of the irregular surfaces of the stainless steel stents after grafting.

CONCLUSION

Hydrophilic polymer surface modification of stainless steel stents decreases initial stent surface platelet accumulation, which may decrease the risk of vessel thrombosis associated with the use of these devices.

Angioplasty and intravascular stents in peripheral vascular disease

Advances in the technique as well as the technology of percutaneous angioplasty over the past 30 years have allowed the percutaneous treatment of many vascular lesions that previously required operative management. PTA, and more recently intravascular stents, have been shown to be effective, safe, and, in some cases, more cost effective than surgical options. Although patients need to be appropriately selected to optimize the treatment plan in individual cases, it is clear that percutaneous treatment, either alone or in combination with surgical procedures, offers a significant advancement in patient care. The success in treating iliac disease is perhaps the most convincing, but evidence is rapidly building to support infrapopliteal procedures, and, as further advances are made in technology, the role of such procedures in distal vessels may be expanded to include more patients. These procedures need to be prospectively evaluated not only for their efficacy, long-term result, and safety, but also for their cost-effectiveness and cost relative to the proven surgical options.

Delayed rupture of aortic aneurysms following endovascular stent grafting

BACKGROUND

Deployment of transfemoral, endovascular stent grafts for treatment of abdominal aortic aneurysms is appealing for several reasons: avoidance of abdominal incision, lack of aortic cross-clamping, potential for regional anesthesia, and shortened hospital stay. Concerns remain, however, regarding the ability of these devices to completely exclude the aneurysm and prevent aneurysm rupture and the long-term integrity of the device. The availability of endografts and the likely development of percutaneous devices have also raised the delicate issue of personnel training for patient selection, endograft implantation, and postoperative follow-up.

PATIENTS AND METHODS

The cases of 2 patients are reported in which Dacron endovascular grafts, anchored proximally and distally by Palmaz stents, were deployed for treatment of infrarenal abdominal aortic aneurysms.

RESULTS

In a patient with and absent distal cuff, choosing this procedure represented a clear error in patient selection. The endograft failed to reach the aortic bifurcation and the aneurysm ruptured, with the death of the patient 4 months postimplantation. In a patient with anatomy suitable for endograft placement, a perigraft leak persisted at the distal anastomosis following device placement. The aneurysm ruptured 14 days postprocedure. Although the patient survived emergent aneurysm repair, he developed acute renal failure.

CONCLUSION

Careful preoperative assessment of aortic anatomy is crucial in selection of patients for transfemoral endovascular graft placement. Lack of a distal cuff of at least 1 cm precludes tube graft implantation. Patients with a perigraft leak are not protected by the endograft from aneurysm rupture. Vascular surgeons must be involved in the preoperative evaluation of these patients and are the only specialty group who can provide the prerequisite care in evaluation and management of postoperative complications.

Iliac artery stent placement with the Palmaz stent: follow-up study

PURPOSE

The long-term efficacy of iliac artery stent placement with the Palmaz stent was evaluated for treatment of limb ischemia.

PATIENTS AND METHODS

Iliac stent implantation for limb ischemia was performed on 108 limbs in 83 patients. Eighty patients (96.4%) were followed up clinically from 1 to 70 months (mean, 25.8 months), and 30 patients (37.5%) were followed up with angiography from 1 to 48 months (mean, 10.4 months). Patients were classified into six categories by using an ischemic ranking profile. Clinical success was defined as a minimum one-category improvement from preprocedure ranking.

RESULTS

The clinical success rate was 98.9% immediately after the procedure and 86.2% at 48 months. Long-term success was statistically more common in patients with higher preprocedure and lower postprocedure ischemic ranking, and in patients without diabetes. Arteriography demonstrated a primary patency rate of 87.5% at latest follow-up, with five occlusions (12.5%) and only two (5.0%) restenoses. Average stenosis was 17.8% at 6 months and 24.7% at 2 years. Stent restenosis was statistically more common with a higher postprocedure pressure gradient. The complication rate was 9.7%, and 30-day mortality was 1.2%.

CONCLUSION

Long-term clinical and angiographic follow-up demonstrates iliac artery stent placement with the Palmaz stent is safe and efficacious for treatment of limb ischemia.

Strecker stents in the femoropopliteal arteries: value of duplex ultrasonography in restenosis assessment

PURPOSE

Experience with Strecker stent implantation in the femoropopliteal arteries has been described; however, few of the reports were prospective studies, and none routinely used site-specific assessment methods for follow-up evaluation of stent patency. The purpose of this study was to evaluate 1-year Strecker stent patency using duplex ultrasound imaging to obtain a more precise delineation of stent restenosis than is possible with other noninvasive assessment modalities.

METHODS

A prospective study involved 52 patients with 57 sites treated by angioplasty and Strecker stent deployment in the femoropopliteal arteries. Assessment included clinical evaluation; ankle-brachial index (ABI) measurements at rest and after exercise; and duplex ultrasound imaging preprocedurally and at 3 and 12 months after the intervention.

RESULTS

All 74 stents were deployed successfully in the 35 occluded arteries and 22 stenotic lesions. Acute reocclusion occurred in 6 (10%). At 3 months, primary patency was 81% and secondary patency 84%. Mean ( +/- SD) ABIs increased from 0.64 +/- 0.15 at rest and 0.32 +/- 0.17 after exercise to 0.89 +/- 0.14 and 0.68 +/- 0.23, respectively (p < 0.0001). At 12 months, primary patency was 79%, and secondary patency was 82%. Mean ABIs were 0.82 +/- 0.15 at rest and 0.52 +/- 0.22 after exercise at 12 months (p < 0.0002 compared with preprocedural ABIs). Analysis of the length of lesion treated showed betted results with shorter diseased segments, but this was not statistically significant (p > 0.05). Better outcomes were also obtained when one stent was used rather than two stents at 12 months (p = 0.15), but there was no difference at 3 months (p = 0.3). Thirty-four percent of the stented segments progressed from < 20% stenosis at 3 months to > 50% stenosis at 12 months. Overall, 19 (43%) of 44 segments progressed from < 50% stenosis at 3 months to a > 50% stenosis at 12 months. Restenosis seen at 3 months generally was in the native artery just proximal or distal to the stent, but at 12 months, restenosis was mainly inside the stent.

CONCLUSIONS

Strecker stents at 1-year demonstrated satisfactory patency in the femoropopliteal arteries when deployed for angioplasty salvage or recurrent disease. The 3- and 12-month evaluations obtained with duplex ultrasound provided site-specific hemodynamic data for stent assessment. Resting ankle pressures were a poor index of restenosis.

Reaction of the aortic wall to six metallic stent materials

RATIONALE AND OBJECTIVES

We investigated the effects of various metallic stents on the aortic wall.

METHODS

The wires of Gianturco-type expandable metallic stents were plated with gold, silver, or copper or coated with Teflon or silicone. Stents were inserted into the aortas of 15 adult mongrel dogs. The time course of radiologic, macroscopic, and histologic changes in the aorta at the site of the stent was investigated at 1, 2, and 4 weeks after implantation.

RESULTS

The gold-plated stent appeared to produce fewer macroscopic and histopathologic changes in the aorta than the other types of stents. The neointima was thinnest with gold (83.9 +/- 40.3 microns), followed by stainless steel (103.6 +/- 57.0 microns), Teflon (115.0 +/- 30.2 microns), silicone (209.6 +/- 25.9 microns), silver (228.6 +/- 33.8 microns), and copper (unmeasurable). With the copper-plated stent, the aorta suffered severe erosion of the vessel wall, marked thrombus formation, and aortic rupture.

CONCLUSION

Gold is a useful intravascular material because it reacts only minimally with the vessel wall.

The use of expandable metal stents in transplant renal artery stenosis

The management of resistant transplant renal artery stenosis (TRAS) poses difficult problems. There is no consensus on the most appropriate course of action if severe stenosis recurs despite repeated percutaneous transluminal balloon angioplasty (PTA). Expandable metallic vascular stents have been increasingly successful as an adjunct to PTA in the coronary and peripheral circulation and more recently in the management of resistant native renal artery stenosis. We report four cases in which such stents were successfully used to treat resistant stenosis in transplant renal arteries. The cases illustrate the range of problems that may be caused by TRAS, from resistant hypertension to impending graft failure. The stents were successfully deployed in all four patients. One patient had an acute stent thrombosis successfully treated with immediate thrombolysis and two patients required repeat stenting. In all the cases there was arrest or slowing of previously aggressive recurrent TRAS and at the close of follow-up (4-24 months) all patients had adequate stable allograft function, and satisfactory blood pressure control including the one patient with a significant residual stenosis.

Angioplasty with stent placement in peripheral arterial occlusive disease

Percutaneous transluminal balloon angioplasty (PTBA) is a minimally invasive and effective adjunct treatment for patients with atherosclerotic peripheral vascular disease. This surgical technique involves placing an intraarterial balloon within an obstructing arterial lesion and forcibly dilating the balloon under fluoroscopy. The PTBA technique has become an accepted interventional therapy for iliac artery stenoses. In selected patients with stenotic lesions of the iliac artery, percutaneous transluminal angioplasty (PTA) with the use of an intravascular stent may be an alternative to traditional aortofemoral bypass surgery. The PTA procedure involves only a needle entry site in one or both groins as opposed to an incision exposing the entire abdomen. The hospital stay for the average patient undergoing PTA of the iliac artery is three days as opposed to seven days for the patient undergoing aortofemoral bypass, and the patient may return to normal activity in a much shorter period of time after a PTA procedure.

Use of a balloon-expandable intravascular graft in the management of type B aortic dissection in an animal model

PURPOSE

To evaluate obliteration of an experimental aortic dissection with a balloon-expandable intravascular stent.

MATERIALS AND METHODS

Fourteen adult dogs were divided into two groups. In group 1 (n = 6), a thoracoabdominal aortic dissection was surgically created to observe the natural course of this lesion. In group 2 (n = 8), a balloon-expandable intraluminal vascular graft was introduced via the femoral artery in a dissected aorta to try to obliterate the dissection. Angiography was performed postoperatively and again 6 weeks later before the aortae were explanted for pathologic evaluation.

RESULTS

In group 1, postoperative aortography depicted evidence of aortic dissection in all animals. Autopsy revealed persisting dissection with reentry tear near the celiac axis in five animals. In group 2, placement of a stent at only entry and reentry sites resulted in partial obliteration of the dissection (n = 3). When the entire length of dissected aorta was treated, the dissection was completely obliterated (n = 4).

CONCLUSION

An aortic dissection can be obliterated with a balloon-expandable stent if the entire dissected aorta is treated.

Classical and endovascular surgery: indications and outcomes

For more than 40 years, endarterectomy and bypass grafting have been the primary means of surgically revascularizing peripheral vessels threatened by atherosclerotic disease. However, with today's endovascular technology, stenoses and occlusions in nearly every circulatory system can be approached intraluminally with a wide variety of techniques: thrombolysis, laser angioplasty, atherectomy, balloon dilation, and intravascular stents. Just as exciting is the newer technique of endoluminal grafting, which has extended percutaneous therapy to aneurysmal disease in the thoracic and abdominal aorta and distal arteries, as well as to long-segment occlusive disease. Today's vascular surgeon is in a unique position to combine his or her classical surgical training with these catheter-based interventions. Certainly, the potential advantages of percutaneous therapy as compared to surgical reconstruction are significant: no general anesthesia or lengthy incisions, shorter hospitalization, lower morbidity and mortality, earlier intervention in the course of the disease, and less complicated reapplication in the event of disease recurrence. Undoubtedly, endovascular techniques will become a major component of the vascular surgeon's armamentarium, and as we approach the year 2000, they will be the treatment of choice in nearly every vascular pathology and circulatory system.

Initial experience with the Cragg Endopro System 1 for intraluminal treatment of peripheral vascular disease

PURPOSE

To evaluate the safety and efficacy of a new covered stent, the Cragg Endopro System 1, for intraluminal treatment of peripheral vascular disease in the iliac and femoropopliteal arteries.

METHODS

Forty symptomatic patients with predominantly lengthy stenotic (24) or occlusive (13) lesions or aneurysms (3) in the iliac (19), femoral (19), or popliteal (2) arteries were treated percutaneously with balloon angioplasty followed by implantation of the self-expanding nitinol Cragg stent covered by a woven polyester fabric coated with low-molecular-weight heparin. The mean length of femoropopliteal lesions was 13.0 +/- 1.8 cm, as compared to 6.7 +/- 0.8 cm (p < 0.01) for iliac lesions. Mean percent stenosis was 89% +/- 2% with no significant difference between the arterial segments.

RESULTS

With a total of 52 covered stents implanted, technical success was achieved in 98% (39/40 patients). One tortuous femoral artery aneurysm was not satisfactorily excluded to prevent leakage. Clinical success was seen in all patients with demonstrable improvements in the claudication stage and the ankle-brachial index from a mean 0.54 to 0.92. Three local complications (one hematoma, two false aneurysms) required surgical repair. One distal embolism, one acute thrombosis, and three subacute thromboses were encountered and successfully treated by thrombolysis and/or surgery. One patient with two iliac stents developed contralateral common iliac artery occlusion from a stent partially obstructing the aorta; placement of a covered stent in the blocked artery re-established normal flow. Over an 8-month follow-up with arteriographic re-examination, all iliac stents remained patent. At the femoropopliteal level, two stents were occluded at 4 months; one was successfully dilated, but the other required surgical bypass grafting. A third patient developed a stenotic lesion proximal to the stent; dilation restored adequate inflow to the stent.

CONCLUSIONS

The Cragg Endopro System 1 appears to be effective as an "internal bypass" for iliac and femoropopliteal occlusive disease. More complications and restenosis were seen in femoropopliteal implantations; however, a change in postoperative medication may improve these results. Long-term results will determine if the Cragg Endopro System 1 can achieve a patency equal to conventional bypass grafting.

Transfemoral endovascular stented graft treatment of aorto-iliac and femoropopliteal occlusive disease for limb salvage

BACKGROUND

Endovascular stented grafts employ a new technique that blends intravascular stent and prosthetic graft technologies. These devices may be used to treat arterial aneurysms, occlusive disease, and vascular injuries. This report describes the application of stented grafts to the treatment of limb-threatening ischemia secondary to occlusive disease of the aorta, iliac, and femoral arteries.

METHODS

Three patients with limb-threatening ischemia and severe comorbid medical illnesses were treated with transvascular stented grafts that were composed of 6-mm thin-walled polytetrafluoroethylene grafts and Palmaz balloon expandable stents. The grafts were inserted through a cutdown in an artery remote from the site of occlusion and introduced into the vascular system within 14-Fr introducer sheaths.

RESULTS

Technical success was documented in all three patients with restoration of arterial continuity following stent graft deployment. Patency and limb salvage has been achieved to 1 year. One patient required further dilatation of the proximal stent at 6 weeks. Complications were limited to an iliofemoral deep vein thrombosis in one patient.

CONCLUSIONS

Endovascular stented grafts can be inserted to treat limb-threatening ischemia. Although these initial results are encouraging, greater experience in more patients observed for longer periods of time is necessary before this technique can be advocated for widespread use.

Deposition of platelets and neutrophils in porcine iliac arteries after angioplasty and Wallstent placement compared with angioplasty alone

PURPOSE

This study was designed to compare deposition of 111In-labeled platelets and neutrophils after balloon angioplasty (PTA) alone and PTA plus Wallstents.

METHODS

Histological investigation was performed with scanning electron microscopy (SEM). Fifty percent stenoses of both iliac arteries was created by resorbable ligature in 13 pigs. After 30 days, PTA was performed bilaterally with an additional stenting procedure done on one side. Autologous platelets were labeled and reinfused before the interventional procedure in six pigs, and labeled neutrophils were used in seven pigs. The deposition of the labeled cells was recorded in vivo over 270 min using a scintillation camera. The results were correlated with in vitro measurements.

RESULTS

Scanning revealed significant increase in platelet and neutrophil deposition at the site of the stent compared with the site where PTA alone was undertaken. In vitro measurements confirmed these differences. SEM demonstrated a fibrin lining on the stent surface and numerous adherent platelets. The adjacent arterial lumen was almost completely covered by fibrinous material. The PTA-alone site demonstrated denudation of endothelial cells and less fibrinous material, as well as platelets and leukocytes.

CONCLUSION

The complex interaction in the response of the vessel wall and flowing blood involves both platelet and neutrophil adhesion. The self-expandable vascular endoprosthesis contributes to increased deposition of platelets and neutrophils as seen in this experimental model of nonatheromatous stenosis.

Balloon angioplasty with stent implantation in experimental coarctation of the aorta

BACKGROUND

Balloon angioplasty of coarctation of the aorta is an effective method of treatment but is complicated by tearing of the aortic intima, formation of aneurysms, and restenosis. Stent placement at the time of balloon dilation could prevent restenosis and could also prevent progression of intimal tears to aneurysms. The purpose of this study was to evaluate the feasibility of balloon dilation and implantation of balloon-expandable stents in an experimental model of coarctation and to examine the effect of stent placement at the site of surgically created stenosis.

METHODS AND RESULTS

Coarctation of the aorta was surgically produced in 11 juvenile swine. Simultaneous coarctation angioplasty and stent implantation was performed in 10 animals 34 +/- 7.8 days after surgery. Repeat catheterization was performed 59 +/- 6 days after stent implantation. Five animals underwent reexpansion of stents with subsequent follow-up catheterization. Aortic specimens were examined by light microscopy and scanning electron microscopy. Coarctation angioplasty with stent implantation was successful in all, with an increase in coarctation diameter from 46 +/- 8.5% to 90 +/- 12.2% of proximal aortic diameter (P = .0001). Systolic pressure gradient decreased from 32 +/- 19.8 to 0.5 +/- 2.8 mm Hg (P < .001). All stents were patent at follow-up catheterization, with no evidence of intraluminal thrombosis. Reexpansion in five animals increased the stent diameter from a mean of 77.4 +/- 12.1% to 93 +/- 11.0% of proximal aortic diameter (P = .02). Gross examination of aortic specimens demonstrated formation of neointima over the stent wherever the stent struts were in contact with the aortic wall. The stent occupied a subintimal position and produced minimal compression of the underlying media. Medial compression was noted immediately beneath stent struts, but there was no evidence of intimal or medial dissection.

CONCLUSIONS

Balloon angioplasty with simultaneous implantation of balloon-expandable stents is effective in relieving aortic obstruction in experimental coarctation. Reexpansion of the rigid stent can be performed in an area of surgical aortotomy and coarctation without significant intimal or medial injury. Stent implantation may be useful in preventing restenosis and aneurysm formation after angioplasty of coarctation.

Changing practice patterns in peripheral arterial disease

The development of interventional radiologic techniques during the past decade has changed our approach to the treatment of lower extremity peripheral arterial disease (LE-PAD). Balloon and laser-assisted angioplasty, atherectomy (rotary and directional devices), stent implantation, and thrombolysis as well as combinations of all of these approaches, at times with concomitant or secondary surgery, have been used in our institution. A review of our practice patterns during the past 5 years was performed to analyze changing attitudes and results with these newer techniques. All new patients seen in consultation for LE-PAD during three alternate years were reviewed with regard to demographics, initial complaints, initial treatment modality, initial outcome, indications for and results of secondary treatment, and ultimate outcome (at 1 year). The 603 patients were seen during the following three 12-month periods: 1987 to 1988, 1989 to 1990, and 1991 to 1992. An intention-to-treat analysis revealed (1) the number of patients seen for peripheral arterial disease has increased steadily; (2) in the last year more were initially treated with intervention as the primary modality; (3) the results of such catheter-based procedures improved only slightly over this 5-year period, despite our learning curve and the fact that we discarded several ineffective interventional approaches; (4) the fraction of patients primarily operated on and the excellent results of surgery have not changed; and (5) the number of operations for proximal (aortoiliac) disease has decreased markedly, with a corresponding increase in distal reconstructions. The evolution of our current approach to the treatment of LE-PAD is based on this continuing experience.

Re-expansion of balloon-expandable stents after growth

OBJECTIVES

The purpose of this study was to evaluate the feasibility of re-expansion of balloon expandable intravascular stents and to examine the gross and histologic effects of re-expansion on vascular integrity.

BACKGROUND

Intravascular stents have been used successfully as an adjunct to balloon dilation of congenital pulmonary artery branch stenosis and postoperative stenosis of the pulmonary arteries in children. However, use of rigid stents in children could result in development of relative stenosis at the site of stent implantation with subsequent growth of the child.

METHODS

Stainless steel "iliac" stents were placed in the thoracic aorta of 10 normal juvenile swine by a transcatheter technique. Angiography and re-expansion were performed at a mean of 11 weeks (n = 9) and again at 18 weeks (n = 5). After euthanasia, the aortic specimens were removed for gross and histologic examination.

RESULTS

Stents were successfully implanted in 10 swine. Re-expansion was successfully performed in each animal at 11 weeks and at 18 weeks. Aortic growth produced a relative constriction of the aorta of 20% +/- 10% (mean +/- SD) at the site of stent implantation at both 11 and 18 weeks. Re-expansion produced a significant increase in mean stent diameter from 10.1 +/- 1 mm to 12.3 +/- 1.2 mm at 11 weeks and from 11.2 +/- 0.7 to 13.5 +/- 1.1 mm at 18 weeks after implantation (p < 0.001). Balloon dilation produced a relative increase in stent diameter of 21% +/- 7% at 11 weeks and 18% +/- 4% at 18 weeks. Stent re-expansion was accompanied by plastic deformation of the neointima without neointimal dissection. Where neointima was thick, there was no evidence of neointimal abrasion, but where neointima was thin, areas of localized neointimal abrasion were observed with focal fibrin and platelet adherence to the stent struts. There was no evidence of medial or adventitial hemorrhage or dissection produced by re-expansion.

CONCLUSIONS

Re-expansion of intravascular stents is feasible after growth in juvenile swine without significant injury to neointima, media or adventitia. The results of this study support careful and selective use of intravascular stents as an adjunct to balloon dilation of congenital stenoses in children.

Case report: infected false aneurysm at the site of an iliac stent

False aneurysm formation at the site of iliac artery stent placement is an uncommon but serious complication of the procedure. We report a case of infected false aneurysm at the site of an iliac stent, complicated by renal failure.