Endovascular stents: preliminary clinical results and future developments

Development of a New Biodegradable Intravascular Polymer Stent with Simultaneous Incorporation of Bioactive Substances

Objective

Due to the thrombogenicity and permanent implant nature of metallic stents, bioresorable synthetic polymers have been proposed for stents and local drug delivery systems. Bioresorbable polyesters like poly(D,L-lactide) demonstrated excellent biocompatibility in various tissues. This paper describes a novel method for the molding of these polymers. The specific CESP-process (Controlled Expansion of Saturated Polymers) is characterised by the use of the plasticizer carbon dioxide and allows the incorporation of bioactive substances at physiologic temperatures into the polymer bulk and the production of complex designed implants.

Methods

The CESP-process is characterised by the exposure of an amorphous polymer to an inert gas at high pressure with a significant lower glass transition point. The plasticizing effect makes it possible to process polylactides at a temperature close to room temperature. The low process temperature constitutes a key advantage for thermally sensitive polymers and allows the incorporation of thermally sensitive pharmaceutical additives. To obtain some preliminary information on the biocompatibility, in vitro cell toxicity testing as well as drug release assessment was performed.

Results

Different polymer sheets were produced using the CESP-process. Cytotoxicity was not observed in any molded polymer material. According to the mechanical and biocompatibility results Poly(D,L-lactide) (P-DL-LA) was investigated in the CESP-process. Finite element analysis was used to test the possible geometry of an adequate stent. A helical design was chosen and a stent-prototype was produced using the CESP-process. Peroxidase activity as an incorporated marker enzyme could be measured over 6 weeks. DIfferent drug release profiles were obtained due to various pore sizes of the polymer.

Conclusions

The new CESP-process can be used to process biodegradable polymers and to mold different stent geometries without inducing cytotoxic effects to the material. Furthermore, this procedure permits the simultaneous incorporation of bioactive substances during the molding process. Drug release kinetics can be regulated by different pore sizes of the material.

Coating process and early stage adhesion evaluation of poly(2-hydroxy-ethyl-methacrylate) hydrogel coating of 316L steel surface for stent applications

In this study, a spray-coating method has been set up with the aim to control the coating of poly(2-hydroxy-ethyl-methacrylate) (pHEMA), an hydrophilic polymeric hydrogel, onto the complex surface of a 316L steel stent for percutaneous coronary intervention (PCI). By varying process parameters, tuneable thicknesses, from 5 to 20 microm, have been obtained with uniform and homogeneous surface without crack or bridges. Surface characteristics of pHEMA coating onto metal surface have been investigated through FTIR-ATR, contact angle measurement, SEM, EDS and AFM. Moreover, results from Single-Lap-Joint and Pull-Off adhesion tests as well as calorimetric analysis of glass transition temperature suggested that pHEMA deposition is firmly adhered on metallic surface. The pHEMA coating evaluation of roughness, wettability together with its morphological and chemical stability after three cycles of expansion-crimping along with preliminary results after 6 months demonstrates the suitability of the coating for surgical implantation of stent.

Poly(ethylene carbonate): A thermoelastic and biodegradable biomaterial for drug eluting stent coatings?

A first feasibility study exploring the utility of poly(ethylene carbonate) (PEC) as coating material for drug eluting stents under in vitro conditions is reported. PEC (Mw 242 kDa, Mw/Mn=1.90) was found to be an amorphous polymer with thermoelastic properties. Tensile testing revealed a stress to strain failure of more than 600%. These properties are thought to be advantageous for expanding coated stents. In vitro cytotoxicity tests showed excellent cytocompatibility of PEC. Based on these findings, a new stenting concept was suggested, pre-coating a bare-metal stent with PPX-N as non-biodegradable basis and applying a secondary PEC coating using an airbrush method. After manual expansion, no delamination or destruction of the coating could be observed using scanning electron microscopy. The surface degradation-controlled release mechanism of PEC may provide the basis for "on demand" drug eluting stent coatings, releasing an incorporated drug predominantly at an inflamed implantation site upon direct contact with superoxide-releasing macrophages. As a release model, metal plates of a defined size and area were coated under the same conditions as the stents with PEC containing radiolabelled paclitaxel. An alkaline KO(2-) solution served as a superoxide source. Within 12 h, 100% of the incorporated paclitaxel was released, while only 20% of the drug was released in non-superoxide releasing control buffer within 3 weeks.

Drug-eluting stents and glycoprotein IIb/IIIa inhibitors: combination therapy for the future

BACKGROUND

Although coronary stenting has improved the results of coronary interventions compared to coronary angioplasty alone, in-stent restenosis remains a significant limitation of this procedure. Drug-eluting stents with or without glycoprotein IIb/IIIa inhibitor therapy represent an additional advance in the evolution of this strategy.

METHODS

We review the currently available trials comparing studies of non-drug-eluting and drug-eluting stents using sirolimus and paclitaxel agents and their derivatives.

RESULTS

Ten studies are available that compare drug-eluting to traditional non-drug-eluting stents. A variety of antiplatelet regimes have been used. The majority of these studies are in the process of being published. No head-to-head studies comparing different drug-eluting stents are available.

CONCLUSIONS

Drug-eluting stents using sirolimus and paclitaxel in combination with enhanced antiplatelet strategies represent an important advantage over non-drug-eluting stents for the reduction of in-stent restenosis. The rate at which drug-eluting stents are adapted into widespread practice depends heavily on whether they are safe, efficacious, and cost-effective in various clinical settings.

Thrombogenicity of various endovascular stent types: an in vitro evaluation

PURPOSE

The aim of this study was to evaluate the thrombogenicity of different peripheral stent types in a standardized in vitro model with fresh human whole blood.

MATERIALS AND METHODS

Different stents (N = 77; n = 7 of each of 11 types) were implanted in polyvinyl chloride tubing loops and filled with donor blood samples. After 120 minutes of blood circulation, the thrombin-antithrombin III complex (TAT) levels, beta-thromboglobulin (beta-TG) levels, and platelet counts were assessed.

RESULTS

After 2 hours, significant differences were seen. TAT values (+/- SD) with the investigated stents were 31 micro g/mL +/- 20 (control, no stent), 328 micro g/mL +/- 206 (Saxx stent, peripheral medium CrNi31 L), 651 micro g/mL +/- 760 (Palmaz Corinthian Stent, 316 L stainless steel, electropolished), 1,609 micro g/mL +/- 1,264 (Palmaz Corinthian Stent, 316 L stainless steel, not electropolished), 810 micro g/mL +/- 578 (Palmaz Schatz long medium stent), 569 micro g/mL +/- 347 (Smart Nitinol stent), 1,037 micro g/mL +/- 577 (Megalink peripheral stent), 543 micro g/mL +/- 487 (peripheral stent, electropolished), 1,674 micro g/mL +/- 2,057 (peripheral stent, not electropolished), 3,128 micro g/mL +/- 1,812 (SelfX Nitinol stent, polished), 5,897 micro g/mL +/- 2,380 (SelfX Nitinol stent, unpolished), and 1,458 micro g/mL +/- 887 (bridge stent). The platelet count (x1,000/ micro L +/- SD) was 218 +/- 35 (control, no stent), 188 +/- 22 (Saxx stent), 187 +/- 20 (Palmaz Corinthian stent, electropolished), 135 +/- 37 (Palmaz Corinthian stent, not electropolished), 170 +/- 24 (Palmaz Schatz stent), 180 +/- 36 (Smart Nitinol stent), 159 +/- 26 (Megalink peripheral stent), 173 +/- 17 (peripheral stent, electropolished), 133 +/- 51 (peripheral stent, not electropolished), 123 +/- 37 (SelfX Nitinol stent, polished), 52 +/- 27 (SelfX Nitinol stent, unpolished), and 130 +/- 31 (bridge stent).

CONCLUSION

This standardized study showed a wide range of platelet activation after stent implantation. Electropolishing clearly reduced the thrombogenicity of the stents.

The Octopus Study: rationale and design of two randomized trials on medical effectiveness, safety, and cost-effectiveness of bypass surgery on the beating heart

The Octopus Study consists of two multicenter randomized clinical trials in which coronary artery bypass grafting on the beating heart (off-pump CABG) using the Utrecht Octopus Method is compared to intracoronary stent implantation and conventional CABG. The primary endpoint in the comparison of off-pump CABG versus stent implantation (OctoStent Trial) is medical effectiveness (i.e., absence of reintervention and major adverse cardiac and cerebrovascular events at 1 year after treatment). The primary endpoint in the comparison of off-pump CABG versus conventional CABG (OctoPump Trial) is cerebral safety (i.e., absence of cognitive deficits and cerebrovascular events at 3 months after treatment). Secondary endpoints in both trials include presence and severity of angina, quality of life, exercise capacity, and cost-effectiveness. A total of 560 patients will be enrolled. A random sample of 210 patients will undergo repeat angiography at 1 year to assess angiographic restenosis rate and graft patency. Including 1-year follow-up, the study will last for 3 years. Control Clin Trials 2000;21:595-609

Coronary arterial stents: safety and artifacts during MR imaging

PURPOSE

To investigate the safety and imaging artifacts with different coronary arterial stents and magnetic resonance (MR) imaging sequences.

MATERIALS AND METHODS

The heating, artifacts, and ferromagnetism with different stents were studied with a 1.5-T MR tomograph with ultrafast gradients by using turbo spin-echo, turbo gradient-echo, and echo-planar imaging sequences. Nineteen stents, which were 8-25 mm in length and 3.0-4.5 mm in diameter, were evaluated. Stent deviation induced by the magnetic field and during MR imaging, migration, and heating caused by the radio-frequency pulses were examined. The size of imaging artifacts was measured with all the stents under standardized conditions and with six stents after their implantation into the coronary arteries of freshly explanted pig hearts.

RESULTS

All except two types of stents showed minimal ferromagnetism. No device migration or heating was induced. Turbo spin-echo images had minimal artifacts; larger artifacts were seen on the turbo gradient-echo and echo-planar images. With ultrafast gradients, the artifacts on the echo-planar images were substantially reduced.

CONCLUSION

The studied coronary stents were not influenced by heating or motion during 1.5-T MR imaging. Artifact size differed according to the type and size of the stent and the MR imaging sequence used. Thus, patients with these stents can be safely examined.

Short- and long-term evolution of unstented nonocclusive coronary dissection after coronary angioplasty

OBJECTIVES

We assessed the short- and long-term clinical and angiographic outcome of nonocclusive unstented dissection after percutaneous transluminal coronary angioplasty (PTCA) and its correlation with restenosis.

BACKGROUND

The use of stents has dramatically increased both the number and the cost of coronary revascularization procedures. However, this technique is not completely risk free, and its benefits have not been fully demonstrated in uncomplicated dissections.

METHODS

We studied 129 consecutive patients with 49 nonocclusive dissections after PTCA (grades A to D of National Heart, Lung, and Blood Institute classification) and good distal flow (TIMI [Thrombolysis in Myocardial Infarction] flow grade 3). All patients underwent coronary angiography at 24 h and at six months post-PTCA. Clinical status was assessed every three months in the outpatient clinic. Study subjects were matched with 60 other patients in whom stenting was performed for the presence of dissection.

RESULTS

In the former group, all but two patients (with type E dissection, which evolved to coronary occlusion and myocardial infarction) improved their dissection score during follow-up: at six months only 18 dissections were still angiographically visible, and no clinical adverse events were recorded. In the dissected vessels, the restenosis rate was significantly lower than in those without dissection (12% vs. 44%, p < 0.001); in the stented vessels, the restenosis rate was 25% (15/60).

CONCLUSIONS

In the presence of TIMI flow grade 3, coronary dissection is associated with a favorable outcome and predicts a low restenosis rate. These results caution against the indiscriminate use of intravascular prostheses in the event of nonocclusive coronary dissection.

Phosphorylcholine-coated metallic stents in rabbit iliac and porcine coronary arteries

The arterial wall reaction to phosphorylcholine-coated metal stents was examined in rabbits and pigs. Compared to non-coated stents, no significant difference was found by angiography and histology. We conclude that although phosphorylcholine-coating does not provoke arterial neointima formation or decrease luminal diameter compared to stainless steel stents, the coating does not seem to reduce restenosis.

Extramural vessel wall hematoma causing a reduced vessel diameter after coronary stenting: diagnosis by intravascular ultrasound and treatment by stent implantation

An extramural vessel wall hematoma occurred immediately after implanting a coronary stent in an in-stent-restenosis of the intermedius branch. Angiography showed a significant luminal reduction distal to the intervention site. Intravascular ultrasound revealed an extramural echolucent zone compressing the vessel lumen. Stent implantation compressed the hematoma and allowed adequate myocardial perfusion. This demonstrates the value of intravascular ultrasound (IVUS) in cases of unusual angiographic results which can help to manage complications after coronary intervention.

Angiographic follow-up and clinical experience with the flexible Tantalum Cordis stent

The Cordis stent is a flexible, highly radioopaque intracoronary stent engineered from a single Tantalum filament folded into a sinusoidal helical coil. It is premounted on a semicompliant balloon expandable stent delivery system. From September 1995-March 1996, 147 Cordis stents were deployed in 105 patients (aged 58+/-12 yr, 71% male). Clinical indications for stenting were unstable angina in 59 (55%), stable angina in 41 (38%), and acute myocardial infarction in 7 (7%). The target vessel was the right coronary artery in 45%, the left anterior descending in 31%, and the circumflex artery in 22%. One stent was deployed in a vein graft, and one stent was deployed in a left internal mammary artery graft. Stent deployment was achieved in all but one patient. Acute in-stent thrombosis occurred in 3 patients (2.9%). Two of these patients required urgent coronary artery bypass surgery. Subacute stent thrombosis occurred in 2 patients (1.9%). Minimum lumen diameter increased from 0.70+/-0.41 mm to 3.50+/-0.60 mm following stent placement. All patients received aspirin. Eighty-one patients (77%) received ticlopidine, and 4 patients (4%) received warfarin therapy. The mean hospital stay was 3.4+/-2.3 days. Six-month follow-up angiography was performed on 50 out of 55 eligible patients at one of the two institutions involved in this study. Computer-assisted quantitative coronary angiography defined a restenosis rate of 26%. Repeat revascularization was required in 8 patients (14.5%) at 6-mo follow-up. The Tantalum Cordis intracoronary stent is an effective and safe means of treating coronary lesions, even in patients with unstable ischemic syndromes. Acute and subacute rates of in-stent thrombosis were acceptable, and the long-term angiographic restenosis rates and need for repeat revascularization were favorable.

Clinical outcome at six months of coronary stenting followed by ticlopidine monotherapy

Antiplatelet therapy has been shown to be superior to oral anticoagulation after coronary stent implantation. Different regimens for postinterventional antiplatelet therapy have been proposed. A combination of ticlopidine and aspirin has gained the most widespread use. The relative merit of the different compounds in this combination remains unclear. There are several, partly conflicting, reports on coronary stent implantation followed by aspirin alone, but data on ticlopidine monotherapy are scarce. We conducted a prospective trial of elective coronary stenting followed by ticlopidine monotherapy in 263 consecutive, unselected patients. One-, 2-, and 3-vessel disease was present in 42.9%, 42.6%, and 14.5% of patients, respectively. We deployed a total of 322 stents. All patients received 250 mg of ticlopidine twice daily for up to 6 months. The clinical end points encountered during the hospital stay and at 5.9+/-2.9 months, respectively, were: death (2 [0.8%] and 2 [0.8%]); myocardial infarction (5 [1.9%] and 4 [1.5%]); target vessel occlusion (2 [0.8%] and 4 [1.5%]); bypass surgery (0 and 2 [0.8%]); and repeat angioplasty (2 [0.8%] and 52 [19.8%]). There was 1 vascular surgery (0.4%) and 4 (1.5%) non-procedure-related ischemic cerebrovascular events at follow-up. We conclude that coronary stent deployment followed by ticlopidine monotherapy is safe and effective in an unselected population. The overall clinical outcome at 6 months is good and comparable to that of patients treated with combined antiplatelet therapy. Ticlopidine monotherapy may be a safe alternative for patients with contraindications to aspirin.

Micro stent I, initial results, and six months follow-up by quantitative coronary angiography

The Micro stent (MS) is a balloon expandable stent that allows the treatment of stenoses in distal and tortuous coronary arteries. This prospective study was performed to evaluate initial and late results of MS implantations. A total of 127 MS (101 in native coronary arteries and 26 in saphenous vein grafts) were implanted in 85 patients (1.5 stents/pt, 65 male, and 20 female, age 62, +/-10 yr) with angina pectoris class II-III: 21 (25%), angina pectoris class IV: 41(48%), and acute myocardial infarction: 23 (27%). Indications per segment treated (n=93): elective: 49 (53%); suboptimal balloon angioplasty (PTCA) result: 33 (35%); bailout: 11 (12%). The patients were discharged with 100 mg of aspirin daily unless other indications for oral anticoagulants were present. Procedural success (diameter stenosis of 30% without the occurrence of clinical events within 3 wk) was 85%. Early clinical events (<3 wk included: death:1%; subacute closure: 5%; coronary artery bypass surgery (CABG): 1%; vascular complications: 4%. Late clinical events (3 wk-6 mo) included: acute myocardial infarction:3%, PTCA 5%, CABG 3%, angina class Ill-IV: 4%. Quantitative angiographic results were: the minimum lumen diameter increased from 0.90+/-0.72 before to 3.05+/-0.48 mm (<P0.001) after stent implantation. At follow-up, which was 5.5 mo +/-1.1 mo, 61/79 pts (77%), the loss in diameter was 0.90+/-0.68 mm. The net gain was 1.26+/-0.90 mm. The restenosis rate (diameter stenosis > 50% at FU) was 13%. This study demonstrates high procedural and late success rates of Micro stent implantations.

Introduction to coronary artery stents and their pharmacotherapeutic management

OBJECTIVE

To provide an introduction to coronary artery stents and their pharmacologic management, including anticoagulant therapy and newer antiplatelet regimens.

DATA SOURCES

A MEDLINE and current journal search of relevant articles that evaluated coronary stent success rates and anticoagulation or antiplatelet regimens.

STUDY SELECTION

Data from the use of primarily the Palmaz-Schatz stent were included. Studies using vitamin K antagonists that are not commercially available in the US were excluded unless they compared an antiplatelet regimen with anticoagulation using the international normalized ratio (INR).

DATA SYNTHESIS

Limitations with percutaneous transluminal coronary angioplasty (PTCA), such as ischemic complications and restenosis, have led to the advent of intracoronary stenting. However, the placement of a stent within the coronary artery lumen is associated with a risk of thrombotic events. Despite current postprocedural anticoagulation and antiplatelet regimens, thrombosis occurs at rates ranging from 0.6% to 21%. When anticoagulation is deemed appropriate, it should be used for 1-2 months and the INR should be maintained between 2 and 3.5. Anticoagulation appears to have no effect on the development of restenosis, but has been shown to cause significant hemorrhagic events in 5-13.5% of patients. Newer data continue to define the subsets of patients who may be managed with antiplatelet agents alone. Combinations of aspirin and ticlopidine or aspirin alone may be used to manage patients who fulfill the following criteria: optimal stent placement, high-pressure inflation, and adequate coronary size.

CONCLUSIONS

Coronary artery stenting is a novel approach for the management of coronary artery disease, but is associated with the complication of stent thrombosis. Anticoagulation reduces the risk of stent thrombosis, but is associated with bleeding risk. Selected patients may be successfully managed with antiplatelet agents only. More data are needed to better define the optimal antithrombotic regimen.

Poly-lactic-acid coating for endovascular stents. Preliminary results in canine experimental arteriovenous fistulae

RATIONALE AND OBJECTIVES

The authors evaluate polylactic-acid (PLA) as a coating of vascular endoprostheses in the treatment of experimental arteriovenous fistulae (AVF) in a canine model.

METHODS

Bilateral carotid external jugular AVF were created in five adult dogs. Seven PLA-coated nitinol stents were placed using a transfemoral approach to cover five AVF. Contralateral controls remained untreated. Angiography was performed immediately after stent placement and at weeks 1 and 3, as well as at months 3, 6, and 9. All grafts were removed and underwent histologic examination.

RESULTS

In two cases, the occlusion of the AVF was successful, but misplacement of stents occurred in three cases, which showed occlusion of the parent vessel between week 1 and month 3. One thrombembolic stent occlusion was evident during angiographic control. One vessel occlusion was disclosed distal to the stented arterial segment. Histologic examination revealed a mild inflammatory reaction with the presence of macrophages. However, there was no foreign-body reaction of fragmentation of the vessel wall.

CONCLUSIONS

Histologic examination revealed good biocompatibility of PLA, which is a well-known biodegradable material. Elastic mismatch of the nonelastic coating and the self-expandable nitinol stent led to misplacement, whereas vessel occlusion was probably due to PLA filaments fraying into the vessel lumen. Using a different textile structure, PLA might be a material suitable for coated stents.

Micro stent, quantitative coronary angiography, and procedural results

The Micro stent (MS) is a radiopaque stainless steel balloon expandable intracoronary stent. The stent is mounted on a rapid-exchange delivery system. From August 1994-March 1995, 127 MS were implanted in 85 patients (pts, 1.5 stents/pt, 85 in native vessels and 42 in bypass vein grafts, 61 males and 24 female, age 33-77 yr, mean age 61 +/- 10 yr). Pts studied were scheduled for either elective PTCA (n = 62, 73%) or PTCA for acute myocardial infarction (n = 23, 27%). Elective stent implantation was performed in 45 pts (53%). An MS was implanted because of a suboptimal balloon angioplasty result in 26 pts (31%). The stent was implanted because of threatened or acute vessel closure after balloon angioplasty in 14 pts (16%). During the procedure, 500 mg aspirin and 2 x 7,500 units of heparin were administered intravenously, followed by systemic heparinization for 48 hr. Pts were discharged with 100 mg aspirin daily (n = 50, 59%), or anticoagulant drugs and 100 mg aspirin daily (n = 19, 22%), or anticoagulant drugs only (n = 16, 19%). Angiographic results were analyzed with computer-assisted quantitative coronary arteriography. Angiographic success (defined as a residual stenosis of < 30%) was achieved in 124 of 127 attempts (98%). The mean minimal luminal diameter of the target lesions increased from 0.88 +/- 0.79 mm before stent implantation to 3.08 +/- 0.56 mm (P < 0.001). The percentage of diameter stenosis was reduced from 77.9 +/- 20.9% before to 13.3 +/- 10.5% (P < 0.001) after stent implantation. The average initial gain was 2.53 +/- 1.37 mm. The procedural success rate (defined as a residual stenosis of < 30% without occurrence of major clinical events within 3 wk after procedure) was 84%. Major clinical events included: death 1 pt (1%); cerebrovascular accident, 1 pt (1%); subacute stent closure, 5 pts (6%); coronary artery bypass grafting, 3 pts (4%); false femoral aneurysm, 2 pts (2%). The initial results of Micro stent implantation are promising. No anticoagulant therapy was given to most of the patients (59%). Few vascular and bleeding complications were observed. However, at this stage, no data about the restenosis rate after implantation of a Micro stent are available.

Role of polymers in improving the results of stenting in coronary arteries

This article is a review of recent developments of polymer-related stents mainly employed in the coronary arteries, including polymer-coated stents, biostable stents and biodegradable stents. Polymer paving is covered as well. The problems with the stents currently investigated and the development of new stents are discussed.

Experience with repair of congenital heart defects using adjunctive endovascular devices

The use of endovascular devices as an adjunct to repair of congenital heart anomalies represents a novel but unproven therapeutic approach. Intraoperative implantation of pulmonary arterial stents (5 to 15 mm diameter) was done in 11 patients with pulmonary atresia with ventricular septal defect (n = 4), classic tetralogy of Fallot (n = 2), truncus arteriosus (n = 1), hypoplastic left heart syndrome (stage II [n = 1] and stage III [n = 1] Norwood procedure), and miscellaneous pulmonary arterial stenoses (n = 3), as well as in patients with congenital (n = 1) and postoperative (n = 3) pulmonary venous obstruction and in 1 patient with combined pulmonary arterial and venous obstruction. The stents were effective at achieving immediate patency in all patients. There were two early deaths, one related to acute thrombosis of a small-diameter left pulmonary artery stent. Reintervention because of stent-related pulmonary arterial stenosis was frequently necessary. In five of seven patients who survived more than 1 month after implantation of stent size 8 mm or smaller severe stent-related pulmonary arterial obstruction developed. In four of the five patients with pulmonary vein stent implantation intractable obstruction developed, resulting in death in all three patients who had bilateral pulmonary vein stent implantation. Intraoperative occlusion of apical muscular ventricular septal defect with use of a clamshell device inserted from the right atrial approach was accomplished in four patients. One patient who underwent associated aortic arch reconstruction died as a result of left ventricular hypoplasia. The results in the remaining three patients were favorable on the basis of absence of significant late residual intraventricular shunting, left ventricular dysfunction, or arrhythmia. We conclude that recurrent intraluminal obstruction as a result of neointimal hyperplasia appears to be an eventual certainty in currently designed small-diameter endovascular stents. For this reason, we would recommend standard surgical techniques for repair of obstructive lesions of the pulmonary arterial confluence to maximize growth potential. Device occlusion of muscular ventricular septal defects is feasible but probably only indicated for complex cases of ventricular septal deficiency that otherwise necessitate a left ventriculotomy.

Intraluminal Palmaz stent implantation for treatment of recurrent carotid artery occlusive disease: a plan for the future

While carotid endarterectomy (CEA) has been used commonly and with great effectiveness for de novo carotid occlusive lesions, its success in cases of recurrent disease has been attenuated by a higher incidence of complications and lower durability. Although interventional techniques have been introduced cautiously into the cerebrovascular system, balloon dilation for both primary and recurrent carotid atherosclerotic disease has been successful in establishing an adequate lumen without an increase in embolic complications over surgery. Because the likelihood exists that postdilation restenosis may be as common in the carotid arteries as it is in other vascular segments, the use of intraluminal stenting may mitigate this long-term complication, a benefit that has been demonstrated in other high flow vessels such as the aorta and iliac arteries. To begin an investigation of this hypothesis, we treated a 69-year-old symptomatic man who required a third intervention for recurrent carotid disease. A > 90% stenosis of the distal third of his right common carotid artery was successfully dilated, and a Palmaz stent was deployed without incident. The patient experienced no complications to the percutaneous procedure, and at 15 months posttreatment, he is well and asymptomatic. Although greater clinical experience must be accumulated with this new approach, intraluminal stenting following balloon dilation for recurrent carotid disease may surpass redo CEA in long-term patency and may entail fewer procedural complications.

A comparison of balloon-expandable-stent implantation with balloon angioplasty in patients with coronary artery disease. Benestent Study Group

BACKGROUND

Balloon-expandable coronary-artery stents were developed to prevent coronary restenosis after coronary angioplasty. These devices hold coronary vessels open at sites that have been dilated. However, it is unknown whether stenting improves long-term angiographic and clinical outcomes as compared with standard balloon angioplasty.

METHODS

A total of 520 patients with stable angina and a single coronary-artery lesion were randomly assigned to either stent implantation (262 patients) or standard balloon angioplasty (258 patients). The primary clinical end points were death, the occurrence of a cerebrovascular accident, myocardial infarction, the need for coronary-artery bypass surgery, or a second percutaneous intervention involving the previously treated lesion, either at the time of the initial procedure or during the subsequent seven months. The primary angiographic end point was the minimal luminal diameter at follow-up, as determined by quantitative coronary angiography.

RESULTS

After exclusions, 52 patients in the stent group (20 percent) and 76 patients in the angioplasty group (30 percent) reached a primary clinical end point (relative risk, 0.68; 95 percent confidence interval, 0.50 to 0.92; P = 0.02). The difference in clinical-event rates was explained mainly by a reduced need for a second coronary angioplasty in the stent group (relative risk, 0.58; 95 percent confidence interval, 0.40 to 0.85; P = 0.005). The mean (+/- SD) minimal luminal diameters immediately after the procedure were 2.48 +/- 0.39 mm in the stent group and 2.05 +/- 0.33 mm in the angioplasty group; at follow-up, the diameters were 1.82 +/- 0.64 mm in the stent group and 1.73 +/- 0.55 mm in the angioplasty group (P = 0.09), which correspond to rates of restenosis (diameter of stenosis, > or = 50 percent) of 22 and 32 percent, respectively (P = 0.02). Peripheral vascular complications necessitating surgery, blood transfusion, or both were more frequent after stenting than after balloon angioplasty (13.5 vs. 3.1 percent, P < 0.001). The mean hospital stay was significantly longer in the stent group than in the angioplasty group (8.5 vs. 3.1 days, P < 0.001).

CONCLUSIONS

Over seven months of follow-up, the clinical and angiographic outcomes were better in patients who received a stent than in those who received standard coronary angioplasty. However, this benefit was achieved at the cost of a significantly higher risk of vascular complications at the access site and a longer hospital stay.