Acute clinical and angiographic results with the new AVE Micro coronary stent in bailout management

Switzerland is small in size but big on cardiology

Switzerland is a small country in the heart of Europe and well known worldwide for its Alps, foreign bank accounts, cheese, chocolate and watches. However, it also has made a significant contribution to cardiology, especially interventional cardiology. It was where balloon angioplasty and stenting of obstructed coronary arteries, two of the most stunning advances in cardiology in the last 30 years and the two most frequently performed interventional procedures in cardiology, originated. The author, who recently served as a visiting professor in the University of Geneva, University of Bern and University of Zurich, summarized his personal observations and impressions in this report.

Clinical trends in stent treatment of simple and complex coronary disease

This is a retrospective analysis of a consecutive group of patients from a single medical center who underwent stent implantation. It describes 316 patients who constituted 53% of the angioplasty procedures carried out in a single year. The authors describe the complications and their 1-year follow-up. We aimed to study the short and long-term results of stenting in our centre in relation to multiple clinical and angiographic variables. During 1996, 316 consecutive patients were treated with stent implantation for a total of 381 coronary lesions. The pharmacological protocol methods of stent implantation and patient characteristics were used. Clinical variables were: age 59.1 3 10.7 years, diabetes mellitus 25.3%, hypertension 33.0% and angina pectoris 88.7% (unstable in 44.1%). Previous coronary surgery had been undergone by 9.2%. Multivessel disease was present in 56% of the patients. The indications for stenting were: primary 58.5%, suboptimal results 33.0% and threatened or acute occlusion 8.5%. Angiographic success was 98.9% and clinical success 96.8%. The major in-hospital complications were acute myocardial infarction (2.2%), acute revascularization (0.3%) and major bleeding (0.6%). All occurred within 24 h of revascularization. Repeated angiography was performed in 115 cases (30.2%) at 160.3 3 109.4 days after stent procedure for unstable angina (38.7%), stable angina (26.1%) and other causes (35.2%). The restenosis rate in those catheterized was 38.1%, with an overall clinical restenosis rate of 11.3% during the follow-up period. Restenosis was more prevalent among diabetic patients (17.9 vs 9.15%, P 3 0.02) and patients with prior balloon angioplasty (18.6 vs 9.75%, P 3 0.046). Clinical follow-up was available in 90.8% of the patients for 291 3 112 days. The actuarial survival at the end of the follow-up period was 93.8%. Death/myocardial infarction was associated with unstable angina pectoris (P 3 0.006), hypertension (P 3 0.001), smoking (P 3 0.046) and threatened or acute occlusion (P < 0.001). In the first year of extensive stent use, stenting is associated with high technical and clinical success rates. Long-term results after stent implantation are associated with the occurrence of acute or threatened occlusion, and the in-hospital complications diabetes mellitus and hypertension.

Selection of coronary stents

In clinical practice, the operator must decide which stent is most appropriate for the patient. This article focuses on the features of stent design that make a specific stent more or less suitable for a particular type of lesion or anatomy: the "average" coronary lesion, the lesion situated on a curve, the ostial lesion, the bifurcational lesion, the lesion located at the left main stem, the calcified lesion, the chronic total occlusion, the small vessel, the saphenous vein graft, acute or threatened vessel closure, and special situations such as coronary aneurysms and perforations.

[Stent implantation in palliative central aortopulmonary shunt of congenital cardiopathies with pulmonary hypoperfusion. Experience of 2 cases]

We describe the pioneer experience of balloon angioplasty and stent implantation in the central polytetrafluoroethylene aorto-pulmonary shunt. Two infants 1 and 13 month-old, with cyanotic complex congenital cardiopathy and pulmonary hypoperfusion, presented signs of prosthesis dysfunction with severe and critic hypoxemia. The angioplasty and stent implantation were performed through retrograde femoral arterial approach and "freely" (without a guide catheter) in the first case and venous via by using Judkins right coronary guiding catheter in the second one. Both cases experienced sustained O2 saturation improvement, although the neonate died on the fifth post-procedure day clue to acute renal failure. The postmortem anatomical findings are shown.

Long-term outcome of patients with very long stents for treatment of diffuse coronary disease

OBJECTIVES

The study sought to determine the 6-month clinical outcome of patients who underwent implantation of very long coronary stents to treat diffuse disease and/or long dissections and to compare the findings with those reported in the literature for patients who underwent implantation of multiple short coronary stents.

BACKGROUND

New designs of flexible stents enable the implantation of long stents rather than multiple short, older design stents. The initial experience is very promising but the long-term outcome has not been described yet.

METHODS

Fifty-seven consecutive patients in whom 67 long stents (>/=30 mm) were successfully deployed were included in this study. Six-month clinical and angiographic follow-up was prospectively collected. Patients with recurrent angina underwent coronary angiography without further testing. Patients who remained asymptomatic at the 6-month follow-up visit underwent positron emission tomographic imaging, and those with results suggestive of ischemia underwent coronary angiography. A combined study end point was defined as death, myocardial infarction, and the need for target vessel revascularization.

RESULTS

Only 1 patient (2%) reached a study end point at hospital discharge. An additional 20 patients (total 21 patients [37%]) reached an end point by 6 months. The outcome was not influenced by the clinical presentation (stable or unstable angina) or by the indication for stenting (elective or emergency). Predictors for adverse outcome were multiple stents per narrowing (63% vs 29%, P <. 04), and stents smaller than 3.5 mm (49% vs 22%). Narrowing and stent length were not predictive of a study end point in narrowings that were successfully treated by a single long stent.

CONCLUSIONS

Elective stenting provides an effective solution for patients with diffuse coronary disease provided that a single long stent (usually <40 mm) can cover the full length of the narrowing. The results are better when vessels larger than 3 mm are treated. Compared with multiple short stents, implantation of a single long stent is probably at least as effective, and the procedure is quicker and cheaper and thus should be the preferred approach.

Pathology of bailout coronary stenting in human beings

OBJECTIVES

The aim of this study was to perform detailed postmortem analysis of bailout coronary stenting to gain insights into the mechanism of success or failure of the procedure. Bailout stenting is increasingly used for acute or threatened arterial closure after angioplasty. Few pathologic data from bailout stenting have been reported.

METHODS AND RESULTS

The coronary arteries from 6 cases of bailout stenting were analyzed at autopsy. All stents were placed for extensive coronary dissection or abrupt vessel closure after balloon angioplasty. Twenty stents (11 Palmaz-Schatz and 9 Gianturco-Roubin stents) were placed in 8 coronary arteries, ranging from 1 to 5 stents per artery. After stenting, angiography showed good coronary flow in 3 of 6 cases. All patients died secondary to acute myocardial infarction. Histologically, in all cases, the stents were well opposed to the coronary artery wall, with a focally widely patent lumen by compression of the dissection plane. However, in 4 of 6 cases, there was residual dissection present in the nonstented portion of the arteries proximal, proximal to, and between stents or distal to the stented segment, resulting in focal luminal compression or obstruction. In 2 cases, bailout stenting effectively covered the dissection and prevented luminal compression.

CONCLUSIONS

Bailout stenting for dissection after balloon angioplasty restores lumen patency in the stented segment. Residual dissection in nonstented segments adversely affects outcome and supports the need for continued development of new stents with increased trackability and tapering designs to more effectively treat major coronary dissections.

Therapeutic repositioning of a Gianturco-Roubin II coronary stent after initial deployment

Movement of coronary stents after deployment can produce complications. We report a case of stent migration that led to stent coverage of a distal dissection, obviating the need for placement of a second stent. In this case, stent movement was therapeutic.

Randomised comparison of Micro Stent I with Palmaz-Schatz stent placement for the elective treatment of short coronary stenoses

This randomised trial compared the Micro Stent I and the Palmaz-Schatz stent for the elective treatment of short (<8 mm long), new-onset coronary stenoses. The primary endpoints were restenosis rate and minimal luminal diameter at 6 mo angiographic follow-up. The secondary endpoints were angiographic and procedural success of stenting and a composite clinical endpoint at 6 mo (death, myocardial infarction, and target site revascularisation). A total of 93 patients were randomised. Clinical and angiographic characteristics of the two groups were comparable. Angiographic success of stenting was 96% in both groups, and there were no complications so that the procedural success was also 96% in both groups. The restenosis rate was 29% for Micro Stent I and 27% for the Palmaz-Schatz stent (P = NS). The minimal luminal diameter at 6 mo was 1.75 +/- 0.72 mm in the Micro Stent I group and 1.84 +/- 0.59 in the Palmaz-Schatz group (P = NS). At 6 mo, a clinical endpoint was reached by 21% of the patients in the Micro Stent I group and by 11% in the Palmaz-Schatz group (P = NS). In conclusion, the elective treatment of short coronary stenosis with the Micro Stent I or the Palmaz-Schatz stent resulted in similar early and late outcomes. In particular, the late angiographic results were very similar.

beStent--the serpentine balloon expandable stent: review of mechanical properties and clinical experience

The objective of this study was to present the engineering and clinical aspects of a new balloon expandable coronary stent. A new tubular, serpentine design stainless steel balloon-expandable stent, the beStent, was designed based on clinical requirements for stents and has been clinically evaluated in multiple sites. The stent is featured by terminal gold markers and rotational junctions that assure no shortening upon expansion and lead to orthogonal locking, maximizing radial strength. In terms of methods and results, the stent was clinically evaluated in the framework of a pilot evaluation in a variety of lesion types. The short- and long-term results evaluated during the course of the beStent multicenter pilot evaluation and in our single center study are reported. A variety of patients were included, including patients with long complex lesions, restenosis lesions, and total occlusions. Short-term clinical success with stenting was achieved in more than 97% of the cases. Subacute thrombosis was low in 1% of the cases. Clinical restenosis rates were acceptable with an overall 85% 6 month event free survival. In conclusion, the mechanical features of the stent providing its flexibility, scaffolding properties, radial strength, and absence of shortening were tested in a clinical study, showing that it is safe and effective for treating simple as well as long and complex lesions associated with coronary disease with a relatively low rate of complications.

Multiple coronary stenting in unstable angina: early and late clinical outcomes

We examined clinical outcomes in 110 consecutive patients with unstable angina who underwent multiple coronary stenting over a 32-mo period. The main outcome measures were death, stroke, myocardial infarction, bypass surgery, and repeat angioplasty. The angiographic success rate was 100%, and the procedural success rate was 96%. There were no in-hospital deaths and five (4.5%) patients had a myocardial infarction prior to discharge. There were four (3.6%) stent thromboses with one (0.9%) patient requiring urgent bypass surgery and two (1.8%) requiring repeat angioplasty. At late follow-up (11.9+/-7.1 mo), there was (0.9%) death and three patients (2.8%) suffered myocardial infarction. Three (2.8%) patients underwent late bypass surgery and five (4.6%) had a repeat angioplasty. At follow-up, 86% of patients were event free. We conclude that multiple coronary stenting in unstable angina may be performed with a high procedural success rate and good long-term outcome.

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.

Early and intermediate term clinical outcome after multiple coronary stenting

OBJECTIVE

To examine the immediate and intermediate term clinical outcome of multiple coronary stenting.

DESIGN

Consecutive patients were prospectively entered on a dedicated database. Follow up information was obtained from outpatient and telephone interviews with patients and family physicians.

SETTING

A tertiary referral centre.

PATIENTS

140 consecutive patients underwent multiple coronary stenting between April 1994 and November 1996. Most patients had unstable coronary syndromes.

MAIN OUTCOME MEASURES

Death, cerebrovascular accidents, myocardial infarction (MI), coronary artery bypass surgery (CABG), and repeat angioplasty (PTCA).

RESULTS

The angiographic success rate was 100% and the clinical procedural success rate 93%. The mean (SD) follow up was 11.9 (7.2) months (range 2-32). The mean (SD) number of stents per patient was 2.4 (0.7). The mean (SD) number of lesions treated per patient was 1.4 (0.6). There were four in-hospital deaths (2.9%) and five patients (3.6%) had an MI before hospital discharge. All in-hospital deaths occurred in patients presenting with an acute MI and cardiogenic shock. Three patients (2.2%) had a late MI. One patient with stent thrombosis underwent emergency CABG. Three patients (2.2%) underwent late CABG. Eight patients (5.7%) had a repeat PTCA. Eighty three patients (61.5%) were asymptomatic at follow up and 121 (86.4%) were free from major clinical events.

CONCLUSION

In an era of increased operator experience, high pressure stent deployment, and reduced anticoagulation with antiplatelet treatment alone, multiple coronary stenting may be performed with a high procedural success rate and good intermediate term outcome.

Results of Micro stent implantations in coronary lesions of various complexity

Micro stents appear to be especially suitable for the safe treatment of complex coronary lesions and adverse vessel morphology. Stenting of lesions with type C morphology is associated with a higher restenosis rate than stenting of less complex coronary obstructions.

Deployment of a previously embolized, unexpanded, and disarticulated Palmaz-Schatz stent

Stent embolization is a rare but acknowledged complication of placement of disarticulated (half) Palmaz-Schatz stents. We report a case in which we diagnosed a previously unrecognized, embolized, undeployed half-stent in the distal LAD, causing slow flow, and then deployed the stent where it lay, resulting in improved flow. The literature on treatment of coronary stent embolization and on cutting and preparing half-stents for deployment is discussed.

Acute and 30-day results of the serpentine balloon expandable stent implantation in simple and complex coronary arterial narrowings

We report the acute and 30-day results with a new serpentine-design, tubular, stainless steel, balloon-expandable stent (beStent) in the first 100 patients. One hundred forty-eight stents were used to treat 103 narrowings in the left anterior descending (n = 46), left circumflex (n = 20), and right coronary (n = 37) arteries. There were 85 de novo and 18 restenotic lesions (lesion length: < 10 mm [31], 10 to 20 mm [43] > 20 mm [29]; lesion type: A [10] B1 [29], B2 [20], C [44]; total occlusions, 23. More than 1 stent was used in 31 patients for treatment of long lesions that could not be covered by 1 stent. The stents used were 15-mm (n = 106), 25-mm (n = 38), or 35-mm (n = 4) long. Stent implantation strategy involved predilatation, deployment, and high-pressure dilatation, using the same balloon if possible. Clinical in-hospital success was 97% (2 patients had stent thrombosis that was recanalyzed, with myocardial infarction developing in 1, and 1 patient died on day 14 from retroperitoneal bleeding treated with surgery and complicated by sepsis). One-month event-free survival was 96%, with 1 death on day 21 due to hypertensive crisis. There were no other major adverse cardiac events in this first complex cohort of patients. In conclusion, the initial experience with this stent demonstrates its safety and efficiency for treating simple and complex coronary disease, with a relatively low rate of complications. Long-term clinical follow-up awaits further investigation.

First international new intravascular rigid-flex endovascular stent study (FINESS): clinical and angiographic results after elective and urgent stent implantation. The FINESS Trial Investigators

OBJECTIVES

The purpose of this study was to determine the feasibility, safety and efficacy of elective and urgent deployment of the new intravascular rigid-flex (NIR) stent in patients with coronary artery disease.

BACKGROUND

Stent implantation has been shown to be effective in the treatment of focal, new coronary stenoses and in restoring coronary flow after coronary dissection and abrupt vessel closure. However, currently available stents either lack flexibility, hindering navigation through tortuous arteries, or lack axial strength, resulting in suboptimal scaffolding of the vessel. The unique transforming multicellular design of the NIR stent appears to provide both longitudinal flexibility and radial strength.

METHODS

NIR stent implantation was attempted in 255 patients (341 lesions) enrolled prospectively in a multicenter international registry from December 1995 through March 1996. Nine-, 16- and 32-mm long NIR stents were manually crimped onto coronary balloons and deployed in native coronary (94%) and saphenous vein graft (6%) lesions. Seventy-four percent of patients underwent elective stenting for primary or restenotic lesions, 21% for a suboptimal angioplasty result and 5% for threatened or abrupt vessel closure. Fifty-two percent of patients presented with unstable angina, 48% had a previous myocardial infarction, and 45% had multivessel disease. Coronary lesions were frequently complex, occurring in relatively small arteries (mean [+/-SD] reference diameter 2.8 +/- 0.6 mm). Patients were followed up for 6 months for the occurrence of major adverse cardiovascular events.

RESULTS

Stent deployment was accomplished in 98% of lesions. Mean minimal lumen diameter increased by 1.51 +/- 0.51 mm (from 1.09 +/- 0.43 mm before to 2.60 +/- 0.50 mm after the procedure). Mean percent diameter stenosis decreased from 61 +/- 13% before to 17 +/- 7% after intervention. A successful interventional procedure with < 50% diameter stenosis of all treatment site lesions and no major adverse cardiac events within 30 days occurred in 95% of patients. Event-free survival at 6 months was 82%. Ninety-four percent of surviving patients were either asymptomatic or had mild stable angina at 6 month follow-up.

CONCLUSIONS

Despite unfavorable clinical and angiographic characteristics of the majority of patients enrolled, the acute angiographic results and early clinical outcome after NIR stent deployment were very promising. A prospective, randomized trial comparing the NIR stent with other currently available stents appears warranted.

Abrupt vessel closure: changing importance, management, and consequences

Percutaneous coronary interventions have been performed for 20 years. Despite the success and progress of these interventions, abrupt vessel closure has been a dramatic adverse event of coronary interventions. Closure has frequently led to the major complications of death, myocardial infarction, and emergency coronary artery bypass. Because of the fear of this adverse event and its subsequent complications, the applicability of coronary interventions is sometimes limited. The pathologic characteristics of abrupt vessel closure have been recognized as predominantly caused by dissection, with vessel recoil and thrombus formation playing important secondary roles. The recognition of the lesions at risk for abrupt vessel closure has led to a strategy of lesion-specific device therapy to reduce complications. Similarly the role of antiplatelet and antithrombotic therapies have reduced complications. The earliest methods of dealing with abrupt closure was emergency coronary artery bypass surgery with significant rates of morbidity and mortality. With the advent of second-generation devices and techniques, particularly stents, the management of abrupt vessel closure has been simplified and alternatives to emergency coronary bypass are more available. This article will review the history and current status of the prevention and management of abrupt vessel closure and demonstrate that anticipation and management of this complication have been facilitated with reduction of subsequent complications and increased applicability of coronary interventions.

Initial experience with long coronary stents: the changing practice of coronary angioplasty

The initial experience with the use of long coronary stents (> 30 mm in length) was analyzed retrospectively. Sixty-seven stents were deployed in 58 narrowings in 57 patients (34 AVE Microstents, 16 Nir stents, four Gianturco-Roubin II stents, and 13 Wallstents). Stents were implanted in 22 patients with unstable angina, 34 patients with stable angina, and one patient during direct angioplasty for acute myocardial infarction. Eighteen additional short stents were implanted to cover the entire length of the lesions so that an average of one and a half stents were deployed per patient. The length of the narrowings before stenting was 40 +/- 20 mm and the length of the stented segments was 45 +/- 20 mm. Stents were deployed for "bailout" in 23 narrowings, to improve suboptimal results of balloon angioplasty in 18 narrowings, and electively in 17 narrowings. Twenty of the 67 long stents were deployed in saphenous vein grafts. The success rate of stent implantation was 100%. One patient had a rupture of a saphenous vein graft after deployment of two long stents, with tamponade treated by emergency surgery. One patient had chest pain 18 hours after stent deployment; by the time he arrived at the catheterization laboratory the pain had subsided and the angiogram revealed a patent artery with normal flow. There were no other major complications during the hospital course and 1-month follow-up. We conclude that long coronary stents can be deployed successfully in native coronary arteries and vein grafts. They are useful for elective implantation and extremely helpful in bailout situations. The immediate results are excellent, but long-term outcome is awaited.

Coronary stenting with AVE microstents in acute myocardial infarction

Of 36 patients with acute myocardial infarction (AMI) who were referred for direct or rescue coronary angioplasty, 11 (31%) needed stent implantation. In 7 of them, the stent was implanted because of severe dissection and in 4, because of elastic recoil. All patients were discharged without clinical or electrocardiographic signs of reocclusion. No death, reinfarction or clinical evidence of ischemia occurred during up to 15 months of follow-up.

Early and late assessment of the Micro Stent PL coronary stent for restenosis and suboptimal balloon angioplasty

This prospective study represents the initial assessment of the Micro Stent PL (Arterial Vascular Engineering, Inc.) coronary stent. From one to three radiopaque stainless steel stents, each measuring 4 mm long, were premounted onto specially designed balloon catheters. A total of 123 stents were implanted in 41 patients without procedural failure or complications. Stent dislodgment proved a concern, with 7 of 123 stents (5.7%) moving > 3 mm from the site of placement and late downstream migration occurring in an additional patient. Subacute stent thrombosis occurred in two patients (5%). Six-month angiographic follow-up was available in 37 of 41 patients (90%). Minimal lumen diameter at baseline was 0.93 +/- 0.51 mm, increasing to 2.74 +/- 0.49 mm after stenting, and falling to 1.66 +/- 0.89 mm at 6 months; this represents a late loss of 60% of the initial gain. Restenosis, based on a binary definition of > 50% diameter stenosis, was documented in 18 patients (49%). Advantages of the Micro Stent PL include its radiopacity and marked ease of distal delivery. The potential for stent dislodgment has implications for future stent designs. The role of the Micro Stent PL in managing restenosis is unclear, but it appears useful in the management of dissection and threatened closure after balloon angioplasty.

Endovascular stents: a 'break through technology', future challenges

Coronary stents were developed to overcome the two main limitations of balloon angioplasty, acute occlusion and long term restenosis. Coronary stents can tack back intimal flaps and seal the dissected vessel wall and thereby treat acute or threatened vessel closure after unsuccessful balloon angioplasty. Following successful balloon angioplasty stents can prevent late vessel remodeling (chronic vessel recoil) by mechanically enforcing the vessel wall and resetting the vessel size resulting in a low incidence of restenosis. All currently available stents are composed of metal and the long-term effects of their implantation in the coronary arteries are still not clear. Because of the metallic surface they are also thrombogenic, therefore rigorous antiplatelet or anticoagulant therapy is theoretically required. Furthermore, they have an imperfect compromise between scaffolding properties and flexibility, resulting in an unfavourable interaction between stents and unstable or thrombus laded plaque. Finally, they still induce substantial intimal hyperplasia which may result in restenosis. Future stent can be made less thrombogenic by modifying the metallic surface, or coating it with an antithrombotic agent or a membrane eluting an antithrombotic drug. The unfavourable interaction with the unstable plaque and the thrombus burden can be overcome by covering the stent with a biological conduit such as a vein, or a biodegradable material which can be endogenous such as fibrin or exogenous such as a polymer. Finally the problem of persisting induction of intimal hyperplasia may be overcome with the use of either a radioactive stent or a stent eluting an antiproliferative drug.

Intracoronary stent implantation in native coronary arteries and saphenous vein grafts: a consecutive experience with six types of stents without prolonged anticoagulation

OBJECTIVE

To analyze the results of implantation of six different intracoronary stents without the use of prolonged anticoagulation.

MATERIAL AND METHODS

Between Mar. 30, 1993, and Jun. 30, 1995, 889 patients with 1,194 coronary or vein graft lesions underwent implantation of one of six types of stents-Palmaz-Schatz, Gianturco-Roubin, Wiktor, Micro, Cordis, or Wallstent. The patients were classified into seven groups on the basis of the type of stent that was implanted, including one group with combined use of two or more types of stents. Among the 851 patients with successful stent delivery and without major complications, 801 received only antiplatelet therapy, and 50 received a standard anticoagulation regimen. One-month clinical followup data were obtained in all patients, and clinical events were investigated.

RESULTS

The mean number of stents was 1.8 per lesion and 2.4 per patient. Procedural success was achieved in 93% of the lesions. The clinical success rate at 1 month was 90%. Intravascular ultrasound assessment was performed in 90% of the lesions. The final minimal luminal cross-sectional area of the stent increased from 6.8 to 7.8 mm2 after intravascular ultrasound-guided optimization. Within 1 month, 16 stent thrombosis events (1.9%) occurred. No significant differences were noted in stent thrombosis rates among the various stent cohorts. Multivariate logistic regression analysis revealed that the final stent minimal luminal diameter measured by intravascular ultrasonography was the only variable associated with stent thrombosis.

CONCLUSION

This study showed that six different stents could possibly be inserted without subsequent anticoagulation if optimal stent expansion and total lesion coverage were achieved.

Recent progress in coronary interventions--assessment by quantitative coronary angiography

Coronary balloon angioplasty is now well accepted as an effective therapy for patients with significant coronary artery stenosis. However, a number of deficiencies, including short-term complications, long-term restenosis, and limited application to complex morphologic lesions, restrict the widespread use of this technique. The precise lesion measurement provided by quantitative coronary angiography and intracoronary ultrasonography is a prerequisite for the optimization of balloon dilation or stent implantation. The short-term outcome may be improved by stent implantation, as this can prevent acute closure by acting as a scaffold for the disrupted vessel wall. The indications for percutaneous revascularization have been extended to chronic total occlusion by using a special guidewire, a laser wire and a coronary stent. Local drug delivery techniques to distribute agents to target revascularization sites may play a role in reducing the restenosis rate. Although the limitations of balloon angioplasty have led to the introduction of new devices, it remains to be seen whether these new devices can demonstrate, in a scientific manner, their safety, feasibility and superiority over conventional balloon angioplasty. Percutaneous coronary revascularization therapy may be an acceptable alternative to coronary bypass surgery in the future. However, to confirm this, a large multicenter randomized study is necessary to compare new percutaneous coronary interventional devices with bypass surgery. Additionally, further studies are required to demonstrate the most effective device for treating specific lesions in each individual patient.

Placement of multiple and different stent types for very long dissections during coronary angioplasty

We have been investigating the safety and efficacy of multiple and different stent types placed in the unfavorable situation of a very long dissection (> 20 mm) after coronary angioplasty. We report our preliminary experience in 20 patients who were treated by the following combinations: Palmaz-Schatz and Micro stent (14 patients). Wallstent and Micro stent (4 patients); Wiktor and Micro stent (1 patient); and Palmaz-Schatz, Micro and Wallstent (1 patient). Normal distal flow was restored in all except one (no reflow phenomenon) patient and complete covering of the dissection was obtained in all but two patients. Event-free survival at 30 days was 90% (18 of 20 patients). During follow-up (mean period: 8 +/- 3 months), two patients died. Of the 18 other patients, 16 remained asymptomatic and free of complications. Symptomatic restenosis was treated by standard angioplasty in the two remaining patients. In conclusion, placement of different stent types seems a feasible, safe, and efficient treatment for very long dissections caused by standard angioplasty.

Experience with the AVE Micro stent in native coronary arteries

Experience with implantation of 62 AVE Micro stents is described. Stents were quickly and successfully deployed in 62 of 63 attempts (98.4%), in tortuous coronary vessels, through proximally deployed stents, and under conditions of hemodynamic instability. It is therefore a very attractive choice to treat difficult anatomy during urgent situations.

New stent technologies

Coronary stents were developed to overcome the two main limitations of balloon angioplasty, acute occlusion and long-term restenosis. Coronary stents can tack back intimal flaps and seal the dissected vessel wall, thereby treating acute or threatened vessel closure after unsuccessful balloon angioplasty. After successful balloon angioplasty, stents can prevent late vessel remodeling (chronic vessel recoil) by mechanically enforcing the vessel wall and resetting the vessel size, resulting in a low incidence of restenosis. All currently available stents are composed of metal, and the long-term effects of their implantation in the coronary arteries are still not clear. Because of the metallic surface, they are also thrombogenic; therefore, rigorous antiplatelet or anticoagulant therapy is theoretically required. Furthermore, they have an imperfect compromise between scaffolding properties and flexibility, resulting in an unfavorable interaction between stents and unstable or thrombus-laden plaque. Finally, they still induce substantial intimal hyperplasia that may result in restenosis. Future stents can be made less thrombogenic by modifying the metallic surface or coating it with an antithrombotic agent or a membrane eluting an antithrombotic drug. The unfavorable interaction with the unstable plaque and the thrombus burden can be overcome by covering the stent with a biological conduit, such as a vein, or a biodegradable material that can be endogenous, such as fibrin, or exogenous, such as a polymer. Finally, the problem of persisting induction of intimal hyperplasia may be overcome with the use of either a radioactive stent or a stent eluting an antiproliferative drug.

Coronary artery stenting: indications and cost implications

The practice of coronary stenting is evolving rapidly, with new stent designs, deployment techniques, and adjunctive therapy. In many respects, clinical practice is changing in advance of the availability of supporting data. The consistent excellent angiographic result with stent deployment exceeds that achieved by any other previous interventional device, and the extent to which this accounts for the exponential increase in stent utilization cannot be accurately determined but is undoubtedly considerable. Controlled randomized trials have confirmed that stent deployment is superior to balloon angioplasty in certain lesion subsets or clinical scenarios. These include focal de novo native vessel lesions, lesions with late recoil after balloon angioplasty, acute closure after balloon angioplasty, and proximal left anterior descending coronary artery lesions. In addition, observational data is persuasive in focal coronary saphenous vein graft lesions and aorto-ostial lesions. On the other hand, the evidence supporting the use of stents strictly to improve on a suboptimal result, possibly the most frequent indication, is indirect and circumstantial. Stents are expensive, but it was anticipated that with the reduction in restenosis not only would they be cost-effective but also ultimately would reduce costs. This hope has not as yet been realized. However, there is little question that the introduction of intracoronary stents has been the most significant and exciting development since the introduction of percutaneous revascularization almost 20 years ago. It has revitalized the field.

Improved technique for use of half-stents remounted on a stent delivery system

The use of half-length intracoronary Johnson & Johnson stents has been described in a number of settings. Half-stents are useful for very short lesions, avoidance of bifurcations or side-branches, ostial stenosis, covering gaps between adjacent stents, and for dissection adjacent to stents caused by postdilatation. Previously described methods for use of half-stents have involved bare stents, or significant manipulation of either the stent or the delivery sheath for remounted half-stents. We describe a method for half-stent preparation and delivery that does not involve distortion of the stent or the delivery sheath. The risk of stent loss, as can occur with bare stents, is diminished. The geometry of the stent is preserved since it is not expanded and then recrimped, and the end of the delivery sheath is not flared or distorted, which may interfere with stent delivery.

Short- and long-term clinical and quantitative angiographic results with the new, less shortening Wallstent for vessel reconstruction in chronic total occlusion: a quantitative angiographic study

OBJECTIVES

This study was designed to examine whether oversized implantation of the new, less shortening Wallstent provides a more favorable long-term clinical and angiographic outcome in chronic total occlusions than does conventional coronary balloon angioplasty.

BACKGROUND

Restenosis and reocclusion remain major limitations of balloon angioplasty for chronic total occlusions. Enforced mechanical remodeling by implantation of the oversized Wallstent may prevent elastic recoil and improve accommodation of intimal hyperplasia.

METHODS

Lumen dimension was measured by a computer-based quantitative coronary angiography system (CAAS II). These measurements (before and after intervention and at 6-month follow-up) were compared between the groups with Wallstent implantation (20 lesions, 20 patients) and conventional balloon angioplasty (266 lesions, 249 patients) for treatment of chronic total occlusion. Acute gain (minimal lumen diameter after intervention minus that before intervention), late loss (minimal lumen diameter after intervention minus that at follow-up) and net gain (acute gain minus late loss) were examined.

RESULTS

Wallstent deployment was successful in all patients. High pressure intra-Wallstent balloon inflation (mean +/- SD 14 +/- 3 atm) was performed in all lesions. Although vessel size did not differ between the Wallstent and balloon angioplasty groups, acute gain was significantly greater in the Wallstent group (2.96 +/- 0.55 vs. 1.61 +/- 0.34 mm, p < 0.0001). Although late loss was also significantly larger in the Wallstent group (0.81 +/- 0.95 vs. 0.43 +/- 0.68 mm, p < 0.05), net gain was still significantly greater in this group (2.27 +/- 1.00 vs. 1.18 +/- 0.69 mm, p < 0.0001). Angiographic restenosis (> or = 50% diameter stenosis) occurred at 6 months in 29% of lesions in the Wallstent group and in 45% of those in the balloon angioplasty group (p = 0.5150).

CONCLUSIONS

Implantation of the oversized Wallstent, with full coverage of the lesion length, ensures resetting of the vessel size to its original caliber before disease and allows greater accommodation of intimal hyperplasia and chronic vessel recoil. Wallstent implantation provides a more favorable short- and long-term clinical and angiographic outcome than does conventional balloon angioplasty for chronic total occlusions.

Migration of the AVE Micro coronary stent

The AVE Micro coronary stent is a balloon-expandable stent with a design that is different from the commonly used slotted tubular or coil stents. The stent delivery system is low in profile and very trackable so that it can negotiate tortuous vessels to reach distal lesions. It also can pass through proximally deployed stents easily. Its moderate radioopacity allows precise stent placement. However, as illustrated in the three case reports presented here, the stent struts did not seem to be firmly embedded into the arterial wall after initial deployment, so that stent migration occurred during subsequent passage of a balloon into the stent for poststenting high pressure balloon dilatation. This new phenomenon of stent migration has not been reported previously with other stents.

Six-month clinical and angiographic outcome of the new, less shortening Wallstent in native coronary arteries

BACKGROUND

The new, less shortening, self-expanding Wallstent is characterized by longitudinal flexibility, a protective membrane, a low profile, and a customized range of diameters (3.5 to 6.0 mm). The recent modification of the braiding angle of the Wallstent has resulted in a new device with less shortening on expansion and a concomitant reduction in radial force. We hypothesized that the enforced mechanical remodeling produced by the selection of an oversized Wallstent might result in improved accommodation of subsequent reactive intimal hyperplasia and prevention of chronic recoil of the vessel.

METHODS AND RESULTS

To prove this hypothesis, we recently implanted 44 new, less shortening Wallstents in 35 native coronary arteries in 35 patients with acute or threatened closure after balloon angioplasty, according to a strategy of oversizing of Wallstent diameter and complete coverage of the lesion length. The initial and 6-month follow-up angiograms were analyzed with a computer-based quantitative coronary angiography (QCA) system. Acute gain (minimal luminal diameter [MLD] post minus MLD pre) and late loss (MLD post minus MLD at follow-up) were examined. Stent deployment was successful in 44 of 44 attempts (100%). Nominal stent diameter used was 1.40 mm larger than the maximal vessel diameter. One patient (3%) with a dilated but unstented lesion proximal to the stented segment sustained a subacute occlusion on day 1 associated with myocardial infarction. Event-free survival at 30 days after stent implantation was 97% (34 of 35 patients). Of the 34 patients eligible for 6-month angiographic follow-up, 3 who were asymptomatic declined repeat angiography. MLD (and percent diameter stenosis [% DS]) changed from 0.83 +/- 0.50 mm (72%) pre through 3.06 +/- 0.48 mm (15%) post to 2.27 +/- 0.74 mm (28%) at follow-up. Acute gain was 2.23 +/- 0.63 mm, and late loss was 0.78 +/- 0.61 mm. Angiographic restenosis ( > 50% DS) was observed in 5 of 31 patients (16%) at 6 months, all of whom underwent repeat angioplasty. Thus, the overall event-free survival at 6-month follow-up was 83% (29 of 35 patients).

CONCLUSIONS

The oversized Wallstent implantation with complete coverage of the lesion length conveyed a favorable 6-month clinical and angiographic outcome. The large acute gain obtained by the Wallstent afforded greater accommodation of the subsequent late loss. The enforced mechanical remodeling by oversized new Wallstents may result in prevention of acute and chronic recoil of the vessel wall and subsequently a lower restenosis rate at follow-up.

Stents for intracoronary placement: current status and future directions

The technique of intracoronary stenting has achieved remarkable progress over the last few years. Improved stent deployment techniques and optimization of postprocedural management have dramatically improved the safety of intracoronary stent placement. At present, the incidence of early vessel closure after stenting is even lower than that after standard angioplasty and, as most operators no longer prescribe aggressive anticoagulation, bleeding complications are uncommon. Stenting has become an extremely effective treatment for abrupt or threatened vessel closure or for any suboptimal angiographic result during conventional angioplasty. Furthermore, large prospective trials have demonstrated that its efficacy is superior to that of conventional angioplasty for primary restenosis prevention in focal lesions of some native coronary arteries. Ongoing trials tend to extrapolate these conclusions to saphenous vein graft lesions. Mechanical support of the vessel wall explains the sustained angiographic benefit observed after stenting. Future developments may include the use of stents as a vehicle for local drug delivery in an attempt to further reduce the incidence of restenosis. In view of these results, coronary stents should be considered a new standard therapeutic modality in interventional cardiology.

Coronary lumen at six-month follow-up of a new radiopaque Cordis tantalum stent using quantitative angiography and intracoronary ultrasound

To determine the reliability of geometric (edge-detection) quantitative coronary angiographic analysis (QCA) of restenosis within a new Cordis tantalum stent, QCA and intracoronary ultrasound (ICUS) measurements were compared in both an experimental restenosis model and in the clinical follow-up of patients. In the experimental series, Plexiglas phantom vessels with concentric stenosis channels ranging from 0.75 to 3.0 mm in diameter and with a reference diameter of 3.0 mm were imaged both before and after their insertion in tantalum stents. In the clinical series, the agreement of QCA and ICUS measurements were studied in 23 patients who had undergone coronary implantation of the new tantalum stent and in 23 patients who had undergone balloon angioplasty 6 months previously. The reliability of QCA declined in the presence of the radiopaque stent (accuracy of QCA decreased from -0.07 to -0.12 mm), whereas the reliability of lumen measurements by ICUS was independent of the presence of the radiopaque stent (-0.12 and -0.13 mm). Without the stent, the average minimal luminal diameter (MLD) obtained by QCA of the 1.00 mm Plexiglas vessel was 1.00 +/- 0.01 mm, and the 3.00 mm reference vessel diameter was 2.81 +/- 0.05 mm, providing a 64 +/- 1% diameter stenosis. After introduction of the stent, the average MLD and reference vessel diameter were 0.99 +/- 0.06 and 3.36 +/- 0.17 mm, respectively, providing a diameter stenosis of 71 +/- 2%. ICUS measurements (2.77 mm) of the reference vessel diameter (3.00 mm) were unaffected by the presence of the stent.(ABSTRACT TRUNCATED AT 250 WORDS)

Progression and regression of coronary stenosis in the long-term follow-up of vasospastic angina

BACKGROUND

Whether focal vasospasticity plays a pathogenic role in the progression or regression of coronary atherosclerosis is unknown. To determine whether evidence for such a role exists, we studied long-term changes in coronary luminal measurements in patients with vasospastic angina.

METHODS AND RESULTS

Quantitative coronary angiography and repeated ergonovine provocation tests were performed 45 +/- 16 months apart in 30 patients. All patients had vasospastic anginal symptoms and coronary spasm on the initial provocation test. On the 30 patients, 16 had persistent symptoms of vasospastic angina and showed coronary spasm at the same site on the follow-up angiogram (group 1), while the remaining 14 whose vasospastic anginal symptoms disappeared at follow-up demonstrated a negative response to ergonovine on the follow-up tests (group 2). There was no significant difference in patients' baseline characteristics between the two groups. Long-term changes in minimal (MLD) and mean (MEAN) luminal diameter were measured (in millimeters) after administration of isosorbide dinitrate in 19 spastic and 93 nonspastic segments in group 1 and in 17 previously spastic and 81 nonspastic segments in group 2. Both MLD and MEAN were measured in 210 coronary segments of the 30 patients at baseline and after administration of ergonovine and isosorbide dinitrate by use of a computer-based quantitative coronary angiography system. Stenosis progression and regression of individual lesions were defined as a change in MLD of > or = 0.40 mm. In group 1, both the MLD and MEAN of 19 spastic segments were significantly smaller (progression) at follow-up compared with the initial angiogram (MLD, 2.21 +/- 0.54 initially versus 1.95 +/- 0.65 at follow-up, P < .01; MEAN, 2.80 +/- 0.56 initially versus 2.56 +/- 0.58 at follow-up, P < .01), whereas the MLD and MEAN of 93 nonspastic segments in group 1 were not significantly different between the initial and follow-up angiograms (MLD, 2.47 +/- 0.67 initially versus 2.44 +/- 0.69 at follow-up, P = NS; MEAN, 2.96 +/- 0.69 initially versus 2.91 +/- 0.68 at follow-up, P = NS). In group 2, the MLD of the 17 previously spastic segments significantly improved (regression) at follow-up (MLD, 1.99 +/- 0.68 initially versus 2.24 +/- 0.54 at follow-up, P < .05); the MLD and MEAN of the 81 nonspastic segments were not significantly different (MLD, 2.36 +/- 0.59 initially versus 2.39 +/- 0.60 at follow-up, P = NS; MEAN, 2.81 +/- 0.58 initially versus 2.81 +/- 0.61 at follow-up, P = NS). In group 1, significant stenosis progression of individual lesions was observed more frequently at spastic than nonspastic segments (6 of 19 versus 10 of 93, P < .05), whereas stenosis regression was observed in no spastic and 3 nonspastic segments (P = NS). In group 2, stenosis progression was observed at 1 previously spastic segment and 4 nonspastic segments (P = NS), while significant stenosis regression of individual lesions was seen more commonly in previously spastic than nonspastic segments (6 of 17 versus 7 of 81, P < .01).

CONCLUSIONS

These results have demonstrated in patients an association between persistent vasospastic activity and progression of atherosclerosis and an association between cessation of vasospastic activity and regression of atherosclerosis.