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

Efficacy and safety of intravascular lithotripsy for the treatment of peripheral arterial disease: An individual patient-level pooled data analysis

BACKGROUND

Peripheral arterial disease (PAD) is one of the most common manifestations of atherosclerotic disease worldwide. Peripheral arterial calcification reduces acute success and long-term patency of endovascular therapy for PAD. Several calcium modification devices are available for use in peripheral interventions. Outcomes after peripheral intravascular lithotripsy (IVL), a novel approach using pulsatile sonic waves to treat luminal and medial calcium in patients with PAD, have not been extensively characterized. Therefore, we sought to perform an individual patient-level data (IPD) pooled analysis of available studies to evaluate the efficacy and safety of IVL in the treatment of PAD.

METHODS AND RESULTS

We pooled IPD, including baseline and procedural variables, from five prospective studies which assessed IVL in the treatment of patients with extensive peripheral artery calcification. Final postprocedural percent diameter stenosis (%DS) and procedural angiographic complications were assessed by independent core laboratory. Efficacy endpoints were analyzed using linear mixed effects models and safety endpoints were tabulated overall and by vascular bed. Among 336 patients who underwent endovascular revascularization with use of IVL, there was a significant reduction between pre-procedural and final %DS of 55.1% (95% confidence interval 53.3-57.0%, p < .0001). Core-laboratory assessed lesion-level complications, including flow-limiting dissections (Types D-F), vessel perforation, distal embolization, thrombus, abrupt closure, and no reflow, occurred in 4/328 (1.22%) of treated lesions.

CONCLUSIONS

The present IPD of five prospective studies, marking the largest analysis to date evaluating the use of IVL in significantly calcified PAD lesions, demonstrates this treatment strategy to be both effective and safe.

Impact of Cutting Balloon Angioplasty (CBA) Prior to Bare Metal Stenting on Restenosis A Prospective Randomized Multicenter Trial Comparing CBA With Balloon Angioplasty (BA) Before Stenting (REDUCE III)

BACKGROUND

While stent restenosis and late thrombosis still occur even with drug-eluting-stents (DES), there remains a need to explore other strategies for preventing restenosis.

METHODS AND RESULTS

Five hundred and twenty-one patients were randomized: 260 to cutting-balloon angioplasty (CBA) before bare-metal stent (CBA-BMS) and 261 to balloon-angioplasty (BA) before BMS (BA-BMS). Intravascular ultrasound (IVUS)-guided procedures were performed in 279 (54%) patients and angiographic guidance was used in the remainder. Minimal lumen diameter was significantly greater in CBA-BMS than BA-BMS (2.65+/-0.40 mm vs 2.52+/-0.4 mm, p<0.01) and % diameter stenosis (%DS)-post was less in CBA-BMS than BA-BMS (14.0+/-5.9% vs 16.3+/-6.8%, p<0.01). %DS-follow-up was subsequently less in CBA-BMS than BA-BMS (32.4+/-15.1% vs 35.4+/-15.3%, p<0.05) associated with lower rates of restenosis in CBA-BMS than BA-BMS (11.8% vs 19.6%, p<0.05) and less target lesion revascularization (TLR) in CBA-BMS than BA-BMS (9.6% vs 15.3%, p<0.05). Patients were divided into 4 groups based on the device used before stenting and IVUS use (IVUS-CBA-BMS: 137 patients; Angio-CBA-BMS: 123; IVUS-BA-BMS: 142; and Angio-BA-BMS: 119). At follow-up IVUS-CBA-BMS had a significantly lower restenosis rate (6.6%) than Angio-CBA-BMS (17.9%), IVUS-BA-BMS (19.8%) and Angio-BA-BMS (18.2%, p<0.05).

CONCLUSIONS

Restenosis and TLR were significantly lower in CBA-BMS than BA-BMS. This favorable outcome was achieved because of the lower restenosis rate conferred by the IVUS-guided-CBA-BMS strategy (6.6%). The restenosis rates obtained with this strategy were comparable to those achieved with DES.

Impact of Angiotensin II Receptor Blockers on the Progression and Regression of Coronary Atherosclerosis An Intravascular Ultrasound Study

BACKGROUND

Although angiotensin II receptor blockers (ARB) have been found to reduce the coronary atherosclerotic plaque burden in animal models, it is unknown whether ARB have a similar effect on human coronary arteries.

METHODS AND RESULTS

Serial intravascular ultrasound (IVUS) studies of the left main (LM) coronary artery were performed in 64 patients at baseline and after 7-month follow-up. All patients were divided into 2 groups (ARB group: 23 patients; non-ARB group: 41 patients). Three-dimensional volumetric analysis was done throughout the LM coronary artery, and the volume index (VI; volume/length) was calculated for the vessel (VVI), lumen (LVI), and plaque (PVI). No significant difference was found between the 2 groups in baseline clinical characteristics, including age, gender, blood pressure levels, serum cholesterol levels, the presence of diabetes and smoking status. At baseline VVI, LVI and PVI were similar between the groups. In the non-ARB group, VVI, LVI, and PVI did not change between baseline and follow-up. In the ARB group, PVI significantly decreased during follow-up (9.9 +/-3.1 mm2 vs 9.1+/-2.7 mm2, p<0.01), whereas VVI and LVI were unaffected.

CONCLUSIONS

This preliminary IVUS study suggests that ARB could cause regression of coronary atherosclerosis in humans.

Clinical and quantitative angiographic outcomes following elective implantation of the self-expanding Wallstent for longer coronary artery lesions--final results of the Wellstent native study

BACKGROUND: Implantation of short balloon-expandable stents provides superior clinical and angiographic outcome compared with balloon angioplasty in selected patients. The purpose of the Wellstent study was to evaluate the safety and efficacy of the self-expanding Wallstent combined with aspirin and ticlopidine in patients with stable or unstable angina related to a native coronary lesion up to 45 mm in length. METHODS: 105 patients (111 lesions) with stable (57%) or unstable (43%) angina were included in this prospective multicentre evaluation. Angiography before and after Wallstent implantation and at 6-month follow-up was analysed at the core lab using the CAAS 2 system. The primary end-point was incidence of major adverse cardiac events (MACE) at 30 days. Secondary end-points were angiographic outcome at 6 months and MACE at 6 months and 1 year. RESULTS: Acute procedural success (successful stent implantation with residual stenosis <20%) was achieved in 99%. Mean reference diameter was 3.18 +/- 0.66 mm, minimal luminal diameter was 1.00 +/- 0.50 mm pre- and 2.84 +/- 0.47 mm poststent (diameter stenosis 16 +/- 6%). The mean hospital stay was 2.2 days. At 30 days, 95% of patients were free of MACE. At 6 month and 1 year clinical follow-up, 75% and 71% of patients, respectively, remained free of MACE, the majority of which (19 of 30) were re-interventions at re-angiography. In 90% of eligible patients, MLD at follow-up was 1.65 +/- 0.75 mm (late loss 1.20 +/- 0.66 mm, loss index 0.66), diameter stenosis 42 +/- 15%, with a restenosis rate of 32%. Longer stents were associated with greater luminal loss (P = 0.001) and less-favourable clinical outcome. CONCLUSIONS: Wallstent implantation, combined with aspirin and ticlopidine, achieved excellent acute and 30 day clinical results in a heterogenous high-risk patient group. Clinical outcome at 6 months and 1 year remained good, and most adverse events were re-PTCA during follow-up angiography. The loss index of 0.66 and restenosis rate of 32%, related in part to the use of longer stents, emphasizes the continuing need for effective anti-proliferative therapy.

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.

Long-term clinical outcome after implantation of medium Palmaz (biliary) stents in very large native coronary arteries

Intracoronary stenting has been shown to improve acute and long-term clinical results compared with coronary angioplasty. However, clinical outcome after medium Palmaz biliary (PB) stent implantation in very large native coronary arteries (> 4 mm in diameter) is unknown. This study evaluated restenosis and long-term clinical outcome after PB stenting in large native coronary arteries. Between June 1993 and December 1998, 55 patients with 56 lesions were treated with PB stents. Intracoronary stent deployment was successful in all 56 vessels attempted (100%). The mean stenosis was reduced from 65% +/- 10% to 4% +/- 14%. In 48 of the 56 vessels (86%), vessel size was greater than 4.0 mm in diameter and the mean reference vessel diameter was 4.73 +/- 0.7 mm after stenting. Angiographic success was achieved in 100%. Five patients had postprocedural cardiac enzyme elevation. There was no periprocedural death, emergency coronary artery bypass surgery, repeat target lesion revascularization, or acute stent thrombosis. Long-term clinical follow-up at mean of 28 +/- 15 months was obtained in 96% of the patients. Clinical restenosis rate occurred in 18% of ostial (6/34) and 0% of nonostial (0/22) lesions (P < 0.0001) with an overall clinical restenosis rate of 11%. Repeat angioplasty were performed in these six patients. There were three cardiac and three noncardiac deaths. The overall event-free survival at 1 and 3 years was 92% +/- 4% and 80% +/- 6%, respectively. PB stent implantation in very large native coronary arteries can be performed with a high degree of procedural success and low in-hospital complications. The long-term clinical outcome of patients undergoing PB stenting is associated with excellent event-free survival. However, stenting of ostial lesions remains as an important factor for restenosis even in very large coronary artery stenting.

The Comparison between Self-Expanding and Balloon Expandable Stent Results in Left Anterior Descending Artery

The first Wallstent results had high thrombosis and death. It was reported that the left anterior descending (LAD) artery was the vessel implicated in major complications that occurred in patients who received a Wallstent. Subsequently, Wallstent applications were refrained from with LAD lesions. However, the promising results of second-generation self-expanding Magic Wallstent implantation have been reported recently. The purpose of this study is to assess the immediate and intermediate clinical outcomes of patients undergoing self-expanding Magic Wallstent implantation at the LAD site and to compare those outcomes with those of a similar group of patients undergoing balloon expandable stenting at the same site. Between 1995 and 1999, 255 consecutive patients underwent LAD stenting at our center. The study population was divided into two groups based on the mode of delivery (self-expanding versus balloon-expandable) of stent design. Group I included 97 patients in whom self-expanding Magic Wallstents were implanted. Group II included 158 patients in whom various types of balloon-expandable stents were implanted. Procedural success was defined as successful deployment of the stent in the absence of adverse cardiac events (death, acute myocardial infarction, emergency coronary bypass surgery). Clinical success was defined as the absence of adverse cardiac events (death, acute myocardial infarction, emergency coronary bypass surgery, repeat balloon angioplasty) within the first two weeks. The mean follow-up period was 8 +/- 5.3 months for Group I and 9.8 +/- 7.5 months for Group II. There was no difference in baseline characteristics between the two groups. Fourteen patients in Group I and 22 patients in Group II had bailout procedures. The number of patients with reference vessel diameter less than 3 mm was 37 in Group I and 60 in Group II. The stent length was greater in Group I than in Group II (p = 0.0003). In Group I, stenting improved minimal lumen diameter (MLD) from 0.65 +/- 0.4 mm to 2.35 +/- 0.4 and percent diameter stenosis (PDS) from 76.24 +/- 17.3 to 22.78 +/- 13.6. In Group II, stenting improved MLD from 0.73 +/- 0.4 mm to 2.49 +/- 0.5 and PDS from 76.71 +/- 15.5 to 18.99 +/- 9.6. Final MLD and final PDS improved more in Group II than Group I. Stent could not be delivered in three patients in Group I and nine in Group II. In Group II, six stents were dislocated from its delivery system. Procedural and clinical success and subacute stent thrombosis rates were 93.8%, 85.6%, and 7.2% in Group I, and 93%, 86.7%, and 5.1% in Group II, respectively. Within the first two weeks, death occurred in one patient in each group, acute myocardial infarction in four (Group I) and two (Group II) patients; coronary bypass surgery in three (Group I) and five (Group II) patients, and balloon angioplasty in two (Group I) and four (Group II) patients, respectively. In Group I, following the first two weeks, no patients died, two patients had nonfatal myocardial infarction, and coronary bypass surgery and target vessel repeat balloon angioplasty was required in five and ten patients, respectively. In Group II, one patient died in the follow-up period, there was no nonfatal myocardial infarction, and bypass surgery and target vessel repeat balloon angioplasties were required in three and eleven patients, respectively. None of these differences in clinical events was statically significant. We found that self-expanding Magic Wallstent implantation can be performed in LAD lesions and was associated with a rate of early clinical results and intermediate term clinical results similar to that of balloon-expandable stents in LAD arteries. In conclusion, the Magic Wallstent may confidently be used for LAD lesions. </hea

Angiographic and clinical outcome of a new self-expanding intracoronary stent (RADIUS): results from multicenter experience in Japan

The RADIUS coronary stent featuring a multisegmented slotted tube design and self-expanding nitinol delivery system has a high radial force and flexibility, uniform expansion, and contours to the shape of the vessel. Successful stent deployment was achieved in 104 stable angina patients (106 lesions; 44% LAD, 19% circumflex, and 37% RCA). Mean minimal lumen diameter (MLD) increased from 0.77 +/- 0.46 mm to 2.88 +/- 0.61 mm and mean percent diameter stenosis (% DS) decreased from 73 +/- 14% to 6 +/- 13% immediately after the procedure. At 6-month follow-up, two patients (2%) underwent urgent target revascularization, and cerebral bleeding occurred in one patient (1%). Angiographic follow-up was performed in 94 lesions (89%) and mean MLD and mean % DS were 2.08 +/- 0.92 mm and 30% +/- 24%, respectively. Stent restenosis (>50% diameter stenosis at follow-up) was observed in 16 (17%) of all lesions. The high success rate for stent deployment, low incidence of major adverse cardiac event, and lower restenosis rate after stent implantation indicate that the RADIUS stent is useful for coronary intervention.

Procedural results and late clinical outcomes after percutaneous interventions using long (> or = 25 mm) versus short (< 20 mm) stents

OBJECTIVES

To evaluate clinical outcomes after the use of long coronary stents.

BACKGROUND

The use of long slotted-tube stents has been recently approved in the U.S. to treat long lesions or dissections. Procedural success and long-term outcomes of long versus short stents have not been established.

METHODS

We evaluated procedural success, major in-hospital complications, target lesion revascularization and long-term (one year) clinical outcomes in 1,226 consecutive patients (1,259 native coronary lesions) who underwent a single vessel intervention using a single long (> or =25 mm, 116 patients) or short (<20 mm, 1,110 patients) tubular-slotted stent.

RESULTS

Patients treated with long stents had more diffuse (>10 mm length) lesions (63% vs. 28%, p = 0.001). The mean stent length was 28 +/- 5 mm versus 15 +/- 2 mm for long versus short stent groups (p = 0.001). Overall procedural success was similar in the long versus short stent groups (96% vs. 98%, p = 0.08). However, major in-hospital complications tended to occur more frequently in patients treated with longer stents (3.4% vs. 1.0%, p = 0.04). The rate of periprocedural non-Q-wave myocardial infarction (MI) (creatine kinase-MB > or =5 times normal) was notably higher after long stent implantation (23% vs. 11%, p = 0.001). Target lesion revascularization at one year was 14.5% vs. 13.8% (p = 0.69), and target vessel revascularization rate was 19.6% vs. 17.3% (p = 0.41) in the long versus short stent group, respectively. There was no difference in one year mortality (2.5% vs. 3.5%, p = 0.49) or Q-wave MI (2.7% vs. 1.2%, p = 0.48), and the overall cardiac event-free survival was similar for the two groups (81%).

CONCLUSIONS

The use of single coronary long (> or =25 mm) versus short (<20 mm) stents is associated with: 1) somewhat increased major procedural complications, 2) significantly higher frequency of periprocedural non-Q-wave MIs, and 3) equivalent repeat revascularization risk and cardiac event-free survival out-of-hospital up to one year.

Angiographic and clinical restenosis following the use of long coronary Wallstents

This study assessed clinical and angiographic restenosis following the deployment of the long coronary Wallstent. Between May 1995 and June 1997, 182 Wallstents were deployed in 162 vessels in this unit. Forty-eight percent had an unstable coronary syndrome and 94% had AHA grade B or C lesions. The mean lesion length was 37 +/- 20 mm and the mean stent length was 48 +/- 20 mm. The procedural success rate was 99% and the primary success rate was 93%. Six in-patients suffered subacute stent thrombosis, the majority being in the era of anticoagulation rather than antiplatelet regimes. Seventy-three percent remained free of major adverse clinical events in the follow-up period, but 41% had angiographic restenosis. The Wallstent can be deployed in complex lesions with a high primary success rate and an acceptably low restenosis rate. The optimal management of in-stent restenosis remains to be defined.

Quantitative measurements of in-stent restenosis: A comparison between quantitative coronary ultrasound and quantitative coronary angiography

While quantitative coronary angiography (QCA) remains the standard used to assess new interventional therapies, intracoronary ultrasound (ICUS) is gaining interest. The aim of the study was to determine the relationship between QCA and quantitative coronary ultrasound (QCU) measurements after stenting. Sixty-two consecutive patients with both QCA and QCU analysis after stent implantation were included in the study. The mean luminal diameter (QCU vs. QCA) were 2.74 +/- 0.46 mm and 2.41 +/- 0.49 mm (P < 0.0001), the minimal luminal diameter (MLD) 2.08 +/- 0.44 mm and 1.62 +/- 0.42 mm (P < 0. 0001), and the projected QCU MLD 1.90 +/- 0.42 mm (P < 0.0001 with respect to QCA). Percentage obstruction diameter (QCU vs. QCA) were 41.53% +/- 10.78% and 43.15% +/- 12.72% (P = NS). The stent diameter (QCU vs. QCA) were 3.54 +/- 0.65 mm and 3.80 +/- 0.37 mm (P = 0. 0004). Stent length measured by QCU were longer at 31.11 +/- 13.54 mm against 28.63 +/- 12.75 mm, P < 0.0001 with respect to QCA. In conclusion, while QCA and QCU appear to be comparable tools for measuring corrected stent diameters and stent lengths, smaller luminal diameters were found using QCA. This is of particular relevance to quantitative studies addressing absolute changes in vascular or luminal diameters. Cathet. Cardiovasc. Intervent. 48:133-142, 1999.

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.

Stenting of long coronary artery lesions: initial angiographic results and 6-month clinical outcome of the micro stent II-XL

To evaluate the results of long Micro Stent II (MS-XL) implantations, 119 MS-XLs were implanted in 102 patients (age, 62.83 years). Nineteen stents (16%) were implanted in saphenous vein grafts; 100 stents (84%) were implanted in native coronary arteries. Twenty-five patients (25%) were treated because of acute myocardial infarction (AMI); 30 patients (29%) because of unstable angina or angina class IV, and 47 patients (46%) because of stable angina. Eighty-six de novo lesions (84%) and 16 restenotic lesions (16%) were treated. Indications for stent implantation include elective, 61 patients (60%); suboptimal balloon angioplasty result, 22 patients (21%); and bailout after balloon angioplasty, 19 patients (19%). Because of residual thrombus after stenting, 27 patients (26%) received abciximab. All patients received ticlopidin for 28 days and acetylsalicylic acid. One hundred and seventeen MS-XLs (98%) were implanted successfully. Additional (shorter) MS-II were implanted in 40 patients (39%). The stented segment length was 45 +/- 20 mm. The minimum lumen diameter increased from 0.5 +/- 0.5 mm before to 2.7 +/- 0.5 mm after stent implantation. The acute gain was 2.2 +/- 0.4 mm. Early clinical events (<4 weeks) include death, 3 (3%); subacute stent thrombosis, 1 (1%); non-Q-wave infarction, 2 (2%); CABG, 1 (1%); vascular complications, 2 (2%). Late clinical events (<6 months) include acute myocardial infarction, 5 (5%); reintervention, 6 (6%); CABG, 1 (1%). The procedural success rate was 88%, and the event free survival at 6 months was 76%. Stenting of long lesions with the MS-XL was successful and associated with an acceptable complication rate. Cathet. Cardiovasc. Intervent. 48:105-112, 1999.

Electron-beam CT in the noninvasive assessment of coronary stent patency

RATIONALE AND OBJECTIVES

Coronary artery stents reduce the rate of restenosis in patients who have undergone balloon angioplasty; therefore, the implantation of coronary stents represents an important method in the treatment of coronary stenoses. The authors' purpose was to investigate the usefulness of electron-beam computed tomography (CT) as a noninvasive means of assessing the patency of coronary artery stents in patients who had undergone balloon angioplasty and stent placement.

MATERIALS AND METHODS

Electron-beam CT was used to assess stent patency in 177 patients with 285 stents. Contrast material-enhanced multisection flow studies were performed, and the images were evaluated by three investigators and compared with the findings of coronary angiography.

RESULTS

Cine loop evaluations and time-attenuation curve analysis led to the correct diagnosis in 167 (94.3%) patients, as confirmed with coronary angiography. Stenoses had occurred in 18 of the 194 vessels with stents, and 14 of these were detected with electron-beam CT.

CONCLUSION

Electron-beam CT appears to be a valuable imaging modality in the noninvasive assessment of stent patency in coronary arteries.

Coronary wallstents show significant late, postprocedural expansion despite implantation with adjunct high-pressure balloon inflations

Adjunct high-pressure balloon inflations following the delivery of oversized self-expandable Wallstents may affect their implied late, postprocedural self-expansion. Consequently, we examined 15 "Magic" Wallstents, which were implanted following a strategy of stent oversizing and subsequent adjunct high-pressure balloon inflations (16 +/- 2 atm; all > or = 12 atm). The excellent radiographic visibility of this stent permitted reliable quantitative coronary angiographic measurement of both lumen and stent dimensions (before and after stenting, and at follow-up). At follow-up, extent and distribution of in-stent neointimal proliferation were evaluated with volumetric intravascular ultrasound. Between postintervention and follow-up examination, mean stent diameter increased from 3.7 +/- 0.4 to 4.2 +/- 0.4 mm (p <0.0001); there was no significant difference in late stent expansion between proximal, mid-, and distal stent subsegments. Late stent expansion showed a significant (reverse) relation to maximum balloon size (r = -0.56, p <0.04), but not with follow-up lumen size or late lumen loss. On average, 52 +/- 18% of the stent was filled with neointimal ingrowth; neointimal volume/cm stent length was 64 +/- 22 mm3. Both late stent expansion (r = 0.36, p <0.02) and maximum balloon pressure (r = 0.41, p <0.001) were related to neointimal volume/cm stent but not to follow-up lumen size. Thus, despite high-pressure implantation, Wallstents showed significant late self-expansion, which resulted in larger stent dimensions at follow-up that assisted in accommodating in-stent neointimal proliferation. Conversely, late stent expansion had a significant relation to the extent of in-stent neointimal ingrowth. Beneficial and disadvantageous effects of the late stent expansion appear to be balanced, because a relation to late lumen loss or follow-up lumen dimensions was not found to be present.

Progressive vascular remodeling and reduced neointimal formation after placement of a thermoelastic self-expanding nitinol stent in an experimental model

Despite the improvements afforded by intracoronary stenting, restenosis remains a significant problem. The optimal physical properties of a stent have not been defined. We compared the vascular response to a thermoelastic self-expanding nitinol stent with a balloon-expandable tubular slotted stainless steel stent in normal porcine coronary arteries. Twenty-two stents (11 nitinol and 11 tubular slotted) were implanted in 11 miniature swine. The nitinol stents were deployed using the intrinsic thermal properties of the metal, without adjunctive balloon dilation. The tubular slotted stents were implanted using a noncompliant balloon with a mean inflation pressure of 12 atm. Intravascular ultrasound (IVUS) and histology were used to evaluate the vascular response to the stents. The mean cross-sectional area (CSA) of the nitinol stents (mm2) as measured by IVUS increased from 8.13 +/- 1.09 at implant to 9.10 +/- 0.99 after 28 days (P = 0.038), while the mean CSA of the tubular slotted stents was unchanged (7.84 +/- 1.39 mm2 vs. 7.10 +/- 1.07 mm2, P = 0.25). On histology at 3 days, the tubular slotted stents had more inflammatory cells adjacent to the stent wires (5.7 +/- 1.5 cells/0.1 mm2) than the nitinol (3.9 +/- 1.3 cells/0.1 mm2, P = 0.016). The tubular slotted also had increased thrombus thickness (83 +/- 85 microm) than the nitinol stents (43 +/- 25 microm, P = 0.0014). After 28 days, the vessel injury score was similar for the nitinol (0.6 +/- 0.3) and the tubular slotted (0.5 +/- 0.1, P = 0.73) designs. The mean neointimal area (0.97 +/- 0.46 mm2 vs. 1.96 +/- 0.34 mm2, P = 0.002) and percent area stenosis (15 +/- 7 vs. 33 +/- 7, P = 0.003) were significantly lower in the nitinol than in the tubular slotted stents, respectively. We conclude that a thermoelastic nitinol stent exerts a more favorable effect on vascular remodeling, with less neointimal formation, than a balloon-expandable design. Progressive intrinsic stent expansion after implant does not appear to stimulate neointimal formation and, therefore, may provide a mechanical solution to prevent in-stent restenosis.

Preliminary experience with the NIR coronary stent

We prospectively studied 223 patients (288 lesions) who underwent elective or bail out implantation of 309 NIR stents (Scimed, Boston Scientific Corporation, Galway, Ireland). Most lesions (68.4%) had unfavorable characteristics (type B2 or C). Primary success in stent deployment was achieved in 305 (98.6%). There was no Q-wave myocardial infarction. Emergency coronary artery bypass grafting (CABG) was required in 1 patient and 1 death occurred. Subacute thrombosis rate was 0.4%. Reference diameter was 2.65+/-0.67 mm. Minimum luminal diameter (MLD) increased from 0.62+/-0.45 to 2.69+/-0.57 mm and diameter stenosis decreased from 78.3+/-13.4% to 12.7+/-5.9%. Clinical follow-up was performed in the first 135 patients for 5.3+/-1.6 months and repeat angiography was undertaken in 35 (16%) with recurrence of symptoms at 4.6+/-1.3 months. Clinical restenosis rate was 9.6%. We conclude that the NIR coronary stent exhibits favorable performance characteristics and appears to be safe and efficacious in the treatment of coronary lesions even in the presence of high-risk characteristics.

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.

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.

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.

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.

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.