Balloon Inflation Pressure Research Articles

Radial Force and Wall Apposition of Balloon-expandable Vascular Stents in Eccentric Stenoses: An In Vitro Evaluation in a Curved Vessel Model

Important criteria for optimized stent implantation are high radial force and complete apposition of the stent itself. The aim of this study was to develop a simple method to assess these parameters under controlled experimental conditions and to compare vascular stents of different designs with regard to these parameters. Five balloon-expandable stents of different designs (Jostent Flex, MAC stent, ML-Tristar, ML-Ultra, and S670) were tested. Fourteen stents of each type were implanted in a curved plastic vessel model (curve radius, 10 mm; lumen diameter, 3.5 mm) with use of a balloon inflation pressure of 12 atm. Part of the model was a nonflexible eccentric stenosis which was 2 mm or 8 mm in length. After stent implantation, a stenosis of 10%-70% was induced and radial force of the stent struts was measured at the site of the stenosis. The apposition of the stent to the vessel wall was imaged by high-resolution radiography. Analysis of variance showed significant differences of radial force between the tested stents (P <.001). The ML-Tristar and ML-Ultra stents had the highest radial force with maximum mean values of 687 cN and 846 cN at a stenosis of 70% in the model with the long stenosis. The radial force of the S670 stent was the lowest whereas the MAC stents showed an intermediate radial force. Radial force of the ML-Ultra stent was as much as 3.8 times higher than the force of the S670 stent (P <.001). Fifty percent of the ML-Tristar and ML-Ultra stents did not expand sufficiently to touch the vessel surface at the outer curvature. With an inflation pressure of 17 atm, complete apposition of these stents was achieved. The highest number of apposition irregularities was found in the S670 group (13 of 14 stents), whereas the MAC stents revealed the lowest number of irregular appositions (three of 14 stents). A significant correlation was found between the number of interconnecting struts and the number of irregular apposition events (P <.01). This model allows an accurate in vitro evaluation of different stent parameters, such as apposition to the vessel wall and radial force. None of the investigated stents showed optimal results with respect to both parameters. The apposition behavior was significantly influenced by the architecture of the stents.

Angiography-guided routine coronary stent implantation results in suboptimal dilatation.

The resistance of the atherosclerotic lesion counteracts the expansion of the stent, resulting in suboptimal stent expansion. Intravascular ultrasound provides more precise information on stent expansion than coronary angiography but adds cost and time to the percutaneous transluminal coronary angiography procedure. The aim of this study was to evaluate the need for intravascular ultrasound at routine angiography-guided high pressure stent implantation by comparing stent expansion with predefined intracoronary ultrasound criteria for optimal stent implantation. In 32 patients, 48 stents (35 NIR, 12 AVE, and 1 Cordis) were implanted in A, B, and C stenoses using a high-pressure inflation technique until an optimal result was achieved according to angiography. Stent expansion was then evaluated by intravascular ultrasound as minimal lumen diameter, minimal lumen area, proximal and distal stent area, and a minimal lumen area symmetry index. These variables were then compared with the nominal stent size in vitro. Finally the stents were also evaluated with respect to the MUSIC criteria, ie, strict criteria regarding symmetry, apposition, and vessel geometry according to intravascular ultrasound after stent expansion. Forty-five stents could be completely analyzed. The mean balloon inflation pressure was 12.8 (range, 10-17) atm. The nominal stent size was not achieved in any patient. Minimal lumen diameter attained 77% and minimal lumen area 78% of expected nominal values (p<0.0001), distal stent area 88% (p < 0.001), and proximal stent area 92% (ns). Application of the MUSIC criteria showed that almost all stents (96%) had good stent apposition and symmetry index. Optimal proximal stent entrance was found in 70%. Optimal minimal lumen area in comparison to the reference areas was present in 41%. This lead to fulfilling of all MUSIC criteria in 47% of the stents. If nominal stent size had been achieved, symmetry index and apposition would have been fulfilled in all cases and optimal minimal lumen area increased to 75%. Acceptable proximal entrance however would have decreased to 55% and the fulfillment of all MUSIC criteria would increase only to 52%. In routine angiography-guided stent implantation in stenoses with a wide range of severities using modern stents and high pressure inflation technique to reach a visually optimal result, the nominal stent size was never achieved mainly due to residual intrastent stenosis. If nominal stent size had been achieved, the results would have improved only marginally and would still be suboptimal in almost half of the stents. These results highlight the shortcoming of angiography and the need for intravascular ultrasound in choosing correct stent size.

Implicaciones de la expansión tardía de los stents autoexpandibles sobre la respuesta neointimal: estudio seriado con ecografía intravascular

A unique property of self-expanding stents is the continuous force exerted against the vessel wall, which may induce additional arterial damage with implications on restenosis. The main purpose of this study is to evaluate the consequences of late self-expansion of coronary Wallstents. Eleven patients with Wallstents implanted in native coronary arteries, in whom baseline, post-stenting, after high pressure balloon inflation and at 6-month follow-up intravascular ultrasound were performed. The stented segments were divided in 2-mm cross-sections, that were analyzed independently and carefully matched at each situation using anatomic landmarks. Multiple regression analysis was performed. Late expansion was present in 93% of the studied sections (mean increase in stent area of 2.0 1.9 mm2) and was clearly related to stent oversizing (r = 0.45; p < 0,0001). Although late expansion was a significant positive predictor of neointimal growth (r = 0.63; p < 0.0001), it showed a negative correlation with late luminal loss (r = 0.33; p < 0.0001). No significant correlation was found between optimization of angiographic results with high pressure inflations and late luminal loss. Late expansion is a common phenomenon after Wallstent implantation and is mainly determined by stent oversizing. Despite the fact that this phenomenon is associated with greater neointimal proliferation, it seems to have a net beneficial effect on late luminal loss.

Optimal Stent Expansion by Nominal Pressure Balloon Inflation: an Intravascular Ultrasound Study

Background and Objectives:Intravascular ultrasound (IVUS), following stent implantation, demonstrated a significant degree of underexpansion, despite the initial appearance of an angiographically successful deployment, in first-generation stents. With improvements in stent designs and delivery systems, the current-generation of stents appear to achieve optimal stent expansion. The purpose of this study was to evaluate optimal stent expansion, by nominal pressure balloon inflation, in the current generation of stents. Subjects and Methods: We evaluated 30 patients having had Nir-Sox, Tristar, S670 or Bx Velocity stents successfully deployed at nominal pressure (7-10 atm) with delivery balloon system, between March and September 2001, using IVUS. IVUS criterion for optimal stent expansion was defined as a minimal stent area (MSA) ratio of ≥0.8 of the average reference lumen area. Results:The mean nominal balloon pressure was 8.87±0.9 atmospheres and the mean stent size was 3.38±0.45 mm. In reference segments, the minimal lumen diameter and average lumen area, found from the IVUS, were 3.18±0.51 mm and 8.88±2.92 mm, respectively. In stented segments, the minimal stent diameter and MSA were 2.55±0.46 mm and 6.10±2.08 mm, respectively. In only 11 of the 30 patients (36.7%) was the optimal stent expansion, by IVUS, achieved. Conclusion:Despite the development of a balloon delivery system for the current generation of stents, 63.3% of our study patients did not achieve optimal stent expansion, by IVUS, following nominal balloon inflation. Therefore, additional procedure will be required for optimal stent expansion in the current generation of stents. (Korean Circulation J 2002;32(8):666-673)

Comparison of luminal enlargement by direct coronary stenting versus predilation coronary stenting by three-dimensional volumetric intravascular ultrasound analysis

S tudies using planar intravascular ultrasound (IVUS) have shown that during intracoronary stent implantation, the mechanisms of lumen enlargement are similar to those of balloon angioplasty, with significant plaque redistribution and extrusion, vessel expansion, and plaque reduction. However, these assessments were performed with stents implanted after predilation by balloon. New stents, crimped onto their low-profile flexible delivery systems, with more rapid tapering of the balloon outside of the conical markers, are suitable for direct stenting (DS). DS has become routine in some laboratories. This new therapeutic approach of DS without predilation provides a way to rationalize stent implantation with the potential of less ischemic complications, less use of balloons, and less x-ray exposure. Although DS has become widespread, the mechanism by which it causes lumen enlargement is still unknown. Furthermore, there remains concern about the risk of microplaque embolization with DS. The present 3-dimensional volumetric IVUS study compares the mechanisms of lumen enlargement with DS versus predilation stenting (PDS) using the same contemporary stent design and the same stent length. • • • We retrospectively studied 30 patients with DS and 30 patients with PDS of nonostial, noncalcified, native coronary lesions treated with the same stent design and dimensions (ACS Multilink DUET or TRISTAR stent, Guidant Corporation, Santa Clara, California) and the same stent length (13 mm). The decision to predilate or not to predilate was partly based on general operator attitude. All lesions in both groups had met the inclusion criterion of the physical feasability of preintervention IVUS examination. Consequently, the DS success rate was 100%. For each procedure, the number of inflations, the maximum balloon inflation pressure, and the diameter of the stent used were recorded. Stent-to-artery ratio was defined as the diameter of the stent (according to the linear compliance curve of the balloon and the maximum balloon inflation pressure) divided by the reference luminal diam-

Direct infarct artery stenting without predilation and no-reflow in patients with acute myocardial infarction

Background In patients with acute myocardial infarction (AMI), the rate of microvascular embolization and no-reflow promoted by coronary stenting with the use of conventional techniques (CS) appears to be greater than the one that occurs with balloon angioplasty. The minor invasiveness of direct stenting (DS) of the infarct artery without predilation could be expected to reduce embolization in the coronary microvasculature and no-reflow in patients with AMI. Methods In a cohort of 423 consecutive patients with AMI who underwent infarct-artery stenting, we compared CS and DS in terms of angiographic no-reflow rate and 1-month clinical outcome. Results At baseline patients who underwent DS (n = 110) had a better risk profile compared with the use of CS (n = 313). The incidence of angiographic no-reflow was 12% in the CS group and 5.5% in the DS group (P =.040). The 1-month mortality rate was 8% in the CS group and 1% in the DS group (P =.008). The mortality rate was 11% in patients with no-reflow and 5.6% in patients with a normal flow. Multivariate analysis showed that age, preprocedure patent infarct artery, and lesion length were related to the risk of no-reflow. In the subset of patients with a target lesion length ≤15 mm, the variables independently related to the risk of no-reflow were age, DS, and final balloon inflation pressure. Conclusions DS in patients with AMI may reduce the incidence of angiographic no-reflow, thereby increasing ultimate effective myocardial reperfusion. (Am Heart J 2001;142:684-90.)

A prospective evaluation of angiography-guided coronary stent implantation with high versus very high balloon inflation pressure

Background High inflation pressure (HP) after coronary stent deployment has become a standard approach because it has been associated with a decreased subacute stent thrombosis (SAT) rate. However, the impact of HP on long-term outcomes is still unclear. We compared the long-term results of a strategy of increasing HP (≥12 atm) until the achievement of angiographic success (<20% residual stenosis) with a prespecified very high inflation pressure (VHP) strategy of 20 atm without intermediate inflations. Methods and Results We conducted a parallel-group, nonrandomized study to evaluate the short- and long-term results in 136 consecutive eligible patients who underwent successful single Palmaz-Schatz stent implantation in vessels ≥3 mm. Major adverse cardiac events (MACE), that is, death, myocardial infarction, and target lesion revascularization (TLR), were monitored for a minimum of 6 months. No significant differences were observed between the two strategies in terms of final minimal lumen diameter (HP, 3.0 ± 0.5 vs VHP, 3.1 ± 0.5 mm) and acute gain (HP, 2.1 ± 0.7 vs VHP, 2.2 ± 0.6). The overall rate of subacute stent thrombosis was 0.7%. During a 405 ± 148-day follow-up, 21 (28.8%) patients in the VHP group and 6 (9.5%) in the HP group (P =.005) had MACE, with a TLR rate of 27.4% versus 7.9% (P =.009), respectively. By multivariate analysis, the use of VHP increased the odds of long-term MACE by a factor of 3.48 (P =.009). Among patients undergoing TLR, those treated with VHP had a greater lumen loss (HP, 1.83 ± 0.57 vs VHP, 2.15 ± 0.36 mm, P =.02) and a more frequent pattern of diffuse restenosis (71% vs 16%, P =.06). Conclusions In our study, the two strategies had similar acute and short-term results, but VHP was associated with a poorer long-term outcome. These data provide a rationale for a less aggressive strategy for stent deployment by optimizing rather than attempting to maximize inflation pressure and stent expansion. (Am Heart J 2000;140:804-12.)

Resultados clínicos a largo plazo del implante de stents intracoronarios en la práctica actual

Published Stress and Benestent studies, obtained in selected populations under technical conditions that do not reflect present practice with intercoronary stenting showed a clinical benefit of coronary stenting. To assess clinical longterm outcome of coronary stenting in current practice and to compare coronary lesions with and without Stress/Benestent criteria. 216 consecutive patients with successful placement of 279 stents in 256 lesions and no major in-hospital events. Mean clinical follow-up was 16.7 +/- 10.4 months. Standard technique included seven types, high pressure balloon inflation (15.6 +/- 2.2 atm) and post-stenting treatment of four weeks with aspirin and ticlopidine. Cumulative rates of target lesion revascularization were 9.7% at 6 months, 13.5% at 12 months and 15.1% at 18, 24 and 36 months. Cumulative rates of combined clinical end-point (death, myocardial infarction and target lesion revascularization) were 11.3%, at 6 months, 13.9% at 1 year, 19.3% at 2 years and 21.1% at 3 years. No Stress/Benestent lesions were 193; 75%, and had a higher incidence of target lesion revascularization (17.9 vs 7.5%, Log Rank = 0.015) and combined clinical end-point (22.4 vs 10%, Log Rank = 0.025), than Stress/Benestent lesions. Coronary stenting of no Stress/Benestent lesions have a less favourable clinical longterm outcome. However, clinical outcome in a nonselected population at the present time is similar to the old Stress/Benestent studies, probably because of technical improvements.

Stents intracoronarios en vasos pequeños: resultados clínicos a corto y largo plazo

To assess the clinical outcome of coronary stenting in small vessels (< 3 mm), using high pressure balloon inflation and antithrombotic therapy. Vessel size was evaluated as < or >= 3 mm at the time of procedure and measured at a level of maximum diameter. We studied 234 consecutive patients with placement of 300 stents in 279 lesions, comprising 84 stents implanted in 79 lesions located at small vessels (< 3 mm). The standard technique included high pressure balloon inflation (15.8 +/- 2.2 atm) and post-stenting therapy with ticlopidine and aspirin for one month. Mean clinical follow-up was 17.6 +/- 10 months. Procedural success without in-hospital major events was similar between small and large vessels (93.7 in vessels of < 3 mm vs 93.5% in vessels of >= 3 mm; p = NS). Three small vessels presented subacute stent thrombosis, whereas no thrombotic occlusion occurred in large vessels (3.8 vs 0%; p = 0.006). At two years, small vessels had a lower target lesion revascularization free survival (73.6 vs 90.3%; p < 0.001). After adjustment for variables previously described as predictors of stent restenosis, in multivariate analysis, a small vessel of < 3 mm was an independent predictor of target lesion revascularization (p = 0.001). Although patients with stenting in small vessels did not differ significantly in terms of any cause death (4.6 vs 3.8%; p = 0.7) nor acute myocardial infarction (2.9 vs 1.1%; p = 0.3), event-free survival was significantly lower after two years (69.1 vs 86.6%; p < 0.001). As compared to large vessels, coronary stenting in small vessels was performed with similar rates of initial success, however they had a significantly worse clinical long-term outcome in terms of subacute stent thrombosis and target lesion revascularization at follow-up.

Trombosis subaguda con tratamiento antiagregante en una población no seleccionada de stents intracoronarios: incidencia y predictores

After coronary stenting, the incidence of subacute stent thrombosis have been reduced to 0% using aspirin and ticlopidine, in studies with selected populations and intracoronary ultrasounds. To evaluate the incidence and predictors of subacute stent thrombosis in a nonselected population, using antithrombotic therapy. We studied 285 stents, consecutively and successfully implanted in 268 lesions of 226 patients. We used high pressure balloon inflation without intracoronary ultrasound. Post-stenting protocol included aspirin and ticlopidine during four weeks with no anticoagulation. We defined subacute stent thrombosis as death, acute myocardial infarction myocardial infarction or angiographic occlusion of stent, with TIMI flow 0-1, after the first 24 hours and during the first month. Four patients presented events (1.7%): Three nonfatal myocardial infarction after discharge, with documented angiographic thrombosis of stent, and one death due to in-hospital myocardial infarction. All three non-fatal AMI, occurred in vessels less than 3 mm (p = 0.07) and in patients taking aspirin without ticlopidine (p < 0.001). After discharge, three (17%) of 18 patients with inadvertent discontinuation of ticlopidine presented subacute stent thrombosis, in contrast to none of 25 patients taking ticlopidine without aspirin. Excluded patients with discontinuation of ticlopidine, the incidence of subacute stent thrombosis was 0.5%. After intracoronary stenting in a nonselected population, using antithrombotic treatment with aspirin and ticlopidine, we may expect a rate of subacute stent thrombosis about 1%. Ticlopidine seems to have the main role in preventing subacute stent thrombosis, above all in predisposing circumstances as small vessels.

Effects of increasing balloon pressure on mechanism and results of balloon angioplasty for treatment of restenosis after Palmaz-Schatz stent implantation: an angiographic and intravascular ultrasound study.

Repeat balloon angioplasty is a widely used therapeutic option for in-stent restenosis, but the optimal balloon inflation pressure has not yet been determined. We used angiography and intravascular ultrasound imaging to assess the mechanism and results of lumen enlargement at various inflation pressures. Thirteen consecutive patients with restenosis post-Palmaz-Schatz stent implantation were submitted to a four-step balloon angioplasty using increasing balloon pressure of 2, 4, 8, and >12 atm. As a global result, the lumen size was only 80% of that observed at stent implantation. Significant changes in angiographic minimal lumen diameter, minimal lumen cross-sectional area, and lumen volume were observed after each step except after the highest-pressure inflation. At low inflation pressure (<8 atm), the decrease in neointimal tissue and the stent over expansion explained the lumen enlargement, whereas after further high inflation pressure (>8 atm), only additional stent over expansion was observed. These results suggest that only moderate balloon inflation pressure (up to 12 atm) is needed for angioplasty of post-Palmaz-Schatz stent restenotic lesions.

Optimal Balloon Inflation Pressures for Stent Deployment: High Pressure is Always Good?

Background and Objectives:To reduce the subacute stent thrombosis, the use of high pressure final balloon dilatations and confirmation of adequate stent expansion by intravascular ultrasound has been recommended. The purpose of this study is to compare incidence of stent thrombosis and major cardiac events (MACE between high and moderate pressure balloon technique without using intravascular ultrasound (IVUS guidance. Materials and Methods:We prospectively studied 147 patients (110 males & 37 females, mean; 56.9±9.9 years, 154 lesions who were deployed intracoronary stents with the use of conventional technique except IVUS guidance. According to inflation pressure, patients were divided into two groups;G1 (moderate pressure group, maximum inflation balloon pressure <14ATM, 77 lesion & G2 (high pressure group, maximum inflation balloon pressure ≥14ATM, 77 lesions. We investigated the incidence of stent thrombosis and MACE between two groups during the 10 month follow up examination. Results:1 The mean inflation presure is different between two groups by definition (G1:G2 10.2±1.8;15.2±1.3 ATM p<0.001. 2 The stenotic lesion lengths of the group of patients treated with the moderate pressure techique were longer than those treated under the high pressure technique (G1:G2 19.8±7.1 mm;16.3±4.1 mm p=0.002. 3 There were no significant differences between the moderate pressure group and the high pressure group during the 10 month follow-up examination in terms of MACE(early event (0-14D -subacute thrombosis G1:G2 0:0 death G1;G2 1:1/late events (15D-10M -repeat revascularization:G1;G2 8;7, CABG G1;G2 1;0, Q.M.I G1;G2 1;0). Conclusion:On selected patients, it is possible to consider moderate pressure technique as an other option for coronary stenting. (Korean Circulation J 1998;28(8 :1272-1279

Estudo multicêntrico do implante de stent intracoronário no Rio de Janeiro

To evaluate retrospectively stent implantation (SI) in patients with coronary artery disease (CAD) performed in 7 hospitals in Rio de Janeiro. From June/94 to December/96 2,220 procedures were performed among which we analyzed 783 SI in 660 (29.7%) patients using coronary angiography without digital subtraction. Several types of stents were used: Palmaz-Schatz (40.9%), Gianturco-Roubin (29.1%) e NIR (22.0%). Indications for SI: 1--de novo lesion (67.9%); 2) restenotic lesion (16.0%); 3) sub-optimal results after PTCA (8.2%); 4) abrupt or threatened closure after PTCA (4.9%); 5) chronic occlusion (3.0%). All stents were implanted using high pressure balloon inflation without intracoronary ultrasound guidance. Sub-acute stent thrombosis prevention, in the majority of patients (87.8%) was done with ticlopidine and aspirin. Early outcome: a) the success rate of SI in 770 lesions was 98.0% in 646 (97.9%) patients; b) the clinical success rate in 634 patients was 96.0%; c) the major complications were acute myocardial infarction (1.1%); coronary artery bypass graft (1.4%) and death (0.8%); d) vascular complications with surgical correction and/or bleeding occurred in 3.0%. Late outcome: a) the clinical follow-up of 399 (60.4%) and the coronary angiographies of 121 patients (30.3%) showed in-stent lesion in 79 (19.8%); b) other event rates: myocardial infarction (1.5%); coronary bypass (2.3%); death: 1.0% and other PTCA or similar procedure (12.5%). This multicentric study showed that SI for CAD can be performed with safety, high early success rate, few complications and low rate of cardiac events during the late follow-up.

Long Stent Implantation in Long Coronary Lesions: Immediate and Follow-up Results

Background:The results of new devices for long coronary stenotic lesion is disappointing. We evaluate the feasibility and efficacy of single long coronary stenting for long coronary stenosis, we implanted two types of long stents, newly developed less shortening Wall stent and Gianturco-Roubin II stent. Methods:This study reports on the use of stents in 106 patients with 109 lesions with long lesion. Long coronary disease was defined as a lesion length longer than 20 mm. After the implantation of the stent, the stented coronary segment was dilated further with high pressure balloon inflation to achieve angiographic optimization. Results:The mean age was 59±9 years. Mean stent length was 35±11 mm. Vessel distribution was 2 (2%) left main, 66 (61%) LAD, 10 (9%) LCX and 31 (28%) RCA. Implanted stents were 57 (52%) Gianturco-Roubin II stents and 52 (48%) Wall stents. Procedural success was achieved in 109 (100%) lesions. The MLD at lesion site increased from 0.8±0.4 mm to 3.2±0.5 mm. Procedure associated complications included 4 non-Q myocardial infarction. Angiographic follow up at 6 months was performed on 78 (72%) eligible lesions. There was one myocardial infarction and no death during follow up period. Restenosis by 50% diameter stenosis criteria was present in 39 (50%) of lesions. The target lesion revascularization was performed in 21 (19%) lesions. Conclusions:Stent implantation for long coronary disease is associated with excellent procedural success rates and low complication rates in the majority of patients. However, the restenosis rate is high regardless of the stent used. Further study needs to be done to improve the long-term clinical outcome. (Korean Circulation J 1998;28(6):902-908)

Initial Results after Implantation of Coronary Artery Stents with Antiplatelet Agents

Backgound：The placement of stents in coronary arteries has been shown to reduce acute closure and restenosis in comparison to balloon angioplasty. However, clinical use of intracoronary stents is impeded by the subacute stent thrombosis and hemorrhagic complications associated with the anticoagulant regimen. It’ s known that the complete stent deployment with high pressure inflation and new antiplatelet agents are effective in reduction of subacute thrombosis and hemorrhage. So we evaluated initial results (success and complication rate after high pressure-stent deployment with new anticoagulation protocol. Methods：One hundred and ninety one patients with 201 lesions were treated with 231 stents of various types. The high pressure balloon inflation and antiplatelets agents were used in all cases. Final high pressure balloon inflation guided by IVUS were performed in 23 consecutive cases with incomplete stent deployment according to angiographic findings. Results：1 The indications of stenting (n＝210 were De novo in 124 (59%, bailout procedure in 57 (27%, suboptimal result after PTCA in 19 (8%, and restenosis after PTCA in 14 (6%. The location of lesions were LAD in 101, RCA in 67, circumflex in 28, ramus intermedius in 3, and LMT artery in 2 lesions. Angiographic morphologic characteristics were type A in 2, type B in 158 (B1：57, B2：101, and type C in 22 lesions. 2 The angiographic and clinical success rate was 96% (192/201 and 92% (186/201 respectively. 3 In angiographic analysis, the baseline average reference vessel dirmeter was 3.33±0.35 mm. Baseline minimum lumen diameter(MLD was 0.58±0.29 mm, with baseline percent diameter stenosis of 82.86±8.64%. The final stent diameter was 3.37±0.29 mm, with mean final percent stenosis of 0.63±8.25. The mean MLD after stenting was significantly increased (p 12atm (p<0.001. The length of lesions in GR Ⅰ (cook, GR Ⅱ, and Micro Ⅱ stents were significantly longer than ones in PS, Cordis, Wiktor, Nir (p<0.001. 4 In intravascular ultrasound analysis, the mean lumen CSA at the tightest point within stent increased 11%, from 8.4±2.4 mm 2 at the intial intravascular ultrasound to 9.4±2.1 mm 2 at the final intravascular ultrasound (p<0.001. 5 The procedural andpostprocedural complications were 2 acute closures associated with AMI and emergent CABG, 1 subacute closure which was revascularized by bail out stenting, 5 major hemorrhage requiring transfusion associated with 1 CVA and 2 metabolic acidosis induced by acute renal failure, and 5

One balloon approach for optimized Palmaz-Schatz stent implantation: the MUSCAT trial.

After stent deployment, larger balloons are frequently needed to optimize stent expansion according to angiographic and intravascular ultrasound (IVUS) criteria. The objective of this trial was to assess the feasibility and safety of a single-balloon approach for predilation, stent implantation, and optimization with a differential-compliant balloon allowing for focal overexpansion. We also evaluated the achieved degree of stent expansion according to IVUS criteria. Forty-seven consecutive patients with 50 lesions received single or multiple Palmaz-Schatz coronary stents. The final angiographic diameter stenosis was -2.6 +/- 12.6% (reference diameter, 2.89 +/- 0.44 mm), and the residual lumen area stenosis (IVUS) was 13.0 +/- 12.3% (reference area 10.8 +/- 3.0 mm2). This result was achieved in two steps (first angiographic, then IVUS-guided stent optimization). The balloon inflation pressure increased from 13.1 +/- 3.0 bar at step 1 to 16.1 +/- 3.0 bar at step 2, which resulted in a balloon to artery ratio of 0.97 +/- 0.12 and 1.10 +/- 0.15, respectively, at the low-compliant peripheral balloon segments. The more compliant central balloon segments showed a balloon to artery ratio of 1.09 +/- 0.17 and 1.28 +/- 0.17, respectively. The primary success rate for stent deployment was 94%. Acute complications included two type A and one type B dissection without clinical sequelae. The single-balloon approach for stenting is feasible and safe. The acute result is comparable to that of other studies with IVUS-guided stent optimization, the primary success rate, however, is slightly lower with the presently available catheter.

Percutaneous angioplasty of arteriovenous (Brescia-Cimino) fistulae in children.

The development of a stenosis in a Brescia-Cimino fistula is a major clinical problem that threatens vascular access for dialysis. We reviewed the case notes of 46 children undergoing hemodialysis via Brescia-Cimino fistulae. Ten children (mean age 12.5 years) developed 14 stenoses located in the venous (10), anastomotic (3), or arterial (1) part of the fistula. Three (1 arterial and 2 anastomotic stenoses) of the 14 stenoses were treated surgically; the remaining 11 (10 venous and 1 anastomotic stenoses) were treated by angioplasty. Seventeen angioplasty procedures were performed by the percutaneous venous route under local anesthesia. Mean follow-up was 24 months. Restenosis within 6 months occurred in 5 patients, predominantly those who had angioplasty with low balloon inflation pressures; 1 was treated surgically; 4 underwent repeat angioplasty using higher balloon inflation pressures (3 patients) or a bigger balloon (1 patient). None subsequently developed restenosis. Angioplasty can be safely used to treat stenosis of arteriovenous fistulae, with a high initial (60% freedom from restenosis at 6 months) success rate. In summary, balloon angioplasty, repeated if necessary, is a safe and effective treatment for the majority of stenoses occurring in Brescia-Cimino fistulae. Restenosis can be safely treated by further angioplasty, which is associated with a high rate of ultimate clinical success.

Localized delivery of heparin to angioplasty sites with iontophoresis.

Drug delivery by iontophoresis involves the application of an electric field to move selectively charged drug molecules across biological membranes. The purpose of this study was to assess the efficacy of intravascular iontophoresis in the local delivery of heparin to balloon angioplasty sites by using a recently designed iontophoretic catheter. In vivo heparin iontophoresis was assessed in 33 rats and 21 pigs in four protocols designed to measure the technical determinants of intramural drug deposition, the pharmacokinetics and localization of coronary delivery, and the effect of this technique on platelet deposition following balloon injury. First, iontophoresis of 3H-heparin into the aorta of 33 rats was performed to determine the effects of iontophoretic current, iontophoretic membrane balloon initiation pressure, iontophoresis time, and heparin concentration on intramural drug deposition. Second, iontophoresis of 3H-heparin was performed in 16 porcine coronary arteries to quantitate immediate drug delivery and subsequent wash-out over 24 h. Third, iontophoresis of fluorescent heparin was performed in 8 porcine coronary arteries to define intramural localization of locally delivered drug. Fourth, 111In-labeled platelet deposition was measured 1 h following balloon angioplasty and local iontophoretic heparin delivery in 16 porcine carotid and iliac vessels. Contralateral control vessels that were dilated with the same size balloon and treated with iontophoresis of saline served as controls. Rat aortic studies demonstrated that iontophoresis resulted in 13 times more intramural heparin deposition than passive delivery (passive: 0.3 +/- 0.4 microgram, iontophoresis: 4.6 +/- 1.6 micrograms, P < 0.0004). Iontophoretic membrane balloon inflation pressure had no significant effect on intramural drug deposition, but longer iontophoresis times and higher heparin concentrations resulted in higher levels of intramural heparin (P < 0.05). Porcine coronary studies demonstrated successful intramural deposition of heparin in all arteries without adverse electrical or hemodynamic sequelae, with persistence of the drug for at least 24 h. Localization studies demonstrated immediate deposition of fluorescent heparin in the intima and internal elastic lamina, with subsequent rapid diffusion of the drug into the media. Porcine platelet studies demonstrated that heparin iontophoresis decreased platelet deposition following balloon injury by approximately 66% compared with saline-treated control vessels (heparin-treated: 1.46 +/- 2.51 x 10(8), control: 4.27 +/- 7.02 x 10(8), P = 0.001). This study has demonstrated that local intramural heparin delivery is feasible with an intravascular iontophoretic catheter. Following intracoronary heparin iontophoresis in the porcine model, intramural drug is detected for at least 24 h. Local delivery of heparin with this technique significantly decreases early platelet deposition following balloon injury in peripheral porcine arteries.

Use of Cilostazol, a Novel Antiplatelet Agent, in a Post-Palmaz-Schatz Stenting Regimen

We evaluated the therapeutic efficacy of cilostazol, a novel potent inhibitor of phosphodiesterase, for the prevention of stent thrombosis following implantation of a Palmaz-Schatz stent guided by angiographic visual estimation alone in 71 patients with 84 lesions. Patients received 81 mg of aspirin 3 times daily and 100 mg of cilostazol twice daily after angiographic confirmation of optimal Palmaz-Schatz stent implantation. Of the 84 vessels stented, 65 (77%) were classified as type B2 or C lesions according to the modified American Heart Association/American College of Cardiology classification, and 51 (61%) were <3.0 mm in diameter. Multiple stents were used in 26 patients (31%). The final balloon inflation pressure was 18.3 ± 1.5 atm. The balloon-to-vessel ratio was 1.18 ± 0.16. No patient received heparin or warfarin after the procedure. There were no deaths, Q-wave myocardial infarctions, in- or out-of-hospital stent thrombosis, coronary bypass surgery, or serious side effects such as neutropenia and/or liver dysfunction during the 1-month follow-up period. These results indicate that cilostazol was a safe and effective antiplatelet agent with minimum side effects after Palmaz-Schatz stent implantation.We evaluated the usefulness of cilostazol, a novel antiplatelet agent, for the prevention of stent thrombosis. No deaths, Q-wave myocardial infarctions, stent thrombosis, or serious side effects such as neutropenia occurred during the 1-month follow-up period, which suggests cilostazol is a safe and effective antiplatelet agent after Palmaz-Schatz stent implantation.

Intravascular Ultrasound Analysis of Factors Associated with Suboptimal Stent Expansion after High Pressure Balloon Inflation

Background:The intracoronary stent implantation is regarded as an effective treatment modality of coronary artery disease. However, inadequate stent expansion was associated with subacute stent thrombosis and late restenosis. The high-pressure inflation stenting reduced the incidence of stent thrombosis and restenosis. Therefore, we intended to evaluate factors associated with suboptimal stent expansion after high-pressure balloon inflation. Method:One hundred and thirty eight patients with 150 lesions were treated with 168 stents of various types. Intravascular ultrasound(IVUS images were obtained after angiographic optimization (<10% of residual stenosis with high-pressure inflation stenting. In a subgroup of 61 selected patients with 61 lesions, IVUS images were obtained before predilation of the lesions. The quantitative off-line measurements of IVUS parameters were performed. An optimal stent expansion was defined by IVUS as minimal stent cross sectional area(CSA of ≥90% of the distal reference lumen CSA. Severe calcifications were defined by IVUS as arc of calcium ≥180° . Results:An optimal stent expansion was achieved in 67% of the 150 lesions. At preintervention, severe calcifications were in 10%(5/51 in optimal stent expansion and in 40%(4/10 in suboptimal stent expansion(p<0.05. At postintervention, minimal stent CSA was 8.0mm 2 in optimal stent