Comparison of drug-eluting versus bare metal stents in cardiac allograft vasculopathy

Although not a definitive treatment, percutaneous coronary intervention offers a palliative benefit to patients with cardiac allograft vasculopathy. Given the superior outcomes with drug-eluting stents (DESs) over bare metal stents (BMSs) in native coronary artery disease, similar improvements might be expected in transplant patients; however, the results have been mixed. Consecutive cardiac transplantation recipients at a single center receiving a stent for de novo cardiac allograft vasculopathy from 1997 to 2009 were retrospectively analyzed according to receipt of a DES versus a BMS. The angiographic and clinical outcomes were subsequently evaluated at 1 year. The baseline clinical and procedural characteristics were similar among those receiving DESs (n = 18) and BMSs (n = 16). Quantitative coronary angiography revealed no difference in the reference diameter, lesion length, or pre-/postprocedural minimal luminal diameter. At the 12-month angiographic follow-up visit, the mean lumen loss was significantly lower in the DES group than in the BMS group (0.19 ± 0.73 mm vs 0.76 ± 0.97 mm, p = 0.02). The DES group also had a lower rate of in-stent restenosis (12.5% vs 33%, p = 0.18), as well as a significantly lower rate of target lesion revascularization (0% vs 19%, p = 0.03). At 1 year, DESs were associated with a lower composite rate of cardiac death and nonfatal myocardial infarction (12% vs 38%, p = 0.04). In conclusion, DESs are safe and effective in the suppression of neointimal hyperplasia after percutaneous coronary intervention for cardiac allograft vasculopathy, resulting in significantly lower rates of late lumen loss and target lesion revascularization, as well as a reduced combined rate of cardiac death and nonfatal myocardial infarction.

Preclinical derivation and imaging of autologously transplanted canine induced pluripotent stem cells

Derivation of patient-specific induced pluripotent stem cells (iPSCs) opens a new avenue for future applications of regenerative medicine. However, before iPSCs can be used in a clinical setting, it is critical to validate their in vivo fate following autologous transplantation. Thus far, preclinical studies have been limited to small animals and have yet to be conducted in large animals that are physiologically more similar to humans. In this study, we report the first autologous transplantation of iPSCs in a large animal model through the generation of canine iPSCs (ciPSCs) from the canine adipose stromal cells and canine fibroblasts of adult mongrel dogs. We confirmed pluripotency of ciPSCs using the following techniques: (i) immunostaining and quantitative PCR for the presence of pluripotent and germ layer-specific markers in differentiated ciPSCs; (ii) microarray analysis that demonstrates similar gene expression profiles between ciPSCs and canine embryonic stem cells; (iii) teratoma formation assays; and (iv) karyotyping for genomic stability. Fate of ciPSCs autologously transplanted to the canine heart was tracked in vivo using clinical positron emission tomography, computed tomography, and magnetic resonance imaging. To demonstrate clinical potential of ciPSCs to treat models of injury, we generated endothelial cells (ciPSC-ECs) and used these cells to treat immunodeficient murine models of myocardial infarction and hindlimb ischemia.

Dual manganese-enhanced and delayed gadolinium-enhanced MRI detects myocardial border zone injury in a pig ischemia-reperfusion model

BACKGROUND

Gadolinium (Gd)-based delayed-enhancement MRI (DEMRI) identifies nonviable myocardium but is nonspecific and may overestimate nonviable territory. Manganese (Mn(2+))-enhanced MRI (MEMRI) denotes specific Mn(2+) uptake into viable cardiomyocytes. We performed a dual-contrast myocardial assessment in a porcine ischemia-reperfusion (IR) model to test the hypothesis that combined DEMRI and MEMRI identifies viable infarct border zone (BZ) myocardium in vivo.

METHODS AND RESULTS

Sixty-minute left anterior descending coronary artery IR injury was induced in 13 adult swine. Twenty-one days post-IR, 3-T cardiac MRI was performed. MEMRI was obtained after injection of 0.7 mL/kg Mn(2+) contrast agent. DEMRI was then acquired after injection of 0.2 mmol/kg Gd. Left ventricular (LV) mass, infarct, and function were analyzed. Subtraction of MEMRI defect from DEMRI signal identified injured BZ myocardium. Explanted hearts were analyzed by 2,3,5-triphenyltetrazolium chloride stain and tissue electron microscopy to compare infarct, BZ, and remote myocardium. Average LV ejection fraction was reduced (30±7%). MEMRI and DEMRI infarct volumes correlated with 2,3,5-triphenyltetrazolium chloride stain analysis (MEMRI, r=0.78; DEMRI, r=0.75; P<0.004). MEMRI infarct volume percentage was significantly lower than that of DEMRI (14±4% versus 23±4%; P<0.05). BZ MEMRI signal-to-noise ratio (SNR) was intermediate to remote and core infarct SNR (7.5±2.8 versus 13.2±3.4 and 2.9±1.6; P<0.0001), and DEMRI BZ SNR tended to be intermediate to remote and core infarct SNR (8.4±5.4 versus 3.3±0.6 and 14.3±6.6; P>0.05). Tissue electron microscopy analysis exhibited preserved cell structure in BZ cardiomyocytes despite transmural DEMRI enhancement.

CONCLUSIONS

The dual-contrast MEMRI-DEMRI detects BZ viability within DEMRI infarct zones. This approach may identify injured, at-risk myocardium in ischemic cardiomyopathy.

BMP promotes motility and represses growth of smooth muscle cells by activation of tandem Wnt pathways

We present a novel cell-signaling paradigm in which bone morphogenetic protein 2 (BMP-2) consecutively and interdependently activates the wingless (Wnt)-β-catenin (βC) and Wnt-planar cell polarity (PCP) signaling pathways to facilitate vascular smooth muscle motility while simultaneously suppressing growth. We show that BMP-2, in a phospho-Akt-dependent manner, induces βC transcriptional activity to produce fibronectin, which then activates integrin-linked kinase 1 (ILK-1) via α4-integrins. ILK-1 then induces the Wnt-PCP pathway by binding a proline-rich motif in disheveled (Dvl) and consequently activating RhoA-Rac1-mediated motility. Transfection of a Dvl mutant that binds βC without activating RhoA-Rac1 not only prevents BMP-2-mediated vascular smooth muscle cell motility but promotes proliferation in association with persistent βC activity. Interfering with the Dvl-dependent Wnt-PCP activation in a murine stented aortic graft injury model promotes extensive neointima formation, as shown by optical coherence tomography and histopathology. We speculate that, in response to injury, factors that subvert BMP-2-mediated tandem activation of Wnt-βC and Wnt-PCP pathways contribute to obliterative vascular disease in both the systemic and pulmonary circulations.

Sustained inhibition of epsilon protein kinase C inhibits vascular restenosis after balloon injury and stenting

BACKGROUND

ε protein kinase C (εPKC) is involved in vascular smooth muscle cell (VSMC) activation, but little is known about its function in vascular pathology. We aimed at assessing the role of εPKC in the development of restenosis.

METHODS AND RESULTS

Rat models of aortic balloon injury with or without subsequent stenting were used. Rats were treated with the selective ψεPKC activator ε receptor for activated protein kinase C (ψεRACK), the selective εPKC inhibitor εV1-2, or saline. Both down-stream cascades of the platelet-derived growth factor receptor via extracellular signal-regulated kinase and Akt, respectively, were evaluated in vivo and in VSMC cultures. Intimal hyperplasia with luminal obliteration developed in saline-treated balloon-injured rat aortas (20.3±8.0%), and ψεRACK significantly promoted neointima development (32.4±4.9%, P=0.033), whereas εV1-2 significantly inhibited luminal narrowing (9.2±4.3%, P=0.039). εPKC inhibition led to significantly reduced VSMC extracellular signal-regulated kinase phosphorylation in vivo, whereas Akt phosphorylation was not markedly affected. Neointimal proliferation in vivo and platelet-derived growth factor-induced VSMC proliferation/migration in vitro were significantly inhibited by εV1-2. The inhibition of the platelet-derived growth factor pathway was mediated by inhibiting down-stream extracellular signal-regulated kinase and Akt phosphorylation. In vitro, εV1-2 showed inhibitory properties on endothelial cell proliferation, but that did not prevent reendothelialization in vivo. εV1-2 showed proapoptotic effects on VSMC in vitro. After stent implantation, luminal restenosis (quantified by optical coherence tomography imaging) was significantly reduced with εV1-2 (8.0±2.0%) compared with saline (20.2±9.8%, P=0.028).

CONCLUSIONS

εPKC seems to be centrally involved in the development of neointimal hyperplasia. We suggest that εPKC inhibition may be mediated via inhibition of extracellular signal-regulated kinase and Akt activation. εPKC modulation may become a new therapeutic target against vascular restenosis.

Fractional flow reserve versus angiography for guiding percutaneous coronary intervention in patients with multivessel coronary artery disease: 2-year follow-up of the FAME (Fractional Flow Reserve Versus Angiography for Multivessel Evaluation) study

OBJECTIVES

The purpose of this study was to investigate the 2-year outcome of percutaneous coronary intervention (PCI) guided by fractional flow reserve (FFR) in patients with multivessel coronary artery disease (CAD).

BACKGROUND

In patients with multivessel CAD undergoing PCI, coronary angiography is the standard method for guiding stent placement. The FAME (Fractional Flow Reserve Versus Angiography for Multivessel Evaluation) study showed that routine FFR in addition to angiography improves outcomes of PCI at 1 year. It is unknown if these favorable results are maintained at 2 years of follow-up.

METHODS

At 20 U.S. and European medical centers, 1,005 patients with multivessel CAD were randomly assigned to PCI with drug-eluting stents guided by angiography alone or guided by FFR measurements. Before randomization, lesions requiring PCI were identified based on their angiographic appearance. Patients randomized to angiography-guided PCI underwent stenting of all indicated lesions, whereas those randomized to FFR-guided PCI underwent stenting of indicated lesions only if the FFR was <or=0.80.

RESULTS

The number of indicated lesions was 2.7+/-0.9 in the angiography-guided group and 2.8+/-1.0 in the FFR-guided group (p=0.34). The number of stents used was 2.7+/-1.2 and 1.9+/-1.3, respectively (p<0.001). The 2-year rates of mortality or myocardial infarction were 12.9% in the angiography-guided group and 8.4% in the FFR-guided group (p=0.02). Rates of PCI or coronary artery bypass surgery were 12.7% and 10.6%, respectively (p=0.30). Combined rates of death, nonfatal myocardial infarction, and revascularization were 22.4% and 17.9%, respectively (p=0.08). For lesions deferred on the basis of FFR>0.80, the rate of myocardial infarction was 0.2% and the rate of revascularization was 3.2 % after 2 years.

CONCLUSIONS

Routine measurement of FFR in patients with multivessel CAD undergoing PCI with drug-eluting stents significantly reduces mortality and myocardial infarction at 2 years when compared with standard angiography-guided PCI. (Fractional Flow Reserve Versus Angiography for Multivessel Evaluation [FAME]; NCT00267774).

Development of animal model for calcified chronic total occlusion

Chronic total coronary occlusion (CTO) remains a major problem for percutaneous revascularization, with relatively low primary success rates and a high incidence of restenosis and reocclusion compared with those of subtotal stenoses. No reproducible animal model simulating human CTOs has previously been developed. We hypothesized that an apatite-coated bioabsorbable polymer sponge could be implanted to produce calcified CTO lesions in animal coronary arteries/peripheral arteries. A total of 10 swine and six rabbits were used for this study. The apatite-coated bioabsorbable polymer sponges were implanted into a preselected segment of coronary and peripheral arteries. Four weeks after implantation, both angiography and histopathology were performed to document the presence or absence of CTO lesions. We could reproducibly develop CTO lesions in animal coronary/peripheral arteries that mimic human CTO lesions. These lesions were found to have microvascular channels and microcalcification similar to those of human older CTO lesions and demonstrate the development of adventitial arterioles, a consistent finding in human CTO. This CTO model might provide a platform for evaluating future CTO technologies as well as contributing to a better understanding of CTOs in both educational and practical terms.

Imaging in-stent restenosis: an inexpensive, reliable, and rapid preclinical model

Preclinical models of restenosis are essential to unravel the pathophysiological processes that lead to in-stent restenosis and to optimize existing and future drug-eluting stents.

A variety of antibodies and transgenic and knockout strains are available in rats. Consequently, a model for in-stent restenosis in the rat would be convenient for pathobiological and pathophysiological studies.

In this video, we present the full procedure and pit-falls of a rat stent model suitable for high throughput stent research. We will show the surgical procedure of stent deployment, and the assessment of in-stent restenosis using the most elegant technique of OCT (Optical Coherence Tomography). This technique provides high accuracy in assessing plaque CSAs (cross section areas) and correlates well with histological sections, which require special and time consuming embedding and sectioning techniques. OCT imaging further allows longitudinal monitoring of the development of in-stent restenosis within the same animal compared to one-time snapshots using histology.

The importance of pre-clinical animal testing in interventional cardiology

The treatment of cardiovascular disease has changed dramatically over the past 2 decades, allowing patients to live longer and better quality lives. The introduction of new therapies has contributed much to this success. Nowhere has this been more evident than in interventional cardiology, where percutaneous cardiovascular intervention has evolved in the past 2 decades from a quirky experimental procedure to a therapeutic cornerstone for patients with symptomatic cardiovascular disease. The development of these technologies from the earliest stages requires preclinical experiments using animal models. Once introduced into the clinical arena, an understanding of therapeutic mechanisms of these devices can be ascertained through comparisons of animal model research findings with clinical pathological specimens. This review provides an overview of the emerging role, results of preclinical studies and development, and evaluation of animal models for percutaneous cardiovascular intervention technologies for patients with symptomatic cardiovascular disease.

Intraoperative fluorescence imaging system for on-site assessment of off-pump coronary artery bypass graft

OBJECTIVES

The aim of this study was to evaluate the intraoperative fluorescence imaging (IFI) system in the real-time assessment of graft patency during off-pump coronary artery bypass graft.

BACKGROUND

Intraoperative fluorescence imaging is an intraoperative angiography-like imaging modality using fluorescent indocyanine green excited with laser light. Recently, assessment of graft patency using the IFI system was introduced into clinical use. The feasibility and efficacy of IFI technology in off-pump coronary artery bypass graft has not been systematically compared with other conventional diagnostic modalities.

METHODS

Patients undergoing off-pump coronary artery bypass graft received IFI analysis, intraoperative transit time flowmetry, and postoperative X-ray angiography. In off-line IFI analysis, the graft washout was classified based on the number of heartbeats required for indocyanine green washout: fast washout (<or=15 beats) and slow washout (>15 beats).

RESULTS

A total of 507 grafts in 137 patients received IFI analysis. Of all the IFI analyses, 379 (75%) grafts were visualized clearly up to the distal anastomosis. With regard to anastomosis location, anterior location was associated with a higher percentage of fully analyzable images (90%). More than 80% of images were analyzable, irrespective of graft type. Six grafts with acceptable transit time flowmetry results were diagnosed with graft failure by IFI, which required on-site graft revision. All revised grafts' patency was confirmed by post-operative X-ray angiography. Conversely, 21 grafts with unsatisfactory transit time flowmetry results demonstrated acceptable patency with IFI. Graft revision was considered unnecessary in these grafts, and 20 grafts (95%) were patent by post-operative X-ray angiography. Compared with slow washout, fast washout was associated with a higher preoperative ejection fraction, use of internal mammary artery grafts, and anterior anastomosis location.

CONCLUSIONS

The IFI system enables on-site assessment of graft patency, providing both morphologic and functional information. This technique may help reduce procedure-related, early graft failures in off-pump bypass patients.

In vivo comparison between optical coherence tomography and intravascular ultrasound for detecting small degrees of in-stent neointima after stent implantation

OBJECTIVES

The purpose of this study was to evaluate optical coherence tomography (OCT) for detecting small degrees of in-stent neointima (ISN) after stent implantation compared with intravascular ultrasound (IVUS).

BACKGROUND

The importance of detecting neointimal coverage of stent struts has grown with the appreciation of the increased risk for late stent thrombosis after drug-eluting stent (DES) implantation. Intravascular ultrasound, the current standard for evaluating the status of DES, lacks the resolution to detect the initial neointimal coverage. Optical coherence tomography has greater resolution but has not yet been compared with IVUS in vivo with histological correlation for validation.

METHODS

Intravascular ultrasound and OCT were performed with motorized pullback imaging in 6 pigs across 33 stents, 1 month after implantation. Each pig was euthanized, and histological measurements of vessel, stent, and lumen dimensions were performed in 3 sections of each stent. A small degree of ISN was defined as occupying <30% of the stent area measured with histology. The IVUS, OCT, and histological assessment of ISN were compared in matched cross-sections of the stents with a small degree of ISN.

RESULTS

Eleven stents had a small degree of ISN (average ISN area: 1.26 +/- 0.46 mm(2), and percent area obstruction: 21.4 +/- 5.2%). Compared with histology, the diagnostic accuracy of OCT (area under the receiver operating characteristic curve [AUC] = 0.967, 95% confidence interval [CI] 0.914 to 1.019) was higher than that of IVUS (AUC = 0.781, 95% CI 0.621 to 0.838).

CONCLUSIONS

Optical coherence tomography detects smaller degrees of ISN more accurately than IVUS and might be a useful method for identifying neointimal coverage of stent struts after DES implantation.

Imaging gene expression in human mesenchymal stem cells: from small to large animals

PURPOSE

To evaluate the feasibility of reporter gene imaging in implanted human mesenchymal stem cells (MSCs) in porcine myocardium by using clinical positron emission tomography (PET)-computed tomography (CT) scanning.

MATERIALS AND METHODS

Animal protocols were approved by the Institutional Administrative Panel on Laboratory Animal Care. Transduction of human MSCs by using different doses of adenovirus that contained a cytomegalovirus (CMV) promoter driving the mutant herpes simplex virus type 1 thymidine kinase reporter gene (Ad-CMV-HSV1-sr39tk) was characterized in a cell culture. A total of 2.25 x 10(6) transduced (n = 5) and control nontransduced (n = 5) human MSCs were injected into the myocardium of 10 rats, and reporter gene expression in human MSCs was visualized with micro-PET by using the radiotracer 9-(4-[fluorine 18]-fluoro-3-hydroxymethylbutyl)-guanine (FHBG). Different numbers of transduced human MSCs suspended in either phosphate-buffered saline (PBS) (n = 4) or matrigel (n = 5) were injected into the myocardium of nine swine, and gene expression was visualized with a clinical PET-CT. For analysis of cell culture experiments, linear regression analyses combined with a t test were performed. To test differences in radiotracer uptake between injected and remote myocardium in both rats and swine, one-sided paired Wilcoxon tests were performed. In swine experiments, a linear regression of radiotracer uptake ratio on the number of injected transduced human MSCs was performed.

RESULTS

In cell culture, there was a viral dose-dependent increase of gene expression and FHBG accumulation in human MSCs. Human MSC viability was 96.7% (multiplicity of infection, 250). Cardiac FHBG uptake in rats was significantly elevated (P < .0001) after human MSC injection (0.0054% injected dose [ID]/g +/- 0.0007 [standard deviation]) compared with that in the remote myocardium (0.0003% ID/g +/- 0.0001). In swine, myocardial radiotracer uptake was not elevated after injection of up to 100 x 10(6) human MSCs (PBS group). In the matrigel group, signal-to-background ratio increased to 1.87 after injection of 100 x 10(6) human MSCs and positively correlated (R(2) = 0.97, P < .001) with the number of administered human MSCs.

CONCLUSION

Reporter gene imaging in human MSCs can be translated to large animals. The study highlights the importance of co-administering a "scaffold" for increasing intramyocardial retention of human MSCs.

Fractional flow reserve versus angiography for guiding percutaneous coronary intervention

BACKGROUND

In patients with multivessel coronary artery disease who are undergoing percutaneous coronary intervention (PCI), coronary angiography is the standard method for guiding the placement of the stent. It is unclear whether routine measurement of fractional flow reserve (FFR; the ratio of maximal blood flow in a stenotic artery to normal maximal flow), in addition to angiography, improves outcomes.

METHODS

In 20 medical centers in the United States and Europe, we randomly assigned 1005 patients with multivessel coronary artery disease to undergo PCI with implantation of drug-eluting stents guided by angiography alone or guided by FFR measurements in addition to angiography. Before randomization, lesions requiring PCI were identified on the basis of their angiographic appearance. Patients assigned to angiography-guided PCI underwent stenting of all indicated lesions, whereas those assigned to FFR-guided PCI underwent stenting of indicated lesions only if the FFR was 0.80 or less. The primary end point was the rate of death, nonfatal myocardial infarction, and repeat revascularization at 1 year.

RESULTS

The mean (+/-SD) number of indicated lesions per patient was 2.7+/-0.9 in the angiography group and 2.8+/-1.0 in the FFR group (P=0.34). The number of stents used per patient was 2.7+/-1.2 and 1.9+/-1.3, respectively (P<0.001). The 1-year event rate was 18.3% (91 patients) in the angiography group and 13.2% (67 patients) in the FFR group (P=0.02). Seventy-eight percent of the patients in the angiography group were free from angina at 1 year, as compared with 81% of patients in the FFR group (P=0.20).

CONCLUSIONS

Routine measurement of FFR in patients with multivessel coronary artery disease who are undergoing PCI with drug-eluting stents significantly reduces the rate of the composite end point of death, nonfatal myocardial infarction, and repeat revascularization at 1 year. (ClinicalTrials.gov number, NCT00267774.)

Introducing the first polymer-free leflunomide eluting stent

BACKGROUND

We here describe the pharmacological characteristic, in vivo efficacy, and in vitro mechanisms of a polymer-free leflunomide eluting stent in comparison to its rapamycin-coated equivalent.

METHODS

Stents were coated with 40 mM solutions of leflunomide (L) or rapamycin (R) or were left uncoated (BM). Neointima formation was assessed 6 weeks after implantation into Sprague Dawley rats by optical coherence tomographies (OCT) and histopathology. In vitro proliferation assays were performed using isolated endothelial and smooth-muscle-cells from Sprague Dawley rats to investigate the cell-specific pharmacokinetic effect of leflunomide and rapamycin.

RESULTS

HPLC-based drug release kinetics revealed a similar profile with 90% of the drug being released after 12.1+/-0.2 (L) and 13.0+/-0.2 days (R). After 6 weeks, OCTs showed that in-stent luminal obliteration was less for the coated stents (L:12.0+/-9.4%, R:13.3+/-13.1%) when compared to identical bare metal stents (BM:26.4+/-4.7%; p<or=0.046). Histology with computer-assisted morphometry was performed and demonstrated reduced in-stent I/M thickness ratios (L:2.5+/-1.2, R:3.7+/-3.3, BM:6.7+/-2.3, p<or=0.049 for L and R vs. BM) and neointimal areas (L:0.6+/-0.3, R:0.7+/-0.2, BM:1.3+/-0.4, p<or=0.039 for L and R vs. BM) with stent coating. No differences were found for injury and inflammation scores (L and R vs. BM; p=NS). In vitro SMC proliferation was dose-dependently and similarly inhibited by L and R at 1-100 nM (p=NS L vs. R). Interestingly, human EC proliferation at 10-100 nM was significantly inhibited only by R (p<0.001), but not by L (p=NS).

CONCLUSIONS

The diminished inhibition of EC proliferation may improve arterial healing and contribute to the safety profile of the leflunomide stent.

The porcine restenosis model using thermal balloon injury: comparison with the model by coronary stenting

BACKGROUND

Percutaneous coronary intervention (PCI) continues to revolutionize the treatment of coronary atherosclerosis and technologic advances require a preclinical coronary stenosis model. The purpose of this study was to systematically evaluate a porcine restenosis model of thermal balloon injury compared to stent overstretching.

METHODS

To evaluate this injury model, 22 swine were utilized. For the induction of coronary stenoses, the thermal balloon-to-artery ratio was equal to the range of 1.2-1.3 and was placed at a desired location in the coronary arteries, inflated with 2 atm, and heated to 80 degrees C for 80 seconds. Quantitative coronary angiography was analyzed at baseline, immediately postprocedure, and 4 weeks at harvest. Quantitative coronary ultrasound analysis and histopathologic evaluation were also performed at 4 weeks postprocedure.

RESULTS

A total of 54 coronary arteries (thermal balloon injury [Thermo]; n = 43, coronary stenting [Stent]; n = 11) from a total of 18 animals were analyzed for this study. At 4 weeks postprocedure, significantly greater coronary stenoses were observed in the Thermo Group versus the Stent Group (minimum lumen diameter: 1.00 % 0.63 mm vs. 1.58 % 0.44 mm; p = 0.009, % diameter stenosis [DS]: 66.2 +/- 21.6% vs. 48.1 +/- 11.4%; p = 0.02). There were significant linear correlations between the balloon-to-artery ratio, post %DS and %DS at 4 weeks (balloon-to-artery ratio; r = 0.538; p = 0.0012, post %DS; r = -0.744; p < 0.0001, respectively).

CONCLUSION

This methodology may provide reproducible and consistent coronary stenoses. This model can be useful fnot only for the evaluation of medical devices, but also for technical training in PCI and development of coronary imaging technologies.

Comparison of nonuniform strut distribution between two drug-eluting stent platforms

OBJECTIVE

To compare the difference of strut distribution between two clinically available drug-eluting stent platforms (Bx Velocity and Express II stents) using intravascular ultrasound (IVUS).

BACKGROUND

Nonuniform strut distribution (NSD) has been shown to be associated with increased intimal hyperplasia after drug-eluting stent implantation.

METHODS

IVUS imaging was performed on Bx Velocity (n = 6) and Express II stents (n = 6) after inflation pressures of 10, 16, and 26 atm in a bench test model. Percent NSD was defined as the length of segments with NSD (interstrut angle > 90 degrees) divided by stent length. NSD was also assessed in postprocedure IVUS images in 53 clinical cases (32 Cypher, 21 Taxus) using 3-dimensional IVUS analysis.

RESULTS

Frequency of NSD segment and %NSD were lower in Bx Velocity stents than in Express II stents at the inflation pressures of 16 and 26 atm (%NSD: 16 atm, 0% vs. 13.8 +/- 9.4%; p < 0.005; 26 atm, 1.1 +/- 2.6% vs. 19.9 +/- 6.9% p < 0.0001). In postprocedural images from clinical cases, the frequency of NSD segment and %NSD were lower in Cypher stents than in Taxus stents (%NSD: 0.5 +/- 1.6 vs. 6.8 +/- 7.2; p < 0.0001).

CONCLUSION

NSD segment was observed less in Bx Velocity stents than in Express II stents.

Arteriotomy closure device application following percutaneous coronary intervention may prevent bleeding complications in patients with acute myocardial infarction

The current study was performed to determine whether application of arteriotomy closure devices (ACDs) affect bleeding complications as compared to manual compression in patients with ST-elevated acute myocardial infarction (STEMI) who undergo primary or rescue percutaneous intervention (PCI). 314 consecutive cases of STEMI treated with PCI were retrospectively evaluated. Overall, 82.8% of patients received ACDs with total bleeding rate of 4.2% vs. 11.1% in patients who had manual compression, p=0.042. This difference in bleeding rates did not correlate with any clinical characteristic or utilization of GPIIb/IIIa inhibitors. Accordingly, ACDs can improve the acute results of PCI in STEMI patients.

Novel stent system for accurate placement in aorto-ostial renal artery disease: preclinical study in porcine renal artery model

BACKGROUND

Treatment of aorto-ostial renal artery stenosis has been associated with a lower procedural success and higher complication and restenosis rate, as compared to nonostial lesions. The design and delivery of currently available stent systems in ostial lesions can result in inaccurate stent positioning and placement leading to stent protrusion into the parent vessel lumen or geographic miss. A novel stent system (SquareOne Inc., Campbell, CA, USA) has been designed specifically for aorto-ostial lesions in the renal artery. This stent system aims to provide both tactile and visual confirmation of the ostium at the aorta, allow for improved accuracy during stent positioning and placement, provide complete scaffolding of the lesion at the aortic junction to the native vessel, and enable future vessel reaccess.

METHODS

Stents (n=12) were implanted in both renal arteries of six swine. For histology, two animals were euthanized immediately after stent implantation, and each two animals were then followed up at 2 and 4 weeks, respectively. Intravascular ultrasound (IVUS) studies were performed immediately after stent implantation and at follow-up.

RESULTS

Proper stent positioning and implantation was obtained in all animals. Angiographic and IVUS assessments indicated no dissection or thrombus formation. Histology demonstrated good apposition and endothelialization of the stent strut surface.

CONCLUSION

The unique flared shape of this novel ostial stent system allows for improved accuracy during stent positioning and placement, as well as complete apposition and coverage/scaffolding of the similarly-shaped luminal ostium. Future studies will determine if this novel stent system fulfills the unmet clinical need in aorto-ostial stenoses.

Mechanism of Luminal Gain with Plaque Excision in Atherosclerotic Coronary and Peripheral Arteries: Assessment by Histology and Intravascular Ultrasound

OBJECTIVES

Using intravascular ultrasound (IVUS) and histology, the purpose of this study was to evaluate the occurrence of arterial wall overstretch and Dotter effect following revascularization with a plaque excision (PE) catheter compared with balloon angioplasty.

BACKGROUND

Previous studies have demonstrated the safety and feasibility of plaque excision for the treatment of de novo coronary and peripheral atherosclerotic disease. However, whether mechanical vessel dilatation related to catheter insertion contributes to gains in the final luminal diameter is uncertain.

METHODS

Treatment with PE was assessed in both a porcine model (6 lesions treated with balloon angioplasty or PE) using histology and in humans with IVUS. In the latter part of the study, IVUS study was performed before and immediately following PE in 21 patients with either coronary artery disease (N = 13) or femoral artery disease (N = 8). Ultrasound measures in the femoral artery group were then compared with a control group of atherosclerotic lesions treated with conventional angioplasty that was matched according to lesion location and vessel diameter.

RESULTS

Among individuals with coronary and peripheral arterial lesions treated with PE, the relative increases in luminal area secondary to reductions in plaque volume were 89% and 83%, respectively, with minimal increase in vessel diameter. In contrast, balloon angioplasty was associated with significantly greater vessel expansion and less plaque volume reduction. Vessel dissection also tended to occur less frequently and to a lesser extent with PE.

CONCLUSIONS

Improvement in luminal dimensions using PE is principally due to a reduction in plaque volume rather than mechanical vessel expansion. The potential to increase luminal area while minimizing arterial dissection and barotrauma merits further clinical study with this method of revascularization.