Michael S. Aboodi

Accuracy of optical coherence tomography in the evaluation of neointimal coverage after stent implantation.

OBJECTIVES This study aimed to evaluate the accuracy of optical coherence tomography (OCT) in analyzing the neointimal response to several drug-eluting stent (DES) types by comparing OCT images acquired in vivo with corresponding histological specimens using a nondiseased porcine injury model. BACKGROUND Optical coherence tomography is emerging as a promising endovascular imaging tool for the evaluation of neointimal response after DES implantation. METHODS A total of 84 stents were implanted-22 ML Vision (Abbott Vascular, Santa Clara, California), 22 Xience V (Abbott Vascular), 20 Endeavor (Medtronic, Minneapolis, Minnesota), and 20 Taxus Liberté (Boston Scientific, Natick, Massachusetts) stents-in normal porcine coronary arteries and were harvested at 28 (n=42) and 90 (n=42) days, with the different stent types equally distributed between the 2 follow-up periods. At termination, morphometric evaluation using OCT imaging was performed in all stented arteries. Histological morphometric analysis was performed and correlated with OCT. RESULTS A total of 622 OCT-histology matched frames acquired from all stent designs were analyzed. The luminal (13.7%) and stent (6.1%) areas were consistently larger by OCT compared with histology. The mean neointimal thickness was very similar between techniques (approximately 3.27% variation). There was a high correlation between OCT and histology for the evaluation of neointimal area (R2=0.804), luminal area (R2=0.825), and neointimal thickness (R2=0.789). Correlation for total stent area was poor (R2=0.352). Although the proportion of individual struts determined to be uncovered by OCT and histology was similar, there was significant variation in the estimation of strut coverage between OCT and histology when the neointimal thickness was between 20 and 80 microm. This variation converged for neointimal thicknesses between 80 and 100 microm. CONCLUSIONS Subtle differences in neointimal formation induced by current DES can be reproducibly analyzed in vivo by OCT. However, OCT measurement of stent area seems to have less correlation with histology.

Development of a Novel Prohealing Stent Designed to Deliver Sirolimus From a Biodegradable Abluminal Matrix

Background—We aimed to demonstrate that, by separating endothelial progenitor cell capture from sirolimus delivery through the application of drug to the abluminal surface of the stent, the degree of endothelialization can be enhanced. Methods and Results—Stainless steel R Stents, with biodegradable SynBiosys polymer coating with sirolimus abluminally applied and surface modified with anti-CD34 antibody were prepared at 2 dosages (low-dose sirolimus [LD-Combo, 2.5 &mgr;g sirolimus/mm] and full-dose sirolimus [Combo, 5 &mgr;g sirolimus/mm). These Combo stents and the Cypher stent (10 &mgr;g sirolimus/mm) were deployed in 98 normal porcine arteries and harvested for pharmacokinetic analysis at 0.25, 1, 3, 7, 14, 28, and 35 days. The LD-Combo stents showed faster early release (50% total dose in 72 hours) than the Combo and Cypher. At 30 days, drug release was near complete with both Combo stents, whereas 20% of drug remained on the Cypher stents. To assess efficacy, a total of 50 stents (Xience V=8, Cypher=8, Genous bioengineered R stent=6, LD-Combo=14, and Combo=14) were implanted in 18 pigs for 14 and 28 days. Optical coherence tomography was performed, and stents were harvested for histology. At 28 days, there was less neointimal thickness with Combo (0.173±0.088 mm) compared with Cypher (0.358±0.225 mm), LD-Combo (0.316±0.228 mm), and Xience V (0.305±0.252 mm; P<0.00001). Immunohistochemical analysis of endothelialization showed that Genous bioengineered R stent had the highest degree of platelet endothelial cell adhesion molecule expression (87%) followed by the Combo (75%), LD-Combo (65%), and Cypher (58%). Conclusions—Both optical coherence tomography and histology demonstrate that anti-CD34 sirolimus-eluting stents promote endothelialization while reducing neointimal formation and inflammation.

Vascular Response to Zotarolimus-Coated Balloons in Injured Superficial Femoral Arteries of the Familial Hypercholesterolemic Swine

Background— Drug-coated balloons are rapidly emerging as a therapeutic alternative for the interventional treatment of peripheral vascular disease. The purpose of this study was to test the hypothesis that an angioplasty balloon coated with the mTOR inhibitor zotarolimus (ZCB) would inhibit neointimal hyperplasia in a novel injury-based superficial femoral artery model in the familial hypercholesterolemic swine. Methods and Results— A total of 44 familial hypercholesterolemic swine were included (12 designated to study tissue pharmacokinetics and 32 to study safety and efficacy). Fogarty balloon denudation was performed in all superficial femoral artery segments, followed by balloon angioplasty. In the pharmacokinetic study, a total of 24 ZCBs (300 &mgr;g/cm2) were used. Zotarolimus was detected in arterial tissue at 5 minutes (162 ng/mg of tissue), 24 hours (5.9 ng/mg of tissue), and 28 days (0.007 ng/mg of tissue) after ZCB inflation. In the safety and efficacy study, superficial femoral artery segments were randomized to either high-dose (600 &mgr;g/cm2, n=16), low-dose (300 &mgr;g/cm2, n=16), or paired uncoated balloons (high-dose ZCB control, n=16; low-dose ZCB control, n=16). At 28 days, the percentage of angiographic stenosis was similar among all tested groups. Histological analysis demonstrated a reduction in neointimal formation in both ZCB groups compared with controls (high-dose ZCB 44% reduction, P=0.007; low-dose ZCB 22% reduction, P=0.08). There was no evidence of delayed arterial healing or vascular toxicity in any of the ZCB groups. Conclusions— The single delivery of zotarolimus via coated balloon is feasible, and therapeutic levels are maintained up to 28 days. The ZCB technology appears to be effective in the reduction of neointimal proliferation in the superficial femoral artery of the familial hypercholesterolemic swine.

Coronary bare metal stent implantation in homozygous LDL receptor deficient swine induces a neointimal formation pattern similar to humans.

INTRODUCTION To date, most of all new developments in stent technologies are tested in normal animals. Although invaluable in the evaluation of device safety, the juvenile domestic swine (DS) do not follow the biological healing response occurring in humans following coronary stent implantation. By using a novel swine breed afflicted with familial hypercholesterolemia (FHS), we aimed to analyse the vascular response occurring following bare metal stent (BMS) implantation by comparing in vivo endovascular imaging and histological data. METHODS A total of 26 swine were included in this study (12 FHS and 14 DS). Sixty eight BMS (FHS=28 versus DS=40) were implanted using a 10% overstretch ratio. Imaging evaluation (IVUS and OCT) was conducted in all animals at 30 (n=14) or 90 (n=12) days following stent implantation. After imaging, the stented coronary segments were harvested for histological evaluation. RESULTS At 30 days, the degree of neointimal formation analysed by OCT (%AS=DS 21.9 ± 10% versus FHS 25.4 ± 12%; p=0.18) and histology (DS 24.6 ± 10% versus FHS 23.58 ± 10%; p=0.8) was similar between both animal groups. At 90 days, the degree of neointimal formation in the DS group decreased in all analysed variables (-40% in IVUS neointimal volume, -57% in OCT %AS, and -30% in %AS by histology) compared to the progression of neointimal formation observed in the FHS group (+29% in IVUS neointimal volume, +27% in OCT %AS and +43% in %AS by histology). CONCLUSION The pattern of neointimal formation following BMS implantation in the FHS follows a progressive course that does not occur in the DS. Therefore, by providing a progressive neointimal biological response to BMS implantation, the FHS could serve as an ideal efficacy model for the validation of drug eluting stent technologies.

Evaluation of Efficacy and Dose Response of Different Paclitaxel-Coated Balloon Formulations in a Novel Swine Model of Iliofemoral In-Stent Restenosis

OBJECTIVES The authors aimed to validate a novel iliofemoral in-stent restenosis (ISR) model for the efficacy evaluation of paclitaxel-coated balloons (PCB) using the familial hypercholesterolemic swine (FHS). BACKGROUND Most of the validation work regarding PCB technologies has been performed in the coronary territory of juvenile domestic swine. Although invaluable for safety evaluation, this model is not suited for the evaluation of the efficacy of peripheral PCB technologies. METHODS Twenty-four iliofemoral segments in 12 FHS underwent balloon injury and self-expanding stent placement. After 21 days, the resulting ISR lesions were treated with either 1 μg/mm(2) dose (n = 8), or 3 μg/mm(2) dose (n = 8) PCB (Cotavance, Bayer Pharma AG/MEDRAD, Indianola, Pennsylvania), or with an identical uncoated control balloon (n = 8). RESULTS At termination (28 days after treatment), the percent diameter stenosis by quantitative vascular analysis in the control group was higher (31.2 ± 13.7%) compared with the 1 μg/mm(2) (19.3 ± 14.0%, 38% reduction) and 3 μg/mm(2) (8.6 ± 10.7%, 72% reduction) PCB groups. Intravascular ultrasound analysis showed 36% (1 μg/mm(2) dose, p = 0.04) and 55% (3 μg/mm(2) dose, p < 0.01) reductions in neointimal volume stenosis. In the histological analysis, the control group showed the highest degree of percent area stenosis (65 ± 14.3%). The reductions in percent area stenosis was 13.2% (p = 0.5) and 26% (p = 0.04) in the 1 μg/mm(2) and 3 μg/mm(2) dose groups, respectively. CONCLUSIONS The FHS model of iliofemoral ISR demonstrated a dose-dependent effect on the inhibition of neointimal proliferation of a clinically validated PCB technology. This model represents a positive step toward the efficacy evaluation of PCB in the peripheral vascular territory.

Long-term effects on vascular healing of bare metal stents delivered via paclitaxel-coated balloons in the porcine model of restenosis.

Clinical trials have consistently demonstrated benefits of Paclitaxel‐coated balloons (PCB) in particular clinical situations such as in‐stent restenosis and peripheral vascular interventions. However, the long‐term vascular effects of bare metal stents (BMS) delivered via PCB (PCB+BMS) are still unknown. The aim of this study was to assess the long‐term effects of PCB+BMS on vascular healing and neointimal formation (NF).

Controlled reperfusion with intravenous bivalirudin and intracoronary abciximab combination therapy in the porcine myocardial infarction model.

INTRODUCTION The reperfusion injury (RI) remains a significant limitation of primary PCI, therefore we evaluated the role of intracoronary abciximab and bivalirudin for anticoagulation on myocardial salvage and RI in the porcine model of ischemia/reperfusion. MATERIALS AND METHODS Myocardial infarction was induced in 23 pigs by 60-minute over-the-wire (OTW) balloon occlusion of the LAD. Animals received intravenous bivalirudin and then five minutes prior to reperfusion, either a coronary downstream infusion of abciximab (n=11) or saline (n=12) through the central lumen of an OTW catheter. All animals were followed for 48 hours. RESULTS Histological analysis showed that infarct area (IA) and area at risk (AAR) were comparable between groups (IA/AAR%: 57.6 ± 8% vs. 57.1 ± 7%, p=0.8). Confirming this trend, biochemical markers (troponin I, TNF-alpha, IL-6, hsCRP, adiponectin, and VCAM) and left ventricular ejection fraction were also similar at 48 hours. Adhesion markers like ICAM and P-selectin were significantly decreased in the study group, nevertheless histological evidence of leukocyte extravasation was similar. The enhancement of apoptosis by TUNEL was comparable in both groups. The number of hemorrhagic infarctions confirmed by micro and macroscopic evaluation tended to be higher in the study group (70% vs. 20%, p=0.07). CONCLUSIONS Despite lowered concentrations of adhesion molecules, intracoronary abciximab with peripheral bivalirudin is not superior to bivalirudin unaided in terms of myocardial salvage caused by RI in the porcine ischemia/reperfusion model. This might be due to local hemorrhage caused by abciximab.

Paclitaxel-iopromide coated balloon followed by "bail-out" bare metal stent in porcine iliofemoral arteries: first report on biological effects in peripheral circulation.

AIMS Despite recent abundance of data on drug-coated balloon technology, the biological effects of paclitaxel coated balloon (PCB) treatment followed by bare metal stent (BMS) implantation in peripheral arteries (simulating bail-out stenting, a common clinical scenario), have not been published. METHODS AND RESULTS PCB technology containing a paclitaxel-iopromide coating and identical iopromide-coated controls (without paclitaxel) were used in 16 porcine ilio-femoral arteries. The biological effects of inflating one (PCBx1) or two sequential (PCBx2) paclitaxel coated balloons before BMS implantation were compared to the single application of a control balloon (CCBx1; contrast coated balloons). At 30 days PCBx2 displayed significantly reduced late lumen loss by angiography (58% reduction vs. CCBx1; p=0.04) and neointimal area by histomorphometry (35% reduction vs. CCBx1 and 30% vs. PCBx1; p=0.02). Similarly, percent area stenosis in the PCBx2 group was reduced by 45% as compared to CCBx1 and PCBx1 (p=0.04). At this time, all parameters of vessel wall healing (including injury score, inflammation, and endothelialisation) following drug coated balloon treatment were comparable to the control group. CONCLUSIONS Paclitaxel delivery to porcine ilio-femorals using PCB followed by BMS implantation effectively decreased neointimal proliferation. More extensive and prolonged proliferative response of the vessel after stenting (necessitating higher drug dose) could potentially explain the undetectable effect of PEBx1 relative to CCBx1 in this pilot study. Histological analysis confirmed the safety and biocompatibility of PCB technology.

Catheter-Based Endomyocardial Delivery of Mesenchymal Precursor Cells Using 3D Echo Guidance Improves Cardiac Function in a Chronic Myocardial Injury Ovine Model

The administration of bone marrow-derived stem cells may provide a new treatment option for patients with heart failure. Transcatheter cell injection may require multi-imaging modalities to optimize delivery. This study sought to evaluate whether endomyocardial injection of mesenchymal precursor cells (MPCs) could be guided by real-time 3D echocardiography (RT3DE) in treating chronic, postinfarction (MI) left ventricular (LV) dysfunction in sheep. Four weeks after induction of an anterior wall myocardial infarction in 39 sheep, allogeneic MPCs in doses of either 25 × 106 (n = 10), 75 × 106 (n = 9), or 225 × 106 (n = 10) cells or nonconditioned control media (n = 10) were administered intramyocardially into infarct and border zone areas using a catheter designed for combined fluoroscopic and RT3DE-guided injections. LV function was assessed before and after injection. Infarct dimension and vascular density were evaluated histologically. RT3DE-guided injection procedures were safe. Compared to controls, the highest dose MPC treatment led to increments in ejection fraction (3±3% in 225M MPCs vs. −5±4% in the control group, p < 0.01) and wall thickening in both infarct (4±4% in 225M MPCs vs. −3±6% in the control group, p = 0.02) and border zones (4±6% in 225M MPCs vs. −8±9% in the control group, p = 0.01). Histology analysis demonstrated significantly higher arteriole density in the infarct and border zones in the highest dose MPC-treated animals compared to the lower dose or control groups. Endomyocardial implantation of MPCs under RT3DE guidance was safe and without observed logistical obstacles. Significant increases in LV performance (ejection fraction and wall thickening) and neovascularization resulted from this technique, and so this technique has important implications for treating patients with postischemic LV dysfunction.

Epicardial catheter-based ventricular reconstruction: a novel therapy for ischaemic heart failure with anteroapical aneurysm

OBJECTIVES Surgical ventricular reconstruction has been used to treat ischaemic cardiomyopathy with large akinetic or dyskinetic areas. However, application of this approach requires a sternotomy, cardiopulmonary bypass and a left ventriculotomy. This study assessed the feasibility and efficacy of minimally invasive, off-pump, epicardial catheter-based ventricular reconstruction (ECVR) in an anteroapical aneurysm ovine model. METHODS Left ventricular (LV) anteroapical myocardial infarction was induced percutaneously by coil embolization of the left anterior descending coronary artery. Eight weeks after infarction, via mini left thoracotomy and without cardiopulmonary bypass, ECVR was performed in six sheep. The scar was excluded by placing anchor pairs on the LV epicardial anterior wall and the right ventricular side of the interventricular septum under fluoroscopic guidance. LV performance was evaluated before, immediately after device implantation and after 6 weeks by echocardiography. Terminal histopathology was performed. RESULTS ECVR was completed expeditiously in all animals without complications. Parameters obtained 6 weeks after device implantation were compared with baseline (pre-device). End-systolic volume was decreased by 38% (25.6 ± 6.1 ml vs baseline 41.2 ± 7.2 ml, P = 0.02) with preservation of stroke volume. Ejection fraction was significantly increased by 13% (48.5 ± 7% vs baseline 35.8 ± 7%, P = 0.02). The circumferential strain in the anterior septum (-7.67 ± 5.12% vs baseline -0.96 ± 2.22%, P = 0.03) and anterior wall (-9.01 ± 3.51% vs baseline -4.15 ± 1.36%, P = 0.01) were significantly improved. The longitudinal strain in apex was reversed (-3.08 ± 1.53% vs baseline 3.09 ± 3.39%, P = 0.01). Histopathology showed full endocardial healing over the anchors with appreciable reduction of the chronic infarct in the LV. CONCLUSIONS ECVR without cardiopulmonary bypass is a less invasive alternative to current standard therapies, reverses LV remodelling and improves cardiac performance in an ovine model of anteroapical aneurysm.