A randomized animal study evaluating the efficacies of locally delivered heparin and urokinase for reducing in-stent restenosis

Role of IN-1233 in the prevention of neointimal hyperplasia after stent placement in a rat artery model

PURPOSE

To evaluate the efficacy of an activin receptor-like kinase (ALK) 5 inhibitor, IN-1233, for the prevention of neointimal hyperplasia after bare stent placement in a rat common iliac artery (CIA) model.

MATERIALS AND METHODS

All experiments were approved by the committee of animal research. A self-expanding metallic bare stent (2 mm × 6 mm) was inserted into the left CIA of 26 Sprague-Dawley male rats (300-360 g) under fluoroscopic guidance. IN-1233 was injected via the intraperitoneal route daily in 13 rats for 8 weeks after stent placement (group A); the other 13 rats underwent stent placement only (group B). Angiography was performed immediately and 4 weeks and 8 weeks after stent placement. Rats were sacrificed at 8 weeks after stent placement, and histologic findings were obtained. The neointimal area (NA), percentage of neointimal hyperplasia (%NH), and neointimal-to-medial area ratio (N/M) were assessed and compared between the two groups.

RESULTS

Stent placement was technically successful. In 25 rats, arteries with stent placement were angiographically patent, whereas 1 rat in group B had an occlusion. The NA (0.31 mm(2) ± 0.09 vs 0.56 mm(2) ± 0.17; P < .001), the %NH (26.16% ± 8.75 vs 44.71% ± 17.75; P < .001) and the N/M (1.93 ± 0.77 vs 4.77 ± 2.26; P < .001) were significantly decreased in group A compared with group B.

CONCLUSIONS

IN-1233 was shown in this study to be effective for the prevention of neointimal hyperplasia after bare metallic stent placement in a rat CIA model.

The Paclitaxel-Eluting Coroflex™ Please Stent Pilot Study (PECOPS I)

BACKGROUND

The alleged superiority of drug-eluting stents over bare metal devices and those with passive coatings is diminished by a higher incidence of late target vessel thrombosis.

METHODS AND RESULTS

Therefore, the one-year clinical outcome of the paclitaxel-eluting Coroflex Please stent in patients with denovo coronary lesions was evaluated in the single-arm PECOPS I pilot study. The clinical data of 96/97 (99%) of the patients included per protocol and of 86/87 (98.9%) of those treated per protocol were available 13.1 +/- 1.8 months following stent deployment. In the inclusion and treatment per protocol groups the incidence of cardiac deaths was 1/96 (1%) and 1/86 (1.2%), of myocardial infarction 3/96 (3.1%) and 1/86 (1.2%), and of target lesion revascularization 9/96 (9.4%) and 8/86 (9.3%). In patients enrolled per protocol two early thromboses (2.1%) occurred one of which two days after premature discontinuation of clopidogrel. In patients treated per protocol one thrombosis was observed after 10 hours. The one-year event-free survival was 83/96 (86.5%) in patients enrolled per protocol and 75/86 (87.2%) in those treated per protocol.

CONCLUSION

The one-year clinical outcome of PECOPS I was within the range of other paclitaxel-eluting coronary stents. The relative small number of patients enrolled in PECOPS I precludes to infer any further conclusions.

The paclitaxel-eluting Coroflex™ please stent pilot study (PECOPS I): Acute and 6-month clinical and angiographic follow-up

BACKGROUND AND OBJECTIVES

Various active stent coatings significantly reduce restenosis rates and target lesion revascularization compared to bare metal stents. Therefore, the procedural and 6-month performance of the new paclitaxel-eluting Coroflex. Please stent was investigated.

METHODS

Ninety-seven patients (66 +/- 7.6 years, 34/97(35.1%) diabetics, 11/97(11.3%) unstable angina) were enrolled per protocol for elective single stent deployment into native coronary de-novo or post-PTCA restenotic lesions (stenosis: >or= 70%, < 100%; reference diameter >or= 2.25 mm and <3.3 mm; lesion length <or= 16 mm) with 13/97(13.4%) lesion type A, 64/97(66%) type B1, 20/97(20.6%) type B2). The mean reference diameter was 2.88 +/- 0.42 mm, the lesion length 10.03 +/- 2.93 mm, and the minimal lumen diameter 0.64 +/- 0.22 mm.

RESULTS

The success rates of procedure and study stent deployment were 100% and 94.8%, respectively. In 5/97(5.2%) two stents were implanted. Follow-up was performed clinically in 86/87(98.9%) and angiographically in 77/87(88.5%) patients after 6.1 +/- 0.7 months. Major adverse cardiac events occurred in 7/87(8%) 1/87(1.2%) subacute thrombosis 10.3hrs post procedure, 1/87(1.2%) myocardial infarction, 5/87(5.7%) target lesion revascularizations. The in-segment stenosis declined from 78 +/- 7.2% to 9.4 +/- 6.2% after stenting increasing to 31.9 +/- 18.6% at follow-up. The in-segment late loss and the late loss index were 0.47 +/- 0.6 mm and 0.23 +/- 0.29 resulting in 6/77(7.8%) in-segment restenoses three each of which were located either within or beyond the stent structure. The outcome was neither influenced by the prevalence of diabetes ( p = 0.4), hypercholesterolemia ( p = 1), hypertension ( p = 1), overweight ( p = 1), nor by the family history of coronary artery disease ( p = 0.7).

CONCLUSION

The data of the paclitaxel-eluting Coroflex. Please stent tested in PECOPS I are within the range other available paclitaxel-eluting stent.

Preclinical restenosis models and drug-eluting stents: still important, still much to learn

Percutaneous coronary intervention continues to revolutionize the treatment of coronary atherosclerosis. Restenosis remains a significant problem but may at last be yielding to technologic advances. The examination of neointimal hyperplasia in injured animal artery models has helped in our understanding of angioplasty and stenting mechanisms, and as drug-eluting stent (DES) technologies have arrived, they too have been advanced through the study of animal models. These models are useful for predicting adverse clinical outcomes in patients with DESs because suboptimal animal model studies typically lead to problematic human trials. Similarly, stent thrombosis in animal models suggests stent thrombogenicity in human patients. Equivocal animal model results at six or nine months occasionally have been mirrored by excellent clinical outcomes in patients. The causes of such disparities are unclear but may result from differing methods, including less injury severity than originally described in the models. Ongoing research into animal models will reconcile apparent differences with clinical trials and advance our understanding of how to apply animal models to clinical stenting in the era of DESs.

Heparin-coated balloon-expandable stent reduces intimal hyperplasia in the iliac artery in baboons

PURPOSE

To examine the effect of heparin-coated balloon-expandable iliac stent placement on intimal hyperplasia in a baboon model.

MATERIALS AND METHODS

Balloon-expandable (Palmaz-Schatz) stents were placed in bilateral common iliac arteries in 20 male baboons (mean weight: 8.8 kg). In each animal, a heparin-coated iliac stent was placed on one side and the contralateral iliac artery received an uncoated stent that served as a control. The iliac artery stents were harvested at 30 days (n = 10) and 90 days (n = 10). Arteriography was performed to assess iliac patency and intravascular ultrasonography was used to determine neointimal and luminal areas. Histologic and morphometric analysis and scanning electron microscopy were performed in the stent-implanted iliac arteries.

RESULTS

One animal was excluded in the 30-day group because of premature death. In the remaining nine surviving animals, seven control stents (78%) and nine heparin-coated stents (100%) remained patent. Morphometric analysis showed that the iliac arteries with heparin-coated stents had larger luminal areas (17%, P <.05), less neointimal area (26%, P <.05), lower neointima-to-media ratios (32%, P <.05), and equivalent medial areas (P =.92) compared to the control group at 30 days. In contrast, all control and heparin-coated stents were patent (100%) in the 90-day group. In that group, the heparin-coated stent group had less neointimal area (28%, P <.05), lower neointima-to-media ratios (42%, P <.05), and equivalent medial area (P =.92) and luminal area (P =.07) compared to the control group.

CONCLUSIONS

The data demonstrate that heparin-coated balloon-expandable stents reduce intimal hyperplasia after iliac artery stent placement. This approach may represent a useful strategy for prolonging luminal patency after iliac stent placement.

In vivo model of intracranial stent implantation: a pilot study to examine the histological response of cerebral vessels after randomized implantation of heparin-coated and uncoated endoluminal stents in a blinded fashion

OBJECT

No animal model currently exists for the examination of time-dependent histological changes occurring in intracranial vessels after endoluminal stent placement. The authors' goal was to develop a reproducible in vivo model of stent implantation in intracranial vessels in dogs that was capable of demonstrating stent-related vascular changes after the implantation of coated and uncoated devices.

METHODS

The authors implanted heparin-coated or uncoated stents in the basilar arteries (BAs) of 11 mongrel dogs. In a 12th animal, one coated stent was implanted in the BA and a second uncoated one was implanted in the distalanterior spinal artery. All the devices were oversized to induce intimal injury. Surviving animals were observed for 12 weeks, after which they underwent repeated angiography before planned death and removal of the brain. Histological studies and computer-assisted morphometric analyses were conducted on stent-treated and untreated sections of the BAs to assess the percentage of stenosis, neointimal proliferation, vessel injury, and inflammation. Perforating vessels partially covered by stent struts ("jailing") were studied for evidence of stenosis or occlusion. The pathologist, interventionists, histopathologist, histopathology technicians, and radiologist were blinded to the stent type. Seven stents (three uncoated and four coated) were removed from the six animals that were observed during the follow-up period. The mean neointimal proliferation was 0.42 mm2 in the group treated with uncoated stents and 0.18 mm2 in the group treated with heparin-coated devices (p = 0.04). Neointimal thickness was significantly increased in the group with uncoated stents (p = 0.04). The mean percentage of occlusion was less (12%) in the group with heparin-coated stents, compared with 22% in the group with uncoated devices (p = 0.07). When comparing results between the heparin-coated and uncoated devices implanted in the five animals that received a single stent only, greater differences (indicating a benefit from heparin-coated stents) were observed in neointimal area (p = 0.009), neointima/media ratio (p = 0.001), neointimal thickness (p = 0.002), and percentage of occlusion (p = 0.009). All brainstem perforating vessels covered by stent struts remained patent.

CONCLUSIONS

This in vivo intracranial stent model was developed to assess proliferative and inflammatory responses to endoluminal stent implantation in the cerebrovasculature. The results indicate that a lower percentage of occlusion occurs 12 weeks after implantation of heparin-coated compared with uncoated stents.

tPA via infusion catheters followed by continuous IV infusion for 3 days prevents intimal hyperplasia after balloon injury

A rabbit model was used to examine the effects of tissue plasminogen activator (tPA) on development of intimal hyperplasia following balloon injury. Thirty-two hereditary hypercholesterolemic (KHC) rabbits underwent percutaneous transluminal coronary artery balloon catheterization and injury to the common iliac artery, after which they were divided into four groups: untreated (control); Dispatch catheterized-30 minutes local saline delivery [D(+)-tPA(-)]; D(+)-30 minutes local tPA delivery (0.6 mg/kg) [D(+)-tPA(30 min)]; and D(+)-30 minutes local tPA + 3 days intravenous infusion (0.6 mg/kg/24 h) [(D(+)-tPA(30 min + 3 d)]. Twenty-eight days later, the intimal cross-sectional areas of all three Dispatch catheterized groups were significantly smaller than those of control groups, as were the intimal/medial area ratios. Moreover, the intima/media ratios of the D(+)-tPA(30 min + 3 d) group were significantly smaller than those of the D(+)-tPA(-) group. Thus, local delivery of tPA via Dispatch catheters followed by continuous intravenous infusion of tPA for 3 days prevented intimal hyperplasia after angioplasty.

Endothelial implants inhibit intimal hyperplasia after porcine angioplasty

The perivascular implantation of tissue-engineered endothelial cells around injured arteries offers an opportunity to study fundamental vascular physiology as well as restore and improve tissue function. Cell source is an important issue because the ability to implant either xenogeneic or allogeneic cells would greatly enhance the clinical applications of tissue-engineered grafts. We investigated the biological and immunological responses to endothelial cell xenografts and allografts in pigs 4 weeks after angioplasty of the carotid arteries. Porcine or bovine aortic endothelial cells were cultured within Gelfoam matrices and implanted in the perivascular space of 42 injured arteries. Both porcine and bovine endothelial cell grafts reduced the restenosis index compared with control by 54% and 46%, respectively. Perivascular heparin release devices, formulated to release heparin at twice the rate of release of heparan sulfate proteoglycan from endothelial cell implants, produced no significant reduction in the restenosis index. Endothelial cell implants also reduced occlusive thrombosis compared with control and heparin release devices. Host immune responses to endothelial implants were investigated by immunohistochemical examination of explanted devices and by immunocytochemistry of serum samples. The bovine cell grafts displayed infiltration of leukocytes, consisting primarily of lymphocytes, and caused an increase in antibodies detected in serum samples. Reduced cellular infiltration and no humoral response were detected in animals that received allografts. Despite the difference in immune response, the biological effects of xenografts or allografts did not differ significantly.