Comparative study of tacrolimus and paclitaxel stent coating in the porcine coronary model

Ultra-hydrophilic stent platforms promote early vascular healing and minimise late tissue response: a potential alternative to second-generation drug-eluting stents

AIMS

Simple surface modifications can enhance coronary stent performance. Ultra-hydrophilic surface (UHS) treatment of contemporary bare metal stents (BMS) was assessed in vivo to verify whether such stents can provide long-term efficacy comparable to second-generation drug-eluting stents (DES) while promoting healing comparably to BMS.

METHODS AND RESULTS

UHS-treated BMS, untreated BMS and corresponding DES were tested for three commercial platforms. A thirty-day and a 90-day porcine coronary model were used to characterise late tissue response. Three-day porcine coronary and seven-day rabbit iliac models were used for early healing assessment. In porcine coronary arteries, hydrophilic treatment reduced intimal hyperplasia relative to the BMS and corresponding DES platforms (1.5-fold to threefold reduction in 30-day angiographic and histological stenosis; p<0.04). Endothelialisation was similar on UHS-treated BMS and untreated BMS, both in swine and rabbit models, and lower on DES. Elevation in thrombotic indices was infrequent (never observed with UHS, rare with BMS, most often with DES), but, when present, correlated with reduced endothelialisation (p<0.01).

CONCLUSIONS

Ultra-hydrophilic surface treatment of contemporary stents conferred good healing while moderating neointimal and thrombotic responses. Such surfaces may offer safe alternatives to DES, particularly when rapid healing and short dual antiplatelet therapy (DAPT) are crucial.

Tacrolimus-eluting carbon-coated stents versus sirolimus-eluting stents for prevention of symptom-driven clinical end points

BACKGROUND

Coating of stents has been shown to minimize the interactions between platelets, stent surface and vascular response following stent implantation. The aim of our study was to compare the tacrolimus-eluting carbon-coated JANUS(®) stent with sirolimus-eluting CYPHER(®) stent for the prevention of symptom-driven clinical end points in a real world clinical setting.

METHODS

This prospective registry with a follow-up period of 24 months was conducted in 90 consecutive patients undergoing coronary artery stenting receiving CYPHER(®) (n = 48) or JANUS(®) (n = 42) stents. The primary end point was a composite of death from cardiovascular causes, nonfatal myocardial infarction and target vessel revascularisation, and the secondary end point was clinically driven in-stent restenosis.

RESULTS

The primary combined endpoint occurred in 38% of patients (n = 16) in the JANUS(®) group compared to 10% (n = 5) in the CYPHER(®) group. The relative risk increase of the composite end point was therefore 63% higher in patients receiving JANUS(®) stents compared to the CYPHER(®) stents (crude HR = 1.63, 95% CI = 1.17-2.28, p = 0.004; adjusted HR = 1.79, CI = 1.26-2.55, p = 0.001). Interestingly, 75% of events in the JANUS(®) group occurred during the first 6 months after stent implantation. Similarly, the rate of clinically driven in-stent restenosis was higher in patients receiving JANUS(®) stent (n = 10, 2%) compared to the CYPHER(®) stent (n = 2, 4%). Concordantly, the relative risk for clinically driven in-stent restenosis was 81% higher in the JANUS(®) group compared to the CYPHER(®) group (crude HR = 1.81, 95% CI = 1.08-3.02, p = 0.02; adjusted HR = 2.24, CI = 1.26-3.96, p = 0.006).

CONCLUSION

The use of tacrolimus-eluting carbon coated JANUS(®) stent was associated with worse clinical outcome compared to the sirolimus-eluting CYPHER(®) stent in clinical routine use.

Durability of antirestenotic efficacy in drug-eluting stents with and without permanent polymer

OBJECTIVES

We sought to assess changes in antirestenotic efficacy of drug-eluting stents (DES) by restudying subjects at 2 time points after coronary stenting (6 to 8 months and 2 years) and to compare differences in time courses of late luminal loss (LLL) between 3 different DES platforms in use at our institution.

BACKGROUND

DES therapy is associated with low levels of LLL at 6 to 8 months. The temporal course of neointimal formation after this time point remains unclear.

METHODS

This prospective, observational, systematic angiographic follow-up study was conducted at 2 centers in Munich, Germany. Patients underwent stenting with permanent-polymer rapamycin-eluting stents (RES), polymer-free RES, or permanent-polymer paclitaxel-eluting stents (PES). The primary end point was delayed LLL (the difference in in-stent LLL between 6 to 8 months and 2 years).

RESULTS

Of 2,588 patients undergoing stenting, 2,030 patients (78.4%) had 6- to 8-month angiographic follow-up and were enrolled in the study. Target lesion revascularization was performed in 259 patients; these patients were not considered for further angiographic analysis. Of 1,771 remaining patients, 1,331 had available 2-year reangiographic data (75.2%). Overall mean (SD) delayed LLL was 0.12 +/- 0.49 mm (0.17 +/- 0.50 mm, 0.01 +/- 0.42 mm, and 0.13 +/- 0.50 mm in permanent-polymer RES, polymer-free RES, and permanent-polymer PES groups, respectively [p < 0.001]). In multivariate analysis, only stent type (in favor of polymer-free RES) predicted delayed LLL.

CONCLUSIONS

Ongoing erosion of luminal caliber beyond 6 to 8 months after the index procedure is observed following DES implantation. Absence of permanent polymer from the DES platform seems to militate against this effect.

The neointimal response to stents eluting tacrolimus from a degradable coating depends on the balance between polymer degradation and drug release

AIMS

To study how the balance between tacrolimus elution and polymer degradation from drug-eluting stents (DES) affects neointimal thickening (NIT) in swine coronary arteries.

METHODS AND RESULTS

We assessed a fast-degrading high dose (2 microg/mm2), a slow degrading low dose (1 microg/mm2) or polymer-only coated DES (Pol) versus bare metal stent (BMS). Coronary segments were pre-injured with a balloon/artery ratio of 1.1 to 1.3. Then stents were implanted at that site with a stent/artery ratio of 1.1, with a follow-up period of 5 to 180 days. Histology showed a well endothelialised neointima (82 +/- 1% in high dose DES vs. 93 +/- 8% in BMS) already at five days, without differences in eNOS expression. Morphometry indicated that neointimal thickness in DES was significantly reduced as compared to BMS and Pol at 28 and 90 days. Polymer degradation products induced a distinct inflammatory response which was effectively suppressed in DES. Between 90 and 180 days, however, the slow degrading low-dose stent showed catch-up of NIT.

CONCLUSIONS

Tacrolimus eluted from a biodegradable stent coating can suppress the inflammatory effect of the coating degradation products if the balance between the drug levels and the degradation products is favorable.

Two year follow-up after treatment of coronary in-stent restenosis with a paclitaxel-coated balloon catheter

BACKGROUND

We are presenting an extension of a previously published trial on the efficacy and safety of a paclitaxel-coated balloon in coronary ISR in a larger patient population and after a complete follow-up of 2 years.

METHODS

Hundred eight patients were enrolled in two separately randomized, double-blind multicenter trials on efficacy and safety using an identical protocol. Patients were treated by the paclitaxel-coated (3 microg/mm(2) balloon surface; Paccocath) or an uncoated balloon. The main inclusion criteria were a diameter stenosis of >or=70% and <30 mm length with a vessel diameter of 2.5-3.5 mm. The primary endpoint was angiographic late lumen loss in-segment. Secondary endpoints included binary restenosis rate and major adverse cardiovascular events (MACE).

RESULTS

Quantitative coronary angiography revealed no differences in baseline parameters. After six months in-segment late lumen loss was 0.81 +/- 0.79 mm in the uncoated balloon group vs. 0.11 +/- 0.45 mm (P < 0.001) in the drug-coated balloon group resulting in a binary restenosis rate of 25/49 vs. 3/47 (P < 0.001). Until 12 months post procedure 20 patients in the uncoated balloon group compared to two patients in the coated balloon group required target lesion revascularization (P = 0.001). Between 12 and 24 only two MACE were recorded, a stroke in the uncoated and a target lesion revascularization in the coated balloon group.

CONCLUSION

Treatment of coronary ISR with paclitaxel-coated balloon catheters persistently reduces repeat restenosis up to 2 years. (ClinicalTrials.gov Identifier: NCT00106587, NCT00409981).

Short- and long-term effects of a novel paclitaxel coated stent in the porcine coronary model

BACKGROUND

Drug eluting stents (DES) are unique in allowing sustained release for weeks after a single short intervention. The challenge with DES still remaining is the combination of a biocompatible drug-eluting matrix including an antiproliferative drug showing efficacy and safety in restenosis prevention. The aim of the present animal studies was to evaluate the novel paclitaxel coated Coroflex. Please stent in the porcine coronary model.

METHODS AND RESULTS

Stents were implanted into LAD and CX arteries of 49 domestic pigs. After 5 days, 4 weeks, 3 months, or 6 months, the animals underwent control angiography including dissection of the stented coronary arteries for histology. After 5 days, 3 and 6 months the Coroflex. Please stent was compared with its uncoated counterpart and a paclitaxel free but polymer coated version. After 28 days, an additional group received the Taxus Express(2) stent. After 5 days, healing with the paclitaxel coated stent was comparable to the uncoated bare metal stent as reflected in a similar neointimal proliferation. Compared to the Taxus stent, the new Coroflex. Please stent showed a similar neointimal proliferation after 4 weeks. Inflammatory reaction was comparable among the bare stent and polymer coated stent groups. Paclitaxel coating was associated with a slightly increased inflammatory reaction with both DES. After 3 and 6 months, all groups showed a similar neointimal proliferation and inflammatory reaction.

CONCLUSION

The present porcine studies demonstrate excellent safety of the new paclitaxel coated Coroflex stent in the porcine coronary stent model.

Resistance to fas-induced apoptosis in cells from human atherosclerotic lesions: elevated Bcl-XL inhibits apoptosis and caspase activation

The inappropriate survival of cells in the neointima contributes to atherosclerotic plaque progression, while apoptosis in the fibrous cap of lesions contributes to myocardial infarction and stroke. Prior genomic-scale transcript profiling of human carotid artery plaque cells with known sensitivity or resistance to fas-induced apoptosis identified candidate genes involved in lesion cell apoptosis. Retroviral overexpression indicated that several candidate factors were not causative, but that Bcl-X(L) conferred complete resistance to apoptosis induced by fas ligation. Resistant cells failed to efficiently activate caspase 8, an effect which was also observed in Bcl-X(L)-transfected cells. Small-molecule Bcl-2/X(L) inhibitors and siRNA knockdown of Bcl-X(L) markedly sensitized resistant cells to apoptosis, and partially restored caspase 8 activation. Caspase 3, 6 and 9 inhibitors reduced caspase 8 activation and blocked apoptosis. Complete knockdown of caspase 9 did not reduce apoptosis, while knockdown of Bid suppressed apoptosis, suggesting that mitochondrial pathways independent of caspase 9, such as Smac/Diablo or AIF, provide a necessary mitochondrial input to efficient caspase activation. Bcl-X(L) appears to modulate lesion cell apoptosis by suppressing mitochondrial amplification of caspase activation loops. The results may have direct implications for controlling plaque instability/progression, and identify a new class of small molecules to inhibit restenosis.

Effects of Oral Prednisone After Stenting in a Rabbit Model of Established Atherosclerosis

OBJECTIVES

The aim of this study was to compare the effects of systemic prednisone in combination with a bare-metal stent (BMS) or a paclitaxel-eluting stent (Taxus, Boston Scientific Corp., Natick, Massachusetts) on neointimal inhibition and vessel healing in an atherosclerotic rabbit model.

BACKGROUND

Inflammation plays a critical role in neointimal formation after coronary artery stenting. The efficacy of immunosuppressive doses of oral prednisone to inhibit in-stent neointimal proliferation was compared with BMS and with a commercially available paclitaxel-eluting stent (Taxus) in a rabbit model of established atherosclerosis.

METHODS

Bilateral iliac artery injury in atherosclerotic New Zealand White rabbits fed an atherogenic diet was followed by stent implantation. Animals randomly received Taxus stents, BMS (Express, Boston Scientific Corp.) and placebo, or BMS and oral prednisone (2.1 mg/kg/day for the first 7 days, followed by 1.4 mg/kg/day for 14 days and 0.7 mg/kg/day for 21 days). Stented arterial segments were harvested at 42 days and processed for light microscopy, immunohistochemistry, and organoid culture.

RESULTS

Compared with control subjects, prednisone-treated animals showed a 30% reduction in percent stenosis (p = 0.009), a 35% decrease in neointimal area (p < 0.003), and a 66% decrement in neointimal thickness (p < 0.001). Taxus stents also reduced all 3 parameters significantly (-34%, -39%, and -83%, respectively), but showed significantly more inflammatory cells and fibrin deposition and less endothelialization compared with the other 2 groups. Plaque burden was equal among groups, as shown by the identical stent and vessel area, and no remodeling was observed.

CONCLUSIONS

Systemic prednisone treatment and Taxus stents reduce neointimal formation compared with BMS. The extent of neointimal reduction is similar between prednisone- and Taxus stent-treated animals; however, Taxus stents resulted in a significantly greater delay in healing. Targeting of inflammatory pathways after percutaneous coronary intervention may be an efficacious way to prevent restenosis without the long-term risk of late thrombosis.

Alterations in the fibrinolytic cascade post-transplant: evidence of a bimodal expression pattern

BACKGROUND

Changes in the fibrinolytic system that occur after cardiac transplantation (CTx) and the factors that influence such changes have been poorly described, yet may be important in determining the varying morphologic features of transplant-related coronary artery disease (TxCAD).

METHODS

Baseline demographic as well as serial clinical information and plasma fibrinolytic levels were prospectively recorded pre-CTx and at multiple time-points post-CTx in 110 de novo cardiac transplant recipients.

RESULTS

We noted a biphasic change in fibrinolytic activity over the first year of CTx with an early immediate decline in plasminogen activator inhibitor-1 (PAI-1) activity (p > 0.001) matched with stable PAP (plasmin) activity corresponding to an "enhanced" fibrinolytic state early post-CTx. This was followed by a significant increase at 6 months (p = 0.004) and 1 year (p < 0.001) in PAI-1 activity concomitant with a significant decline in PAP after 3 months (p = 0.005 at 3 months, p < 0.001 at 6 months, p < 0.001 at 1 year) corresponding to an "impaired" fibrinolytic state late post-CTx.

CONCLUSION

The biphasic nature of the fibrinolytic system observed herein may account for the varying morphologic features of TxCAD.

A pooled analysis of data comparing sirolimus-eluting stents with bare-metal stents

BACKGROUND

Although randomized studies have shown a beneficial effect of drug-eluting stents in reducing the risk of repeated revascularization, these trials were underpowered to compare rates of death and myocardial infarction. The long-term safety of drug-eluting stents has been questioned recently.

METHODS

We performed a pooled analysis of 1748 patients in four randomized trials evaluating the safety of sirolimus-eluting stents as compared with bare-metal stents. Patient-level data were obtained and analyzed by independent statisticians at two academic institutions. The primary safety end point was survival at 4 years. We tested for heterogeneities in treatment effect in patient subgroups.

RESULTS

The survival rate at 4 years was 93.3% in the sirolimus-stent group, as compared with 94.6% in the bare-metal-stent group (hazard ratio for death, 1.24; 95% confidence interval [CI], 0.84 to 1.83; P=0.28). In the 428 patients with diabetes, a significant difference in the survival rate was observed in favor of the bare-metal-stent group over the sirolimus-stent group (95.6% vs. 87.8%; hazard ratio for death in the sirolimus-stent group, 2.9; 95% CI, 1.38 to 6.10; P=0.008). The lower survival rate among patients with diabetes who were treated with sirolimus-eluting stents was due to increased numbers of deaths from both cardiovascular and noncardiovascular causes. No difference in survival rate was detected among the patients without diabetes. Rates of myocardial infarction and stent thrombosis were similar in the two groups.

CONCLUSIONS

In a pooled analysis of data from four trials comparing sirolimus-eluting stents and bare-metal stents, no significant differences were found between the two treatments in rates of death, myocardial infarction, or stent thrombosis. (ClinicalTrials.gov numbers, NCT00233805 [ClinicalTrials.gov] , NCT00381420 [ClinicalTrials.gov] , NCT00232765 [ClinicalTrials.gov] , and NCT00235144 [ClinicalTrials.gov].)