Angiographical follow-up after radioactive "Cold Ends" stent implantation: a multicenter trial

Two decades after coronary radiation therapy: A single center longitudinal clinical study

Objectives

The aim of this study was to evaluate the very long‐term clinical outcome after radioactive stent (RS) implantation and intracoronary β radiation brachytherapy (IRBT).

Background

Radioactive stents (RS) and intracoronary β radiation brachytherapy (IRBT) were introduced to prevent restenosis after percutaneous coronary intervention (PCI). Both techniques were associated with a higher incidence of major adverse cardiac events (MACE) in the short and intermediate‐term follow up as compared to conventional PCI.

Methods

One hundred and thirty‐three patients received radioactive stents (³²P) and 301 patients were treated with IRBT adjunctive to PCI. These groups were propensity matched to respectively 266 and 602 control patients who were treated with routine PCI during the same inclusion period. Endpoints were all‐cause mortality and MACE, defined as all‐cause death, any myocardial infarction or any revascularization.

Results

Median follow‐up duration was 17 years. All‐cause mortality rates were similar in all groups. Adjusted hazard ratios for MACE and mortality in the RS cohort were 1.55 (95% CI 1.20–2.00) and 0.92 (95% CI 0.63–1.34), respectively. Adjusted hazard ratios for MACE and all‐cause mortality in the IRBT cohort were 1.41 (95% CI 1.18–1.67) and 0.95 (95% CI 0.74–1.21), respectively. The difference in MACE rates was predominantly driven by coronary revascularizations in both groups, with a higher MI rate in the IRBT group as well.

Conclusions

Coronary radiation therapy was associated with early increased MACE rates, but the difference in MACE rates decreased beyond 2 years, resulting in a comparable long‐term clinical outcome. Importantly, no excess in mortality was observed.

Postangioplasty Restenosis Followed with Magnetic Resonance Imaging in an Atherosclerotic Rabbit Model

Rationale and Objectives. Testing a quantitative, noninvasive method to assess postangioplasty vessel wall changes in an animal model. Material and Methods. Six New Zealand white rabbits were subjected to atherosclerotic injury, including cholesterol-enriched diet, deendothelialization, and percutaneous transluminal angioplasty (PTA) in the distal part of abdominal aorta (four weeks after deendothelialization). The animals were examined with a 1.5T MRI scanner at three times as follows: baseline (six weeks after diet start and two days after PTA) and four weeks and 10 weeks after-PTA. Inflow angiosequence (M2DI) and proton-density-weighted sequence (PDW) were performed to examine the aorta with axial slices. To identify the inner and outer vessel wall boundaries, a dynamic contour algorithm (Gradient Vector Flow Snakes) was applied to the images, followed by calculation of the vessel wall dimensions. The results were compared with histopathological analysis. Results. The wall thickness in the lesion was significantly higher than in the control region at 4 and 10 weeks, reflecting induction of experimentally created after-angioplasty lesion. At baseline, no significant difference between the two regions was present. Conclusions. It is possible to follow the development of vessel wall changes after-PTA with MRI in this rabbit model.

Eight-year clinical outcome after radioactive stent implantation: a treatment failure without irreversible long-term clinical sequelae

AIMS

To assess the long-term outcome of patients who underwent radioactive stent (RS) implantation.

METHODS AND RESULTS

The RS study population consisted of 133 consecutive patients who underwent RS implantation between November 1997 and July 2000. They were matched using the propensity score method with 266 patients who underwent bare metal stenting (BMS) in the same span. Long-term survival status and information on MACE (death, non-fatal myocardial infarction or any re-intervention) was retrospectively obtained. Eight-year cumulative survival (90.2% vs. 87.4%, p = 0.57) was similar between the RS and BMS group respectively, while 8-year cumulative MACE-free survival was significantly lower in RS patients (42.1% vs. 64.3%, p < 0.001) due to the difference in events (mainly target lesion revascularisations [TLRs]) during the first year of follow-up (cumulative 1-year MACE-free survival: 59.4% vs. 86.7%, p < 0.001); there was no difference in the MACE rate after the first year (p = 0.71). The TLR rate at six months in the RS group was 29.3%, mainly due to edge restenosis and at one year 36.2% (control group: 9.5%, p < 0.001).

CONCLUSIONS

A high incidence of MACE and re-intervention was observed during the first year following RS implantation, mainly related to TLR for edge restenosis. After the first year, the clinical outcome of RS patients was similar to the control group indicating that there are no late adverse effects related to low dose-rate intracoronary radiation therapy.

An integrated TAXUS IV, V, and VI intravascular ultrasound analysis of the predictors of edge restenosis after bare metal or paclitaxel-eluting stents

We used intravascular ultrasound data after stent implantation from the TAXUS IV, V, and VI trials to determine predictors of angiographic stent edge restenosis. In the combined TAXUS IV, V, and VI trials, intravascular ultrasound was performed at implantation in 255 patients with bare metals stents (BMSs) and 276 patients with paclitaxel-eluting stents who underwent quantitative coronary angiography at 9 months. At follow-up, 6 BMSs (2.5%) had proximal edge and 6 BMSs (2.4%) had distal edge angiographic restenosis; 14 TAXUS stents (5.2%) had proximal edge and 1 TAXUS stent (0.4%) had distal edge angiographic restenosis. Although univariate analysis identified external elastic membrane, lumen areas, and plaque burden (external elastic membrane minus lumen/ external elastic membrane) as predictors of 9-month angiographic edge restenosis in the overall cohort and in BMS- and TAXUS-treated patients separately, only edge plaque burden was an independent predictor of 9-month angiographic edge restenosis. Receiver operator characteristic analysis showed that residual plaque burden, but not edge lumen area, was predictive of 9-month angiographic edge restenosis in BMS-treated patients (cutoff 47.7%, c = 0.70, p = 0.0244) and in TAXUS-treated patients (cutoff 47.1%, c = 0.69, p = 0.0137). In conclusion, residual edge plaque burden predicts stent edge restenosis after BMS or TAXUS stent implantation and the optimal plaque burden for stent edge landing zones are the same for BMSs and TAXUS stents, independent of vessel size and edge lumen dimensions.

A HUVEC line with a stable expression of the VEGF121 gene to achieve complete endothelialization of blood conduits

The purpose of this investigation was to establish monoclonal cell lines of HUVEC with the stable expression of the VEGF(121) gene. Such cells are likely to better adhere to the luminal surface of stents or grafts and to promote a complete endothelialization. The eukaryotic expression vector PCD(2)-VEGF(121) was transfected into cell lines of HUVEC mediated by lipofect AMINE. The positive clones were obtained by the screening of G(418). The transcription and expression of the VEGF gene were investigated by RT-PCR and immunocytochemistry, respectively. The experiment of Miles was applied for the assay of the biological activity of the protein of the VEGF produced by the HUVEC lines with transfected PCD(2)-VEGF(121). The growth curve was made for comparison with that of non-transfected HUVEC line cells. The positive clone cells from which transcripted the mRNA of VEGF(121) gene were obtained by RT-PCR. The positive results of the immunocytochemistry were found and the high biological activity of VEGF in the media was detected in the positive clone cells only. The time to achieve the multiplication of the positive clone cells by a factor of 2 was shorter than that of the non-transfected HUVEC line calculated from the growth curve. The HUVEC line of monoclonal cells with the stable expression of VEGF(121) gene has been established successfully and can be employed on the luminal surfaces of foreign blood conduits.

Low-energy gamma-emitting stents inhibit intimal hyperplasia with minimal "edge effects" in a pig coronary artery model

PURPOSE

The objective of this study was to determine the effects of different doses of gamma-emitting radioactive stents on intimal hyperplasia in a porcine coronary stent model at 28 days.

METHODS

Sixty-four bare stents and those coated with palladium-103 [activities of 0 (control), 0.5, 1.0, 2.0, and 4.0 mCi] were implanted in the coronary arteries of 32 pigs. Stented segments were evaluated by histomorphometry at 28 days.

RESULTS

There was significantly more intima in the 0.5- and 1-mCi stents than in controls (4.27+/-0.52 and 4.71+/-1.13 vs. 1.71+/-0.61 mm(2); P<.0001). Neointimal formation in 2-mCi stents was similar to that in controls, while that in 4-mCi stents was reduced compared to that in controls (2.34+/-1.61 and 0.82+/-0.25 vs. 1.71+/-0.61 mm(2); P=NS and P<.05, respectively). Stent margin neointimal response was representative of that within the stent body, with nonsignficant modest increases in intimal area at adjacent nonstented segments in radioactive stent groups. There was a dose-dependent increase in inflammation scores. Radioactive stents had lower intimal smooth muscle and higher fibrin scores. There was an increase in adventitial fibrosis in 1- and 2-mCi stents versus controls (1.26+/-0.99, and 2.25+/-1.27 vs. 0.21+/-0.31; P<.001).

CONCLUSION

Dose-response inhibition of in-stent hyperplasia with minimal "edge effects" occurs with low-energy gamma-emitting stents. An increased inflammatory response at higher doses in palladium-103 stents indicates that later follow-up studies are necessary.

Late vascular response at the edges of sirolimus analogous-eluting stents in diabetic patients: An intravascular ultrasound study

INTRODUCTION

Vascular response at edges of drug-eluting stents is still not well established, particularly in diabetic patients who are prone to aggressive atherosclerosis progression. Recently, Biolimus and Zotarolimus have demonstrated potent antiproliferative effects.

OBJECTIVE

To compare the vascular responses at edges of sirolimus analogous-eluting stents in patients with and without diabetes, using intravascular ultrasound (IVUS).

METHODS

306 edges were analyzed in 153 patients treated with drug-eluting stents and divided in: diabetics (122 edges) and nondiabetics (166 edges). IVUS was performed postintervention and at 6-month follow-up and included 5 mm distal and proximal to the stented segment. Vessel, lumen, and plaque volumes were calculated. Volume variation (follow-up minus basal) was also calculated. Edge restenosis was defined as obstruction >50%.

RESULTS

Baseline characteristics were similar between groups. In both groups the entire lesion length was covered (stent length/lesion length ratio was 1.5 for both groups). There were no differences in edge volumes and restenosis rate between the groups. Among diabetics, there was no significant volume variation. However, in nondiabetic patients there was significant increase in vessel volume in proximal (from 67.1 +/- 22 mm(3) to 72.2 +/- 25 mm(3): P = 0.02) and distal (from 54.4 +/- 22 mm(3) to 59.8 +/- 22 mm(3): P = 0.001) edges.

CONCLUSION

Nondiabetic patients showed a significant positive vascular remodeling in proximal and distal edges of sirolimus analogous-eluting stent. This vascular mechanism was not observed in diabetic patients. Although different vascular responses were observed, restenosis rates were equivalent between the 2 groups at 6-month follow-up.

Effects of stent structure on stent flexibility measurements

Adequate delivery and placement of intracoronary artery stents is dependent on various properties of the stent itself, including flexibility and high-radial strength. Although these properties can be assessed via determination of the bending stiffness and radial stiffness of a stent, the mesh structure of the stent does not lend easily to such measurements. The goal of the present study was to determine an optimal method for determining stent bending stiffness. The four-points bending test was used to evaluate stent flexibility, and the finite element method (FEM) was employed to assess the effect of stent structure on flexibility in stents with differing link structures. The four-points bending test yielded the following bending stiffness values: 85.28 N mm2 for the stent with an S-shaped link; 41.67 N mm2 for the stent with an N-shaped link; 78.79 N mm2 for the stent with a modified W-shaped link; and 188.67 N mm2 for the stent with a W-shaped link. The stent with the point symmetric link configuration (S-, N- and modified W-shaped link) had high flexibility. FEM analysis revealed that low flexibility resulted from interference between the struts at the compressive side. Further, the flexibility predicted from FEM analysis correlated with bending stiffness of the stents. We conclude that use of the four-points bending test yields information that is critical for the design of flexible stents.

Beta emitter systems and results from clinical trials

Vascular brachytherapy has been established as the standard of care for the treatment of in-stent restenosis (ISR). Both beta and gamma emitters are currently in use for the prevention of ISR recurrence. The use of beta sources for vascular application is attractive from both the radiation exposure and safety points of view, and a wide variety of beta sources are available for this application. This review is intended to summarize the clinical trials utilizing beta emitter systems for the treatment of ISR and de novo lesions and their subsequent results.

Endovascular irradiation impairs vascular functional responses in noninjured pig coronary arteries

PURPOSE

To assess the effects of endovascular irradiation on vascular structure and function in pig coronary arteries in the absence of vascular injury.

METHODS AND MATERIALS

Vasomotor responses to contractions of KCl and prostaglandin F2alpha (PGF2alpha), relaxations to endothelium-dependent (substance P, A23187) and -independent (sodium nitroprusside, SNP) agents; endothelial morphology and superoxide anion (02*-) production were investigated in control (naive), sham and irradiated (20 Gy, 32P) arteries 1 month after irradiation.

RESULTS

Contractions to KCl and PGF2alpha in the presence of L-NAME were significantly decreased, relaxations to substance P and A23187 were abolished and SNP-induced relaxation was potentiated in irradiated arteries compared to naive and sham-treated vessels. Scanning electron microscopy (SEM) revealed enlarged endothelial cells (ECs) exhibiting surface microvilli. O2*- production was significantly increased in irradiated vessels (437.0 +/- 37.3 vs. 126.0 +/- 11.6 RLU/s/mg tissue, P < .01).

CONCLUSIONS

One month after brachytherapy, normal pig coronary arteries showed abnormal vascular reactivity, altered endothelial morphology and increased production of O2*-. Lack of relaxation to substance P and A23187 reflects ionizing radiation-mediated damage to ECs, whereas potentiation of relaxation to SNP suggests additional deleterious effects on medial smooth muscle cells (SMCs). Increased O2*- production might have contributed to endothelial dysfunction by scavenging nitric oxide (NO).

Radioisotope stents

Intracoronary stent placement following PTCA improves the long-term outcome of the treated patient, but in-stent restenosis remains problematic, especially in smaller vessels and longer lesions. Intravascular brachytherapy is a rapidly evolving field of research and clinical treatment, with a number of different irradiation techniques being used clinically. Many clinical data are now available that indicate clearly that either <FONT FACE="MetaPress 7">&#110</FONT> or <FONT FACE="MetaPress 7">&#103</FONT> radiation can reduce, and hopefully cure restenosis. The combination of radiation with stents has several distinct advantages over radiation with balloon angioplasty. It should be possible to use the stent as the radioactive source, as the radioactivity levels required by a permanent implant are extremely safe (< 1/1000 of the radioactivity of the least radioactive brachytherapy catheters). Once the stent has been implanted, the procedure is complete; catheter-based brachytherapy requires a second procedure after stent implantation. Unfortunately, in many human studies of the efficacy of radioisotope stents, although an excellent result in terms of a dramatically reduced neointima was seen in the stent, the incidence of an 'edge effect', with a reduced lumen just beyond the stent-edge occurred at an unacceptable rate. The encouraging results of the 'hot ends' study, where the stent ends were made more radioactive to reduce the edge effect, coincided with even more encouraging results from sirolimus drug-eluting stents. As a result, most work on radioisotope stents for the treatment of restenosis has been abandoned. There may, however, be applications for radioisotope stents in the treatment of malignant ducts, such as the esophagus and bronchia, which could justify further study of the devices.