Geographic miss: a cause of treatment failure in radio-oncology applied to intracoronary radiation therapy

Clinical expert consensus document on drug-coated balloon for coronary artery disease from the Japanese Association of Cardiovascular Intervention and Therapeutics

Drug-coated balloon (DCB) technology was developed to deliver the antiproliferative drugs to the vessel wall without leaving any permanent prosthesis or durable polymers. The absence of foreign material can reduce the risk of very late stent failure, improve the ability to perform bypass-graft surgery, and reduce the need for long-term dual antiplatelet therapy, potentially reducing associated bleeding complications. The DCB technology, like the bioresorbable scaffolds, is expected to be a therapeutic approach that facilitates the "leave nothing behind" strategy. Although newer generation drug-eluting stents are the most common therapeutic strategy in modern percutaneous coronary interventions, the use of DCB is steadily increasing in Japan. Currently, the DCB is only indicated for treatment of in-stent restenosis or small vessel lesions (< 3.0 mm), but potential expansion for larger vessels (≥ 3.0 mm) may hasten its use in a wider range of lesions or patients with obstructive coronary artery disease. The task force of the Japanese Association of Cardiovascular Intervention and Therapeutics (CVIT) was convened to describe the expert consensus on DCBs. This document aims to summarize its concept, current clinical evidence, possible indications, technical considerations, and future perspectives.

Failure patterns after intravascular brachytherapy for in-stent coronary restenosis

INTRODUCTION

One strategy to improve the effectiveness of intravascular brachytherapy (IVBT) is to study its failures. Previous investigations described mostly discrete, focal recurrences, typically at the proximal or distal edges of the irradiated segment after plain angioplasty or bare metal stents. We reviewed failure patterns of 30 unselected drug-eluting stent (DES) patients who had follow-up angiograms for recurrence within their IVBT-treated vessel.

METHODS

Records of 53 unselected IVBT patients treated between 2016 and 2021 were reviewed. Thirty of the 53 patients had at least one subsequent percutaneous intervention (PCI) for in-stent restenosis (ISR) after IVBT. Angiographic findings of those 30 patients with ISR within their previously irradiated vessel are reported here.

RESULTS

Of the 30 patients, 21 (70%) developed recurrent ISR within the irradiated segment. Six of the 21 patients who failed within the irradiated segment also experienced ISR proximal or distal to the irradiated segment. Only 15 patients (50%) failed exclusively within the irradiated segment. In nine patients (30%), restenosis occurred proximally and/or distally to the irradiated segment, but not inside of the irradiated segment itself.

CONCLUSIONS

We have shown here that 50% of failures after coronary IVBT for DES ISR occur exclusively within the irradiated segment. An additional 20% of patients had failure within and outside of the irradiated segment. These percentages suggest that a higher radiation dose might improve the long-term patency rates, a conclusion that should be tempered by the lack of universal follow-up.

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.

Clinical expert consensus document on quantitative coronary angiography from the Japanese Association of Cardiovascular Intervention and Therapeutics

Quantitative coronary angiography (QCA) remains to play an important role in clinical trials and post-marketing surveillance related to the safety and efficacy of new PCI devices. In this document, the current standard methodology of QCA is summarized. In addition, its history, recent development and future perspectives are also reviewed.

Quantified frequency-domain optical coherence tomography analysis for the thin-high signals on restenotic tissue after paclitaxel-coated balloon angioplasty

Thin-high signals (THS), detectable by optical coherence tomography (OCT), represent the paclitaxel coverage of in-stent restenotic tissue. This study was conducted to assess the relationship between THS and angiographic outcomes by means of quantified post-procedural frequency-domain OCT (FD-OCT) analysis. From January 2014 to July 2016, 41 patients underwent FD-OCT-guided percutaneous coronary intervention using paclitaxel-coated balloon (PCB) to prevent in-stent restenosis. Of these, we retrospectively enrolled 32 patients (38 lesions) who underwent a 6- to 9-month follow-up angiogram. THS were assessed quantitatively, as THS length and lumen perimeter length were measured using semi-automated software; %THS was calculated by the following formula; total THS area/lumen perimeter area × 100. THS were detected in all 38 lesions that had undergone PCB angioplasty. THS and %THS were significantly higher in lesions without binary restenosis (3.34 ± 2.11 vs. 11.48 ± 8.53 mm², p = 0.001 and 1.49 ± 0.73 vs. 4.42 ± 2.71%, p = 0.001, respectively). Values for THS, which indicates the paclitaxel coverage on restenotic tissue, are associated with reducing restenosis after PCB for in-stent restenosis.

Oral Mycophenolate Mofetil Prevents In-Stent Intimal Hyperplasia Without Edge Effect

Neointimal hyperplasia is in the forefront in in-stent restenosis. Prevention of in-stent restenosis is possible by reducing and inhibiting the hyperplasia of smooth muscle cells. The authors planned this study to test the hypothesis that when administered orally, mycophenolate mofetil (MMF) could inhibit in-stent neointimal hyperplasia. The study included 14 New Zealand rabbits. The rabbits were allocated to 2 different groups: Group 1 included 7 rabbits that were given MMF, 40 mg/kg/day by oral route. Group 2 included 7 rabbits that were not given MMF after the stenting. Sampling materials were taken before and after stenting by incising the artery so as to cover a 5-mm area. The samples taken from the edge of the stent in Group 1 showed focal neointimal cell proliferation, but it was less than that from the control group. Neointimal thickness was 0.048 ±0.009 mm and neointimal area was 0.0925 ±0.019 mm2. Apparent neointimal cell proliferation and thickening of the intimal layer were observed in Group 2. Neointimal thickness at the stent edge was 0.147 ±0.051 mm and the neointimal area was 0.154 ±0.023 mm2. The differences between groups in terms of neointimal thickness and neointimal area were statistically significant (p=0.001 for thickness and p=0.001 for area). In-stent artery samples of Group 1 showed that some subjects had no neointimal cell proliferation, while others had very limited focal intimal thickening. Neointimal thickening was 0.071 ±0.003 mm and neointimal area was 0.073 ±0.003 mm2. In Group 2 apparent, and mostly focal, neointimal cell proliferation and formation of intimal layer were observed in the stent. Neointimal thickening was 0.154 ±0.069 mm and neointimal area was 0.279 ±0.059 mm2. The comparison between groups showed significant differences (p=0.011 for thickness and p=0.001 for area). It was established in the third month that endothelialization was completed in both groups. Oral MMF decreased in-stent intimal hyperplasia without edge effect. It was concluded that for the prevention of in-stent restenosis, studies should be conducted for using systemic immunosuppressive treatments in humans as well.

Interoperator and intraoperator (in)accuracy of stent selection based on visual estimation

OBJECTIVES

The objectives of this study were to evaluate the ability of interventional cardiologists to accurately measure lesion length and select appropriate stents.

BACKGROUND

Inaccurate measurement of lesion length during percutaneous coronary intervention (PCI) increases the risk of restenosis.

METHODS

Interventional cardiologists (n = 40) evaluated 25 matched orthogonal angiographic images that were prescored using quantitative coronary angiography (QCA) by a core laboratory. Visual estimates of lesion length and stent length selection were compared to the maximum QCA value. A 2-4 mm stent overlap of both the proximal and distal lesion edges was considered to be optimal. Based on optimal stent overlap, accurate lesion lengths were those measured from -1 to +4 mm from the QCA. Likewise, appropriate stent lengths were those that measured between +4 mm to +8 mm from the QCA value. Five images were repeated to assess intrarater variability.

RESULTS

Lesion length measurements were short and long for 51.1% (95% CI 47.6-54.6%) and 19.0% (95% CI 16.3-21.9%) of the images, respectively. Stent length selections that were short and long were recorded for 55.0% (95% CI 51.5-58.5%) and 22.8% (95% CI 19.9-25.8%) of the images, respectively. Intrarater variability evaluation indicated that 38.5% (95% CI 31.7-45.6%) of lesion length measurements and 37.5% (95% CI 30.8-44.6%) of stent length selections were >3 mm different between the first and second evaluation of repeated images.

CONCLUSIONS

Visual estimation of coronary lesion length has a high degree of variability, which may lead to inappropriate stent selection. Improving the accuracy of lesion length measurement may improve patient outcomes.

Current treatment of in-stent restenosis

Management of patients with in-stent restenosis (ISR) remains an important clinical problem. Although drug-eluting stents (DES) have drastically reduced the incidence of ISR, treatment of DES-ISR is particularly challenging. ISR mainly results from aggressive neointimal proliferation, but recent data also suggest that neoatherosclerosis may play an important pathophysiological role. Intracoronary imaging provides unique insights to unravel the underlying substrate of ISR and may be used to guide repeated interventions. In this paper, we systematically reviewed clinical trial data with currently available therapeutic modalities, including DES and drug-coated balloons, in patients presenting with ISR within bare-metal stents or DES.

Oxidative stress and pathological changes after coronary artery interventions

Oxidative stress greatly influences the pathogenesis of various cardiovascular disorders. Coronary interventions, including balloon angioplasty and coronary stent implantation, are associated with increased vascular levels of reactive oxygen species in conjunction with altered endothelial cell and smooth muscle cell function. These alterations potentially lead to restenosis, thrombosis, or endothelial dysfunction in the treated artery. Therefore, the understanding of the pathophysiological role of reactive oxygen species (ROS) generated during or after coronary interventions, or both, is essential to improve the success rate of these procedures. Superoxide O2(·-) anions, whether derived from uncoupled endothelial nitric oxide synthase, nicotinamide adenine dinucleotide phosphate oxidase, xanthine oxidase, or mitochondria, are among the most harmful ROS. O2(·-) can scavenge nitric oxide, modify proteins and nucleotides, and induce proinflammatory signaling, which may lead to greater ROS production. Current innovations in stent technologies, including biodegradable stents, nitric oxide donor-coated stents, and a new generation of drug-eluting stents, therefore address persistent oxidative stress and reduced nitric oxide bioavailability after percutaneous coronary interventions. This review discusses the molecular mechanisms of ROS generation after coronary interventions, the related pathological events-including restenosis, endothelial dysfunction, and stent thrombosis-and possible therapeutic ways forward.

Angiographic findings of everolimus-eluting as compared to sirolimus-eluting stents: angiographic sub-study from the Randomized Evaluation of Sirolimus-eluting versus Everolimus-eluting stent Trial (RESET)

Several recent randomized trials comparing everolimus-eluting stent (EES) and sirolimus-eluting stent (SES) reported similar clinical outcomes. This study was aimed to clarify the differences in the angiographic findings of EES as compared to SES. Randomized Evaluation of Sirolimus-eluting versus Everolimus-eluting stent Trial is a prospective multicenter randomized open-label trial comparing EES with SES in Japan. From February to July 2010, 3197 patients were randomly assigned to receive either EES or SES. Of these, angiographic sub-study enrolled 571 patients (EES 285 patients, SES 286 patients). Angiograms were assessed qualitatively and quantitatively at procedure and at 8-12 months in the independent core angiographic laboratory. Late loss of the proximal edges tended to be greater in the EES group than that in the SES group (0.12 ± 0.49 vs. 0.04 ± 0.43 mm, P = 0.05), although late loss in the other segments was similar between the 2 groups. Edge restenosis was mainly observed in EES group, whereas body restenosis was demonstrated in half of SES group. Stent fracture was observed only in the SES group (1.5 %), and peri-stent contrast staining (PSS) tended to be more frequently observed in the SES group than in the EES group (3.6 and 1.5 %, P = 0.18). Restenotic response in the proximal edge was more prominent in the EES group as compared to the SES group. Abnormal angiographic findings such as stent fracture and PSS tended to be more frequent in the SES group.

Radiation therapy for dialysis access stenosis: unfulfilled promise or false expectations

Hemodialysis vascular access dysfunction is a major cause of morbidity and hospitalization in the hemodialysis population at a cost of well over $1 billion per annum. Venous stenosis (due to venous neointimal hyperplasia [VNH]) is the most common cause of polytetrafluroethylene PTFE) dialysis access graft and arteriovenous fistula (AVF) failure. Despite the magnitude of the clinical problem, however, there are currently no effective therapies for this condition. We and others have previously demonstrated that VNH in PTFE dialysis grafts and AVF is composed of smooth muscle cells/myofibroblasts, endothelial cells within neointimal microvessels, and peri-graft macrophages. Radiation therapy blocks the proliferation and activation of all these cell types. The current review will dissect out the available in vitro, experimental, and clinical data on the use of radiation therapy for vascular stenosis in general, and for dialysis access dysfunction in particular. It is important to try and identify whether there is still a role for radiation therapy in this specific clinical setting. We believe that this is a critically important question to answer in view of the huge unmet clinical need that is currently associated with hemodialysis vascular access dysfunction.

Impact of acute gain on clinical outcomes of patients treated with sirolimus-eluting stent. - A sub-analysis study from the STLLR trial-

BACKGROUND

Geographical miss (GM), representing suboptimal drug-eluting stent deployment, is associated with an increased risk of target lesion revascularization (TLR) and myocardial infarction. The impact of suboptimal stenting techniques on clinical outcomes in diabetics remains unknown.

METHODS AND RESULTS

Stent deployment Techniques on cLinicaL outcomes of patients treated with the cypheR(TM) stent (STLLR) is the first multicenter, large trial to prospectively evaluate outcomes associated with sirolimus-eluting stent (SES) deployment techniques. Axial GM and longitudinal GM (LGM), defined as a balloon injured segment or a diseased segment not covered by a SES, were assessed by an independent core laboratory. One-year outcomes between diabetics and non-diabetics and their relationship with GM were assessed. This substudy included 1,336 patients, 28.8% with diabetes. In non-LGM patients, TLR was similarly low in both diabetics and non-diabetics (2.0% vs. 2.0%, P=NS). However, TLR increased 4.1 times in diabetics (8.0%) and 1.9 times in non-diabetics (3.8%) in the presence of LGM (P=0.03). Axial GM had no impact on outcomes. By univariate analysis, stent length, acute gain, and LGM were the predictors of TLR in the total cohort. However, by multivariate analysis, acute gain was the only predictor of TLR (P=0.03), independently of LGM or diabetes.

CONCLUSIONS

Acute gain is the exclusive predictor of TLR after SES implantation. Particularly in diabetics, the negative impact of LGM on TLR seems to be amplified. Diligent SES deployment for larger acute gain is critical to improve clinical outcomes.

Impact of stent deployment procedural factors on long-term effectiveness and safety of sirolimus-eluting stents (final results of the multicenter prospective STLLR trial)

Drug-eluting stent failures were associated with various clinical factors. However, the clinical impact of stent deployment technique was unknown. This study was designed to evaluate the frequency and impact of suboptimal percutaneous coronary intervention on long-term outcomes of 1,557 patients treated with sirolimus-eluting stents (SESs) in 41 US hospitals. All steps of the interventional procedure were scrutinized by an independent core laboratory to determine the occurrence of geographic miss (GM). GM included longitudinal (LGM; injured or diseased segment not covered by SES) or axial GM (balloon-artery size ratio <0.9 or >1.3) mismatches. Patients with and without GM were stratified (GM vs no-GM group). Patients, investigators, and the independent clinical event adjudication committee were blind to study group assignments. The primary end point was 1-year target-vessel revascularization (TVR) rate. Incidences and predictors of GM and safety outcomes were secondary end points. GM occurred in 943 patients (66.5%): 47.6% had LGM, 35.2% had axial GM, and 16.5% had both. One-year TVR rates were 5.1% in the GM group versus 2.5% in the no-GM group (p=0.025). TVR was 6.1% in the LGM versus 2.6% in the no-LGM subgroups (p=0.001). The association of GM with 1-year TVR was independent of clinical or anatomic factors (hazard ratio 2.0, 95% confidence interval 1.0 to 4.02, p=0.05). There was a 3-fold increase in myocardial infarction rates associated with GM (2.4% vs 0.8%; p=0.04). In conclusion, GM occurred frequently during SES implantation and was associated with increased risk of TVR and myocardial infarction at 1 year. These results emphasized the need for improvement in contemporary percutaneous coronary intervention practices and technologies.

Update: aptamers as novel radiopharmaceuticals: their applications and future prospects in diagnosis and therapy

The production of biomaterials with the capacity to bind tightly and specifically to cell surface receptors of malignant cells can greatly benefit cancer diagnosis and treatment. Whereas antibodies have the ability to specifically recognize some tumor cell makers, their large size and immunogenecity markedly limit their value. The development of nuclease-resistant oligonucleotide agents, termed aptamers, offers an alternative to antibodies as targeting, diagnostic, and delivery agents. Using the systematic evolution of ligands by exponential enrichment (SELEX) methodology or other variations, one can select specific sequences that have appropriate binding affinities and specificities against clinically relevant markers from large libraries of oligonucleotide ligands. Aptamers have been found to bind their targets with high specificity and with dissociation constants in the subnanomolar or picomolar range. However, the possibility for the selected aptamers to be developed as targeting agents for diagnostic imaging or targeted radiotherapy purposes has yet to be realized. Peptide-coupling reactions between amino and carboxylic groups offer the possibility of labeling the aptamers with a number of chelators that, coupled with appropriate radionuclides, would generate novel targeted radiopharmaceuticals for the diagnosis and therapy of disease. The unparalleled combinatorial chemical diversity, small size, and modification ability of aptamers is expected to meet the criteria for robust, generic drug discovery technology and open new horizons for the development of future radiopharmaceuticals.

Use of sirolimus-eluting stents for treatment of in-stent restenosis: long-term follow-up

OBJECTIVES

The aims of this study were to assess (i) the feasibility, safety and efficacy of sirolimus-eluting stents (SESs) in treating in-stent restenosis (ISR), (ii) the risk factors for recurrent ISR, and (iii) the long-term major adverse cardiac events (MACE).

METHODS

Between May 2002 and April 2004, 100 consecutive patients with evidence of myocardial ischaemia and 112 ISRs in native coronary arteries were treated using SESs. We evaluated the rate of procedural and clinical success, the incidence of in-hospital and long-term MACE, the recurrence rate of ISR after 6-8 months, and the risk factors for recurrent ISR and follow-up MACE.

RESULTS

Forty-five percent of the lesions were directly stented. After stent implantation, the minimal lumen diameter increased from 0.51 +/- 0.32 to 2.50 +/- 0.32 mm in the stents and to 2.30 +/- 0.35 mm in the lesions (acute gain 1.99 +/- 0.37 mm). The procedural success rate was 99%. The clinical success rate was 88%. MACE occurred in 2.0% of patients during hospitalisation and in 12.8% after a median follow-up of 15.1 months (interquartile range 8.4-19.7). The recurrence rate of ISR was 11.8% after a median follow-up of 7.7 months (interquartile range 7.4-8.4). The risk for recurrent ISR was significantly higher in patients with diabetes or hypertension, in those aged more than 65 years and in female patients, as well as in the lesions with a small minimal lumen diameter. Three-vessel disease and age were risk factors for MACE.

CONCLUSIONS

This study confirms the feasibility, safety and effectiveness of using SESs to treat ISR, and identifies a risk profile for recurrent ISR and MACE.

Dose perturbation caused by stents: experiments with a model 90Sr/90Y source

PURPOSE

Biological effects of intravascular brachytherapy are very sensitive to discrepancies between the prescription and the applied dose. If brachytherapy is aimed at in-stent restenosis, shielding and shadowing effects of metallic stents may change the dose distribution relative to that produced by the bare source. The development of new generations of stents inspired us to a new experimental study in this field. The effect was studied for 14 stents which we have recently encountered in clinical practice.

METHODS

The model source was a continuous 20-mm column of (90)Sr/(90)Y solution sealed in a 1-mm-I.D. Plexiglas capillary. The dose distribution in the Plexiglas phantom was mapped using GafChromic MD-55-2 film. The stent masses varied from 2.5 to 25 mg; the strut thicknesses, from 0.075 to 0.15 mm; and the atomic numbers of stent materials, from 24 (Cr) to 79 (Au).

RESULTS

Dose perturbations depend on a variety of stent features. Local reduction of the mean dose rates near the reference distance (r(0) = 2 mm) varied from 11% to 47%. No simple correlation was found between these data and stent characteristics, but it seems that the atomic number of the stent material is less important than the strut thickness and mesh density.

CONCLUSION

The results provide a warning that clinical indications for in-stent radiation therapy must always be confronted with another aspect of the patient's history: the kind of implanted stent. Intravascular brachytherapy using pure beta sources may be recommended only for patients "wearing" light, thin-strut stents. The presence of thick-strut stents is a contraindication for this modality, due to excessive dose perturbation.

Neointimal progression and luminal narrowing in sirolimus-eluting stent treatment for bare metal in-stent restenosis: a quantitative intravascular ultrasound analysis

BACKGROUND

Recurrent restenosis may occur after drug-eluting stent implantation for in-stent restenosis (ISR) of bare metal stents (BMSs), especially in areas involving drug-eluting stent gaps.

METHODS

To investigate the details of neointimal progression and luminal narrowing after the treatment of ISR using sirolimus-eluting stents (SESs), serial intravascular ultrasound analysis was performed in 65 patients with ISR at postintervention and at 6-month follow-up. The total stented segment was categorized into 3 compartments: new SES (N), new SES and old BMS overlap (N/O), and old BMS (O). In each of the 190 compartments, serial intravascular ultrasound parameters were analyzed at the cross section of the maximum change in neointimal area (delta neointimal area) from postintervention to follow-up or the minimum lumen area at follow-up if delta neointimal area was 0. Minimum lumen area in each compartment was also investigated serially.

RESULTS

At postintervention, lumen area was the smallest in compartment N/O (N 5.8 +/- 1.5, N/O 5.1 +/- 1.3, O 6.0 +/- 1.4 mm2, P = .005). Not only the average of maximum delta neointimal area (N 0.2 +/- 0.4, N/O 0.2 +/- 0.4, O 0.8 +/- 1.0 mm2, P < .0001) but also the frequency of minimum lumen area decreasing from > or = 4.0 mm2 at postintervention to < 4.0 mm2 at follow-up (N 4.0%, N/O 5.1%, O 23.5%, P = .012) was the largest in compartment O.

CONCLUSIONS

Neointimal progression and consequent luminal narrowing tend to occur where BMS is uncovered with SES in treatment of ISR, even in the absence of an obvious stenosis at postintervention.

Randomized comparison between intracoronary β-radiation brachytherapy and implantation of paclitaxel-eluting stents for the treatment of diffuse in-stent restenosis

BACKGROUND AND PURPOSE

Intracoronary brachytherapy was the primary therapeutic option for the treatment of in-stent restenosis (ISR) during the last years. Especially for the treatment of diffuse ISR (lesions >10mm), beta-source brachytherapy was significantly superior to singular balloon angioplasty. Despite lacking clinical database, the implantation of drug eluting stents recently became a common procedure for the treatment of ISR. This randomized trial aimed to compare the efficacy of beta-brachytherapy with beta-radioisotopes (90)Sr/(90)Y and paclitaxel-eluting stent implantation for the treatment of diffuse ISR.

MATERIAL AND METHODS

Thirty-seven patients with diffuse ISR were randomly assigned to beta-brachytherapy after balloon angioplasty (Beta-Cath in 17 patients) or paclitaxel-eluting stent implantation (Taxus-Express2 in 20 patients). Six-month clinical follow-up was obtained for all patients, while angiographic follow-up was available for 30 patients.

RESULTS

Binary ISR (restenosis >50%) within target segment was observed in three patients treated with Beta-Cath, of which one needed target segment revascularisation for recurrent ISR, whereas no significant restenosis occurred in the patients treated with Taxus-Express2 (P=0.037). No further major adverse cardiac (target segment revascularisation, myocardial infarction, death) was found in either group (P=NS). Stent implantation was the more time-saving (31+/-11 min versus 60+/-23 min, P<0.001) procedure.

CONCLUSIONS

Although this trial revealed a significant reduction of binary restenosis in the Taxus-Express2 arm, we found no difference in clinical outcome after implantation of paclitaxel-eluting stents for the treatment of diffuse ISR when compared to beta-brachytherapy.

Comparison between drug-eluting stents and beta-radiation for the treatment of diffuse in-stent restenosis: clinical and angiographic outcomes

BACKGROUND

Initial reports on drug-eluting stents (DES) for the treatment for in-stent restenosis (ISR) show very good outcomes. Nevertheless, few data are available on direct comparison with intracoronary brachytherapy (IBT). The aim of this study was to compare brachytherapy and DES in treatment of diffuse ISR.

METHODS

One hundred forty-one consecutive patients with diffuse ISR were treated with IBT (68 patients; beta (90Sr/90Y) emitters) or with DES (73 patients; 32 with sirolimus-eluting and 41 with paclitaxel-eluting stents). Angiographic and clinical follow-up was scheduled within 9 months.

RESULTS

The first 74 lesions were treated with IBT (group 1) and the latter 74 with DES (group 2). The two groups were well matched for clinical/angiographic characteristics. At follow-up, restenosis rates were 37.8% (28/74) in IBT group and 14.9% (11/74) in DES group (P = .0028). A diffuse pattern of recurrence was more frequent after IBT (20/74 vs 6/74, P = .005). A worse outcome after IBT was associated with the "edge effect," accounting for most failures. Recurrence within the original restenotic stent was similar in both groups (12.9% vs 14.9% in groups 1 and 2 respectively, P = .8).

CONCLUSIONS

Drug-eluting stents are more effective than IBT with beta-irradiation in reducing recurrence rates after treatment of diffuse ISR. In case of failure, the pattern of restenosis is more benign after treatment with DES.

Predictors of recurrent in-stent restenosis after beta-radiation: An analysis from the START 40/20 trial

OBJECTIVE

The purpose of this study was to identify potential predictors, including clinical, procedural, angiographic, and intravascular ultrasound (IVUS) parameters, for recurrent in-stent restenosis (ISR) following beta-radiation 90Strontium/Yttrium (90Sr/Y) in a large multicenter trial.

BACKGROUND

Although adjunct brachytherapy reduces recurrent ISR after primary catheter-based intervention, recurrence of stenosis after brachytherapy still occurs.

METHODS

We analyzed 185 IVUS cohort patients in the STent And Restenosis Therapy (START) 40/20 trial where a 40-mm, 90Sr/Y, radioactive source train was exclusively used for treatment of ISR to be treatable with a 20-mm balloon.

RESULTS

Thirty-nine patients underwent target lesion revascularization. Preliminary univariate analysis showed that age, smoking, balloon/artery ratio, geographic miss, minimum lumen diameter, and diameter stenosis at baseline were associated with target lesion revascularization, while none of IVUS variables were (minimum lumen area, minimum stent area, or residual plaque burden). The multivariate logistic regression analysis showed that younger age, lower balloon/artery ratio, and presence of geographic miss were independent predictors of target lesion revascularization.

CONCLUSIONS

Even with adjunct beta-radiation therapy, initial mechanical optimization, such as appropriate balloon sizing and positioning, may be critical for the prevention of recurrent ISR.

A Phase II study of external-beam radiotherapy and endovascular brachytherapy with PTA and stenting for femoropopliteal artery restenosis

PURPOSE

To assess the safety and seek evidence of efficacy of combined external-beam radiotherapy (EBRT) and endovascular brachytherapy in the treatment of stenotic vascular lesions.

METHODS AND MATERIALS

Seventeen patients with high risk for restenosis of femoropopliteal arteries were enrolled in this study from February 2000 to August 2002. The external beam radiotherapy regimen consisted of 10 Gy in 5 fractions of 2 Gy, starting on Day 0. This was followed on Day 6 by angiography, stent placement, and intraluminal brachytherapy to a dose of 10 Gy at 1.2 mm from stent surface. The EBRT was continued from the same day to another 10 Gy in 2 Gy daily fractions for 5 days.

RESULTS

The follow up ranged from 33 months to 60 months. At the time of analysis 15 of 17 patients were alive with patent stents. Of these, 10 were symptom-free. Two patients died of unrelated causes.

CONCLUSIONS

The combination of EBRT and endovascular brachytherapy provided adequate dose distribution without any geographical miss or "candy wrapper" restenosis. No incidence of aneurysmal dilation of radiated vascular segment was observed. The treatment was feasible, well tolerated, and achieved 88% stenosis free survival.

Edge restenosis: impact of low dose irradiation on cell proliferation and ICAM-1 expression

BACKGROUND

Low dose irradiation (LDI) of uninjured segments is the consequence of the suggestion of many authors to extend the irradiation area in vascular brachytherapy to minimize the edge effect. Atherosclerosis is a general disease and the uninjured segment close to the intervention area is often atherosclerotic as well, consisting of neointimal smooth muscle cells (SMC) and quiescent monocytes (MC). The current study imitates this complex situation in vitro and investigates the effect of LDI on proliferation of SMC and expression of intercellular adhesion molecule-1 (ICAM-1) in MC.

METHODS

Plaque tissue from advanced primary stenosing lesions of human coronary arteries (9 patients, age: 61 +/- 7 years) was extracted by local or extensive thrombendarterectomy. SMC were isolated and identified by positive reaction with smooth muscle alpha-actin. MC were isolated from buffy coat leukocytes using the MACS cell isolation kit. For identification of MC flow-cytometry analysis of FITC-conjugated CD68 and CD14 (FACScan) was applied. SMC and MC were irradiated using megavoltage photon irradiation (CLINAC2300 C/D, VARIAN, USA) of 6 mV at a focus-surface distance of 100 cm and a dose rate of 6 Gy min-1 with single doses of 1 Gy, 4 Gy, and 10 Gy. The effect on proliferation of SMC was analysed at day 10, 15, and 20. Secondly, total RNA of MC was isolated 1 h, 2 h, 3 h, and 4 h after irradiation and 5 microg of RNA was used in standard Northern blot analysis with ICAM-1 cDNA-probes.

RESULTS

Both inhibitory and stimulatory effects were detected after irradiation of SMC with a dose of 1 Gy. At day 10 and 15 a significant antiproliferative effect was found; at day 20 after irradiation cell proliferation was significantly stimulated. Irradiation with 4 Gy and 10 Gy caused dose dependent inhibitory effects at day 10, 15, and 20. Expression of ICAM-1 in human MC was neihter inhibited nor stimulated by LDI.

CONCLUSION

Thus, the stimulatory effect of LDI on SMC proliferation at day 20 days after irradiation may be the in vitro equivalent of a beginning edge effect. Extending the irradiation area in vascular brachytherapy in vivo may therefore merely postpone and not inhibit the edge effect. The data do not indicate that expression of ICAM-1 in quiescent MC is involved in the process.

Six years experience in intracoronary brachytherapy procedures: patient doses from fluoroscopy

Typical patient dose levels during intracoronary brachytherapy (ICB) procedures using beta sources were determined across a sample of 221 treatments. Dose-area product values, fluoroscopy time and number of frames per procedure, with median values of 62 Gy cm2, 17.0 min and 1493 images, respectively, resulted in a 20% to 50% increase in the values measured for percutaneous transluminal coronary angioplasty procedures in the same medical centre (median values 41 Gy cm2, 14.3 min and 1078 images). Likely reasons for this increase include the additional complexity of ICB, the need for recording and reporting every step of the treatment, getting the essential parameters for the volume determination of the lesion and therapeutic radiation dose calculation and, finally, the learning curve for this kind of procedure. A high concentration skin dose distribution during ICB procedures was measured and in 12% of the patients peak skin doses higher than 1.5 Gy were confirmed. 10 patients were submitted to clinical follow-up and skin injuries were not identified.

Pathological Effects of Pulmonary Vein beta-Radiation in a Swine Model

INTRODUCTION

Atrial fibrillation (AF) may be triggered by ectopic beats originating in sleeves of atrial myocardium entering the pulmonary veins (PVs). PV isolation by means of circumferential ostial or atrial radiofrequency ablation is an effective but also a difficult and long procedure, requiring extensive applications that can have serious potential complications. Our objective was to examine pathological effects of PV beta-radiation, particularly the ability to destroy PV myocardial sleeves without inducing PV stenosis and other unwanted effects, in order to establish its potential feasibility for the treatment of AF.

METHODS AND RESULTS

Ten minipigs were studied. A phosphorus-32 source wire centered within a 2.5-mm diameter balloon catheter (Galileo III Intravascular Radiotherapy System, Guidant, Santa Clara, CA, USA) was used to deliver beta-radiation to the superior wall of the right PV trunk. Pathological analysis was performed either immediately after ablation (2 pigs) or 81 +/- 27 days later (8 pigs). Acute effects of PV beta-radiation consisted of endothelial denudation covered by white thrombus, elastic lamina disruption, and PV sleeve necrosis. Late effects consisted of mild focal neointimal hyperplasia that reduced the PV luminal area by only 1.3 +/- 1.8%, elastic lamina thickening, and PV sleeve fibrosis. Four of these 8 PVs were completely re-endothelized. Lesions were transmural in 6 of 10 radiated PVs and segmental, involving 28 +/- 7% of the right PV perimeter.

CONCLUSION

Intravascular beta-radiation can induce transmural necrosis and fibrosis of PV myocardial sleeves without PV stenosis and other unwanted effects, which supports a potential usefulness of this energy source in the treatment of AF.

Implications of the "watermelon seeding" phenomenon during coronary interventions for in-stent restenosis

The occurrence of balloon slippage ("watermelon seeding"; WMS) during treatment of patients with in-stent restenosis (ISR) has been described, but predisposing factors and the potential implications of this phenomenon remain unknown. In the Restenosis Intrastent: Balloon Angioplasty vs. Elective Stenting (RIBS) randomized study, 450 patients with ISR were included. Of these, 42 patients (9%) presented WMS during the procedure. WMS was detected in 26 patients (12%) in the balloon arm and 16 (7%) in the stent arm (P=0.11). In the stent arm, WMS was only noticed during balloon predilation, never during stent implantation. As compared with 408 patients without WMS, patients with WMS had more severe (TIMI flow 1; 21% vs. 8%; P=0.01) and diffuse (length>15 mm: 45% vs. 28%; P=0.02) ISR lesions. Patients with WMS required more balloon inflations, longer total inflation time, had more frequent crossover to stenting or ended the procedure with residual dissections, and eventually obtained poorer acute results (minimal lumen diameter, 2.35+/-0.5 vs. 2.53+/-0.5 mm; P=0.03). In addition, at 6-month follow-up, patients with WMS had a smaller minimal lumen diameter (1.26+/-0.7 vs. 1.61+/-0.7 mm; P=0.007) and a higher restenosis rate (56% vs. 37%; P=0.017). On logistic regression analysis, the WMS phenomenon emerged as an independent predictor of recurrent restenosis (adjusted RR=2.1; 95% CI=1.1-4.1; P=0.04). The WMS phenomenon may complicate treatment of patients with ISR. Long and severe lesions appear to predispose to this technical problem that never occurs during stent deployment. In patients with ISR, WMS is associated with cumbersome procedures and poorer acute and long-term angiographic results.

Determinants of model of renarrowing after beta radiation for in-stent restenosis

It is unknown whether model of renarrowing after beta-radiation for in-stent restenosis (ISR) is influenced by the type of geographic miss (GM).

METHODS

In 166 ISR treated with Galileo, serial quantitative coronary angiographic analysis was done. Minimal lumen diameters and lengths were measured for (1) stent, (2) peri-stent subsegments subjected to angioplasty with/without irradiation, and (3) irradiation margins. GM was defined as: (Type 1) edge injury within the 32P source dose fall-off: 2.0 mm inside and outside the source end marker or (Type 2) overt, nonirradiated injury: beyond the outer 2.0-mm long dose fall-off zone.

RESULTS

Restenosis rate was 28.3% at 8.9+/-4.5 months with 60% located exclusively outside the stent. Type 1 GM was present in 24.7% of proximal edges, whereas Type 2 in 18.1%. Respective percentages for distal edges were 23.5% and 15.7%. Regardless of presence and type of GM, significant late lumen loss occurred only outside the stent. However, the biggest late lumen loss at the proximal edge was induced by the Type 1 GM (0.65+/-0.79, p<0.001), while proximal Type 2 GM was not associated with edge renarrowing (-0.04+/-0.48, p=NS). Both reference lumen diameter and proximal Type 1 GM influenced restenosis independently (OR 0.47; 95%CI 0.24-0.90; p=0.023 and OR 2.46; 95%CI 1.12-5.40; p=0.025).

CONCLUSIONS

Regardless of presence and type of geographic miss, late lumen loss after beta-radiation occurs only outside the stent. However, injury within the proximal 32P dose fall-off but not overt edge injury is associated with the biggest late lumen loss at the respective edge, triggering recurrent restenosis.

“Head-to-head comparison between sirolimus-eluting and paclitaxel-eluting stents in patients with complex coronary artery disease: An intravascular ultrasound study”

BACKGROUND

The aim of this study was to assess neointimal hyperplasia following sirolimus-eluting (SES) and paclitaxel-eluting stents (PES) implantation in a patients with complex coronary disease.

METHOD

Between January to December 2004, 70 patients were enrolled in this study (SES = 37; PES = 33. The primary objective was to assess the efficacy of SES and PES on neointimal proliferation inhibition in patients with complex coronary lesions by volumetric 3D intravascular ultrasound (IVUS) assessment at six-month follow-up.

RESULTS

Baseline clinical, demographic or angiographic characteristics were well balanced in both groups. All procedures as well as hospitalisation were uneventful. The percentage of B2/C lesions in our study was > 90% in both groups. The IVUS-assessed in-stent mean neointimal hyperplasia volume was significantly lower in lesions treated with SES compared to PES (4.1 +/- 11 mm3 vs. 17.4 +/- 23 mm3, p < 0.002) at 6 month follow-up. No difference in both MACE (3.0 versus 6.0%, p = NS) and restenosis (5.4 versus 9.1%, p = NS) were found. The in-segment late loss at six month was 0.26 mm in the SES and 0.48 mm in the PES group (p = NS).

CONCLUSIONS

The present study showed reduced neointimal proliferation after sirolimuseluting as compared to paclitaxel-eluting stents in patients with complex coronary artery disease. Both SES and PES were associated with low rate of angiographic restenosis or major adverse cardiovascular events.

Comparison between sirolimus-eluting stents and intracoronary catheter-based beta radiation for the treatment of in-stent restenosis

We report the outcomes of patients who had in-stent restenosis (IRS) that was treated with intravascular brachytherapy (IVBT) or sirolimus-eluting stent (SES) implantation. The benefit of IVBT for treating ISR is well documented. SES implantation decreases first-time ISR and, in preliminary reports, has been used to treat ISR. Fifty consecutive patients who had ISR were treated; the first 25 patients underwent SES implantation and the next 25 patients were treated with IVBT using a beta-Cath System (a 40-mm strontium-90/yttrium-90 source). Quantitative angiographic and intravascular ultrasound follow-up were performed at 5.2 +/- 1.1 and 12.1 +/- 1.2 months; clinical follow-up was performed at 15 months. SES deployment and IVBT were successful in all patients. At 12-month follow-up, 8 patients who underwent IVBT had angiographic recurrence (4 in the stent and 4 at the stent edge); only 1 patient who underwent SES implantation developed recurrent ISR. At 12 months, in-stent late luminal loss was similar between the SES and IVBT groups (0.35 +/- 0.45 vs 0.34 +/- 0.46 mm, p = 0.9); however, in-stent net luminal gain was higher in the SES group than in the IVBT group (1.32 +/- 0.13 vs 0.57 +/- 0.19 mm, p <0.0001), and in-lesion late luminal loss was higher in the IVBT group (0.48 +/- 0.32 vs 0.16 +/- 0.42 mm, p = 0.004). At 12 months, intravascular ultrasound stent volume obstruction was higher after IVBT versus than after SES implantation (38.7% vs 6.7%, p <0.0001). At 15-month clinical follow-up, 64% and 96% (p <0.01) of patients who underwent IVBT and SES implantation, respectively, were free of major adverse cardiac events. In conclusion SES implantation for the treatment of ISR was effective and superior to catheter-based IVBT in preventing recurrent neointimal proliferation and angiographic restenosis at 1-year follow-up.

Angiographic and clinical outcomes at 8 months of cutting balloon angioplasty and beta-brachytherapy for native vessel in-stent restenosis (BETACUT): results from a stopped randomized controlled trial

The objective of this study was to assess angiographic and clinical outcomes of cutting balloon (CB) angioplasty and concomitant Sr/Y-90 beta-brachytherapy as a treatment modality for patients with native vessel in-stent restenosis (ISR). Procedural advantages over the standard balloon (SB) have been claimed for the CB. Intracoronary brachytherapy preceded by SB angioplasty is regarded as the treatment of choice in patients with ISR. In an interim analysis of a prospective randomized trial designed for 652 patients, 100 consecutive patients with ISR were assigned to treatment with SB angioplasty (n = 51) or CB angioplasty (n = 49), followed in either case by Sr/Y-90 beta-brachytherapy. Quantitative coronary angiography at baseline, postintervention, and at 8 months was performed by an independent central laboratory. More than 90% of target lesions in the overall patient population were diffuse, with 14% of stents totally occluded. Procedural parameters and immediate angiographic outcomes were essentially the same in either study arm. At 8 months, no statistically significant differences were observed in recurrent angiographic restenosis (SB = 26.1%; CB = 29.5%; P = 0.82), target lesion revascularizations (SB = 13.7%; CB = 8.2%; P = 0.53), and major adverse cardiac events (SB = 15.7%; CB = 8.2%; P = 0.36). In this interim analysis, there was no indication of a beneficial effect of CB use over SB use in terms of angiographic or clinical outcomes at 8-month follow-up. CB angioplasty appears to be as safe and efficacious as SB angioplasty in beta-radiation treatment of patients with predominantly diffuse native vessel ISR. It was decided to discontinue the trial.

Long-term clinical outcomes of dissections after intracoronary beta-radiation with rhenium-188-diethylene triamine penta-acetic acid-filled balloon system

BACKGROUND

Intracoronary radiation with a rhenium-188 ((188)Re)-filled balloon is safe and efficiently reduces restenosis, but there is a potential risk of a (188)Re-filled balloon induced dissection. Little is known about the effect of radiation on dissection resolution and the late clinical outcome of dissection after brachytherapy.

METHODS

After successful catheter-based treatments of de novo or restenotic lesion, 256 patients were randomly assigned to the radiation or control group. The (188)Re-filled balloon system was designed to deliver 17.6 Gy in 1.0-mm tissue depth.

RESULTS

Dissections were identified in 15 patients among the 138 patients of the radiation group (10.9%). Additional stents were deployed in 10 patients to cover the flow-limiting dissection. Binary restenosis rate (53.3% vs. 16.3%, p=0.001) and target vessel revascularization (TVR) rate (53.3% vs. 11.1%, p<0.001) were significantly higher in patients with the dissection at 9 months. Geographic miss (GM) was identified in 4 of the 10 patients who underwent additional stenting. Binary restenosis rate in the GM group (100%; 4 of 4 patients) was significantly higher than the non-GM group (33.3%; 2 of 6 patients, p=0.02). Long-term follow-up of the patients with dissections who had not undergone TVR (n=7, mean follow-up duration: 640.7+/-387.3 days) has demonstrated persistent unhealed dissections.

CONCLUSIONS

Intracoronary radiation impairs the healing process after vessel injury and residual dissection after brachytherapy leads to adverse clinical outcomes, which was mainly due to GM in case of stent implantation.

Endovascular gamma irradiation for the prevention restenosis after angioplasty of femoropopliteal de novo stenoses

The purpose of this study was to investigate the effectiveness and detect side effects of centered, overlapped endovascular gamma irradiation after angioplasty of de novo femoropopliteal stenoses. Thirty patients (age 65.3+/-9.2 years) with arterial occlusive disease were prospectively enrolled to receive endovascular gamma irradiation (192-iridium, 14 Gy centered at 2 mm vessel wall) immediately after percutaneous transluminal angioplasty (PTA) of femoropopliteal stenoses. Irradiation overlapped dilatation by 1-2 cm at each end. Follow-up involved angiography after 12 months; duplex sonography; and interviews before and after PTA and at 1, 6, and 12 months follow-up. PTA and centered endovascular irradiation were performed successfully in all patients. Three thromboembolic complications occurred during irradiation. Angiographic and clinical follow-up was possible in 28 patients. The angiographic degree of stenosis was 73.8%+/-16.3% before and 3.6%+/-23.5% after PTA and was 3.5%+/-43.7% at the 1-year follow-up. Restenosis (>50%) of the target lesion developed in three patients (10.7%) and edge stenoses (>30%) in nine patients (32.1%). An aneurysm of the irradiated segment in one patient was treated by stenting. The rate of retreatment was 17.9%. The vessel diameter after endovascular gamma irradiation and PTA of femoropopliteal stenoses remained stable. Restenosis, induction of edge stenoses, and aneurysm were reasons for reinterventions.

Brachytherapy for restenosis after stenting for coronary artery disease: its role in the drug-eluting stent era

PURPOSE OF REVIEW

Recent years have brought remarkable changes to the field of interventional cardiology. The need for repeat intervention due to restenosis, the most vexing long-term failure of percutaneous coronary intervention, has been significantly reduced owing to the introduction of two major advances, the vascular brachytherapy (VBT) and the drug-eluting stents (DES).

RECENT FINDINGS

Vascular brachytherapy has demonstrated its efficacy in limiting recurrence of existing in-stent restenosis. The past 2 years have sealed its reputation, with a variety of studies demonstrating its superiority over conventional therapy in challenging patient subsets with high risk for restenosis recurrence. Moreover, the long-term follow-up confirmed durability of this therapy, and the failures of VBT were characterized as easy to treat. Conversely, DES have shown spectacular efficacy at primarily preventing the first restenosis episode following the initial stent placement. Consequently, the role of VBT may be minimized, as the overall need for repeat revascularization is diminished as a result of the wide acceptance of DES. Furthermore, if the capacity of DES to treat in-stent restenosis is confirmed in randomized trials, they may eventually supersede VBT as the therapy of choice for in-stent restenosis.

SUMMARY

At present, VBT is the proven and durable therapeutic choice for patients with complex, diffuse in-stent restenosis who would otherwise have a very poor prognosis for long-term event-free survival. DES have emerged as remarkably effective in minimizing the first restenosis occurrence; they also represent a promising and competitive alternative to VBT for the treatment of in-stent restenosis.

Evolution of vascular brachytherapy over time: Data from the RENO-registry analysis

OBJECTIVE

To study the evolution of procedural variations in vascular brachytherapy (VBT) and their relationship to medium-term outcome.

METHODS AND RESULTS

The RENO (European Surveillance Registry with Novoste Beta-Cath) prospectively collected procedural and clinical outcome data on 1098 patients treated with VBT. Patients were divided for this analysis into Group-I, the first 50% registered, and Group-II, the last 50% registered. Shorter 30-mm source trains were more commonly used in Group-I (p<0.001) while longer 40-mm (p=NS) and 60-mm (p<0.001) source trains were more commonly used in Group-II. Mean dwell time for radiation seeds was longer in Group-II compared to Group-I (4.20+/-1.48 min vs. 4.14+/-1.44 min; p<0.05). Mean radiation dose was higher in Group-II (19.73+/-3.33 Gy vs. 17.92+/-2.68 Gy; p<0.001). Cutting balloons were more frequently used in Group-II (p<0.001). There was significant drop in the incidence of geographic miss in Group-II (3.2% vs. 9%; p<0.00005). There were nonsignificant trends towards reduction in angiographic restenosis, target vessel (TV) revascularisation, death and major adverse cardiac events (MACE).

CONCLUSION

There has been a learning curve and evolution of VBT techniques over time. In general, there has been an increase in radiation source length, use of cutting balloons, dwell time and radiation dose. This has resulted in significant reduction of geographic miss and a trend towards improve clinical outcomes. Continued development may result in further improvement in the treatment of patients with in-stent restenosis (ISR).

Centered endovascular irradiation to prevent postangioplasty restenosis of arteriovenous fistula in hemodialysis patients; Results of a feasibility study

PURPOSE

To report follow-up results of a prospective trial on centered endovascular gamma-irradiation (CEGI) after percutaneous transluminal angioplasty (PTA) for stenosis of arteriovenous fistula in hemodialysis patients.

METHODS AND MATERIALS

Eight patients receiving PTA for recurrent (n = 4) or de novo arteriovenous fistula stenoses were treated with CEGI with iridium-192 (14 Gy). Angiography was performed after 6 and 12 months or if problems reoccurred during hemodialysis. Parameters of hemodialysis and duplex sonography were determined the day before and after PTA and after 1, 3, 6, 9, and 12 months.

RESULTS

CEGI was performed successfully and without complications in seven patients. In six patients, restenosis occurred 6-52 weeks (mean 20.8 +/- 17.9 weeks) after PTA and required PTA. Parameters of hemodialysis and duplex sonography deteriorated during follow-up.

CONCLUSIONS

Centered endovascular gamma-irradiation with iridium 192 immediately after PTA of fistula stenoses was a safe and feasible method but did not prevent restenosis.

ISR II study: A long-term evaluation of sirolimus-eluting stent in the treatment of patients with in-stent restenotic native coronary artery lesions

The aim of this pilot study was to determine the safety and long-term efficacy of treating intrastent restenosis (ISR) with the slow-release sirolimus-eluting stent Bx Velocity (Cypher stent) without intravascular ultrasound (IVUS) guidance. Of patients who received a bare metal stent implantation and presented an ISR, 30-80% of the patients will develop a second restenosis within the stent, at the stent edges or both. To date, intravascular brachytherapy using beta- and gamma-radiation has been the only effective treatment for ISR. Twenty-three patients with ISR and evidence of ischemia were treated with Cypher stent. Clinical information was collected 1, 8, 12, and 24 months after stent implantation. During the first 8 months of the study, in-stent lumen diameter remained essentially unchanged from postprocedure in 80% of the case. The target lesion repeat revascularization (TLR) was 17%, of which 50% were oculostenotic reflexes. Only one patient presented a restenosis greater than 70%. During the 2-year study period, the TLR rate was 17%; the major adverse coronary event rate was 26%, and the non-Q-wave myocardial infarction (MI) rate was 9%. There were no reports of death, coronary artery bypass grafting, or Q-wave MI during the study. This study demonstrates the feasibility of using sirolimus-eluting stents without IVUS guidance for the treatment of ISR, providing long-term stability of immediate results.

Intracoronary brachytherapy following drug-eluting stent failure. It's still not time to hang up the spikes!

Drug-eluting stents (DES) have significantly reduced the incidence of restenosis. Although the results obtained with these novel antiproliferative devices are encouraging, recent reports have shown that DES are not completely immune from restenosis. Therefore, the broad use of DES has inevitably led to a major issue: treatment of DES failure. Intracoronary brachytherapy (IBT) represents an important advancement for treatment of in-stent restenosis (ISR) and has led to important pathophysiological insight on the restenotic process. To date, IBT, when properly used, still represents the gold standard for treatment of ISR. However, experience with IBT is for treatment of ISR occurring with bare metal stents (BMS). Whether IBT may be used with the same safety and efficacy profile as an adjunctive treatment for ISR following DES implantation is still unknown. In this article, we report the outcome of a series of patients with DES failure treated with IBT. IBT for treatment of DES failure was shown to be both safe and efficient and, therefore, until ISR exists, IBT still remains an important player in this growing and even more challenging setting.

Angiographic and three-dimensional intravascular ultrasound analysis of combined intracoronary beta radiation and self-expanding stent implantation in human coronary arteries

This study tested the combination of vascular brachytherapy (VBT) and self-expanding Wallstent implantation in coronary lesions of patients at high risk for restenosis as assessed angiographically by quantitative coronary analysis and by 3-dimensional intravascular ultrasound analysis. Twenty-nine "de novo" lesions were managed with a self-expanding stent alone (n = 19) or with a self-expanding stent after beta-VBT (n = 10) in 27 patients who had been identified by high levels of plasma angiotensin-converting enzyme as being prone to myointimal growth after stent implantation. At 6 months, the increase in stent strut diameter was similar in the 2 groups by quantitative coronary analysis and 3-dimensional intravascular ultrasound (Delta mean stent strut diameter -0.33 +/- 0.3 vs -0.40 +/- 0.3 mm, p = 0.5; Delta stent area -11.8 +/- 6.1 vs -12.0 +/- 6.1 mm(2), p = 0.9; Delta stent volume -96.9 +/- 112 vs -83.5 +/- 73 mm(3), p = 0.7; for groups treated with VBT and self-expanding stents and only self-expanding stents, respectively). In-stent neointimal proliferation was decreased in the group treated with VBT and self-expanding stents (minimal luminal diameter 2.5 +/- 0.8 vs 1.88 +/- 0.8 mm, p = 0.04) by quantitative coronary analysis (minimal luminal area 6.7 +/- 2.5 vs 4.1 +/- 1.9 mm(2), p = 0.01), by intravascular ultrasound, and proliferation volume (84.6 +/- 66.4 vs 159.2 +/- 103.5 mm(3), p = 0.05) by 3-dimensional intravascular ultrasound. Positive vessel and luminal remodelings were observed in 50% of the group treated with VBT and self-expanding stents and in 11% of the group treated only with self-expanding stents (p = 0.02). The combined use of VBT and self-expanding stents is a novel approach that enlarges vascular lumen by preventing vessel constriction and neointimal proliferation. The feasibility and good results of this experimental approach suggest that the simultaneous use of these 2 technologies may be an interesting alternative for difficult vascular districts with high restenosis rates, such as peripheral circulation in the lower limbs.

Basic treatment planning parameters for a 90Sr / 90Y source train used in endovascular brachytherapy

Working groups of the AAPM, DGMP, and ESTRO have published recommendations for endovascular brachytherapy, introducing concepts of relevant parameters for dose specification and treatment planning. However, the procedures for this treatment remain often mainly based on trial protocols and manufacturer instructions. Treatment planning requires the essential knowledge of the radial and longitudinal dose distribution, as well as information about geometrical uncertainties. The present study includes a whole data set for daily clinical practice using a commercially available device for endovascular brachytherapy (Novoste Betacath). The dose distribution around the 90Sr seed train was calculated with Monte-Carlo algorithms and verified by film dosimetry. The radial dose profile was determined starting from the surface of the delivery catheter Calculated dose profiles were in good agreement to measured values. The geometrical uncertainties were estimated with a retrospective analysis of 51 patient treatments. This shows the importance of using a safety margin of at least 10 mm between Intervention Length and Reference Isodose Length. Based on the longitudinal dose profile and the necessary safety margins, the maximum treatable intervention length is 25 mm and 45 mm for a 40 mm and 60 mm source train, respectively.

Relation of clinical success in coronary brachytherapy to dose

Intravascular brachytherapy is the primary treatment for coronary in-stent restenosis. Variations in dose in the treated artery may represent a potential cause of treatment failure. We compared dose distributions in patients who had developed recurrent restenosis (treatment failure) with those in patients who remained event free at 9 months (treatment success). We followed 140 patients who were receiving brachytherapy for in-stent restenosis with 4 radiation delivery devices to identify treatment failures and successes. Through a nested case-control construct, treatment failures (n = 14) were compared 1:2 with treatment successes (n = 28) matched by radiation delivery system and in-stent restenosis lesion pattern. The dose absorbed by 90% of the artery encompassed by the external elastic membrane (D(90)EEM) was calculated by applying intravascular ultrasound at 2-mm intervals along the treated lesion. Dose calculations were performed using dose kernel integration techniques generated from Monte Carlo simulations. The mean minimum D(90)EEM in treatment failures was 7.46 +/- 1.98 Gy, and that in treatment successes was 8.87 +/- 1.13 Gy (p = 0.007). Using a minimum dose threshold of 8.4 Gy, a minimum D(90)EEM <or=8.4 Gy occurred in 13 patients (93%) whose treatment failed but only in 9 patients (32%) whose treatment was a success (p <or=0.001). No confounding variables were found to be statistically significant between treatment failures and successes. In conclusion, current brachytherapy dose prescriptions allow for inter- and intralesion variations in dose. Arteries that receive <or=8.4 Gy at any point along the external elastic membrane are more likely to result in treatment failures. Dosimetry guided by intravascular ultrasound may be critical to ensure adequate dose delivery and outcomes.

No change in endothelial-dependent vasomotion late after coronary irradiation

PURPOSE

Mechanical injury from balloon angioplasty and stenting is known to cause prolonged endothelial dysfunction, even distal to the injured segment. Intravascular irradiation therapy is associated with delayed healing response and may therefore also impede endothelial functional recovery. This study was conducted to assess endothelial function late after the irradiation of atherosclerotic coronary arteries.

METHODS AND MATERIALS

In 15 patients (8 with additional radiation and 7 with stenting only), directly after the intervention and at 6-month follow-up, endothelial function of the distal segment was studied by assessment of coronary diameter after intracoronary acetylcholine (Ach). Coronary flow reserve (CFR) and intravascular ultrasound (IVUS) investigation were performed for unequivocal interpretation of angiographic data.

RESULTS

No significant different response to Ach could be detected at baseline nor at follow-up (-17 +/- 14% vs. -17 +/- 15% for radiation vs. nonradiation at baseline, P=1.0; -8 +/- 11% vs. -9 +/- 13% at follow-up, P=.8). IVUS data revealed more constrictive remodeling in the nonradiation patients, but a minimal increase in mean plaque area in the radiation patients compared with a significant decrease in nonradiation patients (+4% vs. -25%, P=.02).

CONCLUSIONS

Irradiation of atherosclerotic coronary arteries does not affect endothelium-dependent vasodilatation acutely or at 6 months. Irradiated segments demonstrated less negative remodeling but higher plaque burden than the controls did.

Local drug delivery in restenosis injury: thermoresponsive co-polymers as potential drug delivery systems

The success of percutaneous transluminal coronary angioplasty in treatment of acute coronary syndromes has been compromised by the incidence of restenosis. The physical insult of balloon insertion can damage or remove the endothelial monolayer, thereby generating a prothrombotic surface. The resulting inappropriate response to injury can also lead to penetration of inflammatory cells, conversion of the underlying media to a synthetic phenotype, deposition of extracellular matrix, constrictive remodeling, and neointimal hyperplasia. While stent implantation at the time of balloon insertion has offset some of these events, inflammatory responses to the implanted biomaterial (stent) and intimal hyperplasia are still prominent features of the procedure, leading in 20-30% of cases to in-stent restenosis within a year. Systemic delivery of drugs designed to offset in-stent restenosis injury has been largely unsuccessful, which has led to the development of strategies for coating stents with drugs for local delivery. Drug-eluting stents constitute an innovative means of further reducing the incidence of restenosis injury and clinical trials have shown encouraging results. This review focuses on properties of a class of environment-sensitive hydrogels, the N-isopropylacrylamide-based thermoresponsive co-polymers, on their potential roles as stent coatings, on their demonstrated ability to incorporate and release drugs that modify vascular endothelial and smooth muscle cell functions, and on issues that still await clarification, prior to their adoption in a clinical setting.