The effect of endovascular irradiation on platelet recruitment at sites of balloon angioplasty in pig coronary arteries

Radiation-induced cutaneous vasculopathy of the breast: a rare case report

BACKGROUND

Radiation therapy is often indicated as part of the treatment for breast cancer and is therefore used frequently worldwide. Vasculopathy is a general term used to describe any condition that affects blood vessels. We present a case report of a patient who presented with vasculopathy as a rare late side effect of radiation therapy to the breast.

CASE PRESENTATION

This 66-year-old woman was initially treated with breast-conserving surgery for early-stage receptor-positive left breast carcinoma. She received postoperative radiation therapy and hormonal treatment with tamoxifen. She developed sudden spontaneous painless ecchymosis spread over the whole irradiated area 1.5 years after finishing her radiation therapy. Tumor relapse was excluded. There was no associated vasculitis. The cause was presumed to be multifactorial. She had a history of smoking and was known to have hyperlipidemia. She had undergone several surgical treatments at the left breast one year after her initial breast-conserving treatment and was taking tamoxifen. Anti-inflammatory medicine and treatments increasing local blood flow were prescribed. The ecchymosis resolved completely within one month.

CONCLUSIONS

Vasculopathy can occur as a rare late side effect of radiation therapy. It can be reversible. Prevention begins with carefully treating precipitating factors.

Interventional strategies to manage heart failure in patients with cancer

The unique clinical circumstances that are typically encountered by cardiology providers when caring for patients undergoing treatment for cancer require an in-depth understanding of the recommended treatments for the diagnosis and management of heart failure and ischemic heart disease. It is also recognized that there is not a broadly described clinical research basis from which to provide guidance when specific clinical decision making is required. Thus, it is imperative that cardiology and oncology closely collaborate when difficult patient decisions arise. Engaging each discipline together with active patient involvement in clinical care will undoubtedly provide optimal care for our patients.

Cardiovascular disease associated with radiotherapy: activation of nuclear factor kappa-B

There have been several recent reports of an increased risk of cardiovascular disease after radiotherapy. Hence, with an increasing number of cancer survivors, the incidence of cardiovascular disease caused by radiotherapy will increase. The existence of a type of vascular disease, or vasculopathy, induced by radiotherapy has been known for decades. It is important to identify and understand the molecular causes of this vasculopathy to determine preventive strategies. Recently, a chronic inflammation with similarities to atherosclerosis has been observed, with activation of the transcription factor nuclear factor kappa-B (NF-κB) as a possible cause. However, the trigger for NF-κB activation is unclear although it may be that reactive oxygen species or direct DNA damage is involved. To minimize the risk of cardiovascular disease in vulnerable patients, careful selection of patients, radiation dose and fractionation are important, together with the development of new techniques that reduce radiation dose to the blood vessels. In the light of the finding of an interaction between risk factors for cardiovascular disease and radiotherapy, it is reasonable to modify these factors including diabetes mellitus, hyperlipidaemia, hypertension and smoking. We believe that preventive strategies focusing on NF-κB can reduce the risk of future adverse cardiovascular events.

Sustained inflammation due to nuclear factor-kappa B activation in irradiated human arteries

OBJECTIVES

The aim of this study was to investigate gene expression networks related to cardiovascular disease in radiated human arteries.

BACKGROUND

Recent epidemiological studies have shown that radiotherapy is associated with cardiovascular disease years after treatment. However, the molecular mechanisms underlying late effects of radiation are poorly described.

METHODS

Arterial biopsies from radiated and nonradiated human conduit arteries, from the same patient, were simultaneously harvested during microvascular free tissue transfer for cancer-reconstruction in 13 patients, 4 to 500 weeks from radiation treatment. Radiated and nonradiated arteries were compared, with Affymetrix (Santa Clara, California) microarrays on a subset of the material to generate candidate genes. A Taqman (Applied Biosystems, Foster City, California) low-density array of 45 selected genes was designed for analysis of the whole material.

RESULTS

Thirteen genes were synchronously expressed in all patients (p = 0.0015), including CCL8, CCL3, CXCL2, DUSP5, FGFR2, HMOX1, HOXA9, IL-6, MMP-1, PTX3, RDH10, SOD2, and TNFAIP3. A majority of differentially regulated genes related to the nuclear factor-kappa B (NF-kappaB) signaling pathway and were dysregulated even years after radiation. The NF-kappaB activation was confirmed by immunohistochemistry and immunofluorescence.

CONCLUSIONS

In the present study, we found sustained inflammation due to NF-kappaB activation in human radiated arteries. The results are supported by previous in vitro findings suggesting that deoxyribonucleic acid injury, after radiation, activates NF-kappaB. We also suggest that HOXA9 might be involved in the regulation of NF-kappaB activation. The observed sustained inflammatory response can explain cardiovascular disease years after radiation.

Irreversible electroporation attenuates neointimal formation after angioplasty

Restenosis following coronary angioplasty represents a major clinical problem. Irreversible electroporation (IRE) is a nonthermal, nonpharmacological cell ablation method. IRE utilizes a sequence of electrical pulses that produce permanent damage to tissue within a few seconds.

METHODS AND RESULTS

The left carotid arteries of eight rats underwent in vivo intimal damage using two Fogarty angioplasty catheters. The procedure was immediately followed by IRE ablation in four rats, while the remaining four were used as the control group. The IRE ablation was performed using a sequence of ten dc pulses of 3800 V/cm, 100 micros each, at a frequency of ten pulses per second, applied across the blood vessel between two parallel electrodes. The electrical conductance of the treated tissue was measured during the electroporation to provide real-time feedback of the process. Left carotid arteries were excised and fixated after a 28-day follow-up period. Neointimal formation was evaluated histologically. The use of IRE was successful in three out of four animals in a way that is consistent with the measurements of blood vessel electrical properties. The integrity of the endothelial layer was recovered in the IRE-treated animals, compared with control. Successful IRE reduced neointima to media ratio (0.57 +/-0.4 versus 1.88 +/-1.0, P = 0.02).

CONCLUSIONS

We report for the first time the in vivo results of attenuation of neointimal formation using IRE. Our study shows that IRE might be able to attenuate neointimal formation after angioplasty damage in a rodent model of restenosis. This approach may open new venues in the treatment of coronary artery restenosis after balloon angioplasty.

Intracoronary photodynamic therapy reduces neointimal growth without suppressing re-endothelialisation in a porcine model

OBJECTIVE

To examine the effects of intracoronary PhotoPoint photodynamic therapy (PDT) with a new photosensitiser, MV0611, in the overstretch balloon and stent porcine models of restenosis.

METHODS

28 pigs were injected with 3 mg/kg of MV0611 systemically 4 h before the procedure. Animals were divided into either the balloon overstretch injury (BI) group (n = 19) or the stented group (n = 9). After BI, a centred delivery catheter was positioned in the artery to cover the injured area, and light (532 nm, 125 J/cm(2)) was applied to activate the drug (n = 10). Control arteries (n = 9) were not activated by light. In the stented group, the drug was light activated before stent deployment. Serial sections of vessels were processed 14 days after treatment in the BI group and 30 days after treatment in the stented group for histomorphometric or immunohistochemical analysis.

RESULTS

Intracoronary PDT significantly reduced intimal thickness in both BI and stented arteries (about 65%: 0.22 (SEM 0.05) mm v 0.62 (0.05) mm, p < 0.01; and about 26%: 0.40 (0.04) mm v 0.54 (0.04) mm, p < 0.01, respectively). PDT increased luminal area by

CONCLUSION

Intracoronary PhotoPoint PDT with MV0611 reduces intimal proliferation without suppressing re-endothelialisation in a porcine model of restenosis.

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Key Words Collapse

MESH Headings

• Angioplasty, Balloon
• Animals
• Cell Proliferation
• Coronary Restenosis/prevention & control
• Coronary Vessels/injuries
• Feasibility Studies
• Female
• Immunohistochemistry
• Male
• Mesoporphyrins/pharmacokinetics
• Mesoporphyrins/therapeutic use
• Photochemotherapy/methods
• Photosensitizing Agents/pharmacokinetics
• Photosensitizing Agents/therapeutic use
• Random Allocation
• Stents
• Swine
• Tunica Intima

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Grants Collapse

Affiliation(s)

R Waksman Division of Cardiology, Washington Hospital Center, Washington, DC, USA.
I M Leitch
J Roessler
H Yazdi
R Seabron
F Tio
R W Scott
R I Grove
S Rychnovsky
B Robinson
R Pakala
E Cheneau

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Restenosis related to percutaneous coronary intervention has been solved?

Percutaneous coronary intervention (PCI) has become the most important revascularization method in the treatment of coronary artery disease. The major problem in PCI has been renarrowing of the dilated vessel after the procedure (restenosis). The best results in the prevention of restenosis have been obtained by covering the stent with drugs that inhibit cellular growth, thus limiting excessive scar formation inside of the stent. With drug-eluting stents, restenosis has been reduced to one-tenth compared with balloon angioplasty and to one-fourth compared to bare metal stents. Due to drug-eluting stents, PCI is an alternative to bypass surgery. However, restenosis will remain a challenge due to the increased number of procedures and more difficult disease treated with PCI.

Sustained Attenuation of Neointimal Coverage Over the Stent Following Brachytherapy for In-Stent Restenosis Angioscopic Findings

BACKGROUND

The nature of the vessel lumen following vascular brachytherapy (VBT) has not been extensively explored in the clinical setting.

METHODS AND RESULTS

By using angioscopy, 33 stents treated with percutaneous balloon angioplasty with or without VBT for in-stent restenosis after 8.9 +/- 2.1 months of the treatment were followed (VBT =14 lesions; control =19 lesions). Neointimal coverage, stent attachment, and the presence of red or white thrombi were factors that were assessed. The majority of the stents (74%) were fully covered with non-transparent neointima in the control group. In contrast, stent struts were clearly seen in 57% lesions with VBT. The absence of neointima with glittering stent struts were only seen in 29% of lesions in VBT (p = 0.03). Incomplete stent attachment was not detected in the controls, whereas 14% were in VBT (p = 0.17). Red thrombi were observed in 14% with VBT and in 16% in controls, which showed that there was a similar incidence regardless of the treatment. Neither exposure of stent struts (p = 0.5) nor incomplete stent attachment (p = 1.0) was related to thrombi.

CONCLUSIONS

The exposure of stent struts and incomplete stent attachment were occasionally observed by angioscopy even 9 months after VBT for the treatment of in-stent restenosis.

Pravastatin limits endothelial activation after irradiation and decreases the resulting inflammatory and thrombotic responses

Endothelial dysfunction has been implicated in the pathogenesis of atherosclerosis, fibrosis and vascular occlusion after radiation therapy. Statins have been reported to improve endothelial function; however, this beneficial effect on endothelial cells has never been investigated after irradiation. Therefore, using human microvascular endothelial cells from lung that had been irradiated with 5 or 10 Gy, we assessed the effect of pravastatin on endothelial activation by ELISA, cell-ELISA and electrophoretic mobility shift assay and increased blood-endothelial cell interactions by a flow adhesion assay. Pravastatin inhibited the overproduction of monocyte chemoattractant protein 1, IL6 and IL8 and the enhanced expression of intercellular adhesion molecule 1 but had no effect on platelet-endothelial cell adhesion molecule 1 expression. Moreover, pravastatin down-regulated the radiation-induced activation of the transcription factor activator protein 1 but not of nuclear factor-kappaB. Finally, an inhibition by pravastatin of increased adhesion of leukocytes and platelets to irradiated endothelial cells was observed. The effect of pravastatin was maintained up to 14 days after irradiation and was reversed by mevalonate. Pravastatin exerts persistent anti-inflammatory and anti-thrombotic effects on irradiated endothelial cells. Statins may be considered in therapeutic strategies for the management of patients treated with radiation therapy.

PECAM-1 (CD31) is required for interactions of platelets with endothelial cells after irradiation

Sustained adhesion of platelets to endothelial cells (EC) is believed to contribute to thrombosis and vascular occlusions following radiation exposure leading to organ functional impairment and even death. Our objective was to evaluate the role of platelet endothelial cell adhesion molecule (PECAM)-1 in the prothrombotic response of EC after irradiation. Endothelial PECAM-1 expression was determined by cell-enzyme linked immunosorbent assay (ELISA) on human microvascular EC from lung (HMVEC-L) up to 21 days after a 10 Gy irradiation. Platelet- and leukocyte-endothelial cell interactions were assessed using a flow adhesion assay with fluorescently labeled whole blood, and the function of PECAM-1 in these processes was measured by using blocking antibody. PECAM-1 expression was significantly increased on irradiated HMVEC-L and remained elevated at 21 days. Anti-PECAM-1 antibody significantly inhibited adhesion of single platelets and thrombi on irradiated HMVEC-L. This inhibitory effect persisted at day 21. Anti-PECAM-1 also reduced leukocyte adhesion to irradiated HMVEC-L. The up-regulation of endothelial PECAM-1 following radiation exposure is persistent. PECAM-1 plays a key role platelet adhesion/aggregation on irradiated EC. Therefore, strategies targeting this adhesion molecule may prevent the development of radiation pathologies.

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.

Adventitial response to intravascular brachytherapy in a rabbit model of restenosis

BACKGROUND

The incidence of late major adverse cardiac events (MACE) after coronary brachytherapy is higher than in controls. Because expansive remodeling has been shown to correlate with poor clinical outcome after vascular interventions, we studied adventitial changes after intravascular irradiation in a rabbit model.

METHODS

Twenty normolipidemic rabbits underwent balloon injury in both external iliac arteries. One artery was assigned for subsequent irradiation with a 90Y source (15 Gy or 30 Gy at 0.5 mm in the vessel wall). After four weeks morphometric measurements were made and cell density and collagen amount determined. Staining for Ki67 identified proliferating cells; apoptotic cells were identified by TUNEL staining. Proliferative and apoptotic indices were calculated as the number of respective positive cells/total cell count x100.

RESULTS

The neointimal area decreased to 0.27 +/- 0.3 mm2 after irradiation compared with 0.55 +/- 0.2 mm2 in controls (p=0.007), whereas adventitial area increased from 0.62 +/- 0.3 mm2 to 0.87 +/- 0.3 mm2 (p=0.02). Irradiation reduced both the proliferative (0.95 +/- 2.6 vs. 3.73 +/- 4.7, p=0.026) and apoptotic (0.006 +/- 0.02 vs. 0.107 +/- 0.2, p=0.03) indices in the neointima, but not in the other arterial-wall layers. Collagen amount and arterial remodeling did not differ between the groups. There was no difference between 15 and 30 Gy in any of the parameters, although adventitial thickening was more pronounced in the high-dose group.

CONCLUSIONS

In normolipidemic rabbits, intravascular beta-irradiation after balloon angioplasty is associated with an increase in neoadventitia and a reduction of neointima. It is conceivable that this phenomenon may contribute to the increased incidence of late MACE after vascular brachytherapy.

Irradiation increases the interactions of platelets with the endothelium in vivo: analysis by intravital microscopy

Adhesion of platelets to the endothelium is believed to be a major factor contributing to thrombosis and vascular occlusion after radiotherapy or endovascular irradiation. In the present study, platelet-endothelium interactions were analyzed in vivo by intravital microscopy in mesenteric venules of mice according to three parameters: (1) platelet rolling, (2) platelet adhesion, and (3) the presence of platelet clusters. A 10-Gy total-body irradiation of mice resulted in an increase in the frequency of appearance of these three types of platelet-endothelium interactions in postcapillary venules 6 and 24 h after exposure, whereas only minor alterations were seen in large venules. In addition, the duration of platelet adhesion was increased 24 h after irradiation in both postcapillary and large venules. However, P-selectin was not up-regulated on the platelet membrane and platelet-leukocytes were not seen rolling together, suggesting that changes in platelet-endothelial cell interaction result from endothelial cell activation rather than platelet activation. Our data suggest that irradiation transforms resting endothelial cells to a pro-adhesive surface for platelets, which could ultimately lead to thrombosis.

Inflammatory reaction and changes in expression of coagulation proteins on lung endothelial cells after total-body irradiation in mice

Inflammatory reaction is a classical feature of radiation exposure, and pneumonitis is a dose-limiting complication in the handling of hematological disorders treated with total-body irradiation. In the present study, we first evaluated the inflammatory response in C57BL6/J mice exposed to lethal doses of gamma rays treated with antibiotics or not. Both interleukin 6 and KC (also known as Gro1) were increased in the plasma 10 to 18 days after radiation exposure, independent of bacterial infection, whereas fibrinogen release was linked to a bacterial infection. Furthermore, both Il6 and KC were increased in the lungs of irradiated mice. Our second objective was to characterize the endothelial cell changes in the lungs of total-body-irradiated mice. For this purpose, a quantitative RT-PCR was used to determine the expression of genes involved in inflammatory and coagulation processes. We found that the adhesion molecules P-selectin and platelet endothelial cell adhesion molecule 1 were up-regulated, whereas E-selectin remained unchanged. Tissue factor expression was up-regulated as well, and thrombomodulin gene expression was down-regulated. The investigation by immunohistochemistry of adhesion molecules confirmed the increase in the basal expression of both P-selectin and platelet endothelial cell adhesion molecule 1 on pulmonary endothelial cells. All together, our results suggest the involvement of endothelial cells in the development of radiation-induced inflammatory and thrombotic processes.

Use of restenting should be minimized with intracoronary radiation therapy for in-stent restenosis

Restenting at the time of intracoronary radiation therapy (IRT) for in-stent restenosis (ISR) potentially increases the risk of late total occlusion (LTO) of the treated vessel. Prolonged antiplatelet therapy with clopidogrel (6 months) has been shown to be effective in reducing LTO risk. The purpose of this study was to assess the impact of restenting on clinical outcomes following IRT for ISR with 6 months of clopidogrel. We retrospectively evaluated 1,275 patients with 6-months clinical follow-up who were enrolled in radiation trials for ISR using gamma- and beta-emitters conducted at Washington Hospital Center. Patients were analyzed according to whether additional stents were deployed at the time of IRT. The predominant indication for restenting was to optimize the final angiographic result in the event of tissue prolapse or to cover edge dissections. All patients received a minimum of 6 months of clopidogrel. Baseline clinical and angiographic characteristics were similar between the restented and nonrestented groups. Radiation was delivered successfully in all cases. At 6 months, patients treated with additional stents and IRT had a significantly higher rate of target vessel revascularization than patients without additional stents (24.6% vs. 18.7%; P = 0.011). Restenting caused more frequent late thrombosis, late total occlusion, and Q-wave myocardial infarction than no restenting (4.0% vs. 2.2%, P = 0.09; 6.1% vs. 4.3%, P = 0.14; and 1.9% vs. 0.4%, P = 0.009, respectively). Restenting for the treatment of ISR is associated with increased adverse events and should be avoided after intracoronary radiation therapy for in-stent restenosis, as restenting results in a higher recurrence rate and the potential for increased late total occlusion.

Late thrombosis after gamma-brachytherapy

Late stent thrombosis (> 30 days after treatment) is a new phenomenon occurring after vascular brachytherapy. We report the analysis of 11 patients with late thrombosis after gamma-irradiation treatment of in-stent restenosis. All patients had in-stent restenosis and angina. Contributing factors to late thrombosis include long stents, small distal vessels, and complex lesion morphology.

Late acute thrombotic occlusion after endovascular brachytherapy and stenting of femoropopliteal arteries

OBJECTIVES

The aim of this article is to underline the importance of this complication after endovascular brachytherapy (EVBT) and intravascular stenting of the femoropopliteal arteries occurring in a running randomized trial.

BACKGROUND

Endovascular brachytherapy has been proposed as a promising treatment modality to reduce restenosis after angioplasty. However, the phenomenon of late acute thrombotic occlusion (LATO) in patients receiving EVBT after stenting is of major concern.

METHODS

In an ongoing prospective multicenter trial, patients were randomized to undergo EVBT (iridium 192; 14 Gy at a depth of the radius of the vessel +2 mm) after percutaneous recanalization of femoropopliteal obstructions. Of the 204 patients who completed the six months follow-up, 94 were randomized to EVBT.

RESULTS

Late acute thrombotic occlusion occurred exclusively in 6 of 22 patients (27%) receiving EVBT after intravascular stenting and always in concomitance with reduction of antithrombotic drug prevention (clopidogrel). Conversely, none of the 13 patients with stents and without EVBT (0%; p < 0.05) and none of the 72 patients (0%; p < 0.01) undergoing EVBT after simple balloon angioplasty presented LATO.

CONCLUSIONS

Late thrombotic occlusion occurs not only in patients undergoing EVBT after percutaneous coronary recanalization but also after stenting of the femoropopliteal arteries and may compromise the benefits of endovascular radiation. The fact that all our cases with LATO occurred concomitantly with stopping clopidogrel may indicate a possible rebound mechanism. An intensive and prolonged antithrombotic prevention is probably indicated in these patients.

Prevention of stent thrombosis following brachytherapy and implantation of drug-eluting stents

The implementation of coronary brachytherapy and especially the application of drug-eluting stents for the prevention of in-stent restenosis are of vital importance in the field of interventional cardiology. Despite undeniable benefits of these new methods a potential increased risk for the occurrence of stent thrombosis as a result of the mode of action of these new methods has to be taken into consideration. The prevention of stent thrombosis following coronary brachytherapy and implantation of drug-eluting stents is therefore of particular importance to assure the success of these forward-looking technologies. This article provides an overview of current data regarding the incidence of stent thrombosis following brachytherapy and implantation of drug-eluting stents and it's implication for clinical practice.

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).

Possible impact of iridium-192 source centering on restenosis rate after femoro-popliteal angioplasty and endovascular brachytherapy in Vienna-2 study

PURPOSE

Endovascular brachytherapy (EVBT) has been proven to significantly reduce restenosis after percutaneous transluminal angioplasty (PTA). The object of this analysis was to assess the possible correlation between iridium-192 source non-centering and angiographic-determined restenosis.

MATERIALS AND METHODS

A total of 113 patients with long-segment lesions of the superficial femoro-popliteal artery (SFA) were randomized to receive either PTA alone or PTA followed by EVBT in the Vienna-2 study. This analysis was performed on a subgroup of 34 out of 57 patients, who received PTA+EVBT. Angiographic restenosis was defined as lumen reduction of more than 50%. Angiograms taken immediately after PTA (34 patients) and at follow-up (25 patients) were analyzed. The distance between the vessel wall and the actual position of the source at the time of EVBT was measured (in mm) and correlated with the follow-up vessel lumen diameter. Measurements were performed at points at a distance of 10 mm from each other. The dose was determined at the luminal surface and at the reference depth of 2 mm into the vessel wall for different distances from the source.

RESULTS

Among the 622 measured points, 62 (10.0%) were within restenotic areas; 560 (90.0%) were in arterial segments without proven angiographic restenosis. As far as source centering is concerned, 7.9% of restenotic points were observed when the maximum distance to the arterial wall was <3 mm and 9.6% for 4 mm, respectively. The percentage of restenotic points increased up to 15.9% when the maximum distance to the arterial wall was 5 mm and reached 22.2% when it was >5 mm.

CONCLUSIONS

The proportion of restenotic points significantly increased with source non-centering. This observation was interpreted as being related to a decrease in dose at the target. When the maximum distance between the source and the vessel surface was >5 mm, the dose at the reference depth (2 mm into the vessel wall) decreased to values lower than 5 Gy.

Centered versus noncentered source for intracoronary artery radiation therapy: a model based on the Scripps Trial

BACKGROUND

The Scripps Trial was a randomized study of intracoronary artery radiation therapy with iridium 192 used to treat restenotic vessels. We used the intravascular ultrasound data from the Scripps Trial to investigate whether a lumen-centered gamma or beta radiation source would reduce radiation dose heterogeneity compared with the noncentered source position used.

METHODS

Analysis included 28 patients with stent placement in 20 native vessels and 8 saphenous vein grafts enrolled in this trial. Radiation dosimetry for gamma radiation was calculated to deliver 800 cGy to the far field target, provided the maximum dose to the near field target did not exceed 3000 cGy. Prescribed dosimetry for beta radiation by use of yttrium 90 was 1600 cGy at 2 mm distance from the source.

RESULTS

The calculated average minimum source to target distance by use of a lumen-centered source increased by 0.18 mm from 1.70 +/- 0.25 to 1.88 +/- 0.36 mm, whereas the maximum distance decreased by 0.17 mm from 3.64 +/- 0.60 to 3.47 +/- 0.43 mm (P <.05). On the basis of these distances, the maximum radiation dose, as well as radiation dose heterogeneity (ratio of maximum to minimum), would have been reduced in 22 of 28 patients by use of a lumen-centered gamma or beta source (P <.005). The reduction in dose heterogeneity was substantially greater with a beta source compared with a gamma source (48% vs 16% reduction).

CONCLUSIONS

Centering of the intracoronary artery radiation therapy delivery catheter within the vessel lumen can significantly reduce radiation dose heterogeneity when compared with a noncentered source position. This dose reduction is substantially greater for a beta compared with a gamma source.

Intracoronary beta-radiation of de novo coronary lesions using a (186)Re liquid-filled balloon system: six-month results from a clinical feasibility study

Vascular brachytherapy has shown to be effective for in-stent restenosis, but efficacy in de novo lesions remains uncertain. We evaluated feasibility and outcome of intracoronary beta-radiation therapy in de novo coronary lesions using a (186)Re liquid-filled balloon system. Thirty-three patients received 20 Gy (186)Re beta-radiation immediately after balloon angioplasty. The 6-month restenosis rate was 41% (12/29) and restenosis was located within the target lesion in eight patients and at the edges of the injured and irradiated segment, outside the target lesion, in four patients. At 6 months, four patients (12%), all stented during the initial procedure, had experienced a late (> 30 days) total occlusion. Intracoronary beta-radiation therapy of de novo coronary lesions using (186)Re is technically feasible. No reduction in restenosis was observed. The high incidence of late total occlusions may have been prevented by avoiding new stent implantation and prolonging double antiplatelet therapy.

The restenosis story: is intracoronary radiation therapy the solution?

Restenosis remains a major limitation of percutaneous transluminal coronary intervention. Stenting made an important contribution in restenosis reduction, but in-stent restenosis is becoming a growing problem. Although radiation therapy was traditionally used to kill relatively fast-growing tumor cells, it has also been used to clinically treat benign but problematic hyperplastic conditions. In addition, in vitro studies have shown that radiation inhibits serum-stimulated growth of arterial smooth muscle cells and fibroblasts, and decreases collagen synthesis by fibroblasts. The effects of radiation on neointimal inhibition after vascular injury were investigated in animal models using various catheter- and stent-based endovascular approaches (brachytherapy) as well as externally delivered x-irradiation. These studies have consistently shown that ionizing radiation delivered by the endoluminal approach results in remarkable suppression of neointima formation. However, animal studies also demonstrate altered vessel wall healing with increased thrombogenicity. The catheter-based approach with gamma- or beta-emitters showed feasibility and appears promising in early human clinical trials, whereas the strategy of using radiation stents is more problematic in the clinical arena. A number of randomized multicenter trials have been initiated and the results are eagerly awaited. More work needs to be done to define the optimal dosage, and to study the short- and long-term vascular biologic effects of brachytherapy. Additionally, if this form of therapy proves efficacious in the large, randomized, clinical trials, its cost-effectiveness will then need to be established. This review touches on some of the basic concepts involved in using the strategy of endovascular irradiation therapy for restenosis prevention after percutaneous coronary intervention and reviews the evidence of clinical efficacy and safety.

High-dose external beam irradiation inhibits neointima formation in stented pig coronary arteries

PURPOSE

To evaluate high-dose external beam irradiation (EBRT) in a pig coronary stent preparation because low and intermediate-dose EBRT failed to show inhibition of neointima formation in stented animal models.

METHODS AND MATERIALS

Thirty-five stents were implanted in the coronary arteries of 17 pigs. Seven pigs were exposed to a single dose of 21 Gy EBRT immediately after stenting. Ten stented, nonirradiated pigs served as controls. After 4 weeks, the study arteries and myocardium were examined by light and scanning electron microscopy.

RESULTS

Compared with controls, 21 Gy EBRT resulted in a larger lumen area (7.57 +/- 1.67 mm2 vs. 4.00 +/- 1.63 mm2, p <0.001), a smaller neointima area (0.47 +/- 0.43 mm2 vs. 3.36 +/- 2.26 mm2, p <0.001) and a smaller maximal intimal thickness (0.16 +/- 0.09 mm vs. 0.68 +/- 0.31 mm, p <0.001). Unresorbed intramural hemorrhages and adherent mural thrombi were present in the irradiated vessels, which also showed incomplete re-endothelialization. The irradiated hearts demonstrated diffuse interstitial and perivascular inflammation and fibrosis.

CONCLUSIONS

EBRT at 21 Gy to the entire heart significantly inhibited neointima formation in stented pig coronary arteries but also resulted in incomplete re-endothelialization, myocardial inflammation, and fibrosis. Improvements in localization and delivery techniques are required to allow clinical implementation of this technique.

Intracoronary irradiation and stent placement in a chronic total coronary occlusion: long-term clinical, angiographic, and intracoronary ultrasound follow-up

Intracoronary irradiation emerges as a promising method in a variety of restenosis prone coronary lesions. We report the acute and long-term clinical, angiographic, and ICUS follow-up of a patient who underwent a successful angioplasty with stent placement in a chronic coronary occlusion with adjuvant gamma-intracoronary radiation.

Irradiation and postangioplasty restenosis: a recent overview

One of the most intriguing developments in recent years towards prevention of restenosis after angioplasty is the use of ionizing radiation. The background for the use of radiation treatment for this application is sound, since radiation is used not only to treat malignant cancerous growths but also is used for treatment of benign hyperplastic disorders such as post-surgical keloid formation and recurrence of pterygium after surgical removal. Restenosis can be considered a form of overexuberant wound healing triggered by angioplasty. Ionizing radiation inhibits serum-stimulated proliferation of many cell types including fibroblasts and smooth muscle cells in vitro and also suppresses the synthesis of collagen by cultured fibroblasts. Liermann who showed inhibition of post-stent restenosis first used ionizing radiation for restenosis prevention clinically in iliac and iliofemoral arteries. Subsequently, extensive animal studies in various restenosis models have shown a profound inhibitory effect of catheter-based radiation (endovascular brachytherapy) on neointima formation and overall vessel shrinkage (negative remodeling). Based on these results clinical trials have been initiated with several types of devices and isotopes. Among these are 192Ir, 32P, 90Y, 90Sr/Y and 188Re. Additionally, radioactive stents have been developed; devices for clinical use are made radioactive at the microCi level by surface implantation of 32P ions. Results from early clinical trials are encouraging and brachytherapy appears safe for clinical use and at an appropriate dose, may be highly effective for restenosis prevention.