Endoluminal beta-radiation therapy for the prevention of coronary restenosis after balloon angioplasty. The Dose-Finding Study Group

Sonotherapy, antirestenotic therapeutic ultrasound in coronary arteries: the first clinical experience

We studied the safety and feasibility of intracoronary sonotherapy (IST) and its effect on the coronary vessel at 6 months. Thirty-seven patients with stable or unstable angina were included (40 lesions). The indication was de novo lesion (n = 26), restenosis (n = 2), in-stent restenosis (n = 11), and a total occlusion of a venous bypass graft. After successful angioplasty, IST was performed using a 5 Fr catheter with three serial ultrasound transducers operating at 1 MHz. IST was successfully performed in 36 lesions (success rate, 90%). IST exposure time per lesion was 718 +/- 127 sec. During hospital stay, one patient died due to a bleeding complication. At 6-month follow-up, one patient experienced acute myocardial infarction, eight patients underwent repeat PTCA. No patient underwent CABG. Late lumen loss was 1.05 +/- 0.70 mm with a restenosis rate of 25%. IVUS analysis revealed a neointima burden of 25% +/- 11%. IST can be applied safely and with high acute procedural success. Sonotherapy-related major adverse events were not observed. Late lumen loss and neointimal growth were similar to conventional PTCA approaches. These results justify the initiation of randomized clinical efficacy studies.

Deposition of (90)YPO(4) and (144)CePO(4) radioisotopes on polymer surfaces for radiation delivery devices

Intravascular irradiation with beta emitters inhibits restenosis in arteries after balloon angioplasty or stent implantation. Yttrium-90 ((90)Y, T(1/2)=64 h) and cerium-144 ((144)Ce, T(1/2)=286 d) emit beta particles (E(max)=2.28--3.50 MeV) having an ideal energy range for brachytherapy delivery system. In this article, a previously reported method for depositing (32)P on poly(ethylene terephtalate) (PET) surfaces is generalized and modifications that allow deposition of other beta-emitting radioisotopes, such as (90)Y and (144)Ce, are demonstrated. PET films were first coated with chitosan hydrogel and then adsorbed different amounts of phosphoric acid (PA) in aqueous solutions. Yttrium was deposited onto the surface as YPO(4) after the films were immersed in YCl(3) solutions. 1 muCi (90)YCl(3) (2 x 10(-9) g) was used in each sample as a tracer for measuring the deposition efficiency, which is defined as the percentage of YCl(3) deposited on the surface compared to the amount of YCl(3) in solutions before the deposition. In order to improve the safety of brachytherapy treatments, polyurethanes were used to seal the deposited radioisotopes on the surface to minimize the leakage of the isotopes into the patients. The generality of this method presented here for a wide variety of particular radioisotopic components allows design of a broad range of versatile radioisotope sources.

New approaches to preventing restenosis

For over a quarter of a century percutaneous coronary interventions have been used to treat patients with coronary artery disease, yet restenosis continues to be a problem. This review discusses the advances being made to overcome restenosis, particularly the development of drug eluting stents

Effects of beta-radiation using a holmium-166 coated balloon on neointimal hyperplasia in a porcine coronary stent restenosis model

Brachytherapy is a promising method of preventing and treating coronary stent restenosis. The present study was designed to observe the therapeutic effects of a radioactive balloon loaded with Holmium-166 ((166)Ho) in a porcine coronary stent restenosis model. A radioisotope of (166)Ho was coated onto the balloon surface using polyurethane (20 Gy at 0.5 mm depth). Stent overdilation injuries were induced in 2 coronary arteries in each pig (n=8). Four weeks after the injury, control balloon dilation was performed in one coronary artery (Group I) and radiation therapy using the (166)Ho coated balloon in the other coronary artery (Group II) in each pig. Follow-up coronary angiography and histopathologic assessment were performed at 4 weeks after the radiation therapy or the control balloon dilations. With regard to complete blood cell counts, liver function tests, lipid profiles and coagulation tests, there were no differences between the baseline and after radiation. On quantitative coronary angiographic analysis, reference and target artery diameter showed no differences between the 2 groups before, or 4 and 8 weeks after stenting. On histopathologic analysis of groups I and II, the injury score was 1.34+/-0.09 and 1.32+/-0.10, the area of internal elastic lamina was 4.99+/-0.17 mm(2) and 4.82+/-0.20 mm(2), and the luminal area was 3.20+/-0.10 mm(2) and 3.45+/-0.14 mm(2), respectively (p=NS). The neointimal area was 1.78+/-0.11 mm(2) in group I and 1.36+/-0.12 mm(2) in group II (p=0.017), and the histopathologic area of stenosis was 35.1+/-1.6% in group I and 27.6+/-1.9% in group II (p=0.005). In conclusion, beta-radiation of the stented porcine coronary artery using a radioactive (166)Ho coated balloon inhibited stent restenosis without any side effects.

Clinical outcome of percutaneous transluminal coronary rotational atherectomy in patients with end-stage renal disease

The clinical results of percutaneous transluminal coronary rotational atherectomy (PTCRA) in dialysis patients were retrospectively evaluated in comparison with coronary artery bypass grafting (CABG). From 1997 to 2001, 44 consecutive dialysis patients with 61 lesions underwent PTCRA and 55 consecutive dialysis patients underwent CABG. The initial success rate of PTCRA was 98%. The PTCRA group had a shorter hospital stay (13+/-17 vs 60+/-35 days, p=0.0001) and a lower rate of complications (11% vs 42%, p=0.001) than the CABG group. Although neither event-free survival without death nor myocardial infarction (MI) was significantly different between the CABG and PTCRA groups during the mean follow-up period of 21+/-14 months, 20 patients (45%) in the PTCRA group needed repeat revascularization of the target lesion. In conclusion, PTCRA may be a safe alternative modality for revascularization of high-risk CABG candidates, with excellent short-term results although the long-term outcome is inferior to that of CABG because of the higher restenosis rate.

Additional stenting promotes intimal proliferation and compromises the results of intravascular radiation therapy: an intravascular ultrasound study

BACKGROUND

Vascular brachytherapy (VBT) reduces in-stent restenosis (ISR). However, additional stenting at the time of radiation may be associated with a worse outcome.

METHODS AND RESULTS

Intravascular ultrasound (IVUS) was performed after VBT and at 6 months follow-up in 79 native artery ISR patients treated with gamma-radiation who participated in the Washington Radiation for In-Stent restenosis Trial (WRIST), Gamma-1, and Angiorad Radiation Technology for In-Stent restenosis Trial in Coronaries (ARTISTIC) trials. Patients were treated with (192)Ir at 14 or 15 Gy at 2 mm from the source. Additional stents were used to treat the ISR lesions in 45 patients; these patients were then compared with the 34 patients treated without restenting. Paired measurements included stent, lumen, and intimal hyperplasia volumes. After the VBT procedure, intimal hyperplasia volume was smaller in the group treated with additional stents (54 +/- 33 mm(3) vs 34 +/- 33 mm(3), P =.012), but minimal lumen area was similar between the 2 groups (4.3 +/- 1.5 mm(2) vs 4.7 +/- 1.4 mm(2) respectively, P = NS). Between the time of the VBT procedure and follow-up, intimal hyperplasia volume increased by 27 +/- 19 mm(3) in the restented group and by 9 +/- 21 mm(3) in the group treated without additional stents (P =.014). At 6 months, intimal volume was similar in the 2 groups, but minimal lumen area was slightly smaller in the group treated with additional stents (3.4 +/- 1.8 mm(2) vs 4.2 +/- 1.7 mm(2), P =.053). Patients treated with additional stents had more target lesion revascularizations than the group treated without additional stents (38% vs 15%, P =.02).

CONCLUSIONS

Additional stenting reduces intimal hyperplasia within the stents acutely. However, it compromises the benefit of VBT by promoting higher intimal regrowth within months after radiation.

Intracoronary beta-irradiation with a rhenium-188-filled balloon catheter: a randomized trial in patients with de novo and restenotic lesions

BACKGROUND

Restenosis requiring reintervention is the main limitation of coronary angioplasty. Intracoronary irradiation reduces neointimal proliferation. We studied the efficacy of a self-centering liquid rhenium-188-filled balloon catheter for coronary beta-brachytherapy.

METHODS AND RESULTS

After successful coronary angioplasty with or without stenting, 225 patients (71% de novo lesions) were randomly assigned to receive 22.5 Gy intravascular beta-irradiation in 0.5-mm tissue depth (n=113) or to receive no additional intervention (n=112). Clinical and procedural data did not differ between the groups except a higher rate of stenting in the control group (63%) compared with the rhenium-188 group (45%, P<0.02). After 6 months of follow-up, late loss was significantly lower in the irradiated group compared with the control group, both of the target lesion (0.11+/-0.54 versus 0.69+/-0.81 mm, P<0.0001) and of the total segment (0.22+/-0.67 versus 0.70+/-0.82 mm, P<0.0001). This was also evident in the subgroup of patients with de novo lesions and independent from stenting. Binary restenosis rates were significantly lower at the target lesion (6.3% versus 27.5%, P<0.0001) and of the total segment (12.6% versus 28.6%, P<0.007) after rhenium-188 brachytherapy compared with the control group. Target vessel revascularization rate was significantly lower in the rhenium-188 (6.3%) compared with the control group (19.8%, P=0.006).

CONCLUSIONS

Intracoronary beta-brachytherapy with a rhenium-188 liquid-filled balloon is safe and efficiently reduces restenosis and revascularization rates after coronary angioplasty.

Correlates of failure following treatment with Sr-90 beta irradiation for in-stent restenosis

We sought to determine the correlates of failure following intracoronary radiation therapy (IRT) with Sr-90 using the Novoste Beta-Cath system for the treatment of in-stent restenosis (ISR) in a broad range of patients. IRT has been shown to be more efficacious compared to placebo for the treatment of ISR in large randomized trials. However, even in patients treated with IRT, major adverse cardiac events occur in approximately 20% of cases on follow-up. This trial sought to elucidate the correlates of failure following successful IRT for ISR. To determine the correlates of IRT failure, we retrospectively compared the demographics, lesion characteristics, and clinical outcomes of 102 consecutive patients with ISR treated with Sr-90 from September 1998 to July 2001. IRT failure was defined as death, myocardial infarction (MI), or target vessel revascularization (TVR) due to repeat ISR on follow-up. A comparison of the clinical and angiographic profile of IRT failures (n = 16) vs. IRT successes (n = 86) revealed that a history of smoking (75% vs. 40%; P = 0.012), current use of calcium channel blockers (84% vs. 45%; P = 0.013), ostial location of target lesion (44% vs. 16%; P = 0.020), and mean posttreatment minimal luminal diameter (MLD; 1.64 +/- 0.19 vs. 2.21 +/- 0.29 mm; P < 0.001), respectively, were correlated with failure using univariate analysis. After multivariate regression analysis, the correlates of failure that remained significant were treatment of an ostial lesion (OR = 31.2; 95% CI = 2.6-382.7; P = 0.007) and final posttreatment MLD (P < 0.001). Ostial location of target lesion and smaller posttreatment MLD are correlated with subsequent death, MI, and TVR following therapy with Sr-90 for ISR.

[Intracoronary brachytherapy: a meta-analysis]

Intracoronary brachytherapy aims at a reduction of in-stent restenosis by lessening neo-intimal proliferation. To assess its clinical potential, a systematic review of the literature indexed in the standard biomedical bibliographic databases selected eight prospective randomized clinical trials; seven of them, comparing coronary brachytherapy and non-treatment or placebo, have been included in the present meta-analysis. This analysis confirms the angiographic benefit of this procedure, as reported in the individual studies; it also shows, however an excess of clinical adverse effects not exhibited by any individual trial. Therefore, intracoronary brachytherapy cannot be recommended as routine practice, while one cannot rule out its interest in special situations.

Clinical and angiographic acute and follow up results of intracoronary beta brachytherapy in saphenous vein bypass grafts: a subgroup analysis of the multicentre European registry of intraluminal coronary beta brachytherapy (RENO)

OBJECTIVE

To assess clinically and angiographically the feasibility, safety, and effectiveness of vascular brachytherapy (VBT) in saphenous vein bypass grafts (SVG).

PATIENTS AND METHODS

67 of 1098 (6.1%) consecutive patients of the European registry of intraluminal coronary beta brachytherapy underwent treatment for 68 SVG lesions by VBT using a Sr/Y(90) source train (BetaCath). Clinical follow up data were obtained for all of them after a mean (SD) of 6.3 (2.4) months and angiographic follow up was performed in 61 patients (91.0%) after 6.9 (2.0) months.

RESULTS

58 (86.6%) patients were men, their mean (SD) age was 66 (10) years, 28 (41.8%) had unstable angina, and 21 (31.3%) had diabetes. Fifty three (77.9%) lesions were in-stent restenosis, 13 (19.1%) de novo lesions, and 2 (3.0%) non-stented restenotic lesions. Mean (SD) reference diameter before the intervention was 4.19 (0.52) mm, mean (SD) lesion length was 23.56 (20.38) mm, and mean (SD) minimum lumen diameter measured 0.73 (0.62) mm. Mean (SD) acute gain was 3.02 (0.88) mm. The prescribed radiation dose was 20.1 (3.2) Gy. Pullback manoeuvres were performed in 17 (25.0%) of cases. Most patients received combined aspirin and thienopyridin treatment for 6 or 12 months after the procedure. Technical success was obtained in 62 (91.2%) treated lesions and in-hospital major adverse cardiac events occurred in 4.5%. At follow up, mean (SD) reference diameter was 4.20 (0.53) mm, minimum lumen diameter 2.94 (1.50) mm, and late loss 0.86 (1.25) mm. The overall major adverse cardiac events rate was 26.7%.

CONCLUSION

VBT of SVG is feasible and safe. At follow up the reintervention rate and cardiac morbidity and mortality seem to be favourable, considering that interventions in SVG usually are associated with the highest risks.

Endovascular brachytherapy after percutaneous transluminal angioplasty of recurrent femoropopliteal obstructions

PURPOSE

To test the preventive effect of endovascular brachytherapy (EVBT) on restenosis following secondary angioplasty in patients with presumed neointimal restenosis in the femoropopliteal segment.

METHODS

From March 1997 through May 2000, 100 patients (58 men; mean age 70 years, range 45-87) with postangioplasty femoropopliteal segment restenoses were enrolled and randomized to treatment with repeat angioplasty and EVBT (n=51) or to angioplasty alone (n=49) as control. The groups were similar with regard to demographics and lesion characteristics. High-dose-rate EVBT was performed with (192)Ir irradiation without a centering device (12 Gy for a reference vessel radius of 3 mm and a 2-mm reference depth). Primary endpoint in the 1-year follow-up was recurrent obstruction >50% documented by duplex ultrasound; the secondary endpoint was clinical improvement.

RESULTS

Only 44 (86%) of 51 patients received adequate EVBT due to technical failure, so the 7 failures were included with the controls in the per-protocol adherence analysis. At 1 year, the patients receiving EVBT had a restenosis rate of 23% (10/44), which differed significantly (p<0.028) from the 42% (23/56) rate in controls. Clinical results tended to be better with EVBT, but differences did not achieve statistical significance.

CONCLUSIONS

EVBT without a centering device reduced restenosis significantly in patients with recurrent stenosis after angioplasty, which confirms previous results in primary long-segment femoropopliteal obstructions.

Beta emitter systems and results from clinical trials

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

Reno, a European postmarket surveillance registry, confirms effectiveness of coronary brachytherapy in routine clinical practice

PURPOSE

To assess, by a European registry trial, the clinical event rate in patients with discrete stenotic lesions of coronary arteries (de novo or restenotic) in single or multiple vessels (native or bypass grafts) treated with beta-radiation.

MATERIALS AND METHODS

Between April 1999 and September 2000, 1098 consecutive patients treated in 46 centers in Europe and the Middle East with the Novoste Beta-Cath System were included in Registry Novoste (RENO).

RESULTS

Six-month follow-up data were obtained for 1085 patients. Of 1174 target lesions, 94.1% were located in native vessels and 5.9% in a bypass graft; 17.7% were de novo lesions, 4.1% were restenotic, and 77.7% were in-stent restenotic lesions. Intravascular brachytherapy was technically successful in 95.9% of lesions. Multisegmental irradiation, using a manual pullback stepping maneuver to treat longer lesions, was used in 16.3% of the procedures. The in-hospital rate of major adverse cardiac events was 1.8%. At 6 months, the rate was 18.7%. Angiographic follow-up was available for 70.4% of the patients. Nonocclusive restenosis was seen in 18.8% and total occlusion in 5.7% of patients. A combined end point for late (30-180 days) definitive or suspected target vessel closure was reached in 5.4%, but with only 2% of clinical events. Multivariate analysis was performed for major adverse cardiac events and late thrombosis.

CONCLUSIONS

Data obtained from the multicenter RENO registry study, derived from a large cohort of unselected consecutive patients, suggest that the good results of recent randomized controlled clinical trials can be replicated in routine clinical practice.

[Computer-assisted reconstruction of coronary vessels]

End stage coronary artery disease with linear stenosis of the main vessels despite several coronary interventions is a current challenge for surgical treatment. As the long term results are mainly determined by the pathology of the coronary vessels a simple revascularisation with arterial or venous grafts provides no adequate solution of the problem. An exactly controlled 3D-reconstruction of the coronary vessels enabling selective thrombendarteriectomy (TEA) seems to be a new approach, that may be limited by neointimal hyperproliferation of the coronary vessels. Intraoperative brachytherapy may be a tool to inhibit this process.

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.

[Brachytherapy for coronary restenosis: state of art in 2003]

Based on therapeutic approach for benign diseases, vascular brachytherapy decreases smooth vascular muscle cells proliferation and multiplication which lead to the formation of the neo-intima. The radioactive positive action affects arterial recoil due to post angioplasty vessel injury. Randomised studies has shown good angiographic results up to 6 months of follow-up, with 50% in-stent restenosis rate decrease and on the analysed segment as well. Decrease on Mace and TLR show statistically significance. Results don't correlate with emitter and bêta emitters had been introduced in France recently. Vascular brachytherapy is actually indicated for in-stent restenosis, there is no evidence to perform this treatment for de novo lesion. Geographic miss, source centering, late thrombosis and pullback procedure may interfere with treatment quality. IVUS allows best target volume determination to a higher quality level. Internationals guidelines such as Eva-Gec-Estro recommendations could increase treatment safety and enable development of an optimal technique.

Improved outcome with novel device for low-pressure PTCA in de novo and in-stent lesions

PURPOSE

Complex lesion morphology requiring the use of high pressure to effect lumen expansion and in-stent restenosis (ISR) remain two indications that challenge conventional PTCA balloons. We report on a new PTCA device that is designed to provide precise, low-pressure dilatation of both de novo and in-stent lesions.

METHODS

The FX miniRAIL catheter (FX) has an integral wire positioned external to a dilating balloon and a short, 12-mm guidewire lumen distal to the balloon. The balloon inflates against the guidewire and the external wire to prevent slippage and to introduce high focal longitudinal stresses at low inflation pressures. In this initial study, the FX was used in 37 lesions (25 de novo, 12 in-stent; vessel reference diameter=2.73+/-0.49 mm) in 30 patients. A stepwise inflation protocol and QCA were used to determine the balloon pressure at which the stenosis was resolved (stenosis resolution pressure, SRP).

RESULTS

All lesions (100%) were easily reached, crossed and dilated without complication. The SRP was 4.5+/-2.9 atm, and no balloon slippage was observed. Residual stenosis after FX was 26.39+/-13.29%. Minor dissections (Types A and B) were observed in eight lesions (21.6%). Target lesion revascularization (TLR) and target vessel revascularization (TVR) at follow-up (8.1+/-1.5 months) were 8.3% and 12.5%, respectively.

CONCLUSION

The design of the FX is versatile and appears to provide for a safe, effective and improved low-pressure PTCA technique in de novo and in-stent lesions.

Predictors of late cardiac events following treatment with Sr-90 beta-irradiation for instent restenosis

BACKGROUND

Intracoronary radiation therapy (IRT) with Sr-90 using the Novoste Beta-Cath system has been shown to be an effective therapy for instent restenosis (ISR), but the temporal occurrence of cardiac events and the predictors of late complications require further investigation.

METHODS

We analyzed the demographics, lesion characteristics and clinical outcomes of 138 consecutive patients with ISR treated with IRT from September 1998 to March 2002. Major adverse cardiac events (MACE) were defined as death, myocardial infarction (MI) or target vessel revascularization (TVR). Characteristics of early (< or =8 months) and late (>8 months) failures were analyzed.

RESULTS

Thirty-two (23.1%) of 138 patients had MACE on follow-up; 25% (8/32) of failures occurred late after treatment with IRT. A comparison of the clinical and angiographic profile of early and late failures using univariate analysis indicates no correlations to late failure following IRT. Duration to failure after IRT was 14.25+/-3.69 months in the late group compared to 4.63+/-2.86 months in the early group (P<.001).

CONCLUSIONS

Late MACE after IRT with Sr-90 for ISR occur beyond the traditional period for clinical restenosis in 25% of cases and are difficult to predict. Further study is warranted to identify patients at risk for the development of late complications after IRT.

Beta-radiation therapy for long lesions in native coronary vessels: a matched comparison between de novo and in-stent restenotic lesions

OBJECTIVE

The purpose of this study was to evaluate effectiveness and to compare clinical outcome of intracoronary beta-radiation to treat long lesions (>20 mm) in patients with de novo stenosis vs. patients with in-stent restenosis (ISR).

METHODS

A matched comparison of 44 patients with 63 de novo lesions and 48 patients with 63 ISR lesions (>20 mm) treated with intracoronary beta-radiation was performed.

RESULTS

Stents were implanted in 65.1% of de novo and 19% of ISR lesions (P=.001). Radiation doses delivered were 17.2+/-3.0 vs. 20.3+/-3.0 Gy at 2 mm from the source center for de novo and ISR lesions. There was no difference in the incidence of in-hospital events. Clinical follow-up at 16.4+/-6.7 months showed no difference in major adverse cardiac events (MACE) between de novo and ISR patients (27.3% vs. 25%, P=.8). Late total occlusions (LTOs) occurred in eight patients (four in each group) treated with stents at the time of radiation and after discontinuation of ticlopidine. By multivariate analysis, stent implantation was the only predictor of late occlusions (OR 8.25, 95% CI 1.73-38.46, P<.008). Restenosis rates were similar for de novo and ISR lesions (29.3% vs. 23.2%, P=.46), as well as target lesion revascularization (TLR) and target vessel revascularization (TVR) rates (22.7% vs. 22.9% and 29.5% vs. 29.2%, respectively).

CONCLUSIONS

Intracoronary beta-radiation gives comparable results when used to treat de novo or ISR lesions provided new stent implantation can be avoided. Long-term combined antiplatelet therapy is mandatory for patients who receive new stents at the time of radiation treatment.

Effects of brachytherapy on intimal hyperplasia in arteriovenous fistulas in a porcine model

PURPOSE

The hypotheses of this investigation were that endovascular radiation would reduce intimal hyperplasia in arteriovenous fistulas (AVFs) and that this reduction would be associated with decreased expression of vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF)-A, and tumor necrosis factor (TNF)-alpha.

MATERIALS AND METHODS

Bilateral end jugular vein-to-side carotid artery fistulas were constructed in pigs. At 48 hours, one AVF was randomly selected for endovascular radiation with (192) Iridium. The contralateral fistula received no radiation and served as a control. Animals in group 1 (n = 7) received 14 Gy of radiation at a depth of 2 mm and tissue was harvested at 29 days; animals in group 2 received 7 Gy of radiation at a depth of 2 mm and tissue was harvested at 29 days (n = 8); and animals in group 3 received 7 Gy of radiation at a depth of 2 mm and tissue was harvested at 56 days (n = 8). The area and maximum thickness of intimal hyperplasia were then measured blindly. Immunohistochemical results for VEGF, PDGF-A, and TNFalpha were obtained and analyzed blindly by assigning a score of 0-3, with 0 indicating no staining and 3 indicating maximum staining.

RESULTS

Irradiation with 14 Gy caused severe fibrosis in the media of the vein, with thrombosis of three of seven AVFs. Compared with the control group, the group that underwent irradiation with 7 Gy had significantly reduced intimal area at 56 days (9.9 mm(2) +/- 4.9 vs 2.1 mm(2) +/- 1.1; P =.001). This reduction correlated with significant reduction in the expression of VEGF (score of 2.2 +/- 0.1 vs 1.2 +/- 0.2; P =.001) and TNFalpha (1.3 +/- 0.1 vs 0.9 +/- 0.1; P =.04).

CONCLUSION

Fourteen grays is an excessive radiation dose for veins, causing medial fibrosis and thrombosis of the AVF. Irradiation with 7 Gy effectively inhibited the formation of intimal hyperplasia in AVF. This inhibition correlated with decreased expression of VEGF and TNFalpha.

Dosimetric comparison between high-precision external beam radiotherapy and endovascular brachytherapy for coronary artery in-stent restenosis

PURPOSE

Several drawbacks of endovascular brachytherapy for the treatment of coronary artery in-stent restenosis may be addressed by high-precision external beam radiotherapy (EBRT). The dosimetric characteristics of both treatment techniques were compared.

METHODS AND MATERIALS

The traversed volume of 10 coronary artery stents during the cardiac cycle was determined by electrocardiographically gated multislice spiral CT in 10 patients. By use of this traversed volume, high-precision EBRT treatment plans were generated for stents in the left circumflex (LCx), left anterior descending (LAD), and right coronary artery (RCA). The maximum dose to the nontargeted major coronary arteries was determined and compared to similar data calculated for endovascular brachytherapy.

RESULTS

High-precision EBRT targeted at LCx stents contributed a mean maximum dose (D(max)) of 83.5% (range: 71.6-95.3%) and 16.3% to the LAD and RCA, respectively. Targeted LAD stents contributed a mean D(max) of 39.3% (range: 14.5-94.8%) and 5.2% (range: 0-13.4%) to the LCx and RCA, respectively. Targeted RCA stents contributed a mean D(max) of 6.2% (range: 0-12.4%) and 5.8% (range: 0-11.5%) to the LCx and LAD, respectively. Endovascular brachytherapy targeted at LCx stents contributed a mean D(max) of 1.7% (range: 0.7-2.7%) and 1.0% (range: 0.6-1.4%) to the LAD and RCA, respectively. Targeted LAD stents contributed a mean D(max) of 5.2% (range: 0.5-11.4%) and 0.7% (range: 0.4-1.1%) to the LCx and RCA, respectively; targeted RCA stents contributed a mean D(max) of 0.3% (range: 0.2-0.5%) and 0.2% (range: 0.1-0.3%) to the LCx and LAD, respectively.

CONCLUSIONS

Although the doses distributed throughout the heart were higher for high-precision EBRT compared to endovascular brachytherapy, they are expected to be clinically irrelevant when nontargeted major coronary arteries are not closely situated to the targeted vessel segment. These encouraging results warrant further investigation of high-precision EBRT as a potential alternative to endovascular brachytherapy for the treatment of coronary artery in-stent restenosis.

Delivered dose and vascular response after beta-radiation for in-stent restenosis: retrospective dosimetry and volumetric intravascular ultrasound analysis

BACKGROUND

Observations from previous intracoronary radiation therapy trials noted a considerable discrepancy between the prescribed radiation dose and the dose actually delivered. The aims of this study were to investigate the effect of actual delivered dose on vascular changes and to test the appropriateness of the current dose prescription.

METHODS AND RESULTS

Serial volumetric intravascular ultrasound (IVUS) analysis was performed in 30 in-stent restenosis cases treated with a 40-mm (90)Sr/Y source train. The fixed dose was prescribed at 2 mm from the centerline of the source train (18.4 Gy at 2 mm for reference diameter < or =3.35 mm and 23 Gy for diameter > or =3.36 mm). Only stent segments with full radiation coverage and device injury were enrolled and divided into 2-mm-long subsegments (n=202). D(S90)EEM (the minimum dose absorbed by 90% of the external elastic membrane surface) was calculated as the delivered dose corresponding to each segment, assuming that the radiation catheter occupied the same position in the vessel as the IVUS catheter. Mean D(S90)EEM of 23.5+/-5.82 Gy (range 12.3 to 41.7 Gy) was delivered to these subsegments. Overall, intimal hyperplasia volume remained constant from postintervention to follow-up (2.23+/-1.10 to 2.32+/-1.09 mm3/m; P=NS). Regression analysis revealed there was no correlation between delivered dose intensity and changes in intimal hyperplasia volume. No particular dose-dependent complications were appreciated in this delivered dose range.

CONCLUSIONS

The current dose-prescription protocol of (90)Sr/Y radiation to native in-stent restenosis lesions may provide substantial inhibition of neointimal reproliferation regardless of the actual delivered dose intensity.

How to fix the edge effect of catheter-based radiation therapy in stented arteries

BACKGROUND

Edge stenosis remains a serious limitation of catheter-based vascular brachytherapy (VBT). This study aims to identify the mechanisms and evaluate strategies to minimize edge restenosis in patients treated with VBT.

METHODS AND RESULTS

Thirty-four porcine stented coronary arteries were irradiated (doses of 15 or 22 Gy) with (192)Ir trains of either 6 seeds (23 mm) with 0 mm coverage at the distal stent edge and 10 mm at the proximal stent edge or 14 seeds (55 mm) centered at the distal edge of the stent with 27.5 and 14.5 mm coverage at the distal and proximal edges, respectively. After VBT, an additional 13-mm stent was positioned overlapping the distal margin of the first stent. Animals were killed at 28 days, and arteries were analyzed. Longer radiation margins were associated with reduced intimal area (IA) at the stent edge: 2.3+/-0.9, 3.6+/-2.0, and 5.3+/-2.2 mm(2) with 15 Gy for a radiation margin of 14.5, 10, and -13 mm (-13 versus 10, P=0.06; 10 versus 14.5, P=0.06). Additional stenting was associated with an increase of IA: 4.0+/-2.3 mm(2) at the overlapped segment. Increasing the dose to 22 Gy resulted in a reduction of the IA at the overlap segment to 1.31+/-0.57 mm(2) with 14 seeds (27.5 mm coverage) but was not helpful with 6 seeds (0 mm coverage): IA, 5.56+/-2.28 mm(2).

CONCLUSIONS

Extending the radiation margins to 14.5 mm from each end of the stent minimized the edge-effect phenomenon. A higher dose is essential to eliminate further increases in IA at the overlapped segment with additional stents.

Comparative survival of dialysis patients in the United States after coronary angioplasty, coronary artery stenting, and coronary artery bypass surgery and impact of diabetes

BACKGROUND

The optimal method of coronary revascularization in dialysis patients is controversial. The purpose of this study was to compare the long-term survival of dialysis patients in the United States after PTCA, coronary stenting, or CABG.

METHODS AND RESULTS

Dialysis patients hospitalized from 1995 to 1998 for first coronary revascularization procedures after renal replacement therapy initiation were identified from the US Renal Data System database. All-cause and cardiac survival was estimated by the life-table method and compared by the log-rank test. The impact of independent predictors on survival was examined in a Cox regression model. The in-hospital mortality was 8.6% for 6668 CABG patients, 6.4% for 4836 PTCA patients, and 4.1% for 4280 stent patients. The 2-year all-cause survival (mean+/-SEM) was 56.4+/-1.4% for CABG patients, 48.2+/-1.5% for PTCA patients, and 48.4+/-2.0% for stent patients (P<0.0001). After comorbidity adjustment, the relative risk (RR) for CABG (versus PTCA) patients was 0.80 (95% CI 0.76 to 0.84, P<0.0001) for all-cause death and 0.72 (95% CI 0.67 to 0.77, P<0.0001) for cardiac death. For stent (versus PTCA) patients, the RR was 0.94 (95% CI 0.88 to 0.99, P=0.03) for all-cause death and 0.92 (95% CI 0.85 to 0.99, P=0.04) for cardiac death. In diabetic (versus PTCA) patients, the RR for CABG surgery was 0.81 (95% CI 0.75 to 0.88, P<0.0001) for all-cause death and 0.71 (95% CI 0.64 to 0.78, P<0.0001) for cardiac death, and the RR for the stent procedure was 0.99 (95% CI 0.91 to 1.08, P=NS) for all-cause death and 0.99 (95% CI 0.89 to 1.11, P=NS) for cardiac death.

CONCLUSIONS

In this retrospective study, dialysis patients in the United States had better long-term survival after CABG surgery than after percutaneous coronary intervention. Stent outcomes were relatively worse in diabetic patients. Our data support the need for large clinical registries and prospective trials of surgical and percutaneous coronary revascularization procedures in dialysis patients.

Pathophysiological effects of radiation on atherosclerosis development and progression, and the incidence of cardiovascular complications

Radiation therapy while important in the management of several diseases, is implicated in the causation of atherosclerosis and other cardiovascular complications. Cancer and atherosclerosis go through the same stages of initiation, promotion, and complication, beginning with a mutation in a single cell. Clinical observations before the 1960s lead to the belief that the heart is relatively resistant to the doses of radiation used in radiotherapy. Subsequently, it was discovered that the heart is sensitive to radiation and many cardiac structures may be damaged by radiation exposure. A significantly higher risk of death due to ischemic heart disease has been reported for patients treated with radiation for Hodgkin's disease and breast cancer. Certain cytokines and growth factors, such as TGF-beta1 and IL-1 beta, may stimulate radiation-induced endothelial proliferation, fibroblast proliferation, collagen deposition, and fibrosis leading to advanced lesions of atherosclerosis. The treatment for radiation-induced ischemic heart disease includes conventional pharmacological therapy, balloon angioplasty, and bypass surgery. Endovascular irradiation has been shown to be effective in reducing restenosis-like response to balloon-catheter injury in animal models. Caution must be exercised when radiation therapy is combined with doxorubicin because there appears to be a synergistic toxic effect on the myocardium. Damage to endothelial cells is a central event in the pathogenesis of damage to the coronary arteries. Certain growth factors that interfere with the apoptotic pathway may provide new therapeutic strategies for reducing the risk of radiation-induced damage to the heart. Exposure to low level occupational or environmental radiation appears to pose no undue risk of atherosclerosis development or cardiovascular mortality. But, other radiation-induced processes such as the bystander effects, abscopal effects, hormesis, and individual variations in radiosensitivity may be important in certain circumstances.

Determination and application of the reference isodose length (RIL) for commercial endovascular brachytherapy devices

BACKGROUND AND PURPOSE

During the last years endovascular brachytherapy has been established as a new field in radiotherapy. In a recent recommendation of the EndoVAscular, Groupe Européen de Curiethérapie, European Society for Therapeutic Radiation Oncology, Working Group the reference isodose length (RIL) has been introduced as a central parameter for treatment planning. It is defined as the vessel length at the reference depth enclosed by the 90% isodose. The dose is normalized to 100% at the reference depth (i.e. lumen radius plus 1 mm into the vessel wall) at the central plane. In order to avoid a geographic miss the clinical target length has to be encompassed by the RIL.

MATERIAL AND METHODS

RILs are determined by Monte Carlo calculations and GafChromic film dosimetry for three endovascular brachytherapy devices currently in clinical use (192Ir seed ribbon, 32P wire source, 90Sr seed train). For all measurements, phantoms and devices the sensitive layer of GafChromic film is located in a plane at 2+/-0.1 mm parallel to the axis of the source delivery catheter. The EGSnrc code system is applied to calculate the dose profile at 2 and 3 mm distance from the source axis.

RESULTS

For the ten seed 192Ir source calculated RIL at 2 mm radial distance is 30.2 mm whereas the measured RIL is 33.5 mm. In case of a 20 mm 32P wire source with two steps the calculated RIL of 36.6 mm shows excellent agreement compared with the measured value of 36.2 mm. The calculated RIL of a 40 mm 90Sr seed train was 35.8 mm compared to a measured value of 34.8 mm.

CONCLUSION

As a compromise between calculated and measured RIL values at 2 and 3 mm radial distances we propose to use a RIL of 30 mm for the 192Ir ten seed ribbon, 36 mm for the32P wire source with two steps and 35 mm for the 40 mm 90Sr seed train. These parameter values can be used to define the maximum intervention length for endovascular sources.

Randomized trial of 90Sr/90Y beta-radiation versus placebo control for treatment of in-stent restenosis

BACKGROUND

After conventional treatment of in-stent restenosis, the incidence of recurrent clinical restenosis may approach 40%. We report the first multicenter, blinded, and randomized trial of intracoronary radiation with the use of a 90Sr/90Y beta-source for the treatment of in-stent restenosis.

METHODS AND RESULTS

After successful catheter-based treatment of in-stent restenosis, 476 patients were randomly assigned to receive an intracoronary catheter containing either 90Sr/90Y (n=244) or placebo (n=232) sources. The prescribed dose 2 mm from the center of the source was 18.4 Gy for vessels between 2.70 and 3.35 mm in diameter and 23.0 Gy for vessels between 3.36 and 4.0 mm. The primary end point, ie, clinically driven target-vessel revascularization by 8 months, was observed in 56 (26.8%) of the patients assigned to placebo and 39 (17.0%) of the patients assigned to radiation (P=0.015). The incidence of the composite including death, myocardial infarction, and target-vessel revascularization was observed in 60 (28.7%) of the patients assigned to placebo and 44 (19.1%) of the patients assigned to radiation (P=0.024). Binary 8-month angiographic restenosis (> or =50% diameter stenosis) within the entire segment treated with radiation was reduced from 45.2% in the placebo-treated patients to 28.8% in the 90Sr/90Y-treated patients (P=0.001). Stent thromboses occurred in 1 patient assigned to placebo <24 hours after the procedure and in 1 patient assigned to 90Sr/90Y at day 244.

CONCLUSIONS

The results of this study demonstrated that beta-radiation using 90Sr/90Y is both safe and effective for preventing recurrence in patients with in-stent restenosis.

Endovascular gamma irradiation of femoropopliteal de novo stenoses immediately after PTA: interim results of prospective randomized controlled trial

PURPOSE

To report an interim analysis of whether centered endovascular irradiation with the iridium 192 ((192)Ir) source immediately after percutaneous transluminal angioplasty (PTA) of de novo femoropopliteal stenoses lowers the restenosis rate.

MATERIALS AND METHODS

Thirty patients undergoing PTA to treat femoropopliteal stenoses were randomized for prophylaxis against restenosis with centered endovascular irradiation with a (192)Ir source (a dose of 14 Gy 2 mm deep to the vessel wall, irradiation group) or no irradiation (control group). Angiographic follow-up was available for 22 patients at 6 months (irradiation group, n = 10) and 12 patients at 12 months (irradiation group, n = 6). Duplex sonography, treadmill testing, and interviews were performed the day before and the day after PTA and after 1, 3, 6, 9, and 12 months. Results of angiography, duplex sonography, treadmill testing, and interviews were evaluated with a t test and multivariate analysis of variance (clinical characteristics, chi(2) test).

RESULTS

Baseline characteristics were comparable in the two groups. Interim analysis of the 6-month follow-up data revealed a trend toward a significantly lower restenosis rate in the irradiation group. The change in the degree of stenosis compared with that after PTA was -14.7% +/- 20.8 (mean +/- SD) in the irradiation group versus 37.7% +/- 27.3 in the control group (P =.001) and became even more marked at 12 months (-9.5% +/- 34.5 vs 45.5% +/- 40.7 [P =.03], respectively). The follow-up results of treadmill testing and interviews showed a nonsignificant benefit for the irradiation group. One thromboembolic complication occurred during irradiation. No side effects were observed during follow-up.

CONCLUSION

Endovascular irradiation with a centered (192)Ir source immediately after PTA of de novo femoropopliteal stenoses reduces the restenosis rate.

Coronary artery brachytherapy

Coronary artery disease is the leading cause of mortality in the West with over 1.2 million angioplasties performed annually. Despite the introduction of stents, restenosis occurs in 30-40% of vessels, which until recently has only been treated effectively by coronary artery bypass surgery. Coronary artery brachytherapy appears to provide an alternative, less invasive remedy. The mechanisms of restenosis and how these are inhibited by radiation are described here. The practicalities of radiation delivery and the history of the development of intravascular radiation as an effective clinical tool are outlined. Finally, the pitfalls of the current technology and the areas in which future research must be targeted for the field to develop are discussed.

Two-year angiographic follow-up of intracoronary Sr90 therapy for restenosis prevention after balloon angioplasty

BACKGROUND

Postcoronary angioplasty vascular brachytherapy (VBT) has emerged as a successful intervention for restenosis prevention in some clinical scenarios. Longer-term follow-up after VBT in de novo nonstented lesions has not been reported.

METHODS AND RESULTS

Thirty patients treated with post-percutaneous transluminal coronary angioplasty (PTCA) VBT with Sr90 underwent clinical and angiographic follow-up at 6 and 24 months. Specific vessel segment quantitative coronary angiographic analyses were performed to identify radiation edge effects. Nineteen patients who had not undergone index procedure stenting or target vessel revascularization (TVR) over the 2-year period were analyzed separately. Of the 30 patients, 3 underwent TVR by 6-month follow-up. An additional 4 patients required TVR between 6 and 24 months. In the total cohort of 26 patients undergoing angiographic follow-up at 6 and 24 months, an increase in minimal lumen diameter of the initial target segment was noted at 6 months compared with postprocedure analysis (2.31+/-0.48 versus 2.04+/-0.43 mm, P<0.05). At 24 months, this was no longer significant (2.19+/-0.61 mm). In the proximal segments of the entire cohort and the nonintervened subgroup, the principal late loss occurred over the first 6 months with no additional late loss at 2-year follow-up. The distal segments remained stable over the entire follow-up period.

CONCLUSIONS

Although some late failures of post-PTCA VBT are seen between 6 and 24 months, most treated vessels remain stable with no late loss or additional luminal increase beyond the 6-month period. This suggests that late aneurysm formation and significant late edge restenosis are unlikely in VBT after PTCA of de novo lesions for up to 2 years.

Geographical miss and restenosis during catheter-based intracoronary beta-radiation for de novo lesions

OBJECTIVES

We sought to determine the impact of geographical miss (GM) on restenosis rates after intracoronary beta-radiation therapy for de novo lesions.

BACKGROUND

GM is the situation in which injured vessel segments (VSs) are receiving low-dose radiation and is accounted for edge restenosis. Its impact on the overall restenosis rates remains to be determined.

METHODS

We analyzed 330 patients (356 vessels) treated according to the Beta Radiation in Europe (BRIE) and the Dose Finding study protocols. Using quantitative coronary angiography (QCA), the effective irradiated segment (EIRS), its edges and the total VS were analysed. The edges of the EIRS that were injured constituted the GM edges. Restenosis was defined as diameter stenosis > 50% at follow-up. GM was determined by the simultaneous electrocardiographic-matched, side-by-side projection of the source and balloons deflated and surrounded by contrast, at the site of injury, in identical angiographic projections.

RESULTS

In 20.5% of the vessels, GM was non-interpretable due to inadequate filming. GM occurred at 30.4% of the interpretable edges and 53% of the interpretable vessels that were analysed. Edge restenosis was significantly increased in the GM compared to non-GM edges (13.16% vs. 4.17%, respectively, P = .001), both in the proximal (P = .03) and the distal (P = .001) edges. GM associated with stent injury significantly increased edge restenosis (P = .006). GM related to balloon injury tended to be associated with increment in edge restenosis (P = .07). The restenosis in the EIRS was similar between vessels with and without GM (17.78% and 14.85%, respectively, P = .6). GM was associated with significant increment in the restenosis at the analyzed VS (31.85% vs. 21.48%, P = .05).

CONCLUSIONS

GM is strongly associated with edges and restenosis in the analysed VS. GM does not increase restenosis in the EIRS.

Dose distributions for 90Y intravascular brachytherapy sources used with balloon catheters

The dose distribution around an intravascular brachytherapy 90Y line source with centering balloon catheters was measured with a plastic scintillator, TLD and radiochromic film. The absolute dose rates measured with the three detectors in a solid water phantom at 1, 2 and 3 mm distance from the centering balloon surfaces are in agreement within 3.5%, when the detectors are calibrated with the same 90Sr/90Y source. The dose rates measured with the plastic scintillator in the solid water phantom are in agreement with those directly measured in water. The measured relative dose distributions can be reproduced by Monte Carlo calculations. Also, the influence of the balloon diameter on the dose rate can be reproduced by the calculations. The dose rate calibration routinely performed with the plastic scintillator was checked for fifty-one sources with a well chamber and with another dedicated dose rate checking device. These measurements show that the consistency of the calibration of these sources was better than 10%. In a previous paper absolute dose rates for five other 90Y sources measured with TLD and radiochromic film in a solid water phantom were compared with those obtained with the plastic scintillator in water [Piessens and Reynaert, "Verification of absolute dose rates for intravascular beta sources," Phys. Med. Biol. 45, 2219-2231 (2000)]. Differences of 25 to 41%, depending on the balloon diameter, were reported. In this paper we show the evidence for three main reasons for these previously observed discrepancies: an inconsistency between a detector calibration performed with a 6 MeV electron beam and with a calibrated 90Sr/90Y source from NIST (16%), inaccuracies of the measuring distances in the solid water phantom (maximum 7.5%) and a time instability of the plastic scintillator, probably due to radiation damage (6%).

Visual assessment of procedural results following treatment with Sr-90 beta-radiation for instent restenosis

BACKGROUND

Visual assessment (VA) of postprocedural % diameter stenosis (DS) is used routinely in clinical practice to determine the adequacy of coronary intervention. Although VA has been shown to underestimate final %DS after balloon angioplasty compared to quantitative coronary angiography (QCA), the impact of this effect on clinical outcomes following treatment with intracoronary radiation therapy (IRT) with Sr-90 for instent restenosis (ISR) is unknown.

METHODS

To determine the effect of VA on the rate of major adverse cardiac events (MACEs) after IRT for ISR, we compared the clinical outcomes of 102 consecutive patients based on postprocedural %DS by QCA vs. %DS by VA. MACE was defined as death, M1 or need for target vessel revascularization (TVR).

RESULTS

MACE rates for the 102 consecutive patients grouped according to postprocedural %DS by QCA and VA were compared. The mean %DS by QCA was 30.7%, while the mean %DS by VA was 12.5%. The mean %DS by VA across the QCA subgroups were 13.67%, 10.71% and 13.37%, respectively (P = .244). Fifty-two patients (51.0%) had %DS > 30% by QCA with the highest MACE percentage occurring in this subgroup.

CONCLUSION

VA underestimated the %DS compared to QCA, and it was associated with worse MACE following treatment with Sr-90 for ISR.

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).

The "shielding" effect of the guide wire during coronary brachytherapy with P-32 source

Intracoronary beta irradiation (use of beta radiation for intracoronary irradiation) is an effective method in reducing neointimal proliferation after successful angioplasty and stent implantation. However, long-term results may be influenced by absolute dose and by the homogeneity in dose distribution. In our study, we investigated dose perturbation due to the presence of a conventional guide wire during irradiation. The Galileo III centering catheter and P-32 beta source were used. The 55 MD GAF Chromic foil was positioned within a phantom made of PMMA. The dose distribution at cylindrical surfaces has been assessed using GAF Chromic dosimetric foil MD55 (Nuclear Associates, USA). Our study demonstrated the significant dose reduction of 46% in the most "shaded" area. The dose reduction to 80% or less occupy the 60 degrees sector. This phenomenon can cause progression of late restenosis. In conclusion, the results suggest that technical improvements in centering catheter construction should be made to eliminate the "shielding" effect of the guide wire.

Dose heterogeneity may not affect the neointimal proliferation after gamma radiation for in-stent restenosis: a volumetric intravascular ultrasound dosimetric study

OBJECTIVES

The goal of this study was to use serial (postirradiation and follow-up) volumetric intravascular ultrasound (IVUS): 1) to evaluate the actual distribution of gamma radiation in human in-stent restenosis (ISR) lesions, and 2) to analyze the relationship between neointimal regrowth and the delivered radiation dose.

BACKGROUND

The relationship between the neointimal regrowth and delivered dose during the treatment of ISR remains unknown.

METHODS

We analyzed 20 actively (gamma emitter) treated, native artery ISR patients from the Washington Radiation for In-Stent restenosis Trial (WRIST) that met the following criteria: on both postirradiation and six-month follow-up IVUS imaging, > or =80% of the external elastic membrane circumference could be identified throughout the treated length including the lesion and proximal and distal reference segments. Intravascular ultrasound images were digitized every 1 mm. Proximal and distal reference and stented segment luminal and adventitial contours were imported and reconstructed. The source was placed circumferentially at the site of the IVUS catheter and longitudinally according to the relationship between the radioactive seeds and stent edges. Using Monte Carlo simulations, dose volume histograms for the adventitia and intima were calculated. The relationship between the neointimal regrowth and calculated doses were evaluated.

RESULTS

There was large dose heterogeneity at both the intimal and adventitial levels. Most of the sites (93%) received >4 Gy at the adventitia, and all of the sites received >4 Gy at the intima. There was no relationship between neointimal regrowth and radiation dose.

CONCLUSIONS

Although there may be large dose heterogeneity, gamma irradiation (using a fixed dose prescription) appears to deliver a sufficient dose to prevent neointimal regrowth.

Five-year clinical follow-up after intracoronary radiation: results of a randomized clinical trial

BACKGROUND

Several clinical trials indicate that intracoronary radiation is safe and effective for treatment of restenotic coronary arteries. We previously reported 6-month and 3-year clinical and angiographic follow-up demonstrating significant decreases in target lesion revascularization (TLR) and angiographic restenosis after gamma radiation of restenotic lesions. The objective of this study was to document the clinical outcome 5 years after treatment of restenotic coronary arteries with catheter-based iridium-192 (192Ir).

METHODS AND RESULTS

A double-blind, randomized trail compared 192Ir to placebo sources in patients with restenosis after coronary angioplasty. Over a 9-month period, 55 patients were enrolled; 26 were randomized to 192Ir and 29 to placebo. At 5-year follow-up, TLR was significantly lower in the 192Ir group (23.1% versus 48.3%; P=0.05). There were 2 TLRs between years 3 and 5 in patients in the 192Ir group and none in patients in the placebo group. The 5-year event-free survival rate (freedom from death, myocardial infarction, or TLR) was greater in 192Ir-treated patients (61.5% versus 34.5%; P=0.02).

CONCLUSIONS

Despite apparent mitigation of efficacy over time, there remains a significant reduction in TLR at 5 years and an improvement in event-free survival in patients treated with intracoronary 192Ir. The early clinical benefits after intracoronary gamma radiation with 192Ir seem durable at 5-year clinical follow-up.

Dosimetric measurements in isolated human coronary arteries: comparison of commercially available iridium(192) with strontium/yttrium(90) emitters

BACKGROUND

Intravascular brachytherapy is being applied more and more in patients with coronary artery disease for the prevention of restenosis subsequent to balloon angioplasty, in particular after stent implantation. Several radiation sources (beta- and gamma-emitters) are available in clinical routine. It was the purpose of this study to compare the radiation doses at the level of the adventitia in diseased and stented human coronary arteries for (192)Ir and (90)Sr/Y emitters in routine use. In contrast to previously published work, we performed dosimetry instead of calculating depth-dose distribution by use of the Monte Carlo system.

METHODS AND RESULTS

Postmortem calcified human coronary artery segments were stented and placed in an organ bath. Commercially available gamma-emitters ((192)Ir; Cordis Checkmate) and beta-emitters ((90)Sr/Y; Novoste Beta-Cath) were used. Relative dose distributions along the adventitia were measured by a specially designed scintillation detector system. Whereas dose perturbations caused by stents and calcified plaque were negligible for the (192)Ir source, radiation from the beta source was significantly impaired (as much as 40%) at the level of the adventitia (3.0-mm vessel diameter). Dose perturbation was clearly dependent on the extent and severity of calcification, less affected by stent material.

CONCLUSIONS

Dose perturbation caused by calcified plaque and metallic stents is significant for beta-sources. This dosimetric difference between beta- and gamma-emitters in diseased coronary arteries should be considered when calculating doses in intravascular brachytherapy.

Increased expression of macrophage colony-stimulating factor after coronary artery balloon injury is inhibited by intracoronary brachytherapy

BACKGROUND

The mechanisms underlying the reduced neointimal proliferation (NP) by intracoronary brachytherapy (ICBT) are unknown. We hypothesized that ICBT inhibits NP by reducing expression of macrophage colony-stimulating factor (M-CSF).

METHODS AND RESULTS

Thirty coronary arteries from 10 pigs were divided into 3 groups of 10 each: control (C), balloon injury (BI), and BI followed by ICBT (16 Gy at 0.5-mm tissue depth with a (32)P balloon system). Pigs were killed at 24 hours (n=3) and at 7 (n=4) and 14 (n=3) days. Expression of M-CSF was assessed by Western blot, ELISA, and quantitative immunostaining. Persistently increased levels of M-CSF after BI (to 1.4+/-0.2 nmol/L [ELISA] and 29.4+/-4.9% of cross-sectional area stained [immunocytochemistry]; P< 0.001 versus control for both) were observed in the injured arteries. Treatment of BI arteries with ICBT reduced M-CSF expression compared with BI alone (to 0.7+/-0.1 nmol/L [ELISA] and 13.5+/-2.9% of cross-sectional area stained [immunocytochemistry]; P<0.001 versus BI and P=NS versus control for both) and remained similar to control M-CSF expression for the 14-day study period. Neointimal thickness increased after BI (to 4.8+/-2.9 mm(2); P<0.001 versus control), but this was reduced by ICBT (1.4+/-0.4 mm(2); P<0.001 versus BI).

CONCLUSIONS

In porcine coronary arteries, BI is associated with increased expression of M-CSF and NP, but neither occurs after ICBT. The beneficial effects of ICBT on NP involve inhibition of M-CSF expression.

A prospective single-center registry for the use of intracoronary gamma radiation in patients with diffuse in-stent restenosis

Based on single-center prospective registry data, the study evaluates short- and long-term results of intracoronary gamma radiation in patients with diffuse in-stent restenosis in the reality of routine clinical practice. Percutaneous coronary intervention and subsequent catheter-based irradiation with iridium-192 was performed in 84 vessels (81 patients) with diffuse in-stent restenosis. Repeat coronary angiography was performed in 35 patients with clinical restenosis. With a mean follow-up of 12.0 +/- 0.5 months, major adverse cardiac events were observed in 29 (34.5%) patients, including 2 cases of cardiac death, 3 myocardial infarctions, 21 target lesion revascularizations, and 4 target vessel revascularizations. Five of six patients with total occlusion of the target vessel at baseline developed target lesion restenosis. Late total occlusion of the target vessel was observed in four patients. The 1-year event-free survival rate was 69.8%. Total occlusion of the target vessel at baseline was the single independent predictor of cardiac events at 1-year follow-up (P < 0.001). In patients with a target lesion in the left anterior descending artery, predictors of cardiac events also included female sex (P = 0.014), current smoking (P = 0.014), stenting during brachytherapy session (P = 0.02), and smaller reference vessel diameter at baseline (P = 0.01). The results of our registry are similar to those of randomized trials. As applied in routine clinical practice, intracoronary gamma radiation is a feasible, safe, and effective tool in the treatment of diffuse in-stent restenosis. Late events in the entire group were predicted by total occlusion at baseline.

Five-year clinical and angiographic follow-up after intracoronary iridium-192 radiation therapy

BACKGROUND

Ionizing gamma radiation has been shown to reduce neointimal formation and the incidence of restenosis after balloon angioplasty and stenting in clinical trials. However, the long-term effects of this therapy are unknown. The first cohort of patients to receive intracoronary gamma radiation after balloon angioplasty for the prevention of restenosis have completed a 5-year angiographic and clinical follow-up. The outcome of these patients is presented and discussed.

METHODS

Twenty-one patients with unstable angina (22 arteries) underwent standard balloon angioplasty. Intracoronary radiation therapy was performed immediately after the intervention using an Iridium-192 source wire hand-delivered to the angioplasty site. All patients were followed clinically and Quantitative Coronary Analysis (QCA) was performed at 6, 24, 36 and 60 months.

RESULTS

Target lesion revascularization occurred in six lesions, three of which were total occlusions (two early within 30 days and one occurred at 2 years), and one patient had a myocardial infarction attributable to a nontarget vessel. Serial QCA detected a binary restenosis rate of 28.6% (n=6) at 6 months. The late loss (0.29 mm) and loss index (0.25) remained low at 2, 3 and 5 years. Angiographic complications included four aneurysms (two procedure related and two occurring within 3 months). At 2 years, only one aneurysm increased in size (46 vs. 27 mm(2)); and at 3 and 5 years, all aneurysms remained unchanged. No other angiographic complications were observed.

CONCLUSION

The early clinical and angiographic effects of intracoronary gamma radiation were maintained at 5 years without further increase in the aneurysm formation or apparent new adverse effects related to the radiation therapy between 2 and 5 years.

Restenosis: Intracoronary Brachytherapy

Though interventional strategies have revolutionized the management of patients with symptomatic coronary artery disease, in-stent restenosis has emerged as the single most important limitation of long-term success following percutaneous coronary intervention. Once present, in-stent restenosis is extraordinarily difficult to treat, with conventional revascularization techniques failing in 50% to 80% of patients. Intracoronary radiation, or brachytherapy, targets cellular proliferation within the culprit neointima. Clinical trials have demonstrated that brachytherapy is a highly effective treatment for in-stent restenosis, reducing angiographic restenosis by 50% to 60% and the need for target vessel revascularization by 40% to 50%. The benefits of intracoronary brachytherapy may be particularly pronounced in certain patient subgroups (eg, those with diabetes, long lesions, or lesions in saphenous vein bypass grafts), but comes at the cost of an increased rate of late stent thrombosis and the need for extended antiplatelet therapy. The role of brachytherapy in the arsenal of the interventional cardiologist will continue to evolve, particularly in light of the unprecedented recent advances with the use of drug-eluting stents for restenosis prevention.

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.