Intracoronary Brachytherapy for Restenosis: 20 Years of Follow-Up

BACKGROUND/PURPOSE

Intracoronary brachytherapy (ICB) has mainly been used to treat in-stent restenosis following percutaneous coronary intervention and was virtually abandoned about 20 years ago. However, patients treated with this strategy are still alive and some teams continue to perform this therapy. We aimed to investigate the very long-term clinical outcome of patients treated with ICB.

METHODS/MATERIALS

A total of 173 consecutive patients who had been treated with ICB at a large tertiary referral centre between 1998 and 2003 were included. The primary endpoint of the study was all-cause mortality. The secondary endpoints were as follows: occurrence of major adverse cardiac events (MACE, defined as all-cause death, non-fatal myocardial infarction, or target vessel revascularization), cardiac death, and presence of angina at the end of follow-up.

RESULTS

Patients' mean age at the time of ICB was 64 ± 10 years and 77 % were male. Restenosis (bare metal stent vs. balloon angioplasty) was the only indication for ICB. Unstable angina was present in 34 % of the patients. Follow-up was available for 166 patients. After a mean follow-up of 20 ± 1.3 years, 66 % of the patients had died (including 74 patients (67 %) with cardiac death). Cumulative MACE rate at 20 years was 96 %.

CONCLUSIONS

Very long-term follow-up of patients with in-stent restenosis treated with ICB confirmed a high all-cause mortality rate mainly due to cardiac causes and MACEs.

Coronary intravascular brachytherapy for in-stent restenosis: A review of the contemporary literature

Intracoronary stent restenosis (ISR) is a clinically relevant challenge in the modern era. Heterogeneity in patient- and lesion-specific factors can further compound this clinical challenge. Coronary intravascular brachytherapy (IVBT) was the standard therapeutic approach for ISR prior to the advent of drug-eluting stents (DES). Despite prospective data describing the superiority of DES over IVBT for treating de novo ISR, IVBT remains a treatment option for patients with complex disease. The purpose of this review is to evaluate the historical and contemporary literature surrounding IVBT in order to elucidate its role in modern cardiac care and to describe opportunities for future investigations to improve patient selection. Herein, we provide a review of the contemporary literature describing IVBT as a safe and effective treatment option for patients with recurrent, refractory ISR after multilayer DES and no good surgical or mechanical option. Combination therapy with emerging technologies such as DCBs may further increase efficacy.

Intravascular Brachytherapy for the Management of Repeated Multimetal-Layered Drug-Eluting Coronary Stent Restenosis

BACKGROUND

Because of the widespread acceptance of percutaneous coronary intervention with drug-eluting stents as an effective treatment strategy for in-stent restenosis, it is common to encounter multimetal layer stent restenosis in the recent years. This study aimed to evaluate the clinical outcomes of such patients treated with intravascular brachytherapy (IVBT) in comparison with other percutaneous options.

METHODS AND RESULTS

We enrolled patients who underwent percutaneous coronary intervention during the period between 2011 and 2015 for recurrent drug-eluting stents in-stent restenosis with at least 2 layers of stents at the lesion site. This analysis compared patients who underwent treatment with IVBT and those who did not (non-IVBT group). The primary end point measured was major adverse cardiac events defined as a composite of target lesion revascularization, myocardial infarction, and all-cause mortality at 12 months. Adjusted associations were measured using propensity score matching. A total of 328 percutaneous coronary intervention patients met the eligibility criteria, of which 197 patients received IVBT, and 131 patients underwent routine percutaneous intervention. The primary end point was significantly lower in patients undergoing IVBT (13.2% and 28.2%; P=0.01). A propensity score matching for risk factors of in-stent restenosis identified 182 patients. The advantages of IVBT with regard to 1-year major adverse cardiac events were confirmed in this matched cohort (13.2% and 30.8%; adjusted hazard ratio [95% CI]: 0.37 [0.18-0.73]; P<0.01).

CONCLUSIONS

In this analysis, IVBT led to significantly lower major adverse cardiac events in patients with multilayered drug-eluting stents restenosis when compared with other percutaneous options at 1-year follow-up.

Late results (>10 years) of intracoronary beta brachytherapy for diffuse in-stent restenosis

INTRODUCTION

Until the development of drug-eluting stents (DES), diffuse in-stent restenosis (ISR) was the main limitation of bare-metal stents in percutaneous coronary intervention (PCI). Among the different treatments available, intracoronary brachytherapy (BT) emerged as one of the most promising, although it was almost abandoned with the increasing use of DES.

OBJECTIVE

To assess the Portuguese experience with 90Sr/90Y beta brachytherapy for the treatment of diffuse ISR regarding long-term (>10 years) major adverse cardiac events (MACE) and angiographic restenosis.

METHODS

This single-center, retrospective, observational study included 12 consecutive patients treated between January and June 2001, mean age 58.6±9.9 years (range 43-77 years), 11 male. All had chronic stable angina, 75% had dyslipidemia, 58% had hypertension, 50% had peripheral arterial disease, 42% had diabetes and 50% had multivessel disease. Recurrent ISR was present in half of the patients and 11 had normal left ventricular function. After balloon dilatation, BT was performed using an Sr90/Y90 (Novoste Beta-CathTM) beta radiation source. All patients remained under dual antiplatelet therapy until scheduled nine-month follow-up angiography. Patients were followed for the occurrence of death (all-cause and cardiovascular), non-fatal myocardial infarction (MI), revascularization, stent thrombosis and angiographic restenosis. MACE were defined as the combined incidence of cardiac death, MI and urgent target vessel revascularization.

RESULTS

In all cases there was both clinical and angiographic success. In a mean follow-up of 10.9±2.5 years, 19 events occurred in seven patients: death in three (25%), only one cardiac (8.3%); ST-elevation MI in one (related to a non-target vessel) (8.3%); and 15 revascularizations in five (42%), of which nine were of the target vessel (mainly in the first two years). There was only one case of probable stent thrombosis. Angiographic restenosis at nine months was 27% (three out of 11 patients), of which two were total occlusions. Ten-year MACE-free survival was 42% (5 patients).

CONCLUSIONS

Intracoronary beta brachytherapy for the treatment of diffuse ISR in this small cohort of patients proved to be safe and efficacious, with no late adverse events related to intracoronary radiation.

Absorbed dose assessment of cardiac and other tissues around the cardiovascular system in brachytherapy with 90Sr/90Y source by Monte Carlo simulation

Cardiac disease is one of the most important causes of death in the world. Coronary artery stenosis is a very common cardiac disease. Intravascular brachytherapy (IVBT) is one of the radiotherapy methods which have been used recently in coronary artery radiation therapy for the treatment of restenosis. (90)Sr/(90)Y, a beta-emitting source, is a proper option for cardiovascular brachytherapy. In this research, a Monte Carlo simulation was done to calculate dosimetry parameters and effective equivalent doses to the heart and its surrounding tissues during IVBT. The results of this study were compared with the published experimental data and other simulations performed by different programs but with the same source of radiation. A very good agreement was found between results of this work and the published data. An assessment of the risk for cardiac and other sensitive soft tissues surrounding the treated vessel during (90)Sr/(90)Y IVBT was also performed in the study.

Chronic total occlusion due to diffuse in‐stent restenosis: is brachytherapy the solution?

Percutaneous coronary intervention of chronic total occlusions (CTO) is associated with a significantly higher incidence of reocclusion and restenosis compared with non-total occlusions. Randomized and observational trials have demonstrated the effectiveness of intracoronary brachytherapy (ICBT) for the prevention of recurrent in-stent restenosis. However, limited data are available on the effectiveness of ICBT in patients with totally occluded in-stent restenosis. The authors assessed the long-term outcome of patients treated with intracoronary gamma radiation for totally occluded in-stent restenotic lesions. Percutaneous coronary intervention and subsequent catheter-based irradiation with iridium-192 was performed in 100 patients (103 vessels) with diffuse in-stent restenosis. At baseline, CTO of the target vessel at the site of the stent was present in 15 vessels (14.5%). Follow-up data were collected during follow-up visits and from telephone interviews. Repeat coronary angiography was performed in symptomatic patients with clinical restenosis. Clinical and angiographic characteristics were similar between the two groups, although there was a trend towards more unstable angina at the index procedure in CTO patients (66.7% versus 41.4%; p = 0.12) compared with patients without non-total occlusions. A higher percentage of patients (53.3%) with CTO required longer radiation sources (14 seeds, covering a length of 55 mm), compared with 23.9% of patients with non-total occlusion (p = 0.04). With a mean follow-up period of 47.5 +/- 24.0 months, major adverse cardiac events (MACE) were observed in 10 of 15 patients (66.7%) with CTO compared with 25 out of 88 patients (28.4%) without CTO (p = 0.009). According to multivariate analysis, total occlusion of the target vessel at baseline was the single independent predictor of MACE at one-year follow-up (relative risk 16.2, 95% confidence interval 4.2-62.9; p < 0.0001). This study shows that the use of gamma radiation for the prevention of recurrence of in-stent restenosis in patients with CTO does not seem to be as effective as in patients with non-total occlusions. Furthermore, CTO was an independent predictor of worse outcome at long-term follow-up in this study.

Treatment of patients with in-stent restenosis

Treatment of patients with in-stent restenosis (ISR) remains a technical challenge. This problem has been reduced since the advent of drug-eluting stents (DES), but continues to represent a significant burden during daily practice in interventional cardiology. Treatment of ISR after bare-metal stent implantation has evolved and currently DES constitute the intervention of choice. However, DES may also develop ISR. The best therapeutic alternative for patients suffering from ISR after DES implantation remains to be elucidated. This review will focus on treatment of patients with ISR emphasising currently available alternatives, technical issues, limitations and future perspectives.

Management of total restenotic occlusions

Among lesions with in-stent restenosis (ISR), the in-stent chronic re-occlusions (ISR-CTO) is a subset with particularly unfavourable features regarding both the repeat procedure success and the prevention of lesion recurrence. A review of the literature and personal databases reveals that the prevalence of complete occlusive ISR represents about 5-10% of all CTO lesions, with little evidence regarding the successful long-term treatment. In fact, these lesions had been excluded from large contemporary trials dealing with the best modality for ISR management, and which showed eventually the superiority of drug-eluting stents (DES) as compared to brachytherapy. Only a limited experience exists with brachytherapy for ISR-CTOs, showing an inferior outcome as compared to non-occlusive ISRs. The lack of large study experience is true also for DES, so that only anecdotal experience in small series of patients is available. In some of the recent studies of DES in CTOs, again, ISR-CTOs were not included. Our own experience shows a slightly lower primary success rate of about 70% in ISR-CTOs as compared to 85% in primary CTOs, with a slightly higher recurrence rate with DES of 25%. ISR-CTOs are a clinical problem that had not been systematically addressed. However, we hope that this lesion subset may be of less relevance in the future when the use of DES in lesions which are prone for lesion recurrence will lead to less diffuse and occlusive ISR, and leaves rather focal and better manageable recurrent lesions.

Secondary revascularisation following intracoronary brachytherapy

Intracoronary brachytherapy (ICB) was developed as an attempt to prevent restenosis after percutaneous coronary interventions. Early clinical experiences showed impressive results especially in the subset of patients with in-stent restenosis. This led to the design of large multicentre trials that demonstrated the efficacy of ICB as adjunctive therapy in patients with in-stent restenosis as compared to conventional treatment. Despite these outstanding initial results, several limitations arose such as late thrombosis, edge effect or late catch-up phenomenon. These, together with the difficult logistic process to implement the ICB in the cath lab and the development of the drug-eluting stent shelved definitely the technique. This review describes the potentials and limitations of this therapy, as well as the current status in the drug-eluting stent era.

Dosimetry study for beta-radiation treatment of in-stent restenosis

Intravascular brachytherapy (IVBT) has been recognised as a treatment modality for reducing coronary restenosis after angioplasty and stent-implantation procedures. For the treatment of in-stent restenosis using beta-emitter (188)Re, delivering adequate doses to the entire vessel wall is not possible without the potential of overdosing tissues. A method to measure the dose distribution, perturbation and percentage depth dose using plane-parallel and cylindrical tissue-equivalent phantoms has been developed. Good agreement was found between experimental results and Monte Carlo simulation performed using MCNP4C code. The dose given to the affected area in the vascular region for intravascular radiation treatment was 15-30 Gy. Dose inhomogeneity beyond the stent surface decreased significantly with increasing radial distance. In the region close to the stent outer surface (>0.5-mm radial distance), a dose reduction of 11-17% due to the stent was observed. However, the dose perturbations due to the physical properties of metallic stents were found to be significant in IVBT for in-stent restenosis by using measured dose profiles in phantoms. The method can provide accuracy in beta isotope in vivo dosimetry results for treatments involving short-range dose distributions and provide a relatively high-level spatial resolution for detection.

Vascular changes and black hole phenomenon after coronary brachytherapy: a pathologically distinct entity

Restenosis remains an important issue even after coronary brachytherapy despite its efficacy in the treatment for in-stent restenosis. The acute and chronic changes in vascular wall are unique following brachytherapy. The restenotic tissue post coronary brachytherapy is relatively acellular and appears echolucent in intravascular ultrasound examination. This is dubbed the "black hole" phenomenon. Despite the similarity in the mode of action of brachytherapy and drug eluting stent implantation, the black hole phenomenon seems to be uncommon after drug-eluting stent implantation except in those patients who have had prior brachytherapy, bare-metal placement and after treatment of saphenous venous graft stenosis. It is possible that not all neointima in stents are created equal. We should propose that neointima be considered primary neointima if it forms after bare metal stenting, secondary neointima if it forms after CBT or DES, and perhaps tertiary if after combined CBT and DES. This type of classification may prove useful for research or clinical purposes. Almost certainly black hole phenomenon results from a modified neointima. However, we do not know whether this is the same restenotic tissue that was present before CBT but just depleted of its cellular element secondary to autolysis or a newly formed tertiary neointima? It is also not clear whether the changes in vascular wall and restenosis are similar after CBT or drug-eluting stent placement. However, there are some unique vascular changes that seem to be common after both of these procedures.

Long-term outcomes after intracoronary Beta-irradiation for in-stent restenosis in bare-metal stents

OBJECTIVE

We sought to characterize the long-term outcomes of patients undergoing intracoronary brachytherapy using Beta- irradiation (Beta-BT).

BACKGROUND

Beta-BT is effective in reducing angiographic restenosis as well as target vessel revascularization (TVR) in patients with in-stent restenosis (ISR) after bare-metal stenting (BMS).

METHODS

81 consecutive patients undergoing Beta-BT for ISR (irradiated length 32 [32-54] mm) after BMS in native vessels (n = 79) or saphenous vein grafts (n = 2) between 2001 and 2003 were followed. Major cardiac events (MACE), including cardiac death, nonfatal myocardial infarction (MI), and TVR occurring > 1 year or > 1 year were assessed 5.2 (4.4-5.6) years after the index procedure.

RESULTS

During the entire follow-up period, the total MACE rate was 49.4%. Within the first year and at > 1 year, MACE rates were 25.9% and 23.5%, cardiac death occurred in 2.4% and 6.2%, and nonfatal MI in 6.2% and 12.3% for annual cardiac death/MI rates of 8.7% at < 1 year and 4.1% thereafter. TVR was required in 19% at < 1 year and in 16% of patients later on. The only independent predictor of MACE occurring < 1 year was an irradiated vessel length > 32 mm (odds ratio [OR] 2.73, 95% confidence interval [CI] 1.10-6.78; p = 0.03). The best, albeit not statistically significant, predictor of MACE occurring at > 1 year was the presence of diabetes mellitus (OR 2.49, 95% CI 0.94-6.57; p = 0.07).

CONCLUSIONS

Patients undergoing Beta-BT for ISR after BMS carry a substantial risk of MACE also beyond the first year, with annual cardiac death and nonfatal MI rates of 1.5% and 2.9% up to 5 years postprocedure.

Efficacy and safety of absorbable metallic stents with adjunct intracoronary beta radiation in porcine coronary arteries

BACKGROUND

Absorbable metallic stents (AMS) utilizing Mg alloy carry advantages over permanent metallic stents because of their potential to eliminate stent thrombosis, chronic inflammation, or artifacts with noninvasive imaging. These stents, however, are associated with a modest degree of late recoil and intimal hyperplasia. The aim of the study was to test whether adjunct vascular brachytherapy (VBT) compared to AMS alone can overcome these limitations.

METHODS

Juvenile domestic pig coronary arteries underwent implantation of either AMS (n = 11) with prior adjunct VBT utilizing Sr/Y-90 beta source seeds, with a dose of 24 Gy at 2 mm from the source, or AMS alone (n = 11). At 28 days following intravascular ultrasound, vessels were harvested and analyzed by histomorphometry.

RESULTS

Intravascular ultrasound analysis indicated that at follow-up, though statistically not significant, lumen and stent areas in the segments deployed with AMS following radiation were larger than those deployed with AMS alone (3.94 +/- 1.38 and 3.53 +/- 1.75 vs. 2.99 +/- 1.05 and 3.58 +/- 1.48). Extrastent plaque and intrastent plaque areas in the same segments were smaller (2.76 +/- 0.82 and 0.24 +/- 0.47 vs. 3.25 +/- 1.94 and 0.58 +/- 0.81). Morphometric data indicate that vessels in the VBT + AMS group showed characteristics of delayed healing and re-endothelialization. Neointimal area was significantly lower in the VBT + AMS group (0.49 +/- 0.34) compared to AMS (1.3 +/- 0.62, P = 0.001). Lumen area of the VBT + AMS was larger when compared with AMS alone (2.49 +/- 0.82 vs. 1.75 +/- 0.51, P = 0.02).

CONCLUSION

VBT as an adjunct to AMS further reduces the intimal hyperplasia and improves the lumen area when compared to AMS alone but does not have any impact on late recoil.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Comparison of six-month angiographic and three-year outcomes after sirolimus-eluting stent implantation versus brachytherapy for bare metal in-stent restenosis

To evaluate long-term effectiveness of sirolimus-eluting stent (SES) implantation for diffuse bare metal in-stent restenosis (ISR), we compared 6-month angiographic and long-term (3-year) clinical outcomes of SES implantation and intracoronary brachytherapy (ICBT). SES implantation for diffuse ISR was performed in 120 consecutive patients and their results were compared with those from 240 patients treated with beta-radiation with balloons filled with rhenium-188 and mercaptoacetyltriglycine. The radiation dose was 15 or 18 Gy at a depth of 1.0 mm into the vessel wall. The primary end point was 3-year major adverse cardiac events including myocardial infarction, cardiac death, and target lesion revascularization. The 2 groups were similar in baseline clinical and angiographic characteristics. Lesion lengths were 25.1 +/- 14.2 mm in the SES group and 24.5 +/- 10.4 mm in the ICBT group (p = 0.15). In-stent acute gain was greater in the SES group than in the ICBT group (2.23 +/- 0.62 vs 1.91 +/- 0.54 mm, p <0.001). We obtained 6-month angiographic follow-up in 287 patients (79.7%). In-segment angiographic restenoses were 7.4% (7 of 94) in the SES group and 26.4% (51 of 193) in the ICBT group (p <0.05). Two myocardial infarctions (1 in each group) and 5 deaths (4 in SES group, 1 in ICBT group) occurred during 3-year follow-up. At 3 years, survival rates without target lesion revascularization (94.1 +/- 2.2% vs 84.6 +/- 2.3%, p = 0.011) and major adverse cardiac events (92.5 +/- 2.4% vs 84.2 +/- 2.4%, respectively, p = 0.03) were higher in the SES than in the ICBT group. In conclusion, compared with ICBT, SES implantation for diffuse ISR is more effective in decreasing recurrent restenosis and improving long-term outcomes.

Four-year results after brachytherapy for diffuse coronary in-stent restenosis: will coronary radiation therapy survive?

BACKGROUND

Prior to the introduction of drug-eluting stents (DES), diffuse coronary in-stent restenosis (ISR) was mainly treated by brachytherapy (BT), with good short-term and mid-term results. However, there exist limited data on the long-term effects of BT that justify its continuous use.

MATERIALS AND METHODS

Two hundred patients with diffuse ISR treated with intravascular BT were retrospectively followed over 4 years. Group A (n=134) was treated with the noncentered (90)Sr/Y BetaCath radiation system, whereas Group B (n=66) was treated with the centered 32P Galileo source wire system. Primary endpoints after 4 years were target lesion restenosis (TLS) and target lesion revascularization (TLR). Secondary endpoints were target vessel revascularization (TVR) and nontarget vessel revascularization (NTVR), as well as major adverse cardiac events (MACE).

RESULTS

Follow-up at 4 years yielded a TLS rate of 37.6% (Group A, 40.8%; Group B, 31.1%; P=.48). TLR was performed in 34.8% of patients (37.5% in Group A vs. 29.5% in Group B; P=.55). Ten percent of patients underwent coronary bypass surgery. Percutaneous coronary intervention was performed more often in Group A (27.5%) than in Group B (19.7%), while TVR was less frequent in Group A (10.0%) than in Group B (18.0%). NTVR was undertaken in 25.0% of Group A patients versus 21.3% of Group B patients, and MACE occurred in 1.7% of Group A patients versus 3.3% of Group B patients. These differences were not statistically significant (P>.05).

CONCLUSIONS

While excellent short-term and mid-term results after coronary BT are widely accepted, a high TLS rate can be observed after 4 years. The potential superiority of DES to BT will depend on the availability of long-term clinical data.

A meta-analysis of randomised controlled trials assessing drug-eluting stents and vascular brachytherapy in the treatment of coronary artery in-stent restenosis

OBJECTIVE

We undertook a meta-analysis of randomised trials assessing the outcome of vascular brachytherapy (VBT) or DES for the treatment of coronary artery ISR.

METHODS AND RESULTS

Studies utilising DES or VBT for ISR were identified by a systematic search. Data was pooled and combined overall effect measures were calculated for a random effect model in terms of deaths, myocardial infarctions, revascularisation, binary restenosis, mean late luminal loss and major adverse cardiac events (MACE). Fourteen eligible studies (3103 patients) were included. Neither therapy had any effect on mortality or myocardial infarction rate. VBT reduced the rate of revascularisation (RR 0.59, 95%CI 0.50-0.68), MACE (RR 0.58, 95%CI 0.51-0.67), binary restenosis (RR 0.51, 95%CI 0.44-0.59) and late loss (-0.73 mm, 95%CI -0.91 to -0.55 mm) compared to balloon angioplasty and selective bare metal stents (BMS) alone at intermediate follow-up and MACE (RR 0.72, 95%CI 0.61-0.85) at long-term follow-up. DES reduced the rate of revascularisation (OR 0.51, 95% CI 0.36-0.71), MACE (OR 0.55, 95% CI 0.39-0.79) and binary restenosis (OR 0.57, 95% CI 0.40-0.81) compared to VBT but follow-up was limited to 9 months.

CONCLUSIONS

VBT improves the long-term outcome of angioplasty compared with BMS alone in the treatment of ISR. DES appears to provide similar results to that of VBT during short-term follow-up.

Mechanisms of late lumen loss after antiproliferative percutaneous coronary intervention using beta-irradiation in a porcine model of restenosis

BACKGROUND

The short-term results for the prevention of coronary restenosis after intravascular brachytherapy (IVBT) and use of drug-eluting stents (DESs) are excellent. The long-term results either lack or present with late complications (e.g., late thrombosis and late catch-up phenomenon leading to late restenosis even years after the initial procedure). Both IVBT and DESs mediate their potent antirestenotic effects via a cytostatic mechanism, but the cardiovascular pathology at late time points after the use of these antiproliferative therapies is incompletely understood. This study investigated the long-term effects of antiproliferative beta-irradiation in a clinically relevant porcine coronary model to address the pathophysiology of late coronary restenosis after antiproliferative vascular interventions.

METHODS

We performed percutaneous transluminal coronary angioplasty (PTCA) in two major coronary arteries in 12 domestic crossbred pigs. One of the two balloon-injured segments was randomly assigned to receive immediate beta-irradiation (PTCA+IVBT group) using a noncentered delivery catheter (20 Gy; Novoste Beta-Cath System, Novoste, Norcross, GA, USA). The animals were sacrificed after 14 days (n=6) or 3 months (n=6).

RESULTS

The luminal area in the PTCA+IVBT group decreased significantly 3 months after the intervention as compared with that in the PTCA group (PTCA 3.45+/-0.46 mm2 vs. PTCA+IVBT 1.22+/-0.26 mm2; P=.0017). This lumen loss was primarily due to shrinkage of the external elastic lamina area (negative arterial remodeling; PTCA 5.22+/-0.27 mm2 vs. PTCA+IVBT 3.42+/-0.45 mm2; P=.0064), which was accompanied by an increase in the adventitial area (PTCA 3.07+/-0.2 mm2 vs. PTCA+IVBT 5.41+/-0.5 mm2; P=.0049).

CONCLUSIONS

The application of antiproliferative radiation in a porcine coronary model caused an early beneficial effect (reduction of intimal-medial lesion and luminal gain) that was followed by a late lumen loss primarily due to negative arterial remodeling. This mechanism may in part help us understand the pathophysiology of late adverse events occurring after IVBT.

Implementing a best-treatment strategy with intracoronary brachytherapy for in-stent restenosis in patients at high risk for recurrence

BACKGROUND

The deployment of drug-eluting stents (DES) to treat bare-metal stent restenosis [in-stent restenosis (ISR)] has become routine practice, with a consequential decline in the use of intracoronary brachytherapy (ICBT). However, there are concerns as to the long-term safety profile of DES, particularly in terms of late stent thrombosis. In addition, an appropriate treatment strategy for stenosis within DES has not been developed. The aim of this study was to examine the efficacy of best treatment with ICBT for ISR in patients at high risk for future recurrence.

METHODS

Forty-seven consecutive patients with symptomatic ISR with at least one or more increased risk criteria for recurrence were treated with beta-radiation. The patients received best treatment based on avoidance of previously reported procedural risk factors for recurrence (incomplete stent apposition, dissection, geographical miss, and damage to the noninjured vessel segment), deferring ICBT when provisional stenting was performed. A beta-radiation dose of 20 Gy was used, and clopidogrel was prescribed for at least 6 months.

RESULTS

Treatment was successful for all patients without in-hospital complications. ICBT increased the total intervention procedure time by 15+/-10 min. ISR length was 25.4+/-11.5 mm. The angiographic minimal luminal diameter (MLD) was 2.24+/-0.43 mm after ICBT versus 0.75+/-0.58 mm at baseline (P<.05). On 9-month follow-up, the MLD was 1.93+/-0.48 mm (P<.05 vs. baseline). Binary restenosis was detected in six (13%) patients. At 29.7+/-9.3 months of follow-up, target lesion revascularization or target vessel (nonlesion) revascularization was performed in 17 (36%) patients. Only one patient suffered a myocardial infarction, and no deaths were observed.

CONCLUSION

The adoption of a best-practice protocol for the use of ICBT to treat ISR can result in a safe and effective clinical and angiographic outcome. Under these circumstances and with appropriate patient selection, ICBT may continue to be of value despite the popular use of DES.

Acute lumen overdilation improves outcome after brachytherapy of in-stent restenosis

BACKGROUND

The aim of our study was to test the impact of acute lumen overdilation on neointimal hyperplasia and late lumen size after vascular brachytherapy for in-stent restenosis (ISR).

METHODS

Forty-seven ISR lesions located in 47 coronary arteries in 44 consecutive patients underwent beta brachytherapy with serial intravascular ultrasound studies. Vessel, lumen, and stent cross-sectional area were measured at 1-mm steps. Based on an interpolated reference cross-sectional area, each cross section was assessed as overdilated (lumen cross-sectional area>interpolated reference cross-sectional area) or not overdilated (lumen cross-sectional area <interpolated reference cross-sectional area).

RESULTS

Overall, 502 sections were overdilated and 673 sections were not. Overdilated sections had a larger final lumen cross-sectional area (8.02+/-1.98 vs. 6.90+/-2.23 mm2, P<.001) and more recurrent neointimal hyperplasia (1.59+/-2.17 vs. 0.31+/-1.79 mm2, P<.001), but a smaller follow-up area stenosis (-1.03+/-32.99% vs. 22.15+/-20.75%, P<.001). This was especially true in smaller arteries (angiographic reference<3.0 mm) where larger follow-up lumen cross-sectional area and a corresponding smaller area stenosis were present (5.38+/-1.98 vs. 4.84+/-1.88 mm2 and 6.90+/-31.57% vs. 28.61+/-21.86%, P<.01 and P<.001, respectively).

CONCLUSIONS

Especially in small arteries, the strategy of acute lumen overdilation during balloon angioplasty prior to beta vascular brachytherapy treatment of ISR lesions has a favorable long-term result.