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

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.

Long-term clinical and angiographic outcome of patients with occlusive in-stent restenosis treated with (32P) beta-brachytherapy

The objective of this study was to determine the safety and efficacy of (32)P beta-brachytherapy in totally occlusive in-stent restenosis (ISR). Patients with occlusive ISR were generally excluded from the randomized clinical trials on intracoronary brachytherapy (utilizing either gamma- or beta-sources) that have shown reductions in restenosis rate and need for revascularization procedures. We analyzed short- and long-term effects of (32)P beta-brachytherapy (20 Gy) in 27 patients (28 lesions) with occlusive ISR and 84 (99 lesions) patients with nonocclusive high-risk ISR. The primary outcome measure was frequency of in-lesion angiographic binary restenosis at 7 months. Secondary endpoints were rates of major adverse cardiac events (MACE), target vessel revascularization (TVR), clinically driven TVR, and target lesion revascularization (TLR). (32)P beta-brachytherapy was feasible and safe and provided similar postprocedural angiographic results in the two clinically comparable groups. However, the 7-month binary restenosis rate was higher in the occlusive group, as were the MACE and late total occlusion rates. Multivariate logistic analysis of the overall population indicated occlusive pattern to be the only independent predictor of angiographic restenosis. In both groups, recurrent lesions most often showed a focal pattern with significant reduction of length. Although safe and effective in high-risk ISR, (32)P brachytherapy at 20 Gy does not appear to be sufficient to avoid long-term restenosis in patients with occlusive lesions. Further studies should determine the most suitable source and dosage of brachytherapy for patients with occlusive ISR.

Novel Approaches to Reduce Restenosis

Percutaneous coronary intervention (PCI) has become the major technique of revascularization and is replacing cardiac bypass surgery. PCI is typically performed today with a combination of balloon dilatation and stents, with some 80% of the procedures followed by stent implantation. After balloon dilatation, an acute recoil response can be responsible for some 30% immediate loss of the vessel lumen at the end of the procedure. Restenosis is the late loss (within 6-9 months) of the lumen of the artery due to vessel shrinkage (negative remodeling) and an intense proliferative response to the local injury. Stents reduce restenosis by 30% by preventing acute recoil and reducing long-term negative arterial remodeling. Yet, long-term pressure of the stent struts against the vessel wall stimulates an increased arterial proliferative response, which is the major cause for stent restenosis. Limiting the proliferative response by local radiation (brachytherapy) have reduced restenosis, at a cost of increased late thrombogenicity and delayed vessel healing. Drug-eluting stents have shown extremely promising results in limiting restenosis. Rapamycin and paclitaxel are the major drugs in eluting stents in clinical use today, having reduced restenosis to less than 10%. Local cellular and genetic therapy approaches are currently at preclinical phases. The future of percutaneous revascularization remains bright and will enhance the effectiveness of PCI as the primary revascularization therapy for coronary artery disease.

Predictors of 32P beta brachytherapy failure in patients with high-risk in-stent restenosis

BACKGROUND

The effectiveness of coronary radiation therapy for the treatment of in-stent restenosis (ISR) has been established in several randomized clinical trials. The efficacy of this treatment in the general population is less well established.

METHODS AND MATERIALS

We report our experience in 118 consecutive patients with nonselected high-risk ISR who had undergone successful percutaneous coronary intervention and brachytherapy with (32)P beta-irradiation and who were prospectively enrolled in a quantitative angiographic and clinical follow-up protocol at 7 months after the index procedure. The aim of this study was to investigate the independent predictor of angiographic restenosis after (32)P brachytherapy treatment.

RESULTS

Of the patients, 28.8% were diabetics. The mean lesion and mean radiated lengths were, respectively, 30.1 +/- 17.2 and 43.8 +/- 16.9 mm. The ISR pattern was diffuse in 96% of the treated lesions; in particular, 22.1% presented an occlusive pattern and 37.1% a proliferative pattern. At follow-up angiographic, restenosis and major adverse cardiac events (MACE) rates were, respectively, 20.8% and 29.6%. The univariate predictors of angiographic restenosis were procedural geographic miss, pattern IV ISR, manual pullback maneuver of the radiation source, preprocedural lesion percentage stenosis and preprocedural lesion MLD. At logistic regression analysis, only geographic miss and pattern IV ISR were independent predictors of post intracoronary radiation therapy (IRT) angiographic restenosis.

CONCLUSION

These data indicate that 7-month angiographic restenosis after (32)P IRT in complex patients with ISR is not a frequent event and is predicted mainly by an occlusive lesion at baseline and by procedural geographical miss.