Coronary brachytherapy in the drug-eluting stent era: don't bury it alive

Intracoronary β‐irradiation enhances balloon‐injury‐induced tissue factor expression in the porcine injury model

Intracoronary brachytherapy (ICBT) effectively reduces restenosis but is associated with late thrombosis. Since tissue factor (TF) is an important mediator of arterial thrombosis, we tested the hypothesis that ICBT results in persistently augmented TF expression. Coronary arteries from 12 pigs were randomized to: control (C; no injury), oversized balloon injury (BI), or BI followed by ICBT. Animals were sacrificed at 1, 7, 14, or 60 days postprocedure, and coronary arteries collected for expression analyses and immunostaining. ICBT-treated arteries had higher TF antigen and activity at all time-points compared to BI arteries (Western blot: 16 571 +/- 2090 vs 10 135 +/- 2939 densitometric units, p = 0.001; ELISA: 0.42 +/- 0.13 nM vs 0.25 +/- 0.14 nM, p = 0.001; TF activity assay: 0.303 +/- 0.11 nM vs 0.18 +/- 0.07 nM, p = 0.01; immunohistochemical staining: 30.6 +/- 6.6% vs 11.5% +/- 3.2%, p = 0.01). TF expression increased following BI, increased further following ICBT, and persisted for the duration of the study. We conclude that TF expression increases after BI, but is further increased and persists for a longer duration following ICBT, suggesting that a TF-mediated mechanism may play a role in late thrombosis following ICBT.

Low-energy gamma-emitting stents inhibit intimal hyperplasia with minimal "edge effects" in a pig coronary artery model

PURPOSE

The objective of this study was to determine the effects of different doses of gamma-emitting radioactive stents on intimal hyperplasia in a porcine coronary stent model at 28 days.

METHODS

Sixty-four bare stents and those coated with palladium-103 [activities of 0 (control), 0.5, 1.0, 2.0, and 4.0 mCi] were implanted in the coronary arteries of 32 pigs. Stented segments were evaluated by histomorphometry at 28 days.

RESULTS

There was significantly more intima in the 0.5- and 1-mCi stents than in controls (4.27+/-0.52 and 4.71+/-1.13 vs. 1.71+/-0.61 mm(2); P<.0001). Neointimal formation in 2-mCi stents was similar to that in controls, while that in 4-mCi stents was reduced compared to that in controls (2.34+/-1.61 and 0.82+/-0.25 vs. 1.71+/-0.61 mm(2); P=NS and P<.05, respectively). Stent margin neointimal response was representative of that within the stent body, with nonsignficant modest increases in intimal area at adjacent nonstented segments in radioactive stent groups. There was a dose-dependent increase in inflammation scores. Radioactive stents had lower intimal smooth muscle and higher fibrin scores. There was an increase in adventitial fibrosis in 1- and 2-mCi stents versus controls (1.26+/-0.99, and 2.25+/-1.27 vs. 0.21+/-0.31; P<.001).

CONCLUSION

Dose-response inhibition of in-stent hyperplasia with minimal "edge effects" occurs with low-energy gamma-emitting stents. An increased inflammatory response at higher doses in palladium-103 stents indicates that later follow-up studies are necessary.

Clinical outcome of patients undergoing low aggressive angioplasty combined with brachytherapy and short-term dual antiplatelet therapy for in-stent restenosis

OBJECTIVE

The impact of vessel injury on the outcome of patients undergoing percutaneous coronary intervention combined with brachytherapy for in-stent restenosis is under investigation. We report our clinical experience adopting a low aggressive balloon angioplasty technique, to limit vessel trauma, associated with brachytherapy and short-term dual antiplatelet therapy.

METHODS

Forty-nine consecutive patients, undergoing percutaneous coronary intervention with brachytherapy for symptomatic in-stent restenosis, were prospectively observed for a median time of 21 + or - 8 months. Clinical follow-up included anginal status, death, myocardial infarction and repeat revascularization; only patients with evidence of ischaemia repeated coronary angiography. Low aggressive angioplasty consisted in the use of a conventional balloon with a balloon to artery ratio < or = 1, avoiding high inflation pressures and the use of other devices. Dual antiplatelet therapy was continued for 3-6 months.

RESULTS

Early angiographic result was good and the need for additional stent implantation was low (3.9%). At follow-up, we did not observe death, acute myocardial infarction or stent thrombosis, but 10 patients repeated coronary angiography for recurrence of ischaemia: disease progression was present in two cases (4.1%). Restenosis emerged in the remaining eight patients (16.3%): two cases showed restenosis within the target lesion segment, one case within the injured segment, one case within the radiated segment, and four cases at the edges. The consequent new revascularization was surgical in three patients and percutaneous in seven patients.

CONCLUSIONS

Our data suggest that low aggressive angioplasty followed by brachytherapy and short-term dual antiplatelet therapy for in-stent restenosis is related to a good outcome, with a low restenosis rate and without stent thrombosis.

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

Intracoronary β-irradiation prevents excessive in-stent neointimal proliferation in de novo lesions of patients with high plasma ACE levels. The BetAce randomized trial

BACKGROUND

This study evaluated vascular brachytherapy (VBT) as a potent antiproliferative treatment to prevent in-stent restenosis (ISR) after coronary angioplasty of de novo lesions in patients carrying the D allele of the I/D polymorphism of the ACE gene and high ACE plasma levels (>34 U/l).

METHODS AND MATERIALS

A prospective randomized trial was designed to detect a 30% improvement in the minimal lumen diameter (MLD) of the stenotic artery, as measured by quantitative coronary analysis (QCA), 6 months following VBT at the time of stented angioplasty. All patients were carriers of the D allele of the ACE gene, with plasma ACE levels >34 U/l.

RESULTS

Thirty-one patients (33 stenoses) were allocated to stent implantation (control group) and 30 patients (31 stenoses) to VBT and stented angioplasty. After angioplasty, in-stent MLD was similar in the two groups. At 6 months in the control group, in-stent MLD had decreased to 1.74+/-0.8 versus 2.25+/-1.05 mm in the VBT group (P=.04). The mean in-stent diameter was 2.3+/-0.8 mm in the control group versus 2.9+/-1.05 mm after VBT (P=.02), and the restenosis rate was 37.5% versus 17.9%, respectively (P=.08). At 6 months, a higher need for target vessel revascularization (TVR) was observed in the control group: 35.5% versus 13.3% (P=.04).

CONCLUSIONS

This randomized study confirms that patients with high plasma ACE concentrations are exposed to an increased risk for ISR after coronary stenting. The preventive use of VBT in these patients reduced neointimal formation by 65% such that the MLD at follow-up was increased by 29% compared with the control group.

Preclinical restenosis models and drug-eluting stents: still important, still much to learn

Percutaneous coronary intervention continues to revolutionize the treatment of coronary atherosclerosis. Restenosis remains a significant problem but may at last be yielding to technologic advances. The examination of neointimal hyperplasia in injured animal artery models has helped in our understanding of angioplasty and stenting mechanisms, and as drug-eluting stent (DES) technologies have arrived, they too have been advanced through the study of animal models. These models are useful for predicting adverse clinical outcomes in patients with DESs because suboptimal animal model studies typically lead to problematic human trials. Similarly, stent thrombosis in animal models suggests stent thrombogenicity in human patients. Equivocal animal model results at six or nine months occasionally have been mirrored by excellent clinical outcomes in patients. The causes of such disparities are unclear but may result from differing methods, including less injury severity than originally described in the models. Ongoing research into animal models will reconcile apparent differences with clinical trials and advance our understanding of how to apply animal models to clinical stenting in the era of DESs.

Effectiveness of sirolimus-eluting stent implantation for treatment of in-stent restenosis after brachytherapy failure

The impact of the use of sirolimus-eluting stents (SESs) in the treatment of in-stent restenosis in previously irradiated sites has not been adequately evaluated. Fifteen consecutive patients who underwent percutaneous coronary interventions using SESs in lesion sites previously intervened with intracoronary radiation therapy were identified. All stents were implanted successfully, and there were no major in-hospital complications. At 30-day follow-up, there was 1 case of subacute thrombosis that led to target lesion revascularization (TLR). At 6 months, 2 patients underwent TLR because of recurrent angina with angiographic restenosis, and 1 patient underwent target vessel revascularization distally to the SES site; no other major adverse cardiac events occurred at long-term follow-up (mean 17 +/- 8 months).

Impact of major side branch on periprocedural enzyme elevation and long-term outcome in patients undergoing percutaneous coronary intervention and brachytherapy for in-stent restenosis

Side branch occlusion is 1 mechanism for the increase of creatine phosphokinase-MB after percutaneous coronary intervention and is associated with long-term adverse events. We studied 248 patients who underwent brachytherapy for in-stent restenosis with and without side branches, compared levels of creatine phosphokinase-MB with procedural, in-hospital, and long-term clinical outcomes, and found that patients with side branches have increased levels of creatine phosphokinase-MB after percutaneous coronary intervention and higher rates of restenosis, target vessel, and target lesion revascularization at 6-month follow-up.