Chronic stable angina revascularization drug eluting stents


 * Associate Editor(s)-In-Chief: Lakshmi Gopalakrishnan, M.B.B.S.

Overview
The hierarchical Bayesian meta-analysis (2004) demonstrated a significant reduction in the rate of angiographic restenosis and major adverse cardiac events observed with the drug-eluting stent (sirolimus or paclitaxel) in comparison to the bare-metal stents; however, there was no evidence that they affect mortality or myocardial infarction rates. A recent update on drug-eluting stents (2008), reported similar success rates and side effects associated with both the Cypher (sirolimus eluting) and the TAXUS (paclitaxel eluting) stents; hence, suggested a similar benefit may be replicated in routine clinical practice. The prevention of neointimal hyperplasia is no longer the ultimate goal and has been replaced by the development of more biocompatible and bioabsorbable stents that facilitate adequate endothelialization.

Paclitaxel-eluting stent studies
The clinical outcome with the use of paclitaxel depends on whether it is a polymer-based or not. Based on the results of the DELIVER-I study, paclitaxel without a polymer carrier did not demonstrate a positive clinical outcome despite an improvement noted in the angiographic parameters. However, on the contrary a polymer-based paclitaxel significantly improved clinical outcomes demonstrated by the TAXUS-IV and TAXUS-VI trials.


 * The DELIVER trial (2004) demonstrated a significant reduction only in the angiographic late lumen loss (0.81 versus 0.98; p=0.003) at follow-up with non-polymer-based paclitaxel-coated stent compared to bare metal stent respectively among 1043 patients with focal denovo coronary lesions. Thus, the study concluded paclitaxel-coated stent decreased the neointimal proliferation compared with the bare-metal stent; however, this reduction was insufficient to meet the prespecified primary end-point of target-vessel failure (11.9% in the polymer-coated stent group versus 14.5% in the bare metal stent group; p=0.12) and the secondary end point of binary restenosis (14.9% in the polymer-coated stent group versus 20.6% in the bare metal stent group; p=0.076).


 * In the TAXUS-IV trial (2004), 1314 patients who were receiving a stent in a single, previously untreated coronary artery stenosis with a mean vessel diameter of 2.75 mm and a mean lesion length of 13.4 mm at baseline, were randomized to receive either a bare-metal stent (n=652) or a slow-release polymer-based, paclitaxel-eluting stent (n=662), to assess the incidence of neointimal hyperplasia and restenosis with paclitaxel. At 9-month follow-up, a significant reduction in the rate of ischemia-driven target-vessel (12% in the BMS group versus 4.7% in the TAXUS group; relative risk 0.39; 95% CI, 0.26 to 0.59; p=less than 0.001), target-lesion revascularization (11.3% in the BMS group versus 3% in the TAXUS group; relative risk 0.27; 95% CI, 0.16 to 0.43; p=less than 0.001) and the rate of angiographic restenosis (26.6% in the BMS group versus 7.9% in the TAXUS group; relative risk 0.30; 95% CI, 0.19 to 0.46; p=less than 0.001) was observed in the TAXUS group. However, the rate of all cause of mortality including MI (4.7% in the BMS goup and 4.3% in the TAXUS group; p=NS) and stent thrombosis (0.6% in the BMS goup and 0.8% in the TAXUS group; p=NS) during a 9-month follow-up did not differ between the two groups. Thus, the study concluded in comparison with bare-metal stents, the slow-release, polymer-based, paclitaxel-eluting stent is safe and markedly reduced the rates of clinical and angiographic restenosis at nine months.


 * In the TAXUS-VI trial (2005), 448 patients with long, complex coronary artery lesions were randomized to receive either a drug-eluting TAXUS Express-2 stent or an uncoated Express-2 control stent, to assess the efficacy of paclitaxel-eluting stent in the treatment of complex coronary stenoses with a mean lesion length of 20.6mm at baseline. At 9-month follow-up, a significant 53% reduction of target-vessel revascularization (9.1% in the TAXUS group and 19.4% in the control group; p=0.0027) and a significant reduction from 32.9% in the control group to 9.1% in the TAXUS for the binary restenosis at the stented area was observed in the TAXUS group (p=less than 0.0001). However, the incidence of major adverse cardiac events at 9-month follow-up, was similar among both the groups: 16.4% in TAXUS and 22.5% in the control group (p=NS). Thus, the study concluded that the TAXUS Moderate Release stent system is safe and effective in the treatment of long, complex coronary artery lesions; hence, providing the evidence base for more widespread use of drug-eluting stents in contemporary clinical practice.


 * Clinical follow-up at 2 years (2007) post-stenting was available in 98.6% of the TAXUS group and 95.6% of the control group. The incidence of major adverse cardiac event at one- and two-year follow-up was 16.4% and 21.3% in the TAXUS group when compared with 22.5 and 25.1% in the control group, respectively. A significant difference in the target-vessel revascularization was maintained at two-year follow-up (TAXUS 13.9%; control 21.9%; P=0.0335). There was also a significant reduction in the cumulative one- and two-year survival rates free from target-vessel revascularization (91.7 and 90.3% in the TAXUS group versus 80.0 and 79.0% in the control group; p=less than 0.001).


 * At 5-year follow-up (2009), the overall rate of major adverse cardiac events was found to be similar among both the groups (27.8% in control and 31.3% in TAXUS; p=0.61), including similar rates for stent thrombosis, target-vessel revascularization (23.7% in control and 22.2% in TAXUS; P=0.45). Thus, the study concluded since the TAXUS MR stent demonstrated similar rates of target-vessel revascularization, incidence of major cardiac event and reduced the rate of target-lesion revascularization in comparison to the control through five years, it is may be beneficial to use paclitaxel-eluting TAXUS moderate-release for long, complex coronary artery lesions. However, the cause for the increased rate of non-target lesion revascularization (5.1% in control and 10.9% in TAXUS; p=0.0274) associated with TAXUS remains unclear.

Sirolimus-eluting stent studies
In contrary to the paclitaxel-eluting stent studies, the trials that assessed the effect of sirolimus have tested only the polymer-based sirolimus-eluting stent.


 * In the SIRIUS study (2003), 1058 patients with complex coronary artery disease due to the presence of diabetes, mean lesion length of 14.4 mm and a mean vessel diameter of 2.80 mm at baseline, were randomized to receive either a sirolimus-eluting stent or a standard stent to evaluate the effect of sirolimus in the reduction of restenosis after PCI. At 9-month follow-up, a significant reduction in the frequency of neointimal hyperplasia within the stent was observed with the sirolimus-eluting stents, as assessed by both angiography and intravascular ultrasonography. Subgroup analyses revealed a significant reduction in the rates of angiographic restenosis and target-lesion revascularization in all subgroups examined. Thus, the study concluded that sirolimus-eluting stent provided beneficial results in patients with complex coronary lesions and also significantly reduced the rate of neointimal proliferation, restenosis and associated clinical events.


 * In the SIRIUS trial, 459 with an LAD stenosis and a mean length of 14.0mm at baseline, were randomized to percutaneous intervention with either sirolimus-eluting stent or bare-metal stents, to evaluate the benefit of drug-eluting stent secondary to the reduction of restenosis rate in the management of LAD stenosis. The study reported a significant reduction in the rate of binary in-stent restenosis in the SES group (2% in the SES group versus 41.6% in the BMS group; RR 0.05; p=less than 0.001). A significant 59% reduction in the one-year major adverse events including death, MI or target vessel revascularization was noted in the SMS group (9.8% SMS group versus 24.9% BMS; RR 0.39; p=less than 0.001). Thus, the study concluded for LAD stenosis, the revascularization rate with sirolimus-eluting stent was similar to that of the single vessel bypass surgery at one-year.


 * Both the RESEARCH registry and the Swiss registry demonstrated significant benefit with the use of sirolimus in routine clinical practice. The RESEARCH registry (2004) reported a significant reduction in the rate of target-vessel revascularization for sirolimus group (3.7% in the sirolimus versus 10.9% in the BMS; p=less than 0.001). The Swiss registry (2004) also demonstrated a 95.6% significant event-free survival noted in the sirolimus group as observed during a 6-9 month follow-up.


 * The Cypher stent registry (2004), demonstrated similar benefits such as survival-free of major adverse cardiac event (96.4% in the SES group versus 82.8% in the BMS group; p=less than 0.05) and significant reduction in the rate of restenosis observed with the use of sirolimus-eluting stent for the treatment chronic total coronary obstruction.