Comparison of Biomatrix Versus Gazelle in ST-Elevation Myocardial Infarction (STEMI)

Background

Stent Study:

A routine invasive strategy using percutaneous coronary intervention (PCI) has been shown to improve survival and freedom from recurrent myocardial infarction compared to a thrombolysis in patients with acute ST-elevation myocardial infarction (STEMI). In addition to standard medical treatment, PCI with the use of coronary artery stents not only eliminate the underlying stenotic lesion, but afford a mechanical mean of plaque stabilization, normalize coronary blood flow, reduce shear stress, and local intracoronary thrombosis. Notwithstanding, the implantation of coronary artery stents is associated with arterial injury initiating a vasculo-proliferative cascade and as a result provoke structural changes of the vessel wall. The implantation of bare-metal stents (BMS) during primary percutaneous coronary interventions (P-PCI) in STEMI patients resulted in restenosis in up to 20% of patients and has not been shown to reduce the rate of mortality and reinfarction. Randomised trials and meta-analyses showed that the use of drug-eluting stents (DES) compared with BMS in patients with STEMI significantly reduces the rate of target lesion revascularization (TLR) without negative impact on the rate of death and myocardial infarction up to one year.

However, there remain important caveats surrounding the safety of DES in patients with STEMI and evidence of harm may only arise during longer term follow up. DES implantation into culprit lesions of patients with acute coronary syndromes has been identified as independent predictor of late stent thrombosis. DES as opposed to BMS implanted into a pro-thrombotic, inflammatory milieu of ruptured plaques in STEMI patients may lead to aneurysmal changes of the adjacent vessel wall. First generation DES implanted into STEMI lesions were found to be associated with substantial delay in healing compared to BMS. Moreover, DES implanted into STEMI lesions have been associated with a higher frequency of incompletely apposed struts and uncovered struts as assessed by OCT compared with DES implanted into stable lesions. These data suggest a significantly increased risk of late thrombotic complications related to DES. The phenomenon of aneurysmal change of the vessel wall may lead to incomplete stent apposition, which in turn may predispose to late complications such as stent thrombosis, recurrent myocardial infarction, and death. In conclusion, although coronary artery stents constitute a routine medical intervention to improve the acute and long-term result in STEMI patients, only very limited information exists as to the long-term clinical outcome and structural changes of the adjacent vessel wall.

First generation DES with controlled release of sirolimus or paclitaxel from durable polymers have reduced angiographic and clinical measures of restenosis in patients with STEMI. Limus analogues are more effective as site-specific agents than paclitaxel to reduce neointimal growth and repeat revascularisation procedures. However, late stent thrombosis is more germane to first-generation drug-eluting stents than to bare-metal stents owing to delayed healing and re-endothelialization. Furthermore, hypersensitivity reactions from the polymers may further increase the risk of stent thrombosis. These effects may be particularly pronounced in ruptured plaques of STEMI patients due to the direct contact with the necrotic core.

The biolimus-eluting stent to be studied in the present proposal has several features, which attenuate the above mentioned adverse effects. First, the polymer-drug combination is applied solely to the abluminal stent strut surface (rather than circumferential), thus maximizing the exposure to the vessel wall while minimizing release into the circulation. Second, the drug (biolimus A9) is released from a biodegradable polymer, which completely degrades into carbondioxide and water during a 6-9 months period, rendering the stent more closely to a BMS. Recently, the safety and efficacy of the biolimus-eluting stent using a biodegradable polymer was demonstrated in a large trial of 1,707 patients undergoing PCI. While the overall results showed non-inferiority for all safety and efficacy endpoints as compared with the sirolimus-eluting stent, the biolimus-eluting stent showed improved outcome in terms of MACE, stent thrombosis and TLR in the pre-specified subgroup of STEMI patients.

While clinical data as described above show a favorable safety and efficacy profile, the promising results ot the subgroup analysis require confirmation in a dedicated randomized trial in the subset of patients with STEMI. The present study is therefore designed to compare the safety and efficacy of the biolimus-eluting Biomatrix stent with a bare-metal stent of otherwise identical design in a prospective, multi-center, randomized, controlled trial in patients with acute ST-elevation myocardial infarction. To address the issue of late acquired stent apposition and stent strut coverage, an imaging substudy using grayscale IVUS and OCT will be performed.

Imaging Substudy:

1. Stent Imaging Substudy The implantation of drug eluting stents into a pro-thrombotic, inflammatory milieu of ruptured plaque in STEMI patients may lead to aneurysmal changes of the adjacent vessel wall possibly leading to incomplete stent apposition, which in turn may constitute a risk factor for late complications with adverse outcome. Delayed and incomplete stent strut coverage and endothelialization is another vessel wall reaction and possibly related to adverse late outcome by increasing the risk of late stent thrombosis. OCT provides a valuable modality for the assessment of stent strut coverage with 10x higher resolution than IVUS. Recently, biolimus-eluting stents have been shown to result in more complete stent strut coverage after 9 months as compared to sirolimus-eluting stents in the OCT substudy of the LEADERS trial. To compare the biological behaviour of a newer generation DES with biodegradable polymer as compared to a bare-metal stent, an imaging substudy using IVUS and OCT for detailed analyses of the post-procedural and follow-up vessel wall behaviour will be performed.

B)Plaque Imaging Substudy Although the short-term outcome of patients with ACS and STEMI has improved in recent years, clinical outcome at one year remains complicated by recurrent myocardial infarction and death in 10-15% of patients. Previous studies using angioscopy suggest delayed plaque healing, persistent thrombus, and recurrent plaque rupture as principal mechanisms for lesion progression and its clinical complications. However, these studies are limited by a small sample size, omission of follow-up imaging, lack of correlation with easily accessible serum markers, and unavailability of high resolution imaging technology such as OCT. Moreover, it is estimated that patients with ACS have more than one ruptured plaque in >40-80% of cases, which frequently are left untreated and therefore may contribute to long-term adverse clinical outcome.

Frequency, distribution, composition (TCFA versus non TCFA), and time-related changes of plaques of the entire coronary tree in patients with STEMI have not been documented so far, mainly due to technical limitations of the OCT imaging method. New-generation OCT systems available for the present study will allow the systematic assessment of long coronary segments. The combination of IVUS-VH and OCT will substantially improve the accuracy for detection of plaques and especially of TCFA.

Therefore, new insights regarding the frequency, distribution, composition and evolution of coronary artery plaques and their prognostic impact on patients clinical outcome can be expected from the present study. Since patients with ST-segment elevation myocardial infarction suffer from a recurrent ischemic event rate of 5-10% during the first year, these findings may have important therapeutic implications for the medical treatment of affected patients to further reduce the risk of recurrence and improve prognosis.

Objective

To establish superiority of the biolimus-eluting (Biomatrix) stent compared with an otherwise identical bare-metal stent (Gazelle) in terms of the composite endpoint of death, target-vessel related myocardial infarction at 1 year.

Imaging Substudy To compare neointimal thickness and strut coverage between both stent types in lesions of STEMI patients at 13 months and assessment of frequency, distribution and time related changes of culprit versus non culprit lesions of patients with acute ST-segment elevation myocardial infarction.

Methods

Stent study

This is a prospective, multi-center, randomized, assessor-blind, trial to be conducted at several swiss and european interventional cardiology sites. A total of 1100 patients will be randomized on a 1:1 basis to either the biolimus-eluting stent with biodegradable polymer or a bare-metal stent. The number of stents is not limited per patient, but it must be consistently implanted according to the assigned treatment allocation. All patients will be followed clinically for up to 5 years after stent implantation.

Imaging substudy

100 of 1100 randomized patients fulfilling the specific inclusion criteria (see above) will undergo IVUS-VH and OCT of the culprit lesions prior to and after stent implantation as well as during follow up. Moreover, IVUS-VH/OCT will be performed in all three major epicardial vessels at baseline and follow up. The imaging study will be performed at the University Hospital Bern, Geneva, Lausanne and Cardiocentro Lugano, all Switzerland.