Immediate, Midterm Outcomes Encouraging for Bioresorbable Scaffolds in STEMI

Using a bioresorbable scaffold (BRS) in patients with ST-segment elevation myocardial infarction (STEMI) is feasible and carries favorable in-hospital and 6-month outcomes, according to a study published online October 30, 2014, ahead of print in EuroIntervention. Outcomes are similar whether single or multiple overlapping BRS are used.

“However, this initial experience does not actually support… unrestricted [bioresorbable vascular scaffold (BVS)] use in STEMI patients,” note Alfonso Ielasi, MD, of Bolognini Hospital (Seriate, Italy), and colleagues. “Larger randomized trials of head-to-head comparison versus contemporary standard of care and longer follow-up are required to assess fully the potential clinical benefit of BVS in STEMI patients.” 

Procedural success (primary endpoint), which was defined as BRS implantation at the culprit lesion with less than 30% final stenosis and TIMI 3 flow without in-hospital MACE, was achieved in all but 2 patients (97.3%); no difference was observed between the single and overlapping BRS groups. One patient had a reinfarction stemming from subacute scaffold thrombosis 5 days after an inferior STEMI, and 1 patient who had an anterior STEMI caused by a complete occlusion of the mid LAD had “slow-flow” phenomenon with final TIMI flow 2.

By 6 months, 2 patients had a nonfatal MI, 3 underwent TLR, and 2 developed subacute BRS thrombosis, with outcomes similar between the single and overlapping groups. All events were successfully treated with repeat PCI. There were no deaths, and no patients required CABG.

New-Generation DES Should Remain Standard of Care

Accumulated evidence shows that “new-generation [everolimus-eluting stents] should be considered the first choice during [primary] PCI,” according to Dr. Ielasi and colleagues, who note that randomized trials are needed to compare BRS with DES in STEMI patients.

“In our single-arm study, 6-month follow-up suggests that BVS could be associated with a potentially higher event rate compared to the new-generation DES, particularly in terms of thrombosis,” Dr. Ielasi told TCTMD in an email, adding that low use of intracoronary imaging to guide implantation in the registry could have influenced the occurrence of events.

The 6-month event rate “suggests the need for meticulous lesion evaluation and scrupulous PCI techniques when implanting BVS (ie, pre- and postimplantation intravascular imaging may result in an adequate vessel diameter evaluation and in an eventual additional postdilation),” he said.

Highlighting the potentially increased risk of thrombosis with BRS, Stephen Ellis, MD, of the Cleveland Clinic (Cleveland, OH), pointed out in an email to TCTMD that the scaffolds have struts that are about twice as thick as those of DES, “theoretically making the former more thrombogenic. This could be especially problematic in a setting already at high risk for thrombosis (STEMI).”

Nonetheless, “BVS [implantation] is feasible and at least reasonably safe in the setting of STEMI,” Dr. Ellis added. “That said, all of the studies of BVS for STEMI are small, and given concerns raised theoretically and noted in GHOST about scaffold thrombosis, caution should be urged until the question of BVS vs DES for STEMI can be studied in a sufficiently powered RCT.”

Theoretical Advantages, Drawbacks to BRS

According to Dr. Ielasi and colleagues, “the implantation of a permanent device in the vessel wall can be associated with important limitations, such as durable caging of the vessel with consequent permanent impairment of the vasomotion, side-branch jailing, impossibility of late lumen enlargement, noninvasive imaging, and future surgical revascularizations.”

Some of those problems might be overcome by BRS, which have “been designed initially to accomplish the same goals as metallic-platform DES (seal dissections, prevent acute recoil, and inhibit neointimal hyperplasia) and then to overcome their limitations, disappearing entirely within 3 years and restoring native pristine vessel state,” the authors write.

“Furthermore,” they note, “theoretical advantages of BVS implantation during STEMI may be related to the younger age of typical STEMI patients, who may live many years after successful [primary] PCI, thus deriving a benefit of not having a permanent metallic prosthesis in their coronary arteries.”

But the devices also have potential shortcomings, Dr. Ielasi said: “BVS appear to not be suitable for implantation in every subset of culprit lesion (particularly if it is located at or distally to calcified and/or tortuous vessel segments) and patient (ie, the elderly or patients with contraindications to prolonged dual antiplatelet therapy).”

In addition, he said, the thicker struts of BRS may represent “a potential trigger for a recurrent thrombosis in case of suboptimal BVS-to-vessel apposition and/or suboptimal platelet anti-aggregation.”

The rate of subacute scaffold thrombosis thus far reported in the literature “may suggest the need for more studies on the matter and might suggest a procedure guided by intravascular imaging (pre- and post-BVS implantation),” the investigators write.

Source: 
Ielasi A, Cortese B, Varricchio A, et al. Immediate and midterm outcomes following primary PCI with bioresorbable vascular scaffold implantation in patients with ST-segment myocardial infarction: insights from the multicentre “Registro ABSORB Italiano” (RAI registry). EuroIntervention. 2014;Epub ahead of print.

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