Bioresorbable Scaffolds Show Promise in Select STEMI Patients
The implantation of fully bioresorbable vascular stents (BVS) is feasible in select patients with ST-segment elevation myocardial infarction (STEMI), according to a small study published online January 6, 2014, ahead of print in the European Heart Journal. Comprehensive imaging analysis showed improved flow rates and good scaffold apposition at 30 days.
The second-generation everolimus-eluting BVS (ABSORB, Abbott Vascular, Santa Clara, CA) is a balloon expandable device consisting of a polymer backbone of poly-L-lactide acid coated with a thin amorphous matrix of poly-D and L-lactide acid polymer (strut thickness 157 mm). The majority (80%) of the everolimus is eluted within the first 30 days, and both polymers are fully bioresorbable.
Researchers led by Robert Jan van Geuns, MD, of Erasmus Medical Center (Rotterdam, The Netherlands), looked at 49 STEMI patients (intent-to-treat population) assigned to treatment with the BVS at their institution from November 2012 to April 2013.
Manual thrombectomy was performed in three-quarters of patients, and direct stenting in one-third. A total of 65 scaffolds were implanted, with 12 patients receiving overlapping scaffolds; procedural success was 97.9% (n = 48).
In quantitative coronary angiography (QCA) analysis, baseline TIMI flow was 0 in half of patients. After implantation, there were no cases of TIMI flow 0, with TIMI flow III achieved in 91.7% of patients. No angiographically visible residual thrombus was observed post-procedure.
On optical coherence tomography (OCT) analysis (n = 31), mean lumen area was 8.02 ± 1.92 mm2, minimum lumen area was 5.95 ±1.61 mm2, and minimum flow area was 5.62 ±1.66 mm2. Incomplete scaffold apposition (ISA) was observed in 20 patients with a mean ISA area of 0.118 + 0.162 mm2 and a mean percentage of malapposed struts per patient of 2.80 ±3.90%. There were 7 scaffolds (22.6%) with > 5% malapposed struts.
After 30 days, there were no instances of target lesion failure, TVR, emergency CABG, clinically driven TLR, cardiac death, or scaffold thrombosis. One patient developed a non-Q-wave MI related to a non-target-vessel lesion and underwent revascularization.
‘Good Acute Performance’
The data “are supportive of feasibility and good acute performance of the BVS for the treatment of patients with acute MI,” Dr. van Geuns and colleagues write.
“A theoretical concern related to the implantation of the BVS in such thrombotic lesions is the fact that scaffold positioning and placement may need a more aggressive lesion preparation (predilatation) compared with standard metal devices, due to its slightly higher profile,” they comment. “We hypothesized that this strategy might be prone to an increase in distal embolization following balloon inflations, favoring no-reflow and reducing the rate of final TIMI-flow III.”
However, the study showed high grade TIMI flow in the vast majority of patients after implantation, the authors write, supporting evidence seen in recently reported large trials evaluating metallic stents in acute MI patients.
“Due to the limited number of patients and events, caution should be made in reaching firm conclusions,” they note, adding that “a head-to-head comparison with the current standard of care” as well as a larger population and longer follow-up will be needed to fully evaluate the performance of the BVS in STEMI patients.
Results Lend Confidence
In a telephone interview with TCTMD, Ajay J. Kirtane, MD, SM, of Columbia University Medical Center (New York, NY), said the data are “very intriguing and it’s nice to see it published in this systematic way” given rumors circulating about BVS being used in this setting in other countries.
Considering the lack of established data on BVS in STEMI patients, “you need things like this to make you feel more confident,” he said, emphasizing that the study focused on specific STEMI patients and not the overall population. “To generalize this to all STEMI patients, at present, might be going a little bit too far.”
The OCT analysis is encouraging, Dr. Kirtane observed, given that adverse thrombotic events are likely to happen within 30 days after stent implantation. “The fact that they had no stent thromboses seen is pretty reassuring,” he said. “There’s nothing that we would worry about based upon these early results that would preclude [a larger analysis].”
Dr. Kirtane related the current state of BVS research to the initial stages of DES study. “The main issue really relates to the same issue that we saw when drug-eluting stents first came out. They were studied in specific lesion subsets and then rapidly expanded through off-label use,” he explained.
But he cautioned going down the same path with BVS since off-label use is risky and the outcomes unknown. “It might be fine in that setting, as drug-eluting stents were shown to be, but you have to be cautious about it and study it so that we can feel confident.”
Appropriate sizing will be an issue for BVS since they are not as easily manipulated as metallic stents, Dr. Kirtane commented. Hence, he said he was not surprised at the high rates of thrombectomy use in the study and predicted increased use of OCT and IVUS in these patients going forward before scaffolds are implanted.
Mean door-to-balloon time was 31.3 minutes, and all patients were treated with unfractionated heparin and dual antiplatelet therapy (aspirin plus prasugrel or clopidogrel).
The scaffold lengths used were 12, 18, and 28 mm, with scaffold diameters of 2.5, 3.0, and 3.5 mm. Mean scaffold length per-lesion was 26.40 mm, and mean scaffold diameter per lesion was 3.2 mm. A highly supportive wire was used in 5 cases and a radial approach was used in just over half of patients (53.0%).
Diletti R, Karanasos A, Muramatsu T, et al. Everolimus-eluting bioresorbable vascular scaffolds for treatment of patients presenting with ST-segment elevation myocardial infarction: BVS STEMI first study. Eur Heart J. 2014;Epub ahead of print.
- Dr. van Geuns reports receiving speakers fees from Abbott Vascular.
- Dr. Kirtane reports participating in studies through his institution, which receives institutional research support from Abbott Vascular, Abiomed, Boston Scientific, Medtronic, and St. Jude Medical.