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TROFI II: Vasomotion more evident with BVS, but issues remain
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Vasomotion was more evident at 3 years in patients with STEMI who underwent primary PCI with a bioresorbable vascular scaffold, compared with an everolimus-eluting stent, but the device was also associated with more dismantling, according to a subanalysis of the TROFI II trial presented at EuroPCR.
The BVS (Absorb BVS, Abbott Vascular), compared with an everolimus-eluting stent (EES; Xience, Abbott Vascular) has been linked to increased rates of early, late and very late thrombotic events, which led to its removal from the U.S. market in 2017. Supporters of the technology, however, have emphasized the importance of focusing on outcomes after the scaffold has fully resorbed.
“At 3 years, the mechanical forces of the BVS applied to the vessel wall should have completely disappeared; and the [infarct-related artery]-dependent microcirculation should be in a stable phase after the remodeling of the infarcted myocardium,” Josep Gomez-Lara, MD, PhD, from the Institut d’Investigacio Biomedica de Bellvitge, Hospital Universitari de Bellvitge, Universitat de Barcelona, L’Hospitalet de Llobregat, Spain, and colleagues wrote in a simultaneous publication in JACC: Cardiovascular Interventions. “However, the vasomotor responses to endothelial-dependent and independent vasomotor drugs, as well as the functionality of its microcirculation, are unknown.”
Study results
To learn more, the researchers compared vasomotor responses of the infarct-related artery to endothelial-dependent and independent vasomotor drugs — acetylcholine and nitroglycerin — in patients who received BVS or EES in the randomized TROFI II study. Patients underwent coronary angiography with vasomotor, microcirculatory and OCT examination at 3 years and vasomotion was defined as a greater than 4% change in mean lumen diameter.
Of 63 patients from the TROFI II study who were screened, 38 — 20 with BVS and 18 with EES — were included in the final analysis.
More than 60% of all patients had paradoxical vasoconstriction to acetylcholine in the peri-scaffold or peri-stent segments, according to the data. However, more patients with BVS, compared with EES, had vasoconstriction to acetylcholine (77.8% vs. 25%; P = .008) and vasodilation to nitroglycerin (61.1% vs. 18.8%; P = .018) in the scaffold or stent segment.
In terms of infarct-related artery microcirculation, the index of microcirculatory resistance was similar for the BVS and EES groups (23.8 vs. 22.4, respectively; P = .781), as were coronary flow reserve (2.4 vs. 1.9, respectively; P = .523), fractional flow reserve (0.91 vs. 0.93, respectively; P = .317) and absolute coronary blood flow (135.5 mL/minute vs. 147.3 mL/minute, respectively; P = .791).
OCT findings showed patients with BVS vs. EES were less likely to have malapposition (0% vs. 31.5%; P = .013) and coronary evagination (0% vs. 68.8%; P < .001). However, scaffold or stent fractures were more common with BVS than EES (52.6% vs. 0%; P = .001). Additionally, numerically fewer patients with BVS vs. EES had uncovered struts (57.9% vs. 81.3%; P = .167), but there were more scaffold or stent structural discontinuities protruding into the lumen, or device dismantling, in patients with BVS vs. EES (26.3% vs. 0%; P = .049).
The researchers cited several study limitations, including the potential for other clinical factors for which they did not account to influence endothelial function; the fact that the endothelial-independent vasomotor test was performed after the endothelial-dependent vasomotor test; and the study’s observational and descriptive nature.
“Further investigations are required to assess the clinical implications of these findings,” the researchers wrote.
Questionable benefits
In an accompanying editorial, Hiroyuki Jinnouchi, MD, Cardiology Today’s Intervention Editorial Board Member Renu Virmani, MD, and Aloke V. Finn, MD, all from CVPath Institute in Gaithersburg, Maryland, noted that the findings add to the knowledge base surrounding BVS while also serving to “temper enthusiasm.”
“The disparate OCT findings (coverage with luminal dismantling) combined with the lack of endothelial-dependent vasodilation suggest major problems with healing with Absorb even at 3 years,” they wrote, adding that this information is necessary to guide duration of dual antiplatelet therapy in patients with BVS.
Overall, they concluded, more evidence is necessary.
“From this study as well as previous work, there is simply not enough data to suggest that long-term benefits with Absorb such as vasomotion outweigh the risks of stent thrombosis that have been reported in multiple studies,” they wrote. “At present, the promise of BVS remains more fiction than fact and if its future is to be realized, long-term responses such as vasomotion and compensatory dilation will need to be conclusively shown.”– by Melissa Foster
References:
Gomez-Lara J, et al. New data on BRS. Presented at: EuroPCR; May 22-25, 2018; Paris.
Gomez-Lara J, et al. JACC Cardiovasc Interv. 2018;doi:10.1016/j.jcin.2018.04.026.
Jinnouchi H, et al. JACC Cardiovasc Interv. 2018;doi:10.1016/j.jcin.2018.05.028.
Disclosure: One author reports he has received institutional research grants from Abbott, Amgen, Biotronik, Boston Scientific and St. Jude Medical. All other authors report no relevant financial disclosures. Please see the editorial for a full list of the editorialists’ relevant financial disclosures.
Perspective
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David J. Moliterno , MD, FACC
The observations from this small study continue to support the general concepts of a resorbable stent — that the resorbable scaffolds do go away over time and leave behind similar vascular dimensions and downstream physiology compared with permanent stents.
However, this study will not affect current practice as there are no attractions, yet potential distractions, to a scaffold with unpredictable and potential deleterious dismantling. For example, DAPT may need to be prolonged further with such a resorbable platform until proof of long-term avoidance of scaffold thrombosis is established.
While this study was not so focused on CV health, but rather potential differences between a resorbable scaffold vs. a permanent stent, it is impressive that despite at least 3 years of presumed measures to improve CV health (eg, smoking cessation, aggressive lipid lowering, cardiac rehabilitation), that the majority of patients (> 60%) still had endothelial dysfunction (ie, paradoxical vasoconstriction to acetylcholine). In fact, that the “cage” had disappeared among most patients receiving the resorbable scaffold, such patients were able to demonstrate this paradoxical vasoconstriction in the stented segment compared with those receiving a permanent stent (78% vs 25%), and that does not seem attractive. Are we again focused on the scaffold vs. stent and not on the patient?
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