PARIS (FRONTLINE MEDICAL NEWS) – Device thrombosis occurred nearly four times more frequently in recipients of the Absorb everolimus-eluting bioresorbable vascular scaffold than with the Xience everolimus-eluting metallic stent during 2 years of prospective follow-up in the randomized AIDA trial.
AIDA (the Amsterdam Investigator-Initiated Absorb Strategy All-Comers Trial) was the first randomized trial designed to compare the Absorb scaffold to a drug-eluting metallic stent in a broad patient population reflecting routine real-world clinical practice. The disturbing AIDA finding follows upon earlier serious concerns raised regarding an increased risk of scaffold thrombosis – and the particularly worrisome complication of late thrombosis – in the ABSORB Japan and ABSORB II trials, Joanna J. Wykrzykowska, MD , reported at the annual congress of the European Association of Percutaneous Cardiovascular Interventions.
Importantly, the AIDA investigators could not identify any predictors of increased device thrombosis risk in Absorb recipients other than the device itself. Neither age, presenting symptoms, lesion characteristics, vessel size, cardiovascular risk factors, nor residual percentage stenosis defined a subgroup of scaffold recipients at particularly increased risk for this serious complication, said Dr. Wykrzykowska of the University of Amsterdam.
The device was approved by the Food and Drug Administration in July 2016. In March 2017 the agency issued a safety alert regarding the Absorb scaffold after release of the 2-year data from the 2,008-patient ABSORB III trial showing a significantly higher rate of target-lesion failure than with the Xience stent. Both devices are marketed by Abbott Vascular.
AIDA was a single-blind multicenter Dutch trial that randomized 1,845 patients undergoing PCI, 55% of whom presented with acute coronary syndrome and 26% of whom had ST-elevation MI. The primary endpoint was target vessel failure, a composite of cardiac death, target vessel MI, or target vessel revascularization. The 2-year cumulative rate did not differ significantly between the two study arms: 11.7% in the scaffold group and 10.7% in the metallic stent recipients.
However, definite or probable device thrombosis occurred in 3.5% of the scaffold group compared with 0.9% of metallic stent recipients, for a highly significant 3.9-fold increased risk. This was associated with a significantly increased 2-year cumulative risk of MI: 5.5% versus 3.2%.
On the basis of this unsettling finding, coupled with the fact that ABSORB II investigators did not find any instance of very late scaffold thrombosis among 63 patients who remained on dual-antiplatelet therapy (DAPT) continuously for up to 3 years, Dr. Wykrzykowska and her coinvestigators have informed AIDA participants of their treatment assignment. They have also recommended that the Absorb recipients go on extended DAPT, even though there is no high-grade evidence as yet that this will prevent late scaffold thrombosis or that the drug-induced increased bleeding risk of prolonged DAPT might cancel or perhaps even outweigh the potential protection against device thrombosis.
On top of all this, implantation of the scaffold entails a longer procedure time and a greater volume of contrast material.
Discussant Mahmoud Hashemian, MD, observed that while bioresorbable vascular scaffolds are “physiologically ideal” because, unlike metallic stents, theoretically they leave no permanent implant to impede vasomotion and serve as a nidus for neoatherosclerosis, to date they have shown no real-world benefits over current-generation drug-eluting metallic stents, but only disadvantages.
“This doesn’t mean we have to feel hopeless. I’m not hopeless at all,” said Dr. Hashemian, an interventional cardiologist at Day General Hospital in Tehran. “I’m sure this [bioresorbable scaffolds] will be the future of our stents. But it needs more work. The company tells me they are going to launch a newer one, maybe next year, with thinner struts and more expandability.”
Asked about the likely mechanism of prolonged thrombosis risk with Absorb, Dr. Wykrzykowska was quick to say no one really knows at this point.
“Technique [predilation at a 1:1 balloon-to-artery ratio with an appropriately sized balloon] can obviously improve things in the short term for early events, but I don’t think we understand the biology of late events. We don’t understand the interaction between the device and the vessel. It’s extremely complex,” she said.
AIDA was funded by an unrestricted educational grant from Abbott Vascular. Dr. Wykrzykowska reported receiving consulting and lecture fees from the company.