Washington Editor

It can scarcely be claimed the drug-eluting cardiovascular stent wars are over, but Abbott Vascular (Temecula, California) now has its bioresorbable vascular scaffold (BVS) in the fight, as the Everbio II trial makes clear. Lead investigator Stéphane Cook of the Hospital and University (Fribourg, Switzerland), said the trial suggested that the two device types were similar in terms of target lesion and all revascularization, but the two DES units bested the BVS on in-segment late lumen loss, which Cook said, "reinforces our primary hypothesis of DES superiority within the 6-12 month timeframe."

Abbott unveiled early data from the Absorb II trial at TCT only to incur some blowback from the chief medical officer at Boston Scientific (BSX; Natick, Massachusetts), who poo-pooed the data as indicative of a device that's not ready for prime time (Medical Device Daily, Sept. 16, 2014). Cook's presentation covered a trial that matched the BVS against Biomatrix Flex stent, a biolimus-eluting offering from Biosensors (Singapore), as well as the BSX Promus stent, which like the Abbott product elutes everolimus.

The 240 patients in Everbio II were divided evenly between the three devices, and Cook said the BVS is "thought to reduce long-term complications," including neoatherosclerosis "and very late stent thrombosis." He said there are data on the device's use in simple lesions, but added that the BVS is finding its way into "complex patients and lesions."

Cook indicated the BVS exhausts its supply of everolimus at three months, about the time the radial strength of the scaffold has likewise disappeared. Mechanical integrity is gone before nine months, and he cited an article from 2010 in the Journal of the American College of Cardiology by Garg and Serruys in depicting the stent mass loss as complete by 24 months. Thus, Cook said, there may be some question as to the risk of restenosis after mechanical integrity is at zero.

The primary endpoint for Everbio II was in-stent late lumen loss at nine months, while secondary endpoints included in-segment late lumen loss and patient-oriented major adverse cardiac events (MACE), including death, myocardial infarct and target-vessel revascularization. Another secondary endpoint, device-oriented MACE, consisted of the same measures as patient-oriented MACE plus thrombosis at nine months as defined by the Academic Research Consortium.

The BVS arm lost two enrollees due to protocol violations while all three arms lost several patients to withdrawn consent between six and nine months. Hypertension was more common in the BVS enrollees, and this group had a lower ratio of patients who had previously undergone bypass. There were no statistically significant differences in measures such as number of diseased or treated vessels per patient, or in lesions treated per patient. One of the important differences between the three articles was strut thickness, which is 81 micrometers for the Promus, 112 micrometers for the Biomatirx and 156 micrometers for the BVS.

Grouping the Promus and the Biomatrix together against the BVS, Cook said the rate of in-stent late lumen loss at nine months was "similar between both groups." This endpoint was a quarter of a millimeter for the two comparator devices and 0.28 mm for the BVS, but the difference did not hit statistical significance. In-segment late lumen loss again failed to reach statistical significance, but the absolute difference was 0.30 for the BVS and 0.19 for the other two. Cook noted "there were no incidents of thrombosis at nine months."

"BVS demonstrated satisfactory angiographic and clinical outcomes" compared to the two stents, Cook observed, and he said the difference in in-segment late lumen loss "may be due to the modest and transient constrictive effect found at scaffold edges." Cook acknowledged, "this study was not powered for non-inferiority to detect differences in clinical event rates," adding that it was a single-center trial, thus limiting the generalizability.

One of the panelists said he was "very impressed" with the numbers on lumen loss, adding that the BVS "at its weakest time point is pretty good. There is no statistically significant difference." The observation was made also that the BVS is "not as good as metallic stents" for lumen loss, but that there is "no more difference than current DES" offerings for this measure.

Also presenting at TCT was David Hildick-Smith, of Sussex Cardiac Center (Brighton, UK) who discussed the PRIMA trial, sponsored by St. Jude Medical (St. Paul, Minnesota). The study tracked migraines and migraines with auras to evaluate the effect of devices for closure of patent foramen ovale against medical management.

Hildick-Smith remarked that the trial was quite difficult, in part because it demanded much of enrollees. "Headache diaries required that patients be very assiduous" about keeping those diaries, and enrollees were assessed at months one and three, then every three months thereafter out to 12 months, which in aggregate constituted a "very heavy burden on the patient."

More than 700 patients were consented, but only 107 were actually enrolled, and Hildick-Smith said "the study was terminated prematurely" due to enrollment problems. Those enrolled were randomized at a 1:1 ratio, but only 41 implants went into the 53 randomized to the device, and one of those did not make it to the 12-month follow-up. Of the 54 randomized to medical therapy, only 43 kept their diaries, he said.

Patients on the study article saw a drop of mean migraine days from 8.0 to 5.1 at one year, but this failed to hit statistical significance against the drop from 8.3 to 6.5 among those on medical management. Reduction in migraine days with aura, a secondary endpoint, likewise exhibited a numerical improvement favoring closure (4.1 days to 1.7 on the device, 4.0 to 3.4 on medical management), and this was good for a p score of 0.01, which Hildick-Smith said was a significant reduction.

The outcome is generally seen as a disappointment, but Hildick-Smith remarked that the use of PFO closure devices for treatment of migraines has experienced a lot of blowback in the UK recently. Still, he asserted, "there does remain a very intriguing relationship" between closure and migraines, at least those with auras, adding, "there is real and tangible benefit that accrues to some migraine patients."

"The results of the Premium trial are eagerly awaited to see if they confirm or refute" the Prima trial's outcome, Hildick-Smith said of the 230-subject study of the Amplatzer.