SORT OUT VIII: Thinner Strut DES Holds Its Own Against Older Stent

Neil Osterweil

June 21, 2018

PARIS — In the ongoing saga of stent vs stent, the latest chapter shows that at 1 year of follow-up, a thin-strut, everolimus-eluting stent with a bioabsorbable-polymer (Synergy, Boston Scientific) was noninferior to a Biolimus-eluting stent (BioMatrix NeoFlex, Biosensors) in an all-comers randomized trial. 

Among 2764 patients randomly assigned to receive one of the devices for treatment of coronary artery disease, the incidence of target-lesion failure (TLF), the primary endpoint, was 4.4% for the Biolimus-eluting stent vs 4.0% for the everolimus-eluting stent.

The absolute risk difference of 0.4% met criteria for noninferiority but didn't quite make it to superiority, reported Michael Maeng, MD, PhD, from Aarhus University Hospital in Denmark, on behalf of co-investigators in the eighth Scandinavian Organization for Randomized Trials with Clinical Outcome (SORT OUT VIII) trial.

A patient-related composite outcome of all-cause mortality, any acute myocardial infarction (MI), and any clinically-driven revascularization also trended in favor of the everolimus-eluting device (hazard ratio [HR], 0.80, P = .052).

"Successful implantation of the allocated stent was more frequent in the thin-strut Synergy group, which may be associated with the lower rate of MI and the patient-related composite endpoint," Maeng said while presenting the findings here at the Congress of the European Association of Percutaneous Cardiovascular Interventions (EuroPCR) 2018.

Secondary endpoints of target-lesion or target-vessel revascularization, cardiac death, or all-cause mortality did not differ between the groups.

The incidence of definite stent thrombosis was 0.9% with the Biolimus-eluting stent and 0.7% with the everolimus-eluting stent. The HR for the difference (0.76) trended in favor of the everolimus-eluting device but missed reaching statistical significance (P = .52).

In the registry-based follow-up study, the Danish investigators enrolled and randomly assigned 2800 patients, 54% with acute coronary syndromes, to receive one of the two stents. The only inclusion criterion was a clinical indication for a drug-eluting stent.

Thirty-six patients were excluded, 25 because of consent withdrawal and 9 because of screening failure.

All of the 1385 patients allocated to the everolimus-eluting stent and 1379 assigned to the Biolimus-eluting stent were included in the analysis.

In each arm, the mean patient age was 67 and 77% of patients were male. Rates of acute coronary syndrome, diabetes, current smoking, hypertension and statin treatment, prior MI, prior percutaneous coronary intervention, and prior coronary artery bypass grafting were similar between the study groups.

Approximately one third of patients in each trial group received more than one stent, and about 22% had more than one lesion treated. The mean stent length in each group was 24 mm.

Bifurcation lesions were seen in about 17% of patients in each group, and type C lesions were seen in 34% in each group.

The noninferiority test for the everolimus-eluting stent was based on the assumption of a TLF rate of 5% at 1 year with the Biolimus-eluting stent.

The investigators plan to follow patients out to up to 10 years, Maeng said at a briefing before his presentation of the data in a late-breaking clinical trials session.

Does Thickness Matter?

Asked at the briefing whether yet another stent comparison study of two commercially available stents was needed, Maeng said that it's important "that we continue to evaluate stents that are on the market because they are changing all the time."

He pointed out that the composition of the BioMatrix device and the polymer in the Synergy device are being changed, which will require continual monitoring of outcomes associated with each stent.

"One of the main purposes of the SORT OUT trials is that we continue to monitor new stents coming on the market to see if they maintain the good results that we are seeing right now with drug-eluting stents," he said.

At the late-breaking trials session, invited discussant Robert Byrne, PhD, from the German Heart Center, Munich, told Maeng that "when you look at the primary endpoint then, your assumption, again, was 5%, and you got 4.4% and 4%, which is really great and shows that we're getting better at estimating the TLF for the sample-size calculation."

He also asked Maeng to expand on the differences the investigators saw in device-delivery failure.

"This is a secondary endpoint, only speculative, but it seems to me that it's not that surprising that a more bulky device with thicker struts might be more difficult to implant than a thinner-strut stent that is more easy to implant in the complex lesions that were included in this study," Maeng replied.

Invited discussant Julinda Mehilli, MD, from the Munich University Clinic, Germany, said, "I think it's important to point out that you are comparing two devices which have biodegradable polymer on it, and they have an important difference, which is the strut thickness, that's why I really believe that we have more delivery [with the] BioMatrix than with the Synergy stent."

However, another panelist, Manel Sabaté, MD, from the Institut Clinic Cardiovascular in Barcelona, Spain, disagreed with the idea that strut thickness may have accounted for the differences seen in AMI between the groups.

He said that strut thickness is likely related to target-vessel MI, which was similar between the treatment groups, but in the patient-oriented endpoint the MI component was any MI.

"So the thickness of the strut itself probably doesn't affect any MI in any other vessel. The thickness will influence the target-vessel myocardial infarction. That's why I think that in this conclusion, the thickness of the strut has nothing to do with any MI presentation of the patient," Sabaté said.

Maeng reiterated that the conclusion was only speculative but pointed out that difficult-to-implant stents may cause the cardiologist to be more aggressive with the guiding catheter or wires or other aspects of the implantation, with the implication that resulting damage to the arterial wall could precipitate an infarct.

The study was supported by grants from Boston Scientific and Biosensors Interventional Technologies. Maeng reported speaking honoraria from Cordis, consulting fees from Medtronic, and travel grants from both companies. Byrne disclosed serving as a speaker or a member of a speakers bureau for B Braun Melsungen AG, Biotronik, Boston Scientific, and research grants from Heart Flow and Boston Scientific. Mehilli has received speaker's fees from Abbott Vascular, Biotronik, Lilly/Daiichi, Sankyo, and Terumo. Sabaté disclosed consulting for Cordis, Abbott, Medtronic, Boston Scientific, and Biotronik.

Congress of the European Association of Percutaneous Cardiovascular Interventions (EuroPCR) 2018. Presented May 23, 2018.

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