Registry Outcomes Support Ultrathin Sirolimus Stent

Neil Osterweil

May 23, 2019

PARIS — Results of a large registry-based study appear to support at least some of the claims of clinical benefit with an ultra-thin sirolimus-eluting stent (Orsiro, Biotronik).

Among more than 74,000 consecutive patients in the Swedish Coronary Angiography and Angioplasty Registry (SCAAR) who received either the sirolimus-eluting stent or one of several other frequently used newer-generation drug-eluting stents (DES), the sirolimus-eluting device was associated with low rates of definite stent thrombosis, a trend toward a lower rate of in-stent restenosis, and a significantly lower rate of target lesion revascularization (TLR), reported Sergio Buccheri, MD, Uppsala University, Sweden.

"These findings corroborate the results of randomized clinical trials in this setting," he said here at the Congress of the European Association of Percutaneous Cardiovascular Intervention 2019.

Although DES with struts thinner than 70 μm and preserved radial strength have demonstrated the potential to offer benefits over other stents in patients undergoing percutaneous coronary intervention (PCI), "it remains unclear whether the use of this technology in the real world can provide incremental clinical benefits over the performance, already excellent, of other modern-generation DES," he said.

Large-Scale Study

For this analysis, Buccheri and colleagues reviewed outcomes for patients whose data were included in SCAAR, a nationwide prospective registry that collects data on the clinical and procedural characteristics for all consecutive patients who undergo PCI in Sweden.

After excluding patients with repeat procedures, those with uncommon clinical indications and those who had received a bare-metal stent, older-generation DES, or a DES implanted in fewer than 1000 patients, they identified 74,131 individual patients. Of this group. 69,570 received a late-model DES and 4561 received the sirolimus-eluting stent.

The comparator stents included Resolute Integrity and Resolute Onyx (Medtronic); Xience Xpedition, Xience Prime, and Xience ProX (Abbott Vascular); Promus Element, Promus Element Plus, Promus Premier and Synergy (Boston Scientific), and Ultimaster (Terumo).

Clinical characteristics were similar between the groups, and mean age was approximately 67 years. The most frequent indication for PCI with stenting was acute coronary syndrome, which occurred in two-thirds of patients in each cohort.

There were some differences in procedural characteristics, however, with patients who received the sirolimus-eluting device having less frequent left main procedures (2.6% vs 5.5%) and shorter total stent length (31.5 vs 35.7 mm).

The authors used propensity-score weighting and covariate balance with a nonparsimonious approach to compensate for the lack of randomization.

They found that rates of all-cause mortality were identical between the groups, occurring in 7.5% of patients in each cohort. Rates of myocardial infarction (MI) were numerically but not statistically higher in patients who received the sirolimus-eluting stent (6.0% vs 5.2%).

There were also no significant differences between the groups in rates of either in-stent restenosis (1.5% vs 2.0%, respectively) or definite stent thrombosis (0.67% vs 0.83%).

For the TLR end point, however, the investigators saw a significant difference in favor of the sirolimus-eluting stent (1.6% vs 2.3%; adjusted hazard ratio, 0.75; P = .013).

Known Unknowns

Invited discussant Rasha Al-Lamee, MD, Imperial College Healthcare, London, said that it is important to have real-world results that back up those reported in clinical trials.

"I think that the promise of these ultra-thin scaffolds or ultra-thin stents is biologically very plausible, that they may have good outcomes for our patients in the long term," she said. "It would make sense that if the struts were thinner, we would have less vessel injury, we'd have less death or less inflammation, perhaps improved healing, and perhaps improvement in our patient outcomes."

She noted, however, that although the investigators did their best to control for confounding factors, "there are always confounders out there that we don't see."

Given the difference in the size of the cohorts, it would be inadvisable to read too much into the numerical but not statistical superiority of the sirolimus-eluting stent for some clinical outcomes, such as in-stent restenosis and definite stent thrombosis, she cautioned.

"Interestingly, in all these studies going forward, it's very difficult for us to improve on some of the outcomes we already have. Even with 74,000 patients, you don't see a difference, really, in stent thrombosis rates, because perhaps the rate of stent thrombosis is so small that we can't incrementally improve really on what we do," she said.

The study was supported by an institutional research grant from Biotronik. Buccheri reported having no conflict of interest. Al-Lamee has reported receipt of honoraria or consultation fees from Philips Volcano.

European Association of Percutaneous Cardiovascular Intervention (EuroPCR) 2019. Presented May 21, 2019.

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