Long-Term Performance and Safety of the Self-Expandable Carotid Stent MER: 5-Year Outcomes from the OCEANUS Study, with Subgroup Analysis Based on Predilatation Before Carotid Artery Stenting

<b>Background</b>: Carotid artery stenting (CAS) with neuroprotection is a widely used treatment for carotid artery stenosis. This study aimed to evaluate the long-term outcomes of CAS using the MER stent (Balton, Poland) and various neuroprotection devices, with subgroup analysis based on predilatation. <b>Methods</b>: A prospective analysis was conducted on patients treated with CAS at four high-volume centers in Poland between October 2016 and May 2017. Patients were stratified into two groups based on whether predilatation was performed. Procedural and clinical outcomes, including major adverse events (MAEs) defined as all-cause death, stroke, and myocardial infarction (MI), were evaluated at 30 days and 5 years post-procedure. Kaplan-Meier analysis and Cox regression models were used to assess event-free survival and predictors of MAEs. <b>Results</b>: The study population consisted of 100 patients (males: 61%) with a mean age of 68 years. Dyslipidemia (84.4% vs. 60.0%, <i>p</i> = 0.007) and smoking (67.3% vs. 44.4%, <i>p</i> = 0.022) differed significantly between the predilatation and non-predilatation groups. The procedural success rate (<30% residual stenosis) was 97%. At 5 years, the overall restenosis rate was 7%, and target vessel revascularization was required in 3% of patients. The cumulative mortality rate was 15%, and two strokes (2%) were recorded. Multivariable regression identified prior CABG as an independent predictor of MAEs (HR 3.5, 95% CI 1.14-10.83, <i>p</i> = 0.03). <b>Conclusions</b>: CAS with the MER stent demonstrated high procedural success and favorable long-term outcomes. Predilatation did not impact outcomes. Neuroprotection was effective in all cases, with no device-related complications reported.