BIO-RESORT TRIAL: Lower Stent Strut Thickness Associated with Lower Rates of Repeat Revascularization

Fahad Alkhalfan, M.D.
By Fahad Alkhalfan, M.D. on

A prespecified analysis of the BIO-RESORT trial demonstrated that patients stent in small coronary vessels were less likely to need repeat revascularization if ultrathin-strut sirolimus-eluting stents were used as compared to the previous generation thin strut zotarolimus-eluting stent. Dr. Rosaly Buiten, the lead authors of this study published in JAMA cardiology, highlights the need to further evaluate the potential benefit of thin stent struts.

As compared to arteries with a wider diameter, the treatment of small coronary arteries with percutaneous coronary intervention (PCI) has been associated with an increased risk of needed revascularization due to in-stent restenosis. With the increasing prevalence of diabetes, a condition associated with atherosclerosis of the small coronary arteries, and the increasing availability of stents with very small lumen diameters, the proportion of patients treated with small-vessel lesions is increasing. Stents with thicker struts and smaller minimum in-stent lumen diameter have previously been demonstrated to be associated with in-stent restenosis. Therefore, the use of stents with reduced strut thickness may be advantageous. The investigators aimed to test this theory in a prespecified analysis of the BIO-RESORT trial.

“This secondary analysis of the randomized BIO-RESORT trial compared all-comers with at least 1 small-vessel lesion treated with thin-strut, very thin-strut, or ultrathin-strut DES. Drug eluting stents with particularly thin struts were found to have the lowest adverse event rate. During 3-year follow-up, there was a significantly lower incidence of target lesion revascularization in patients treated with SES than with previous generation ZES. This difference emerged during the second year of follow-up and was confirmed in patients who underwent single-vessel treatment only (ie, to exclude any potential confounding effect of treating additional nonsmall vessels).” – Dr. Rosaly Buiten, M.D.

In the BIO-RESORT trial, 3,154 patients with obstructive coronary disease were randomly assigned in a 1:1:1 ratio to either ultrathin-strut cobalt-chromium biodegradable polymer sirolimus-eluting stents (SES), or very thin-strut platinum-chromium biodegradable polymer everolimus-eluting stents (EES), or previous-generation thin-strut cobalt-chromium durable polymer zotarolimus-eluting stents (ZES). Using data from the trial, the investigators identified all patients treated with stents in small coronary vessels (less than 2.5mm). The outcome was target lesion failure by 3 years. This was a composite of cardiac death, target-vessel related myocardial infarction, or target lesion revascularization.

Out of the 3,154 patients in the trial, 1,506 patients were identified (525 in SES group, 496 in EES group, and 485 in ZES group). At 3 years, the composite endpoint occurred in 36 patients in the SES group (7.0%), 46 in the EES group (9.5%), and 48 in the ZES group (10.0%) assigned to ZES (SES vs ZES: HR, 0.68; 95% CI, 0.44- 1.05; P = .08; EES vs ZES: HR, 0.93; 95% CI, 0.62-1.39; p = 0.72). While there was no significant difference in the occurrence of cardiac death, target vessel myocardial infarction or stent thrombosis between the three vessel types, the investigators noted a difference in target vessel revascularization between SES and ZES after 1 year (2.1% vs 5.3%; HR, 0.40; 95% CI, 0.20-0.81; P = 0.009). Multivariable analysis showed that after adjusting for possible confounders, SES was associated with a lower rate of target vessel revascularization as compares to ZES (HR, 0.42; 95% CI, 0.20-0.85; P = 0.02). There was no difference in revascularization rate between EES and ZES.

The study found that drug-eluting stents with thin struts were associated with a lower adverse event rate. This difference in the ZES and SES event rates became clear during the second year of follow up. When discussing the implications of the study, Dr. Buiten wrote, “the findings of our analysis suggest that the ultrathin-strut SES may reduce the risk of repeated revascularization in small-vessel lesions, which could have a positive effect on the patients’ comfort and morbidity as well as health care expenditures. As a consequence, operators may consider strut thickness as one of the factors when making their choice of DES for treating small-vessel lesions.” However, the investigator urged caution when drawing a final conclusion from this study. Not only did the ZES and SES differ in strut thickness, but also stent geometry, polymer type, and eluted drug. There is a need for further research to definitively determine if strut thickness was the main driver behind the conclusions of this study.

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