Relationship between stent fracture and stent thrombosis

We read with interest the Review by Tommaso Gori and colleagues (Predictors of stent thrombosis and their implications for clinical practice. Nat. Rev. Cardiol. 16, 243–256 (2019))¹. The authors present the different risk factors that potentially lead to stent thrombosis and the new therapies for this condition. One of the risk factors identified for stent thrombosis is stent fracture, with studies by Kuramitsu and colleagues² and Kan and colleagues³ being cited.

In the study by Kuramitsu and colleagues, 1,035 patients with 1,339 lesions treated with everolimus-eluting stents were followed up for 6–9 months². The incidence of stent thrombosis in the stent fracture group was higher than that in the non-stent fracture group (5.1% versus 0.4%; P = 0.018). In the study by Kan and colleagues, 6,555 patients with 10,751 lesions treated with a drug-eluting stent were followed up for 9–12 months³. Again, the incidence of stent thrombosis in the stent fracture group was higher than that in the non-stent fracture group (4.60% versus 1.03%; P < 0.05). Therefore, Gori and colleagues inferred that stent fracture is associated with stent thrombosis¹.

However, in a study by Umeda and colleagues, in which 793 patients with 874 lesions treated with a sirolimus-eluting stent were followed up for 4 years, no significant difference was observed in the incidence of stent thrombosis between the stent fracture group and the non-stent fracture group (2.9% versus 0.8%; P = 0.148)⁴. In addition, Nakazawa and colleagues reviewed high-contrast, film-based radiographs and performed histopathological analysis of 177 consecutive lesions from the CVPath drug-eluting stent autopsy registry⁵. Only severe stent fracture (with transection causing a gap in the stent segment) was significantly associated with stent thrombosis. In a study of 2,098 patients who had a coronary stent implanted and who underwent follow-up coronary angiography at the Second Affiliated Hospital of Nanchang University, China, between 2012 and 2017, eight patients were found to have stent fracture (four confirmed by intravascular ultrasonography). As of 1 December 2018, the mean duration of follow-up of these eight patients was 903 ± 683 days, and none had developed stent thrombosis (Y.-H.R. and R.-Q.Y., unpublished observations).

In summary, stent fracture and stent thrombosis are both rare but severe complications of coronary procedures with a very complex pathophysiology, but the relationship between them is still uncertain. The classification of coronary stent fracture, the drug coating of the coronary stent and the duration of coronary stent implantation must be carefully considered when exploring the relationship between stent fracture and thrombosis. Perhaps with the increasing awareness of stent fracture, new imaging tools such as intravascular ultrasonography and optical coherence tomography will be used to define the relationship between stent fracture and thrombosis.

There is a reply to this letter by Gori, T. et al. Nat. Rev. Cardiol. https://doi.org/10.1038/s41569-019-0263-5 (2019).