Patients whose first-generation sirolimus-eluting stents (SES) appear fractured on 1-year angiographic follow-up are more susceptible to cardiac events than those with intact SES for at least the next 7 years, according to a retrospective analysis published online July 30, 2015, ahead of print in Circulation: Cardiovascular Interventions.

 Researchers led by Kazushige Kadota, MD, PhD, of Kurashiki Central Hospital (Kurashiki, Japan), performed follow-up angiography at 1 year on 972 patients with 1,795 lesions who had undergone PCI with sirolimus-eluting Cypher stents (Cordis, Johnson & Johnson) at their center between November 2002 and December 2005. 

Stent fracture—defined as the complete separation of stent segments or struts at follow-up angiography—was seen in 10.2% of patients and 5.8% of lesions.

After excluding 18 patients who had died or experienced definite stent thrombosis and 165 lesions with TLR or lost to follow-up within 1 year of implantation, the investigators followed the remaining 954 patients (mean age 68.7 years; 74% men) and 1,630 lesions for a median of 9.1 years.

Patients with stent fracture were more frequently women, while lesions with stent fracture were more likely to be complex and to occur in the RCA and in vessels with larger diameters.

At 8 years, cumulative rates of any TLR and clinically driven TLR as well as those of MI and very late definite stent thrombosis were higher in patients with stent fracture than in those with intact stents. There were no differences between the groups with regard to all-cause or cardiac death (table 1).

Table 1. Clinical Outcomes at 8 Years by Stent Status

The link between stent fracture and increased TLR at 8 years persisted after adjustment for baseline and angiographic factors (HR 1.33; 95% CI 1.02-1.77). Furthermore, a landmark analysis showed the association between stent fracture and both any TLR and clinically driven TLR held true for years 1 to 5 and the period beyond 5 years.

Among patients with very late stent thrombosis, the stent fracture group was less likely to be on dual antiplatelet therapy at the time of the event than the no-stent-fracture group. Specifically, 4 of the 6 patients with stent fracture took only 1 antiplatelet drug and 2 patients took none. In contrast, 2 of the 5 patients without stent fracture were on dual antiplatelet therapy, 2 took 1 drug, and 1 took no drugs.

Adverse Effects of Fracture Persist

Contrary to the current findings, a previous study found that while patients with fractured SES are more likely to experience adverse cardiac events than those with fracture-free stents within the first year after implantation, rates were similar between the groups for years 1 through 4. However, the discrepancy may be due to differences in the definition or degree of stent fracture, the authors suggest. In addition, the current study, with more patients and longer follow-up, may better reflect real-world experience.

While the mechanisms by which stent fracture causes very late stent thrombosis are unclear, the investigators note, factors such as the inflammatory reaction, lack of complete endothelialization of stent struts, and the hypersensitivity reaction of the coronary artery persist beyond 1 year.

The study is limited by its retrospective nature and the fact that extension of dual antiplatelet therapy was not considered for each patient, Dr. Kadota and colleagues acknowledge.

They also caution that it is unclear whether these findings apply to other DES. Nonetheless, they say, with huge numbers of patients already implanted with SES, more careful follow-up is warranted in those with strut fracture.

Source:
Ohya M, Kadota K, Tada T, et al. Stent fracture after sirolimus-eluting stent implantation: 8-year clinical outcomes. Circ Cardiovasc Interv. 2015;Epub ahead of print.

Disclosure:
Dr. Kadota reports receiving lecture fees from Abbott Vascular.

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