Stent thrombosis can be divided into acute stent thrombosis (0–24 hours), nonacute (subacute) stent thrombosis (24–30 days), late stent thrombosis (30 days–1 year), and very late stent thrombosis (> 1 year) according to the time of thrombosis after stent implantation (12). Retrospective studies suggested that preoperative cardiac dysfunction; postoperative Thrombolysis in Myocardial Infarction (TIMI) blood flow < level 3; stent malapposition; high on-treatment platelet reactivity; vascular characteristics such as bifurcation, small vessels, and Type C lesions; and discontinuation of dual antiplatelet drugs were common risk factors for acute stent thrombosis. However, late and very late stent thrombosis is often associated with the rupture of new atherosclerotic plaques, poor late acquired stent adhesion after vascular remodeling, incomplete stent endothelialization, and stent restenosis (4, 13, 14).
Prior studies suggest that acute stent thrombosis prognosis is poor and that mortality is high. Our study revealed that clinical outcomes in patients with nonacute stent thrombosis were worse than those in the de novo lesion group, including an overall increased incidence of MACEs and a primarily higher recurrence rate of myocardial infarction. However, regarding all-cause mortality, the two groups was not significantly different. Multivariate regression analysis suggested that nonacute stent thrombosis, age, sex and cardiac function were independent predictors of combined MACEs.
Our study found that compared with STEMI patients with de novo lesions, patients with nonacute stent thrombosis had more coronary heart disease risk factors and were more likely to have hypertension and hyperlipidemia. At the same time, a higher proportion of patients with nonacute stent thrombosis had a prior cardiovascular history, including prior CABG treatment (9). Our study also found that the nonacute stent thrombosis group had a higher rate of heart failure and a lower left ventricular EF at admission. We also found that a low EF was an independent risk factor for 2-year mortality. The higher event rate before matching in the nonacute stent thrombosis group may be related to the greater number of risk factors in this group of patients.
At present, because of the limited number of patients with stent thrombosis, there are few studies comparing the short-term and long-term prognosis of STEMI caused by nonacute stent thrombosis and de novo lesions, and the already published results are not consistent. Lemesle et al. (7) used CORONOR registry data to analyze 2816 patients with stable coronary heart disease (CHD) with a history of stent implantation. During the follow-up, 121 patients had 132 MIs, among whom 20% had MIs due to late stent thrombosis, and the rest had non-stent-related MIs. STEMI was present in 59% of patients with late stent thrombosis, while NSTEMI was present in the majority (74%) of patients with non-stent-related MI. Mortality was 4 times higher in patients with late stent thrombosis than in patients without stent-related MI at the 5-year follow-up (7). Noaman et al. (9) analyzed data from the Melbourne Interventional Group Registry from 2005 to 2013 and found that there were no significant differences in the short-term outcomes of in-hospital and 30-day mortality or in-hospital and 30-day MACE events between STEMI patients with stent-induced thrombosis and STEMI patients with de novo lesions. Multivariate analysis showed that stent thrombosis was not an independent risk factor for 30-day death or 30-day MACEs in STEMI patients (9). Chechi et al. (8) reported a higher incidence of in-hospital MACEs in STEMI patients with stent-induced thrombosis, but no significant difference was found in new MACEs in patients with de novo lesions at the 6-month follow-up. Furthermore, He et al. (15) compared the outcomes of STEMI due to late in-stent thrombosis and STEMI with second-generation stents and found no significant difference between the two groups in primary outcomes (cardiac death and recurrent myocardial infarction) or secondary outcomes (cardiac death, recurrent myocardial infarction, and target vessel reconstruction) in the hospital and at the 2-year follow-up. In these studies, the sample sizes of patients with stent thrombosis were small in general, and there were some differences between the study subjects. Some studies included only patients with late and very late thrombosis, while others included patients with possible stent thrombosis without angiographic or pathological confirmation, and there were also some differences in baseline data. Our study enrolled nonacute stent thrombosis patients and found no statistically significant difference between the two groups in all-cause death at either the short- or long-term follow-up after propensity score matching was used to reduce confounders in the baseline data. However, the incidence of combined MACEs (all-cause death, recurrent MI, and heart failure readmission) was higher at the 1-year and 2-year follow-ups, suggesting a higher overall event rate among patients with STEMI due to nonacute stent thrombosis, which should arouse more clinical attention.
The incidence of recurrent MI was higher in the nonacute stent thrombosis group than in the de novo lesion group at both the 1-year and 2-year follow-ups. However, the difference was not statistically significant. Previous studies have reported that the incidence of recurrent MI in the stent thrombosis group was higher both in the hospital and at the 6-month follow-up, and most cases of recurrent MI were related to recurrent stent thrombosis (8). Previous literature reported that the recurrence rate of stent thrombosis ranged from 5.9–14.3% (16, 17). This may be related to factors such as nonresponse to antiplatelet drugs, residual thrombotic load and poor stent dilatation in patients with stent thrombosis. These results suggest that enhanced antiplatelet therapy for patients with stent thrombosis and optimized treatment of stent expansion guided by endovascular imaging may reduce the risk of recurrent stent thrombosis and myocardial infarction in these patients.