Stent thrombosis is a recognized complication occurring in 1-2% of patients with coronary artery disease treated by percutaneous coronary intervention (PCI) with stent implantation. Its occurrence is expected to increase with the number of stent implantation procedures done worldwide. Moreover, stent thrombosis is a hot topic in the cardiology community.
Drug-eluting stents (DES), which are increasingly replacing bare metal stents (BMS) because of their higher patency rate, are expected to increase its frequency. Re-PCI is the commonly adopted treatment to re-establish coronary flow to the heart tissue by reopening a stent obstructed by thrombosis. However, little scientific data is available on the outcome of PCI for stent thrombosis in the contemporary DES era.
OPTIMIST is a non-sponsored, independent, large-scale, multi-centre study conducted by 11 hospitals located in the urban area of Rome, Italy. During a period of 2 years (2005-2006) all patients who were admitted to participating hospitals with stent thrombosis and treated by PCI were enrolled. The clinical and procedural data was recorded on a detailed questionnaire and the clinical outcome up to 6 month after intervention was assessed by ambulatory visit or phone contact. Moreover, the efficacy of the procedure to re-establish optimal coronary blood flow was assessed by performing detailed analyses in an independent core laboratory.
During the study, 110 patients were recruited, thus constituting the largest series of patients with stent thrombosis ever collected. A first original observation arising from the study was that stent thrombosis, even if it is a rare event, accounted for 3.6% of the emergency PCI performed in patients with acute myocardial infarction. This data reinforces the perception that stent thrombosis has more than a negligible impact on the contemporary health system and further investigations on its causes and management are called for.
Regarding the supposed increased DES thrombogenicity, the type of data collected in the OPTIMIST study did not allow for the clarification of whether risk of thrombosis is higher after DES or BMS implantation. However, the data supports the hypothesis that stent thrombosis may have different mechanisms of occurrence in different types of stents. Indeed DES thrombosis, compared to BMS, happened more often after 30 days of implantation or after 15 days of antiplatelet drug therapy withdrawal. On the other hand, once stent thrombosis has occurred, we observed that the clinical manifestations, the procedural and the clinical outcomes, are not influenced by the type (DES or BMS) of previously implanted stent.
A primary goal of the OPTIMIST study was to provide data on the clinical outcome of patients with stent thrombosis undergoing urgent PCI in the contemporary era as it was unknown. We discovered that the clinical outcome during the 6-month follow-up, despite good utilization of all the best pharmacological and technical resources, was a disappointing 17% mortality rate and 29% rate of major adverse coronary or cerebral events (death or myocardial infarction or stroke or necessity of a new interventional procedure). These results show that stent thrombosis is not a benign disease and emergency PCI in this setting is still associated with unsatisfactory outcome.
As the individuation of factors associated with worse case outcome may be useful in clinical practice, a series of analyses of the independent predictors of bad outcome was performed in OPTIMIST. Such analyses showed that mortality is significantly higher when stent thrombosis occurred 1 year after stent implantation (i.e. “very late” thrombosis); when the attempted PCI result was not optimal and when a further stent was implanted during the PCI. The first point suggests that clinical surveillance after a successful PCI should not be reduced after 1 year and that the possible value of long-term anti-thrombotic drug administration should be investigated. The other two factors may together provide some interesting suggestions to the interventional cardiologists who must perform emergency PCI procedures in patients with stent thrombosis. Indeed, it seems that they should aim to re-establish optimal coronary blood flow and not to eliminate any residual coronary vessel narrowing by further stent implantations.