Emergency percutaneous coronary intervention for stent thrombosis appears to be associated with disappointing outcomes, according to a presentation at the annual meeting of the European Society of Cardiology.

The OPTIMIST (Outcome of PCI for stent-ThrombosIs MultIcentre Study) trial was a non-sponsored, independent, large-scale, multi-center study conducted by 11 hospitals located in around Rome, Italy. During a period of 2 years (2005-2006) all patients who were admitted to participating hospitals with stent thrombosis and treated by percutaneous coronary intervention were enrolled.

Clinical and procedural data was recorded on a detailed questionnaire and clinical outcome up to 6 month after intervention was assessed by ambulatory visit or phone contact. Moreover, procedure efficacy to reestablish optimal coronary blood flow was assessed by performing detailed analyses in an independent core laboratory.

During the study, 110 patients were recruited, constituting the largest series of patients with stent thrombosis collected to date. A first original observation arising from the study was that stent thrombosis, even if it is a rare event, accounted for 3.6 percent of emergency procedures performed in patients with acute myocardial infarction. These data reinforce 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 merited

The data collected in the OPTIMIST study did not allow for clarification of whether risk of thrombosis is higher after drug-eluting or bare metal stent implantation. However, the data support the hypothesis that stent thrombosis may have different mechanisms of occurrence in different types of stents.

Indeed drug-eluting stent thrombosis, compared with thrombosis in bare metal stents, happened more often after 30 days of implantation or after 15 days post-withdrawal of antiplatelet drug therapy. On the other hand, once stent thrombosis has occurred, clinical manifestations, procedural and clinical outcomes did not appear to be influenced by the type of stent.

Clinical outcome during the six-month follow-up, despite good utilization of all of the best pharmacological and technical resources, was a disappointing 17 percent mortality rate and 29 percent 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 interventions in this setting are 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 independent predictors of bad outcome was performed in OPTIMIST. Such analyses showed that mortality was significantly higher when stent thrombosis occurred one year after stent implantation (i.e. “very late” thrombosis), when the attempted intervention result was not optimal, and when an additional stent was implanted during the procedure.

The first point suggests that clinical surveillance after successful intervention should not be reduced after one 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 perform emergency procedures in patients with stent thrombosis. Indeed, it seems they should aim to reestablish optimal coronary blood flow and not to eliminate any residual coronary vessel narrowing by further stent implantations.

The OPTIMIST study also evaluated the efficacy of novel techniques in the high-risk scenario of stent thrombosis. Previous studies have suggested that thrombectomy using new, specifically-designed devices may facilitate restoration of coronary blood flow in thrombotic lesions by reducing distal embolization of thrombotic debris. In the OPTIMIST study, 1 in every 4 patients was treated using thrombectomy devices as a first strategy. Despite the fact that patients treated by thrombectomy were sicker than the others, no excess adverse clinical events were observed, supporting the safety of this novel approach.

Patients without shock treated by thrombectomy had a five-fold improved rate of optimal coronary flow restoration. This suggests that the role of distal embolization and its prevention may be important only before advanced heart damage has been established.