Stent Thrombosis Secondary to Ticagrelor Resistance as Demonstrated by Thromboelastography

Stent thrombosis is a dreaded complication of percutaneous coronary interventions (PCI). It is a prominent cause of mortality and major bleeding [1]. Antiplatelet therapy has played an important role in mitigating this adverse event, yet it is still a major complication. Clopidogrel, an irreversible P2Y12 inhibitor has been a mainstay of antiplatelet therapy for years. Clopidogrel’s nature as a prodrug means that certain patients have unsatisfactorily inhibited platelet activity due to differences in drug metabolism. This lead to the production of a new generation of P2Y12 inhibitors, most famously ticagrelor and prasugrel, of which ticagrelor provides platelet inhibition without requiring metabolism. This results in more potent and consistent platelet inhibition. Prasugrel is infrequently used as a first-line treatment for acute coronary syndromes (ACS), due to its increased risk of bleeding. Ticagrelor, on the other hand is used more commonly, because of its lower rates of cardiovascular events, cardiovascular death and all cause mortality compared to clopidogrel, while being comparable in its adverse event profile [2]. Stent thrombosis has been shown to be less frequent with ticagrelor than clopidogrel [1]. In fact, stent thrombosis while on ticagrelor is a rare occurrence. To our knowledge, there is only one reported case regarding stent thrombosis in a patient actively treated with ticagrelor [3]. There are numerous platelet function tests (PFT) now available to assess for P2Y12 inhibitor resistance, although guidelines for their use is not clear. We will be presenting a case of stent thrombosis while on treatment with ticagrelor, with resistance demonstrate by thromboelastogram.