Brilinta Resistance: A Rare but Life-Threatening Phenomenon

Document Type

Conference Proceeding

Publication Date


Publication Title

Journal of the American College of Cardiology



P2Y12 receptor blockers are the mainstay of therapy in patients with coronary stents to prevent in-stent restenosis (ISR). Ticagrelor and prasugrel are preferred therapies in acute coronary syndromes given their mortality benefit over clopidogrel. Ticagrelor is often used as the agent of choice given its comparable rate of major bleeding to clopidogrel. Ticagrelor resistance is extremely rare with only four cases being previously documented.


We are presenting a case of a 65 year-old female with PMH of recent NSTEMI (s/p PCI and DES to mRCA), DM, and dyslipidemia who presented with chest pain and a recent positive stress test. A left heart catheterization demonstrated 100% ISR of previously stented mRCA despite complete adherence to dual antiplatelet therapy. A Thrombelastography® Platelet Mapping™ (TEG) result indicated a suboptimal 15.6% inhibition by ticagrelor. A review of concurrent medications did not indicate any significant drug interactions. The decision was made to transition her P2Y12 therapy to prasugrel. A repeat TEG platelet mapping post- transition revealed a suboptimal response of 28.7% with prasugrel. She was discharged on cilostazol, ASA, and prasugrel. VerifyNow™ was used to reassess platelet inhibition post-discharge which revealed yet a suboptimal inhibition of 41% by prasugrel. She was instructed to increase her ASA and prasugrel to 162 mg and 20 mg, respectively which have been tolerated well to this date.


Given a sub-optimal platelet inhibition by ticagrelor as revealed by TEG platelet mapping, I was consulted to evaluate the patient for any significant drug interactions. Subsequently I made the recommendation to transition to prasugrel with appropriate loading and transition strategy (ensure holding ticagrelor for 24h prior to loading with 60 mg of prasugrel).


Ticagrelor resistance is a rare but life-threatening phenomenon. Numerous platelet function tests are available to determine the clinical efficacy of antiplatelets. Although routine use of functional assays are not suggested by guidelines, they can certainly be useful in clinical practice to assess the efficacy of P2Y12 inhibitors.