Subacute saphenous vein graft stent thrombosis due to unusual drug interaction: a case report.

Background: Stent thrombosis is a potentially lethal complication of coronary angioplasty and responsible for 20% of all post-angioplasty myocardial infarctions. Unusual causes may be overlooked and difficult to identify. Case summary: A 70-year-old male with history of triple aortocoronary bypass presented with acute inferolateral ST-segment elevation myocardial infarction (STEMI). Critical stenosis of the vein graft to the right coronary artery was revealed, and with the use of distal embolic protection device, successful angioplasty with stent was performed under double antiplatelet treatment with aspirin and ticagrelor. Two weeks later, he presented again at the emergency department with an acute inferolateral STEMI. Subacute stent thrombosis with complete occlusion of the stented vein graft was evident. Repeated balloon dilatations restored the flow stabilizing the patient; optical coherence tomography showed good stent expansion and apposition. Scrutinizing the patient's history, we discovered comedication with carbamazepine that is a CYP3A4 inducer and reduces ticagrelor's effect. Switching to prasugrel ensured potent antiplatelet treatment, and the patient was discharged 5 days later. The 6-month follow-up was uneventful and free of symptoms. Discussion: Stent thrombosis has dire consequences, and the precipitating factors should always be investigated. Inadequate platelet inhibition secondary to non-compliance to therapy or resistance and suboptimal stent expansion/apposition are its main causes. Drug interactions are an underrecognized factor that may significantly alter the potency of antiplatelet drugs and also lead to stent thrombosis; thus, treatment is essential to be tailored to each patient comedication.