in recent years , drug - eluting stents ( des ) have been demonstrated to dramatically reduce the rate of restenosis and the need for repeat revascularization.1 - 3 ) despite these promising results , stent thrombosis seems to occur more frequently with des and often seems to be associated with clopidogrel resistance.4 ) we report a case of recurrent stent thrombosis associated with clopidogrel resistance in a patient with acute myocardial infarction .
a 63-year - old female was transferred to the emergency department complaining of squeezing chest pain that had increased over the past twelve hours .
she underwent emergent coronary angiography ( cag ) , which revealed critical stenosis in the proximal and middle left anterior descending coronary artery ( lad ) .
she was successfully treated with two paclitaxeleluting stents ( 3.012 mm and 2.528 mm taxus stents , boston scientific , reading , pa , usa ) in the proximal and middle lad ( fig .
she was treated with triple antiplatelet therapy ( aspirin 100 mg , clopidogrel 75 mg , and cilostazol 200 mg daily ) because she was found to be hyporesponsive to clopidogrel when tested for adenosine diphosphase ( adp)-induced platelet aggregation utilizing the verifynow p2y12 point - of - care assay ( 181/0 p2y12 reaction unit/% ) .
three days after discharge , she again developed chest pain and presented to the emergency department with mental confusion associated with acute pulmonary edema .
kinase - mb 34.0 u / l , troponin - i 67.01 ng / ml , troponin - t 5.5 ng / ml ) .
emergency cag , after intubation due to hypoxemia , showed total occlusion of the mid - lad due to stent thrombosis ( fig .
4 ) . after intravenous administration of a glycoprotein iib / iiia receptor blocker ( reopro ) ,
balloon angioplasty was carried out multiple times using a 3.0 mm balloon at 10 - 12 atm because of recurrent , immediate thrombus formation and coronary occlusion .
the next day , however , she complained of severe chest pain again , and the ecg showed marked st - segment elevation in v1-v6 , i , and avl ; and new - onset complete right bundle branch block with left anterior fascicular block ( fig .
she was successfully treated with balloon angioplasty and a final angiogram revealed improved flow over stented lad without intraluminal filling defect . despite the cilostazol medication
, adp - induced platelet aggregation showed that she was still hyporesponsive to clopidogrel ( 171/0 p2y12 reaction unit/% ) .
she was discharged after uneventful recovery with triple anti - platelet therapy using an increased dose of aspirin ( aspirin 200 mg , clopidogrel 75 mg , cilostazol 200 mg daily ) .
we report this case to draw more attention to stent thrombosis associated with clopidogrel resistance after des implantation .
this case shows that a des patient with clopidogrel resistance can be vulnerable to stent thrombosis even if treated with triple anti - platelet therapy , which in recent studies has been shown to be more effective in preventing stent thrombosis than conventional dual anti - platelet therapy .
stent thrombosis is an uncommon but serious complication of coronary artery stents that often presents as myocardial infarction ( mi ) or death . over several trials ,
the incidence of stent thrombosis was 0.58 - 1.3% in des.5)6 ) several factors have been associated with stent thrombosis , including older age , black race , diabetes mellitus , bifurcation lesion , in - stent restenosis lesion , procedure - related factors such as stent malposition , greater stent length , postprocedure acute renal failure , non - compliance to anti - platelet agent and anti - platelet resistance.7 - 9 ) anti - platelet resistance as an independent predictor of stent thrombosis , even several years after implantation of des , increases the risk of stent thrombosis . in this patient ,
stent thrombosis may have been caused by several risk factors , especially anti - platelet resistance .
several therapeutic approaches ( the addition of cilostazol or a glycoprotein iib / iiia inhibitor , increased dosage of clopidogrel and aspirin ) might be taken for a patient with anti - platelet resistance . in our patient , although cilostazol ( 200 mg daily ) was added to conventional dual anti - platelet therapy , recurrent stent thrombosis occurred .
subsequently , the daily dose of aspirin was increased from 100 mg to 200 mg . in the des era ,
stent thrombosis is a fatal complication and anti - platelet therapy has been shown to be very important in preventing stent thrombosis .
thus , assessment of the patient 's responsiveness to anti - platelet agents may be a crucial factor in monitoring these drugs ' therapeutic efficacy and improving clinical outcomes after implantation of des .
recent studies have shown that adequate anti - platelet effects are not achieved in 5% to 45% of the patients taking aspirin and in 4% to 30% of patients taking clopidogrel10)11 ) and therefore suggest that many patients are resistant or only partially responsive to the anti - platelet agents .
currently , however , routine screening for anti - platelet resistance remains a persistent , unresolved issue and further evidence is necessary before it will be possible to recommend this testing as part of standard assessment of pci candidates .
in addition , further prospective studies are needed to set guidelines for optimal treatment of patients with antiplatelet resistance who are at increased risk of stent thrombosis , a catastrophic complication of des implantation .
 drug - eluting stents ( des ) are considered the treatment of choice for most patients with obstructive coronary artery disease when percutaneous intervention ( pci ) is feasible 
 . however , stent thrombosis seems to occur more frequently with des and occasionally is associated with resistance to anti - platelet drugs . 
 we have experienced a case of recurrent stent thrombosis in a patient with clopidogrel resistance . 
 a 63-year - old female patient suffered from acute myocardial infarction and underwent successful pci of the left anterior descending coronary artery ( lad ) with two dess . 
 she was found to be hyporesponsive to clopidogrel and was treated with triple anti - platelet therapy ( aspirin 100 mg , clopidogrel 75 mg , and cilostazol 200 mg daily ) . 
 three days after discharge , she developed chest pain and was again taken to the cardiac catheterization laboratory , where coronary angiography ( cag ) showed total occlusion of the mid - lad where the stent had been placed . 
 after intravenous administration of a glycoprotein iib / iiia inhibitor , balloon angioplasty was performed , resulting in thrombolysis in myocardial infarction ( timi ) iii antegrade flow . the next day , 
 however , she complained of severe chest pain , and the electrocardiogram showed marked st - segment elevation in v1-v6 , i , and avl with complete right bundle branch block . 
 emergent cag revealed total occlusion of the proximal lad due to stent thrombosis . 
 she was successfully treated with balloon angioplasty and was discharged with triple anti - platelet therapy . 
Introduction
Discussion