Rationale and design of the TAXUS Libertē Post-Approval Study: examination of patients receiving the TAXUS Liberté stent with concomitant prasugrel therapy in routine interventional cardiology practice

Myocardial Infarction Risk After Discontinuation of Thienopyridine Therapy in the Randomized DAPT Study (Dual Antiplatelet Therapy)

BACKGROUND

Thienopyridine plus aspirin beyond 1 year after coronary stenting reduces myocardial infarction (MI) risk and increases bleeding risk in comparison with aspirin alone. The hazard associated with late thienopyridine discontinuation and risk factors for MI after discontinuation are poorly defined.

METHODS

In the DAPT Study (Dual Antiplatelet Therapy), after percutaneous coronary intervention and 12 months of thienopyridine (clopidogrel or prasugrel) plus aspirin, eligible patients remained on aspirin and were randomly assigned to continued thienopyridine versus placebo for 18 months. At 30 months, patients stopped the study drug and were observed for 3 months. Cumulative incidence of MI was assessed over 3 months after randomization (months 12-15) and 3 months after study drug discontinuation (months 30-33). The MI hazard for each of these periods was assessed across randomized treatment arms and by DAPT score values <2 or ≥2.

RESULTS

Among the 11 648 randomly assigned patients, the monthly cumulative incidence of MI was lower with continued thienopyridine versus placebo at 12 to 15 months (0.12% versus 0.37%, P<0.001, in all patients; 0.13% versus 0.27%, P=0.02, in patients not treated with paclitaxel-eluting stents), and higher at 30 to 33 months (0.30% versus 0.15%, P=0.013, in all patients; in patients without paclitaxel-eluting stents, 0.18% versus 0.17%, P=0.91). The majority of MIs in both time periods (74% and 76%) were not related to stent thrombosis. After multivariable adjustment, treatment arm independently predicted MI at months 12 to 15 (P<0.001) and 30 to 33 (P=0.011). During months 12 to 15, patients with DAPT scores <2 or ≥2 both had lower rates of MI with continued thienopyridine (MI monthly incidence 0.16% versus 0.51%, P<0.001, for scores ≥2; 0.08% versus 0.24%, P=0.012, for scores<2, interaction P=0.064).

CONCLUSIONS

Discontinuing thienopyridine after either 12 or 30 months is associated with an early increase in MI risk, mainly unrelated to stent thrombosis; the magnitude of risk is highest in the earlier time frame, and lower in patients not treated with paclitaxel-eluting stents. Although higher DAPT scores identify patients with greater absolute ischemic benefit (relative to bleeding harm) with continued thienopyridine therapy, discontinuation at 12 months increases MI hazard regardless of DAPT score group.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00977938.

Evaluating the generalizability of a large streamlined cardiovascular trial: comparing hospitals and patients in the dual antiplatelet therapy study versus the National Cardiovascular Data Registry

BACKGROUND

The Dual Antiplatelet Therapy Study is large streamlined clinical trial designed to evaluate antiplatelet treatment strategies in a broadly inclusive population of subjects treated with coronary stents. Whether large streamlined trials can successfully include a representative group of study sites and patients has not been formally assessed.

METHODS AND RESULTS

Within the National Cardiovascular Data Registry CathPCI Registry, we compared characteristics and outcomes of hospitals participating versus not participating in the Dual Antiplatelet Therapy Study. We also compared clinical and procedural characteristics of trial subjects undergoing percutaneous coronary intervention (PCI) with drug-eluting stents to contemporaneous patients within the National Cardiovascular Data Registry CathPCI Registry. Standardized differences between groups were estimated. Between September 2009 and July 2011, 1.1 million PCIs were performed among 1276 hospitals, of which 309 (24.2%) participated in the Dual Antiplatelet Therapy Study. Participating hospitals were larger (468 versus 311 beds), more frequently located in urban settings (61.2% versus 42.6%), and had higher annual PCI volumes (858 versus 378) compared with nonparticipating hospitals, although hospital case mix and procedural outcomes were similar. Compared with CathPCI patients, trial patients undergoing PCI with drug-eluting stents were similar with respect to race, sex, and rates of diabetes mellitus, hypertension, and smoking, although they had lower rates of prior cardiovascular disease.

CONCLUSIONS

Within the Dual Antiplatelet Therapy Study, clinical trial sites had similar patient case mix and clinical outcomes as nonparticipating sites. Although trial participants were representative of PCI patients with respect to race, sex and most comorbidities, they had a lower prevalence of chronic cardiovascular disease compared with registry patients. Although a streamlined cardiovascular clinical trial may successfully involve a large number of hospitals and rapidly enroll a diverse population of patients, differences between eligible patients and those actually enrolled remained.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov. Unique identifier: NCT00977938.