Long Term Adherence to Clopidogrel and Late Adverse Cardiac Events after Off-Label Use of Sirolimus-Eluting Stents: Results of the MATRIX Registry
March 31, 2008 By Lauren Ciaglo
SCAI-ACCi2 08-Chicago, IL: Results from the MATRIX Registry, a large community-based registry consisting of patients who were treated with drug-eluting stents (DES), were presented today at the SCAI-i2 summit Annual Scientific Sessions in Chicago by Dr. George Dangas of Columbia University Medical Center.
The registry analyzed data from 1,510 patients.  The mean age of patients was 64.811 years and 74.6% were male.   The population for this study varied from previous studies in that 33.3% of patients had a previous myocardial infarction (MI), 44.4% had a prior percutaneous coronary intervention (PCI), 21% had former cardiac bypass grafting surgery (CABG), 33.7% had diabetes, and 27.7% had unstable angina (UA).
Outcomes were evaluated at 2 years following off-label use of sirolimus-eluting stenting (SES) and all patients were to receive aspirin (325 mg daily for 1 month followed by 81 mg indefinitely) along with clopidogrel (75 mg daily for 1 year followed by physician discretion).
At 6 month follow-up, 90% of patients were taking clopidogrel, at one year this number decreased to 82.4%, and at the two year follow-up it had dropped to 65.5%.  Of the 10% that discontinued their clopidogrel use at 6 months, approximately half of them had restarted the medication at either the one or two year follow-up.
At one year, in 9.9% of patients, clopidogrel discontinuation was due to doctors advise, 5.2% was due to bleeding, 2.1% was due to surgery, 1.7% due to rash/allergy, and 0.4% due to cost.  Moreover, 39.5% of patients discontinued the medication for an unknown reason and 41.2% discontinued it because the one year dosing period had ended.
The investigators divided patients into two groups to further evaluate clinical outcomes:
- Those who continued taking clopidogrel and
- Those who ceased taking clopidogrel.
They found that the composite endpoint was significantly higher among patients who were non-adherent to clopidogrel at one year (4.8% vs. 1.4%, respectively, p=0.005).  There were trends toward differences in the rate of cardiac death (1.1% vs. 0.2%, p=0.054), non cardiac death (2.7% vs. 1.0%, p=0.08), and unknown death (1.0% vs. 0.3%, p=0.16) between the two groups. Target lesion revascularization as well as target vessel revascularization (TVR) was significantly lower in the non-adherent group compared with the adherent group (0% vs. 5.5%, p=0.001 and 0.5% vs. 6.1%, p=0.002, respectively).
At two year follow-up, death/myocardial infarction was significantly higher among those who discontinued clopidogrel vs. those who were on clopidogrel .
The researchers found that there were various reasons for clopidogrel non-adherence at one year and this study reiterates the importance of continued adherence to dual antiplatelet therapy following DES implantation. The investigators demonstrated that patients off-clopidogrel at 12 months had higher mortality and fewer repeat coronary procedures at follow-up. In addition based on the reasons for clopidogrel discontinuation, patients who stopped clopidogrel for acute events or side-effects appeared to have a trend towards higher mortality at follow-up. A significant proportion of patients who discontinued clopidogrel were able to be treated again with this agent at a later time point

# Source
- Late Breaking Clinical Trials Session: SCAI Annual Scientific Sessions in partnership with ACC i2 summit, March 31, 2008 Chicago