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Plavix and Drug-Eluting Stents

Doctor and PatientSince coronary stents became available in 1995, their Achilles’ heel has been stent thrombosis. To a large extent, dual anti-platelet therapy with aspirin and thienopyridine such as clopidogrel (Plavix) or ticlopidine (Ticlid) has prevented this catastrophic complication. As drug-eluting stents have come to dominate the interventional landscape, this serious problem is made even more pronounced. Dual anti-platelet therapy has been shown to decrease the frequency of death and MI after stent placement particularly as stent thrombosis often presents as an acute MI.

  • Restenosis and Thrombosis

    The advantage of drug-eluting stents over bare-metal ones is their ability to prevent in-stent restenosis. After any coronary intervention, there is a response to the stretch injury with activation of the smooth muscle cells in the arterial media and eventual production of a neo-intimal layer overlying the stent struts. This neo-intimal hyperplasia may be so vigorous as to narrow or occlude the stent lumen and restrict flow. With drug-eluting stents, sirolimus or paclitaxel are eluted from a matrix bound upon the stent and inhibit the smooth muscle cells’ production of the neo-intima. This inhibition reduces the rate of in-stent restenosis from 25-50% in a bare-metal stent to 1-4% in a drug-eluting one. The problem lies in the drug-eluting stent working too well with minimal or no neo-intima development leaving the stent strut to act as a nidus for thrombus formation and possible acute MI. A bare-metal stent is generally “endothelialized” by 4 weeks but a drug-eluting one may take 9-12 months or longer.

  • Importance of Dual Anti-platelet Therapy

    Any interruption in dual anti-platelet therapy, even as short as a few days, within 12 months of implant dramatically increases the risk of stent thrombosis and MI. Frequently, patients stop the aspirin or thienopyridine due to cost or failure to understand the importance of these medications. They may also be told as part of routine pre-op instructions for minor procedures to stop all “blood thinners” without consideration of this potential complication.

  • Recommendations

    In Feb 2007, the American College of Cardiology published guidelines to prevent the premature discontinuation of dual anti-platelet therapy in patients with drug-eluting stents.

    • Do not stop aspirin or thienopyridine without discussion with the patient’s cardiologist.
    • Consider the patient's ability or willingness to comply with therapy faithfully.
    • Consider any condition that may require an invasive procedure for diagnosis or therapy before stent implant.
    • Delay elective procedures for 12 months if possible.
    • Educate patient and family of the importance of medication compliance.
    • Be aware of potential complications of even brief interruption in therapy.


Reference

Prevention of Premature Discontinuation of Dual Antiplatelet Therapy in Patients with Coronary Artery Stents. JACC 2007; 49:6

Southcoast Physicians Group An affiliate of Southcoast Physicians Group.