Pharmacotherapy During Percutaneous Coronary Interventions

Coronary Interventions 214 thrombolytic pharmacotherapy during PCI to prevent such complications.The goal of this chapter will be to describe different therapeutic agents available to clinicians during PCI and to summarize the most current guidelines regarding their use. Anti-platelet agents AspirinAspirin causes an irreversible inactivation of the cyclooxygenase-1 enzyme required for prostaglandin and thromboxane synthesis, which in turn diminishes platelet aggregation.The use of aspirin for secondary prevention has been shown to decrease overall mortality in patients with established CAD or a CAD equivalent such as diabetes (7-10).Meanwhile, the net benefit for its use in primary prevention is less certain and needs to be weighed against individual risk for major gastrointestinal or extra-cranial bleeding (11).Extensive studies have also shown significant reductions in mortality and morbidity with the use of aspirin in unstable angina (UA) as well as in both non-ST-elevation myocardial infarction (NSTEMI) and ST-elevation myocardial infarction (STEMI).In one of the earliest trials from the Results of a Veterans Administration Cooperative Study, Lewis et al. reported a 51% reduction in incidence of death or acute MI as well as a 50% reduction in rates of nonfatal MI in patients with UA who received aspirin (12).These findings were reproduced in subsequent studies and helped to solidify the role for the use of aspirin in UA (13-14).The RISC trial evaluated the role of aspirin in both NSTEMI and UA patients and again demonstrated that aspirin was associated with a significant reduction in the combined endpoint of death and MI with differences persisting beyond one-year providing evidence for the long-term benefit of aspirin in NSTE-ACS (15).The landmark trial ISIS-2 then expanded the role of aspirin use to standard therapy in STEMI (16).ISIS-2 randomized 17,187 patients presenting with acute STEMI to streptokinase, aspirin, both therapies, or neither, and demonstrated an additive effect of aspirin to thrombolytic therapy.Currently, the ACC/AHA guidelines for the management of UA, NSTEMI and STEMI recommend immediate treatment with aspirin for all patients for indefinite duration (17).The recommendations for the use of aspirin in PCI with stenting are derived from several early clinical trials in which treatment with high dose aspirin (650 mg to 990 mg/day) along with dipyridamole or ticlopidine in percutaneous transluminal coronary angioplasty (PTCA) was compared to placebo.Patients who were treated with aspirin-based regimens uniformly had better outcomes with significant reductions in peri-procedural complications including abrupt vessel closure, dissection or MI (18)(19).Pre-treatment with aspirin monotherapy was tested against aspirin plus dipyridamole and shown to have an independent beneficial effect (20).Subsequent studies comparing high-dose versus low-dose aspirin (1500 mg vs. 80 mg/day) prior to PTCA showed no difference in the incidence of MI or in the rate of major complications and restenosis (21).The most current ACC/AHA recommendations for the use of aspirin in PCI are that higher dose aspirin (300 mg to 325 mg) be given at least 2 hours before PCI as well as for at least 1 month after BMS implantation, 3 months after sirolimus-eluting stent implantation, and 6 months after paclitaxel-eluting stent implantation (17). TiclopidineThienopyridines block the adenosine diphosphate (ADP) receptor P2Y12 on platelet surfaces thereby decreasing platelet activation and aggregation (see section on platelet function www.intechopen.com