**4. Recent evidence and guidelines on DAPT use in patients**

Antiplatelet therapy is an important pharmacological component in preventing atherothrombotic events. Aspirin, a widely used antiplatelet drug, has been found to reduce the risk of recurrent major adverse cardiovascular events (MACE) by around one-fifth [43]. However, the combination of antiplatelets has been reported to achieve better outcomes than the use of aspirin alone [10]. DAPT refers to a therapy that includes aspirin and a P2Y12 receptor inhibitor (clopidogrel, prasugrel, or ticagrelor). When compared to single antiplatelet medication, DAPT has been found to prevent

recurrent major ischemic episodes in patients with ACS or undergoing PCI at the cost of an unavoidable increased risk of major bleeding [10]. Below are guidelines on the effective use of DAPT across various indications.

#### **4.1 Use of DAPT after undergoing percutaneous coronary intervention**

Clinical trials have shown that all the patients receiving PCI require DAPT as it reduces risk of short- and long-term thrombotic events when compared to aspirin. Current guidelines recommend a 6-month DAPT for patients with stable symptoms and a 12-month DAPT for those who have had an ACS [29].

Except for patients who have received a bioabsorbable drug-eluting stent, the clinical setting in which it occurs—stable or unstable—and the patient's bleeding risk are the two most important factors to consider when determining the DAPT duration following PCI. When feasible, extended (at least 12 months) and potent DAPT should be used for these individuals.

#### **4.2 DAPT in stable coronary artery disease**

Platelet inhibition is critical for the treatment and prevention of short- and long-term thrombotic events. The cyclooxygenase-1 inhibitor aspirin and the platelet adenosine diphosphate P2Y12 receptor inhibitors clopidogrel, prasugrel, and ticagrelor are all available as oral antiplatelet medicines for secondary prevention in patients with CAD. The more recent powerful P2Y12 platelet receptor inhibitors prasugrel and ticagrelor have been tested in individuals with ACS, whereas aspirin and clopidogrel have been studied across the entire range of CAD [44].

A 6-month DAPT time is advised for individuals with stable illness following PCI; however, this might be decreased based on the patient's bleeding risk or for safety considerations. The guidelines go beyond specifics and advocate for the use of metallic stents as a first-line therapy, even in patients who are only given a 1-month antiplatelet regimen for safety reasons [45, 46]. DAPT should be continued for 6 months in individuals who have had angioplasty with a drug-coated balloon. This guideline is based on the results of many clinical trials that employed empirical antiplatelet methods.

#### **4.3 DAPT in acute coronary syndrome**

The use of DAPT to inhibit platelet function after an acute coronary syndrome aims to reduce short- and long-term thrombotic consequences [47]. The stent protective effect of DAPT in the first weeks after percutaneous revascularization reduces the risk of stent thrombosis, a potentially fatal event caused by inflammation and endothelial damage associated with mechanical insult during PCI [48]. Long-term therapy has been demonstrated to reduce the risk of subsequent ischemia episodes caused not only by the culprit lesions/vessels, but also by the advancement of atherosclerosis, a phenomenon described as the "patient protective effect" [48].

Several antithrombotic medications have been proposed over time with the goal of offering the best thrombotic protection while minimizing hemorrhagic hazards. However, recent European guidelines advise the use of the two most modern and strong P2Y12 inhibitors (prasugrel and ticagrelor) in patients with or without PCI [49, 50]. The default DAPT length for patients with ACS treated with coronary stenting should be 12 months, while it may be fair to cut it to 6 months in patients with

#### *Dual Antiplatelet Therapy DOI: http://dx.doi.org/10.5772/intechopen.105139*

a high bleeding risk or to extend it to more than 12 months in certain cases. These choices should be made after a thorough assessment of the patients' bleeding and ischemia risks. Although some criteria can aid in the identification of patients who will benefit the most, the requirement to validate surgical tools in clinical practice is well understood. This is especially essential if the DAPT is extended beyond 1 year. A longer dual antiplatelet duration may be considered for patients with this indication who have tolerated this length of DAPT without bleeding problems. In this sense, ticagrelor 60 mg twice daily is advised for patients with a history of myocardial infarction and a high ischemia risk.

### **4.4 DAPT immediately after transient ischemic attack (TIA) or minor stroke**

According to recent *BMJ Rapid Recommendations*, patients with a mild ischemic stroke or a high-risk transient ischemic attack (TIA) should begin dual antiplatelet medication with aspirin and clopidogrel as soon as feasible after the incident, preferably within 24 hours [51]. Dual therapy is favored over aspirin alone, according to the guidelines, because there is a lower risk of recurrent stroke and functional disability with dual therapy. In addition, the guideline committee strongly recommends a shorter term of dual therapy (10–21 days, rather than 22–90 days). Most patients, however, should continue to take a single antiplatelet drug, such as aspirin, continuously. Patients with TIA or mild stroke may benefit from antiplatelet treatment with aspirin and clopidogrel. DAPT with clopidogrel and aspirin (acetylsalicylic acid) within the first 21 days after the index incident was observed to minimize the incidence of recurrent major ischemic events compared to aspirin alone [51]. The recommendations in this clinical practice guideline are based on a linked systematic review sparked by a randomized controlled trial published in August 2018 in the *New England Journal of Medicine* [52].
