CYP2C19 Polymorphism

The goal of this observational study is to use a genetic test to help doctors prescribe the most effective medications after a patient has a stroke. One type of stroke is caused by a blood clot in brain vessels. After a patient has this kind of stroke, they are often given a combination of two blood thinners to prevent it from happening again. One of these blood thinners, called clopidogrel, is less effective in some people due to differences in their DNA. Clopidogrel needs to be activated by a specific enzyme in the body known as CYP2C19. This enzyme does not work as well if there are variations in the section of DNA that tells the body how to make CYP2C19. It can be predicted who has less CYP2C19 enzyme activity with a genetic test. If these patients are given a different blood thinner, it can reduce their risk of another stroke compared to if they are given clopidogrel. The main questions this study aims to answer are: * What are the best strategies to implement this genetic test in the hospital? * Does implementation of this genetic test change providers' decisions on which medication to prescribe after a participant has a stroke? Participants in this study will have a genetic test done onsite looking for variations in the section of DNA that tells the body how to make CYP2C19. This genetic test will only look for 11 known variations; the genome will not be sequenced. The investigators will alert the doctor of the patient's test results so they can prescribe the appropriate blood thinner. Through this, the investigators will learn the best practices for successful implementation of this genetic test.

The goal of this pilot clinical trial is to test the safety and effectiveness of genotype-guided clopidogrel monotherapy in patients presenting with Non-ST-Segment Elevation Acute Coronary Syndrome (NSTE-ACS) who have undergone successful Percutaneous Coronary Intervention (PCI). The main questions it aims to answer are: * Is genotype-guided clopidogrel monotherapy effective in reducing ischemic risk during the first six months following successful PCI? * Is genotype-guided clopidogrel monotherapy safe in terms of reducing bleeding risk during the first six months following successful PCI? Participants will be given genotype-guided clopidogrel monotherapy after their successful PCI procedure and will be monitored for any bleeding or ischemic complications over the next six months. Researchers will compare these results to the typical outcomes associated with traditional Dual antiplatelet therapy (DAPT) to see if genotype-guided clopidogrel monotherapy provides similar or improved protection from ischemic events, but with fewer bleeding complications.

In Ease Asia clinical trials, P2Y12 inhibitor (ticagrelor or clopidogrel) monotherapy after 3-month dual antiplatelet therapy (DAPT) resulted in a lower incidence of clinically significant bleeding, without increasing risk of major adverse cardiac and cerebrovascular events, even if acute coronary syndrome (ACS) following complex percutaneous coronary intervention (PCI) when compared with standard DAPT. Although better understood "East Asian Paradox", finding the right CYP2C19 genotype-guided P2Y12 inhibitor selection to balance maintaining ischaemic prevention and less bleeding remains a topic in real-world clinical practice.