The JCS 2018 “Guidelines on Diagnosis and Treatment of Acute Coronary Syndrome”460 and on “Revascularization of Stable Coronary Artery Disease”461 recommend dual antiplatelet therapy (DAPT) of aspirin plus a P2Y12 receptor antagonist (P2Y12 inhibitor) after stent implantation in patients undergoing percutaneous coronary intervention (PCI) as class I/evidence level A. Therefore, in patients with AF concomitant with undergoing PCI, triple therapy defined as a DAPT plus an OAC for stroke prevention is needed. The gene discussed is P2RY12; the disease is stroke disorder.