Patent Foramen Ovale (PFO) is observed in approximately 20% of healthy adults. In young adults under 60, the presence of PFO increases the risk of stroke by 40-50% compared to those without PFO. Furthermore, the prevalence of PFO is found to be higher in patients who have experienced a stroke than in the general healthy population. When the cause of a stroke in individuals under 60 cannot be determined (cryptogenic stroke), a detailed investigation for PFO is important. Patients with cryptogenic stroke also show a higher incidence of deep vein thrombosis (DVT) in the leg veins.