PJ-424 Smoke-like Echo is Frequently Observed in the Left Atrium in Patients with Paroximal Atrial Fibrillation Having Thromboembolic Risk Factors(Thromboembolism/Antithrombotic therapy/Thrombolysis-4 (H) PJ72,Poster Session (Japanese),The 70th Anniversary Annual Scientific Meeting of the Japanese Circulation Society)