Internal Microstructure of Patent Foramen Ovale Related to Stroke

Inclusion Criteria: 1. Patients aged 16 to 65 years without any known vascular risk factor, including hypertension, hypercholesterolemia, diabetes mellitus, atrial fibrillation, smoking and obesity; 2. Documented PFO with right-to-left shunt ≥ 20 micro-bubbles by c-TCD; 3. Stroke group: history of ischemic stroke (based on brain magnetic resonance imaging) or TIA within 6 months without other identifiable causes (Phase1); 4. Migraine group: history of migraine headaches more than one year without other identifiable causes (Phase2); 5. Control group: incidental finding of PFO without neurological or systemic symptoms (Phase3). Exclusion Criteria: 1. Any identifiable cause of ischemic stroke/TIA or migraine other than PFO; 2. History of stroke or TIA within the past one month; 3. Presence of cardiac enlargement or dysfunction; 4. Presence of coexisting cardiovascular structural malformations/diseases; 5. Presence of carotid artery lesions or coronary artery disease; 6. Presence of deep vein thrombosis or pulmonary embolism; 7. Presence of implanted cardiac devices; 8. Evidence of hypercoagulable state; 9. Allergic to contrast medium; 10. Echocardiographic evidence of intra-cardiac thrombus, mass, tumor or vegetation; 11. Active endocarditis or other infections.