Abstract: AIM To evaluate the efficacy and safety of transcatheter closure in patients with patent foramen ovale (PFO) accompanied with a small atrial septal defect (ASD). METHODSE ighteen PFO patients accompanied with a small ASD (7 males, 11 females; age 21-58 years (36±13) years, including 6 with cryptogenic stroke and 12 with migraine underwent interventional treatments. RESULTS In the 18 patients, the diameter of PFO was 2-4(2.7±0.8) mm and the diameter of ASD was 3-5(4.0±0.7) mm. The distance between two holes was <7 mm in 10 patients, 8-12 mm in 5 patients and >12 mm in 3 patients. Fifteen patients were implanted with single occluder and 3 patients with double occluders. Contrast transthoracic echocardiography (cTTE) showed that all the patients had right-to-left shunt (RLS) pre-operation at rest and that after Valsalva maneuver (VM), a large amount of RLS was indicated. Eighteen patients showed no RLS at rest post-operation. Patients implanted with single occluder showed that after operation and after Valsalva maneuver (VM), a large amount of RLS was indicated in all the patients at 1 month, a small to moderate amount of RLS was found in 11 patients and a large amount of RLS in 4 patients at 3 months, a large amount of RLS in 4 patients and no RLS in the other 11 patients at 6 months. In the 3 patients implanted with double occluders, after VM a large amount of RLS was found at 1 month, a moderate amount of RLS at 3 months and no RLS at 6 months. No fresh infarction lesions were found by brain MRI in the follow-ups for the 6 patients with cryptogenic stroke. Among the 12 patients with migraine, 11 showed significantly improved migraine symptoms at 6 months after the closure procedure. HIT-6 score significantly decreased compare with that pre-operation (66.5±10.4 vs. 42.3±9.5, P<0.01). CONCLUSIONT ranscatheter closure of PFO accompanied with a small ASD is safe and effective, even though RLS still occurs in some patients, especially those implanted with single occluder.