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OBJECTIVESThe purpose of this study was to assess safety and effectiveness of the fourth generation buttoned device in closing atrial septal defects (ASDs) and to test the hypothesis that introduction of double button reduces unbuttoning rate without reducing effectiveness.BACKGROUNDBecause of the high unbuttoning rate (7.2%) with first, second and third generation buttoned devices, the device was modified (fourth generation) so that there were two radiopaque spring buttons 4 mm apart on the button loop attached to the occluder.METHODSDuring a four-year period ending in September 1997, 423 patients, ages 1.5 to 80 years (median 16 years), underwent closure of ASD at 40 medical centers around the world.RESULTSThe ASD size varied between 5 and 30 mm (median 17 mm). The device size varied between 25 and 60 mm. Unbuttoning occurred in 4 (0.9%) of 423 patients. Effective occlusion, defined as no (n = 343) or trivial (n = 34) residual shunt on echo-Doppler studies performed within 24 h of the procedure, was demonstrated in 377 patients (90%). Thus, the unbuttoning rate (0.9 vs. 7.2%) decreased (p < 0.01) while effective occlusion rate (90 vs. 92%) remained unchanged (p > 0.1) with this device, compared with earlier generation devices. During follow-up from one month to five years (23 ± 15 months), 21 (5%) of 417 patients required surgical (n = 12) or transcatheter (n = 9) reintervention, mostly to treat significant residual shunt. In the remaining patients there was gradual reduction and disappearance of the residual shunt. No wire integrity problems were observed.CONCLUSIONSThese data suggest that the fourth generation buttoned device is as effective as earlier generation devices, but without significant unbuttoning. Follow-up results remained good, with a reintervention-free rate of 89% at five years.