Intracardiac echocardiographic (ICE) evaluation of secundum atrial septal defect (ASDs) shows several advantages over transesophageal echocardiography (TEE). The aim of our study is to describe the 3-year results of transcatheter ASDs closure using the Amplatzer septal occluder (ASO) and ICE as the sole imaging tool both to select the device size and to monitor the procedure. Under local anesthesia, 135 consecutive eligible patients with ASDs (male/female = 45/90; mean age 42.2 +/- 19.2 years; BSA 1.71 +/- 0.7 m(2); mean pulmonary arterial pressure 30.4 +/- 11.5 mmHg; mean Qp/Qs ratio 2.1 +/- 0.6) underwent transcatheter closure using ASO and ICE. A 9F-9MHz mechanical transducer was used. Two orthogonal views on the transverse aortic valve and on the longitudinal four-chamber planes were obtained for quantitative ICE measurements, from which the diameters of the implanting ASO waist were to be derived. In all cases, we obtained a proper evaluation of ICE ASDs dimensions, leading to an optimal device size selection (mean size 25.0 +/- 6.7 mm). Moreover, the ICE allowed us to monitor device deployment and to verify the effectiveness of the ASDs stented by ASO. There were no complications related to the procedure or to the use of ICE. During a mean follow-up period of 21.5 +/- 12 months, the cumulative complete occlusion rates were 97.7, 97.0, 97.1, and 98% at 24 hours, 3 month, and 1 and 3 years, respectively. ICE is an effective and safe alternative to TEE and balloon-sizing maneuver during ASDs transcatheter closure procedures, allowing us to avoid the need of general anesthesia and leading to a similarly high percentage of occlusion rates with respect to the conventional method.