Interventions Guided by Three-Dimensional Echocardiography The high temporal and spatial resolution of transthoracic, and particularly transesophageal, 3DE has led to the widespread adoption of this technique to guide interventions Early on, transthoracic 3DE was used to guide endomyocardial biopsy in children, and transesophageal 3DE was used to guide transseptal catheterization.16,35 Today, transcatheter closure of atrial and ventricular septal defects is routinely performed with transesophageal 3DE guidance.36–38 Overall, transesophageal 3DE complements 2DE; it does not replace it It is particularly helpful in situations where defects have irregular or asymmetrical shapes, and to delineate adjacent structures The recommendations by the manufacturers of transesophageal 3DE probes propose that patients should weigh at least 30 kg, which limits the utility of the modality in children Learning Curve The learning curve of 3DE is steep but negotiable Successful implementation requires advocacy and an investment of time by both echocardiographers and sonographers An interactive, hands-on course to teach cropping techniques has been shown to be useful in overcoming the steep part of the learning curve.7 Another approach consists of building familiarity with cardiac morphology by using photographs of anatomic specimens with side-by-side depiction of 3DE images.39 Future Directions Advances in the arena of 3DE will involve technical enhancements, such as improved speed of acquisition and spatial resolution, holographic displays, a wide range of software that has been validated for automated quantification, and enhancements to workflow.40 Refinements in technology will make highresolution 3DE available across the spectrum of sizes of patients We anticipate a miniaturized 3DE transesophageal probe for use in small children With the growing interest in multimodality imaging, 3DE volumetric and anatomic data will be able to be overlaid onto images and measurements that are obtained from other modalities