The pilot study design was selected in order to evaluate the comparative accuracy of ICE imaging and TEE as well as the feasibility of ICE guided management of AF. In Phase 1, the design will ensure that ICE imaging is not inferior to standard TEE for detection of left atrial pathology. In Phase 2, ICE imaging will be performed in patients prior to immediate electrical cardioversion to determine if it is equivalent to the conventional management strategy of electrical cardioversion after anticoagulation for 3 weeks prior to cardioversion.