1. A system for use in a body lumen, the body lumen containing blood, the system comprising: a catheter having a fluid lumen defined therethrough; an imaging assembly having a barrier supported by the catheter, the barrier being reconfigurable from a low-profile shape to an expanded deployment shape projecting distally from a distal end of the catheter and defining an open area which is in fluid communication with the fluid lumen and with an environment external to the barrier through an opening defined by the barrier; an imaging element positioned within or along the barrier such that a tissue surface region adjacent to the open area is able to be visualized through the open area via the imaging element, where the imaging assembly is configured to acquire a tissue surface image of the tissue surface region while at least a portion of the blood is disposed in the body lumen and while the open area remains in fluid communication through the opening with the environment; at least one sensor positioned along a distal portion of the barrier and configured to detect an electrical activity of the tissue surface when the barrier is in the expanded deployment shape; and a processor in electrical communication with the imaging assembly and the at least one sensor so as to receive the detected electrical activity and tissue surface image, the processor configured to map the detected electrical activity and tissue surface image together.