Computed tomography (CT) is a reliable technique for measurement of the LA wall thickness but it cannot be used during the ablation procedure and its extensive use is limited by the need of ionizing radiation. Preliminary data from animal studies support the accuracy of real-time ultrasound imaging modalities such as intracardiac echocardiography (ICE) or Intravascular Ultrasound (IVUS) imaging for measurement of LA wall thickness and monitoring of its acute changes related to catheter ablation.