Magnetic resonance imaging: Description of technology and protocols

Abstract

Since its introduction in the late 1970s, catheter-based radiofrequency ablation has evolved from a primitive and experimental procedure to the mainstay for arrhythmia management it is today. Initial intracardiac catheter navigation was fluoroscopy based, and therefore subject to x-ray limitations and side effects. However, accurate catheter location within the cardiac chambers has required electrophysiologic confirmation of catheter positioning. This led to the development of conventional cardiac mapping techniques. The limitations of fluoroscopy and conventional mapping techniques led to the development of electro-anatomical mapping systems (EAM), in which information regarding catheter position in a 3D space is combined with electrophysiological information in real time to provide an accurate localization of the catheter tip while, at the same time, data regarding electrophysiological properties of the underlying myocardial substrate. Eventually, the mechanisms of more complex arrhythmias, such as atrial fi brillation and scar-based monomorphic ventricular tachycardia, started to be elucidated. This was followed by more diffi cult ablation procedures that required more accurate mapping systems able to provide real-time information. The introduction of EAM combined with Cardiac Computerized Tomography (CCT), cardiac Magnetic Resonance Imaging (cMRI), and real-time intracardiac echocardiography (ICE) allows for more precise mapping with signifi cant improvement in cure rates for ablation procedures. However, most of these techniques are essentially x-ray based and expose the patient and the operator to the noxious effects of ionizing radiation.