MR Prior to Ablation of Scar in Ventricle

KEY FACTS

• Ventricular tachycardia (VT) is potentially lethal arrhythmia that results in very regular, fast heart rate that can lead to reduced cardiac output due to inadequate time for ventricular filling
• Arrhythmogenic substrate for VT is typically abnormal myocardial tissue, which slows myocardial conduction and allows formation of self-sustaining reentrant circuit
• Electroanatomic mapping (EAM) is invasive catheter-based procedure performed by electrophysiologists who use catheters to sample local electrograms at sites along endocardial (and sometimes epicardial) surface of left ventricle to characterize various local electrical conduction properties and identify regions that contribute to VT
• VT ablation is invasive procedure that uses intracardiac catheters to deliver energy locally to destroy arrhythmogenic substrate and prevent recurrence of VT

• Cardiac MR imaging with late gadolinium enhancement (LGE) sequences prior to VT ablation can be used to identify myocardial scar tissue that may serve as arrhythmogenic substrate
• LGE uses intravenous contrast material (gadolinium) that collects in extracellular space, which is present to small degree between myocytes and significantly increased in areas of focal collagen deposition from myocardial scarring
• On T1 cardiac MR of heart, these areas of scar with increased contrast retention are visualized as bright regions in myocardium
• Imaging of VT patients with cardiac devices is possible, although it requires changes to device programming before and after cardiac MR by electrophysiologist or electrophysiologic-trained nurse as well as monitoring throughout exam
• Devices, particularly internal cardioverter-defibrillators (ICD), create large artifacts on cardiac MR LGE imaging that can be reduced by “wideband” LGE sequences