High-resolution contrast-enhanced MRI in a swine model of chronic MI identified epicardial reentry in 19.0% of induced VT morphologies and endocardial reentry in 66.7%.
Does MRI-based visualization of scar morphology correlate with VT activation sequences in a swine model of chronic MI?
High-resolution MRI can visualize complex scar structures at the VT isthmus, potentially aiding preprocedural planning for catheter ablation of unmappable VT.
Absolute Event Rate: 19% vs 66.7%
In catheter ablation of scar-related monomorphic ventricular tachycardia (VT), substrate voltage mapping is used to electrically define the scar during sinus rhythm. However, the electrically defined scar may not accurately reflect the anatomical scar. Magnetic resonance-based visualization of the scar may elucidate the 3D anatomical correlation between the fine structural details of the scar and scar-related VT circuits. We registered VT activation sequence with the 3D scar anatomy derived from high-resolution contrast-enhanced MRI in a swine model of chronic myocardial infarction using epicardial sock electrodes (n=6, epicardial group), which have direct contact with the myocardium where the electrical signal is recorded. In a separate group of animals (n=5, endocardial group), we also assessed the incidence of endocardial reentry in this model using endocardial basket catheters. Ten to 12 weeks after myocardial infarction, sustained monomorphic VT was reproducibly induced in all animals (n=11). In the epicardial group, 21 VT morphologies were induced, of which 4 (19.0%) showed epicardial reentry. The reentry isthmus was characterized by a relatively small volume of viable myocardium bound by the scar tissue at the infarct border zone or over the infarct. In the endocardial group (n=5), 6 VT morphologies were induced, of which 4 (66.7%) showed endocardial reentry. In conclusion, MRI revealed a scar with spatially complex structures, particularly at the isthmus, with substrate for multiple VT morphologies after a single ischemic episode. Magnetic resonance-based visualization of scar morphology would potentially contribute to preprocedural planning for catheter ablation of scar-related, unmappable VT.
Ashikaga et al. (2007) studied Scar-related monomorphic ventricular tachycardia (n=11). High-resolution contrast-enhanced MRI with electroanatomical mapping was evaluated on Incidence of reentry circuits (epicardial or endocardial) among induced VT morphologies. High-resolution contrast-enhanced MRI in a swine model of chronic MI identified epicardial reentry in 19.0% of induced VT morphologies and endocardial reentry in 66.7%.