Abstract 3210: Relationship between Delayed Enhanced MRI and the Low Voltage Border Zone by Electroanatomic Mapping in Porcine Model of Ventricular Tachycardia
Background: The relationship between morphologic features of chronic myocardial scar detectable by delayed enhancement magnetic resonance imaging (DE-MRI) and the occurrence of monomorphic ventricular tachycardia (MVT) remain unclear. Accordingly, the purpose of this study compare DE-MRI and electroanatomic mapping (EAM) based assessment of myocardial scar and the infarct border zone region in a porcine model of MVT.
Methods: Seven pigs underwent anteroseptal myocardial infarction followed by reperfusion. DE-MRI was performed at 10 weeks after infarction and scar size and infarct boarder zone regions were defined by regions 2 and 1 SD above the mean remote myocardial signal, respectively. Scar transmurality was also assessed by DE-MRI. Bipolar voltage mapping studies were performed at the time of imaging to define low voltage scar (amplitude<0.5mV) and the infarct boarder zone region (0.5<amplitude<1.5mV). Surface areas of these low voltage zones and DE-MRI infarct regions were measured and expressed as a percentage of the total LV mass and compared with the scar spatial extent and morphologic features by DE-MRI. Ratios of EAM scar and DE-MRI scar were also calculated and compared with MVT inducibility testing by programmed stimulation in each animal.
Results: Regions of myocardial scar by DE-MRI were significantly greater than the EAM defined scar region in all animals (13.81±4.1% vs. 6.92±4.5%, p<0.01), but the border zone region by DE-MRI was much smaller that of the EAM defined border (1.2±0.6% vs. 14.8±7.9%, p<0.01). Sustained MVT was induced in 6 of 7 animals by programmed stimulation and all 6 inducible animals had transmural infarcts. One pig that was not inducible for MVT was non-transmural and showed reduced scar by EAM compared with inducible animals (ratio= 0.021 vs. 0.57±0.18).
Conclusion: DE-MRI defined scar area is significantly greater than that defined by EAM. Scar transmurality may be an important determinant of low voltage scar and substrate for MVT.