Ventricular Tachycardia in the Setting of Chagasic Cardiomyopathy: Use of Voltage Mapping to Characterize Endoepicardial Nonischemic Scar Distribution.

BACKGROUND: Chagasic cardiomyopathy (CC) is the most frequent nonischemic substrate causing left ventricular (LV) tachycardia in Latin America. Systematic characterization of the LV epicardial/endocardial scar distribution and density in CC has not been performed. Additionally, the usefulness of unipolar endocardial electroanatomic mapping to identify epicardial scar has not been assessed in this setting. METHODS AND RESULTS: Nineteen patients with CC undergoing detailed epicardial and endocardial LV tachycardia mapping and ablation were included. A total of 8494 epicardial and 6331 endocardial voltage signals and 314 epicardial/endocardial matched pairs of points were analyzed. Basal lateral LV scar involvement was observed in 18 of 19 patients. Bipolar voltage mapping demonstrated larger epicardial than endocardial scar and core-dense (≤0.5 mV) scar areas (28 [20-36] versus 19 [15-26] and 21 [2-49] versus 4 [0-7] cm2; P=0.049 and P=0.004, respectively). Bipolar epicardial and endocardial voltages within scar were low (0.4 [0.2-0.55] and 0.54 [0.33-0.87] mV, respectively) and confluent, indicating a dense/transmural scarring process in CC. The endocardial unipolar voltage value (with a newly proposed ≤4-mV cutoff) predicted the presence and extent of epicardial bipolar scar (P<0.001). CONCLUSIONS: CC causes a unique ventricular tachycardia substrate concentrated to the basal lateral LV, with marked epicardial predominance. The scar pattern is particularly dense and transmural as compared with the more erratic/patchy scar patterns seen in other nonischemic cardiomyopathies. Endocardial unipolar voltage mapping serves to characterize epicardial scar in this setting.