Dynamic unipolar voltage criteria of right ventricular septum for identifying left ventricular septal scar.

PURPOSE: The right ventricular (RV) septal unipolar voltage (UV) for predicting left ventricular (LV) septal scar wall thickness (WT) remains to be elucidated. METHODS: From 2013 to 2015, data obtained from RV and LV electroanatomic maps of 28 patients (mean age, 53 ± 16 years; 19 men [67.9%]) with/without identified LV septal scars were reviewed. Patients with an RV septal scar were excluded (n = 90). Direct measurement of septal WT was conducted (mean distance, 10.4 ± 3.3 mm). Patients in group 1 had a normal LV substrate, while those in group 2 had an LV septal scar. Fisher's linear discriminant formula was used to determine the dynamic UV criteria. RESULTS: A total of 552 points were collected: 323 in 12 patients from group 1 and 229 in 16 patients from group 2. The UV of the RV septum is capable of identifying the opposite LV endocardial bipolar scar and is proportional to the WT of the interventricular septum. In the absence of an RV endocardial scar, the formula of "RV septal cut-off value = 0.736 × WT - 0.117 mV" has better sensitivity and specificity for predicting the LV septal scar (0.96 vs. 0.68 and 0.91 vs. 0.80, respectively) than the predefined fixed criteria of 8.3 mV with a net reclassification improvement of 25.7% (P < 0.001). CONCLUSIONS: The combined measurement of UV and WT is more sensitive than the predefined fixed UV criteria for defining deep scars.