Abstract 639: ECG Criteria to Identify Epicardial Ventricular Tachycardia in Non-Ischemic Cardiomyopathy
Background: The value of reported ECG criteria for identifying epicardial (EPI) origin of ventricular tachycardia (VT) in nonischemic left ventricle cardiomyopathy (NILVCM) have not been compared
Methods: To compare ECG criteria for identifying EPI origin we assessed the QRS during pace mapping (PM) from 102 basal superior/lateral EPI and 67 ENDO sites in 13 patients with NILVCM. PM focused within on surrounding the distribution of confluent scar (voltage: ENDO < 1.5 mV, EPI < 1.0 mV). Previously morphology + interval published criteria (pseudodelta wave > 34ms, intrinsicoid deflection time >85ms, shortest RS complex >121ms, maximum deflection index >0.55) were assessed for accuracy. Sixteen VT localized to the EPI and 8 from the ENDO substantiated PM data.
Results: PM sites showed Q wave in lead I more commonly from EPI (91% vs 4%; p< 0.001). The absence of q wave in inferior leads also was more frequent from EPI (99% vs 48%; p< 0.001). The presence of Q wave in lead I identified 88% of VTs localized to the EPI and was seen in only 1/8 ENDO VTs (specificity 88%). None of the remaining criteria was able to achieve a similar sensitivity without a specificity of <50%. We identified criteria that had <95% specificity and sensitivity of <20% with the PMs to create a simple algorithm for identifying EPI VTs This algorithm diagnosed the origin of the VTs with a specificity of 94, 100 and 80% in steps 1,2 and 3, respectively, and a sensitivity/specificity of 92/75% in the last step.
Conclusion: In patients with NILVCM morphologic ECG features that describe the initial vector of QRS identify basal superior/lateral LV-VT localized to the EPI and should prove to be a useful guide for planning VT ablation procedures.