Po-04-163 regional basal rhythm myocardial conduction velocity dispersion predicts ventricular tachycardia circuit sites and associates with lipomatous metaplasia in patients with chronic ischemic cardiomyopathy

Regional myocardial conduction velocity (CV) dispersion has not been studied in post-infarct patients with ventricular tachycardia (VT). We sought to compare 1) the association of regional CV dispersion versus repolarization dispersion with VT circuit sites; 2) myocardial lipomatous metaplasia (LM) versus scar as the anatomic substrate for CV dispersion. Thirty-three patients with Ischemic Cardiomyopathy (ICM) and documented VT were consecutively identified from the Prospective Cohort Study of Mechanistic Associations between Intra-Myocardial Fat Deposition and Ventricular Tachycardia in Cardiomyopathy (INFINITY). We characterized dense and border zone (BZ) infarct tissue by late gadolinium enhancement cardiac magnetic resonance, and LM by computed tomography, with both images registered with electroanatomic maps. Activation repolarization interval (ARI) was defined as the time interval from the minimum derivative within the QRS to the maximum derivative within the T-wave on unipolar electrograms. CV at each EAM point was calculated as the mean CV between that point and five adjacent points along the activation wave front. CV dispersion and ARI dispersion was defined as the coefficient of variation (CoV) of CV and ARI per AHA segment, respectively. Regional CV dispersion per AHA segment exhibited a much larger range than ARI dispersion, with median 0.65 versus 0.24, p<0.001. CV dispersion was a more robust predictor of the number of critical VT sites per AHA segment when compared to ARI dispersion (likelihood ratio χ2 321 vs. 107), with difference of Akaike Information Criterion (△AIC) 214 >10. LM area per AHA segment was more strongly associated with regional CV dispersion than regional scar area [likelihood ratio χ2 102 vs. 75, △AIC 27 > 10, and 6.8% vs. 2.2% increase in Log (CoV_CV) for per 1 cm2 increase of LM and scar area per AHA segment, respectively]. The mean CV amplitude per AHA segment was 24.0 (15.5, 36.2) cm/s versus 55.7 (35,9, 78.6) cm/s in the group with high CV dispersion (>0.65) and the group with a low CV dispersion (<0.65), with p<0.001. Importantly, a subgroup with CoV_CV<0.65 but a similar mean CV 24.0 (20.5, 27.9) cm/s to the group with CoV_CV>0.65 contained a smaller number of critical VT sites, with median 0 (IQR 0, 1) versus 1 (IQR 0, 4), p<0.001. Regional CV dispersion is more closely associated with VT circuit sites than refractory period dispersion, and LM is a critical substrate for regional CV dispersion.