Location of Diastolic Potentials in Reentrant Circuits Causing Sustained Ventricular Tachycardia in the Infarcted Canine Heart

BACKGROUND: The complete reentrant circuit for ablation of reentrant ventricular tachycardia (VT) in humans can rarely be localized by mapping. As a result, surrogate markers, such as diastolic electrical activity, subsequently confirmed by entrainment, have been used. However, ablation at those sites has had variable efficacy. The reasons for this variability are not clear. METHODS AND RESULTS: We correlated activation maps of reentrant circuits in the epicardial border zone of 4-day old infarcted dog hearts with the corresponding ECGs for 45 VTs to determine the regions of the reentrant circuits activated during diastole. In VTs with a figure-8 reentrant pattern, the center point of the central common pathway, the part of the circuit critical for the maintenance of reentry, was activated in early diastole in 32 of 35 VTs (91.4%), in late diastole in 1 (2.9%), and in systole in 2 (5.7%). Regions outside the circuit were rarely activated in diastole. In 10 VTs, the reentrant circuit was characterized by a single reentrant loop. In these circuits, no one region was predicted to be critical for maintenance of reentry, and a segment of the circuits was activated during diastole. However, regions peripheral to the circuit were also activated during diastole. CONCLUSIONS: The pattern of reentrant activation determines the specificity of diastolic activity for locating critical sites for ablation of VT.