Quantitative Analysis of the Duration of Slow Conduction in the Reentrant Circuit of Ventricular Tachycardia After Myocardial Infarction

Background: Few data are available to define the circuits in ventricular tachycardia (VT) after myocardial infarction and the conduction time (CT) through the zone of slow conduction (SCZ). This study assessed the CT of the SCZ and identified different reentrant circuits. Methods: During VTs, concealed entrainment (CE) was attempted. The SCZ was identified by a difference between postpacing interval (PPI) and VT cycle length (VTcl) ≤30 ms. Since the CT in the normally conducting part of the VT circuit is constant during VT and CE, a CE site within the reentrant circuit with (S‐QRS)/PPI ≥ 50% was classified as an inner reentry in which the entire circuit was within the scar, and a CE site with (S‐QRS)/PPI < 50% as a common reentry in which part of the circuit was within the scar and part out of the scar. Results: CE was achieved in 20 VTs (12 patients). Six VTs (30%) with a (S‐QRS)/PPI ≥50% were classified as inner reentry and 14 VTs (70%) with a (S‐QRS)/PPI