Ventricular mapping during atrial and right ventricular pacing: Relation of electrogram parameters to ventricular tachycardia reentry circuits after myocardial infarction

Introduction: Ventricular tachycardia (VT) late after myocardial infarction is usually due to reentry in the border zone of the infarct area. Identification of critical parts of the VT reentry circuit by catheter mapping without needing to induce VT is a desirable goal for VT ablation. The aim of this study was to develop a model to predict reentry circuit locations based on characteristics of sinus or paced electrograms and pace mapping (PM) recorded from the infarct region. Methods: Left ventricular electroanatomic mapping with the CARTO(R) mapping system was performed in 16 male patients with recurrent VT late after myocardial infarction. A total of 1072 left ventricular sites were recorded during atrial pacing (AP) and right ventricular pacing (RVP), and the corresponding electrograms were analyzed for their local activation time (LAT), onset (ONS), end ( END), duration (DUR), and amplitude (AMP) in each pacing sequence. At 1041 of these sites, PM was performed; the resulting stimulus to QRS intervals (S-QRS) was determined at 931 sites, the remaining 110 sites did not capture. All the obtained parameters were compared with the location of 18 ablation target areas with a radius of 2 cm defined by success of radio-frequency (RF) ablation or entrainment during VT, or both. Results: Of 1072 sites, 227 (21%) were in the target and 845 (79%) were outside the target. All parameters were significantly different (p<0.05) in AP and in RVP between inside and outside the target in a univariate analysis. In amultivariate analysis LAT, END, DUR, and AMP in AP, END and AMP in RVP, and S-QRS were independent predictors for the target (p<0.05). A combination of selected parameters of these predictors (DUR in AP, AMP in RVP, and S-QRS) had a specificity of 64% with a sensitivity of 80% for the target. Conclusion: The observations suggest that ablation guided by a combination of abnormal electrograms in different rhythms can be useful to ablate VT and reduce the necessity of VT induction. Anatomically fixed regions of block may be important for reentry and be identifiable during sinus rhythm.