Stepwise approach to substrate modification of ventricular tachycardia after myocardial infarction

Recently, substrate mapping (SM) has been described to facilitate catheter ablation of stable and unstable ventricular tachycardia (VT) after myocardial infarction. However, SM is time consuming with potential disadvantages of multiple ablation lines such as impairment of ventricular function or proarrhythmia. The aim of the present study was to delineate a stepwise approach to SM to shorten procedure time and limit the possibility of complications.

SM was performed in 14 infarct survivors referred for VT ablation using an electroanatomical mapping system (CARTO) to define infarct regions. A new stepwise approach for SM was designed as follows. The initial ablation site was identified by pace- and entrainment mapping in case of stable VT and by pace mapping only in case of unstable VT. Based on the CARTO voltage mapping, linear ablation was done from this site to the center of the scar and perpendicular to the boundary of the scar or to the mitral annulus. Additional lines were performed only when VT remained inducible. A maximum of 3 ablation lines were created during one procedure.

A total of 57 VTs (21 stable, 36 unstable) were induced during the procedures. VT was no longer inducible after the first linear ablation in 2 patients, after the second linear ablation in 6 patients and after the third linear ablation in 3 patients. Either VT or ventricular fibrillation was still inducible at the end of the procedure in 3 patients. Procedure time averaged (291 +/- 85) minutes, fluoroscopy time (10 +/- 7) minutes. VT recurred in 3 patients. Following a second procedure in 2 patients, there were no further VT recurrences. Overall, there was a significant reduction in VT episodes 3 months after [median: 0, interquartile ranges (IQR): 0 - 1] compared with 3 months before ablation (median: 25, IQR: 16 - 105, P < 0.01).

This stepwise approach to SM is effective in facilitating ablation of stable and unstable VT. It reduces procedure and fluoroscopy time, and may help to improve the risk-benefit ratio of VT ablation.