Isochronal late activation mapping in ischemic scar VT: an independent validation using intraoperative mapping

VT ablation is often limited by hemodynamic instability. Substrate-based ablation strategy is often useful, and isochronal late activation mapping (ILAM) in sinus rhythm (SR) to identify deceleration zones (DZ) has been reported to be effective.

We aimed at independently validating ILAM concept using data from comprehensive intraoperative VT mapping.

Panoramic simultaneous endocardial intraoperative mapping was performed using a 112 bipolar electrode balloon. The late potentials in SR were mapped in eight isochrones, each of 15-30ms duration and correlated to the diastolic path of induced VT. Deceleration zone was defined as the presence of three or more isochrones within a radius of one centimetre. This equates to 10-20 cm/s of apparent conduction velocity.

Twenty-five VTs with complete mapped diastolic path were studied in 12 patients. Diastolic path of 17/25(68%) VTs harboured at least one DZ. Overall, 27 DZ were identified with mean of 2.25 per patient. The average conduction velocity in the DZ was 11 ± 2 cm/s.

Conduction slowing identified by isochronal late activation mapping during sinus rhythm colocalized with two-thirds of VT diastolic paths in ischemic heart disease patients.