Identifying VT isthmuses on sinus rhythm maps: an approach based on electrogram frequency and voltage

Ablation therapy is the preferred treatment for ventricular tachycardia (VT), with a primary focus on the Isthmus region. Various indicators, including deceleration zones and local abnormal ventricular activity, have been proposed to aid in identifying the Isthmus on sinus rhythm maps. However, precise Isthmus identification remains a challenge for achieving effective ablation.

We hypothesized that frequency and voltage analysis could enable the identification of Isthmuses on maps obtained during sinus rhythm.

This study included 40 patients (83% male, mean age 28.7 ± 5.6 years, LVEF 41 ± 13.48%) with sustained VT. They underwent mapping procedures using the Ensite X mapping system (Abbott, Abbott Park, IL) with a nearfield algorithm and omnipolar mapping. In 11 patients, sustained VT could be safely induced, allowing for the collection of corresponding maps in both VT and sinus rhythm. Isthmuses were identified on VT maps by the operator (Fig. 1a, Isthmus = white frame).

On VT maps, Isthmus areas (In) demonstrated higher frequency and lower voltage compared to non-Isthmus regions (Out) (In: 371.01 ± 129.34 Hz vs. Out: 288.86 ± 147.74 Hz, p < 0.01; In: 1.12 ± 1.33 mV vs. Out: 2.20 ± 3.90 mV, p = 0.04). A similar pattern was observed on sinus rhythm maps (In: 315 ± 121 Hz vs. Out: 280 ± 141 Hz, p = 0.32; In: 0.60 ± 1.63 mV vs. Out: 2.13 ± 3.98 mV, p < 0.01). Receiver operating curve analysis identified specific frequency and voltage thresholds for Isthmus detection, which were applied to the maps. The threshold-based maps (Fig. 1b) were reviewed by three experienced operators, who agreed that Isthmus detection was improved in 11 out of 11 cases.

Isthmuses of VT display higher frequency and lower voltage patterns compared to the rest of the left ventricle. This characteristic is prevalent during VT and sinus rhythm. Therefore, it could improve Isthmus identification on Sinus rhythm maps.Figure.1