Figure 2.

Data shown are from patient 1, including sinus rhythm voltage map (A) and activation map (B) during ventricular tachycardia; with the duodecapolar mapping catheter positioned over the area of earliest activation and voltage abnormality, entrainment from the distal bipoles was performed with concealed fusion. (C) Postpacing interval 10 ms shorter than the tachycardia cycle length (490–500 ms) likely resulted from high-output pacing and increased virtual electrode size, leading to capture of tissue deeper within the circuit as well as near-field signal, as evidenced by shorter stimulus-QRS vs EGM-QRS timing (yellow lines and arrows), producing a shorter return cycle than expected but consistent with a central isthmus site.³¹ Cryoablation over that site (D) led to slowing and termination of tachycardia. Note that the adjacent, extraepicardial left phrenic nerve was protected from cryothermal energy with retraction and mechanical shielding.