Extended Data Fig. 2: Electrocardiograms demonstrating automatic and re-entrant mechanisms for ventricular arrhythmias from representative cell and vehicle recipients.

(a-c) Electrograms from spontaneous ventricular tachycardia in cell recipient showing characteristics consistent with automatic arrhythmia mechanism. (a) Electrocardiograms from site of earliest activation during spontaneous ventricular tachycardia in cell recipient. Corresponding activation map viewable in Fig. 1d. Electrogram duration=73 ms which is 18% of the ventricular tachycardia cycle length (410 ms). (b) Transient suppression and spontaneous re-initiation of ventricular tachycardia in cell recipient. (c) Instant capture during left ventricular pacing, followed by instant continuation of ventricular tachycardia. Post-pacing interval – tachycardia cycle length ~ 114 ms. (d-e) Electrograms from induced ventricular arrhythmia in vehicle recipients showing characteristics consistent with re-entrant arrhythmia mechanism. (d) Initial fusion evident at onset of right ventricular overdrive pacing during induced ventricular tachycardia. (e) Clean resumption of tachycardia after overdriving pacing. Post-pacing interval – tachycardia cycle length ~ 90 ms.