Fig. 4

Optical mapping with di-2-ANEPEQ confirms hESC-CM grafts can act as an ectopic pacemaker. A cryoinjured heart with GCaMP3+ H7 hESC-CM graft was imaged under spontaneous conditions (no external pacing), and the graft was found to pace host myocardium. a Still image showing the epicardial surface of the heart on the di-2-ANEPEQ channel with the boundaries of cryoinjury scar and graft indicated by white and yellow dotted lines, respectively. Base of the heart to the upper left, apex to lower right. b di-2-ANEPEQ fluorescent signals and ECG trace for this heart with the timing of the ectopic graft-paced beat depicted in panel c indicated by the black arrowhead. c Activation map for a representative graft-paced beat, showing the earliest activating area (blue) starts in the coupled graft footprint, then propagates outward towards the LV base and apex (white to red). d Activation map for a representative host-paced beat, with earliest activation (blue) initiating at the LV apex, then propagating towards the LV base and finally back apically to activate the graft (white to red). Note the slower kinetics of the graft-paced versus host-paced beat. Also, note that both activation maps represent information from a single beat