Figure 5.

Optogenetic termination of VTs by apical ex vivo illumination of TAC hearts with the LED device. (A and B) Intracardiac ECG demonstrating successful termination of VTs with a single 567 nm (A) or 617 nm (B) light pulse (500 ms; 5 mW/mm²; coloured boxes). (C) Quantification of optogenetic termination efficacy averaged per ReaChR-expressing heart (n=6 animals, five individual measurements per animal) or Citrine-expressing heart (n=4 animals, five individual measurements per animal) by the LED device following activation of only the centrally located LED (C) or all four LEDs (A) for up to three consecutive light pulses (500 ms with a 500 ms cycle length, 5 mW/mm²). Each dot represents the average of five individual measurements in one rat. Error bars represent SEM. (D) Representative intracardiac ECG recording of a ReaChR-expressing TAC heart demonstrating 5 Hz apical pacing before, during, and after apical illumination by the 567 nm LED device with all four LED chips activated for 1000 ms (irradiance: 5 mW/mm²). The sensing electrode was attached to the LV free wall. Complete loss of ventricular capture during the entire duration of illumination was observed for all ReaChR-expressing TAC animals (n=4) as only pacing artefacts are observed. (E) Ventricular capture was not affected by illumination of Citrine-expressing control hearts (n=4).