Figure 1

Simultaneous all-optical map and control of cardiac conduction pathway.

(a) Scheme of the wide-field fluorescence macroscope consisting of a LED at a wavelength centered at 625 nm for excitation of the voltage-sensitive dye and a CW laser at 473 nm for ChR2 activation. The system is provided with a random access scanning head comprised of two orthogonally mounted acousto-optical deflectors (AOD x-y). A 1.25x objective is used for imaging and stimulation of the whole mouse heart, a 20x objective is used to focus the fluorescence signal into a central portion (100 × 100 pixel) of a sCMOS sensor operating at a frame rate of 2 kHz. (b) Electrocardiographic recording of a ChR2-expressing heart, showing sinus rhythm with a frequency of 3 Hz. Blue arrowheads represent the ChR2 stimulation performed at 5 Hz (laser power at the sample 4.9 mW, illumination time 5 ms). The orange line represents the LED illumination. (c) Fluorescence image (F₀) of a ChR2-expressing heart stained with voltage sensitive dye (left). Scale bar of 2 mm in yellow. Six representative frames of optical mapping (ΔF/F₀) recorded from the same heart. The electrical activation is reported in red and the baseline in cyan. On the right, corresponding color-scaled isochronal map of the action potential reporting the voltage activation time per pixel. (d) On the left, fluorescence image (F₀) of a ChR2-expressing heart stimulated in the apex either with an electrode (red spot, above) or with ChR2 activation with the blue laser (blue spot, below). The green frame represents the AODs working-field on the sample. Corresponding optical mapping frames (ΔF/F₀) recorded from the same heart are reported next. On the right, corresponding color-scaled isochronal map of the action potential reporting the activation time per pixel.