<i>In vivo</i> imaging of V_m and [Ca²⁺]_i dynamics in rat ventricles during sinus rhythm.

<p>(<b>A</b>) AP (red) and CaT (green) fluorescence signals taken from the 4×4-pixel white-square region highlighted in the top panel (left ventricle). (<b>B</b>) Normalized fluorescence intensity maps (colorbar shown) for V_m and [Ca²⁺]_i during sinus rhythm from the same heart; note the previously mentioned delay between V_m and [Ca²⁺]_i peaks (red arrow indicates electrical wave propagation direction). (<b>C</b>) AP (top traces) and CaT (bottom traces) fluorescence signals taken from three 4×4-pixel square regions from the left ventricle of another heart, showing varying motion artifact effects. Scale bar = 5 mm. For these images, blebbistatin was used to reduce, but not eliminate, the contribution of motion to the signals. For <b>B</b>, non-uniform dye-loading and motion artifact are the cause of signal quality heterogeneity.