Effect of probing depth on fluorescence signal during cardiac optical mapping

To investigate the effect of different probing depths during cardiac optical mapping, the electrical transmural propagation model, and the fluorescence transport model were adopted to simulate the distribution of transmembrane potentials during the transmural propagation and the fluorescence signals coming form three different optical probing depths. The depth-weighted optical action potential is compared with the action potential of the top layer, and the discrepancy is analyzed. The results indicate that the effect of optical probing depth may be ignored as most of the fluorescence only comes from the subsurface (less than 0.5 mm) but the discrepancy of the action upstroke duration, the signal amplitude and duration between two action potentials are enhanced with the increase of the probing depth (greater than or equal to 0.5 mm), especially in the spiral wave activity. So it is necessary to correspondingly correct the judgments of the physiological states of myocardial cells generally obtained by electrodes from the tissue surface.