FIGURE 2.

Voltage Signal-to-Noise Ratio (SNR). (A) Representative rat heart loaded with voltage dye, RH237. Action potentials were analyzed from the same region of interest (ROI) on the epicardial surface (n = 6 action potentials, same heart with diminished light illumination). (B) No measurable change in activation time was noted when the excitation light intensity and SNR was reduced (n = 6 action potentials, same heart). (C) Calculated APD₈₀ values also remained consistent (n = 6 action potentials, same heart). (D) Relationship between SNR and action potential measurements (n = 4 optical signals collected from n = 4 independent heart studies). Epicardial dynamic pacing (160 ms PCL) from the apex of the left ventricle.