Figure 3: High-density electrical mapping.
(a) Representative optical and electrical signals acquired simultaneously from the corresponding numbered electrode locations on a Langendorff-perfused rabbit heart. Scale bar, 7 mm. (b) Top: schematic illustration of a representative optical action potential, unipolar EG and position of the activation time, defined as 
for the optical action potential and 
for the EG. Bottom: correlation of electrical and optical activation times for hearts tested in a variety of states. (c) Interpolated spatial activation maps determined from the electrical and optical measurements. Top: heart paced by the red pair of electrodes on the membrane. Bottom: sinus rhythm. (d) 3D mapping of electrical signalling from both the anterior and posterior surfaces of the heart. Interpolated spatial maps of electrical activation time are projected on a representative rabbit heart geometry, for purposes of visualization. Scale bar, 7 mm.
