Concurrent imaging of metabolic and electric signals in the heart

Cardiac rhythm disorders can result from disturbances in cardiac metabolism. These metabolic changes are tightly linked with specific cardiac electrophysiology (CEP) abnormalities, such as depressed excitability, impaired intra- and extracellular conductivities, wave propagation block, and alteration of conduction velocity, action potential amplitude, and duration. The altered electrophysiology eventually can lead to arrhythmias, fibrillation, and cardiac death; therefore, understanding the spatiotemporal complexity of the relationship between metabolism and electrophysiology is the challenge in developing new approaches for treatment of cardiac diseases. The optical system for simultaneous imaging electrical and metabolic quantities in the heart was developed by scientists at Vanderbilt University. The advantages of their imaging system over others include an optional software camera calibration routine that eliminates the need for precise camera alignment. The system allows for rapid setup, dichroic image separation, dual-rate imaging, and high spatial resolution, and it is generally applicable to any two-camera measurement. The authors provide a detailed description of a camera calibration algorithm along with multiple examples. They demonstrate the capabilities of this type of imaging system for recording not only the transmembrane potential and intracellular calcium, but other signals more directly related to myocardial metabolism, such as [K+]e, NADH, and reactive oxygen species, leading to the possibility of correlative multimodal cardiac imaging. The authors findings appear in the November issue of Experimental Biology and Medicine.