A study of electrical activation of the heart by laser spectrometry. An optical study of cellular action potentials.

The action potentials of working myocardium and conduction tissues, traditionally recorded by intracellular glass microelectrodes, may also be studied at a distance without physical contact using an optical system. The tissues have to be stained with a dye which fluoresces when illuminated by a laser beam, and the spectrum of the fluorescence must be sensitive to variations of the transmembrane action potential. The responses obtained by the microelectrode and the optical systems were tested on several different preparations (sheep and mouse myocardium). Three types of signals were obtained: asynchronous, synchronous and mixed, related to myocardial contraction, the action potential and the excitation-contraction couple, respectively. The use of continuous and pulsed mode laser measurements by optoelectronic methods (photomultiplier, monochromator), and imaging of the electrical activation by a CCD video camera may lead to the development of high definition mapping of myocardial activation which would be used for studying arrhythmias in experimental and even clinical models.