Spectroscopic studies of the human heart conduction system ex vivo: implication for optical visualization.

Fluorescence excitation and emission spectra of the heart tissues specimens have been measured ex vivo with the aim of finding out the optical differences characteristic for the human heart conduction system (the His bundle) and ventricular myocardium. The optimal conditions enhancing the spectral differences between the His bundle and myocardium were found by recording the fluorescence signal in the range from 420 nm to 465 nm under the excitation at wavelengths starting from 320 nm to 370 nm. In addition, the spectral differences between the His bundle and the connective tissue, which is often present in the heart, could be displayed by comparing the ratios of fluorescence intensities being measured at above 460 nm under the preferred excitation of elastin and collagen. The left and right branches of the His bundle were visualized ex vivo in the interventricular septum of the human heart under illumination at 366 nm.