| Visualization of Electical Excitation in the Heart |
| Heart Imaging | |
Every heart beat is triggered by a rapidly propagating electrical excitation front that synchronizes
contractions of the individual myocytes constituting the myocardial wall. Abnormal propagation of this
wave severely compromises the mechanical function of the heart, representing a major cause of
arrhythmias and sudden cardiac death. To observe the electric excitation, we first develop a quantitative
understanding of the voltage-sensitive fluorescent signals by building realistic computer models capable
of predicting optical signals from the optical characteristics of the tissue as well as the three-dimensional
distribution of transmembrane voltage inside the myocardial wall. Imaging electrical excitation waves in
the heart are performed using voltage-sensitive fluorescent dyes. The dye binds to the cardiac myocyte
membrane and responds to changes in the transmembrane potential by changes in excitation and
fluorescence spectra.
We solve the inverse problem, which is the reconstruction of a 3D pattern of electrical activation from a series of optical images. The inverse problem approach is based on detection of multiple scattered photons at various positions around the object. To achieve this we combine methods of diffusion optical tomography with specific knowledge of electrical processes in the heart and their characteristics. To make the problem tractable we focus on a) the detection of stationary highly localized periodic sources of excitation (ectopic foci) and b) the detection of 3D vortices of excitation known as scroll waves. |
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