| Popis: |
Last decade optical mapping technique became a widely-used instrument in cardiac electrophysiology. Optically recorded action potentials (AP's) in single cardiac cells precisely match electrically recorded ones. However, this relationship becomes not so direct in myocardium since optical AP (OAP) is the depth-weighted average of propagating AP and is affected by optical-biological processes (absorption, scattering and reflection). The best way to achieve informative results of electrical activity in the heart is to use both, optical approaches in combination with microelectrode technique.In the Langerdorff-perfused rabbit heart AP's were recorded with glass microelectrodes transmurally across the left ventricle (LV) wall from subepicardium towards subendocardium (3-5 mm, 20-50 steps). Simultaneously we used near-infrared (NIR) voltage sensitive fluorescent dye di-4-ANBDQBS to obtain OAP recordings using EMCCD camera (128x128 pixels, 500 frames/s). OAP's and electrical AP's were recorded using pacing from epicardium and endocardium.In our experiments we found, that AP activation time dependence on myocardium depth had a different shape, depending on pacing the type, distance, and LV geometry at recording site. The shape of the curve showed electrical transmural inhomogeneity of myocardium, which possibly was caused by histological inhomogeneity and different fibers orientation in different layers of myocardium. For the upstroke of OAP's evaluation, optical signals were compared with electrical AP's, recorded and summated transmurally through LV wall depth. Recordings allowed us to evaluate the role of light scattering and how much tissue inhomogeneity was reflected in the morphology of the upstroke of OAP.The obtained data could assist for better understanding of the mechanisms of the excitation wave propagation and for proper evaluation of optical signal in LV of the rabbit.This research is funded by the European Social Fund under the Global Grant measure. |
