Abstract
Cardiac arrhythmias are often triggered by ectopic membrane depolarization originating deep inside the myocardial wall. Here we propose a new method utilizing a novel near-infrared voltage-sensitive fluorescent dye DI-4-ANBDQBS to determine the three-dimensional (3D) coordinates of the sources of such depolarization. We tested the method in live preparations of pig left and right ventricular myocardium (thickness 8-18 mm) and phantoms imitating the optical properties of myocardial tissue. The method utilizes an alternating transillumination approach that involves comparing pairs of simultaneously recorded broad-field epifluorescence and transillumination images produced at two alternating directions of illumination. Recordings were taken simultaneously by two CCD cameras facing the endocardial and epicardial surfaces of the heart at a frame rate up to 3 KHz. In live preparations, we were able to localize the origin of the depolarization wave with a precision of ±1.3mm in the transmural direction and 3 mm in the image plane. The accuracy of detection was independent of the depth of the source inside ventricular wall.
Highlights
Cardiac contraction is triggered by an electrical wave of membrane depolarization rapidly propagating through the entire heart and exciting the ventricles
The orientation of the main axis of the ellipse varies between different views reflecting the change in orientation of myocardial fibers across the thickness of myocardial wall emphasizing the different layers of the myocardium represented in each view
To determine how well this approximation works in our specific application, we tested its accuracy in phantom experiments replicating optical properties of cardiac tissue at 671nm
Summary
Cardiac contraction is triggered by an electrical wave of membrane depolarization rapidly propagating through the entire heart and exciting the ventricles Such waves originate in the pacemaker region known as the sino-atrial (SA) node. Known as optical mapping has been largely limited to the myocardial surface and subsurface myocardial layers [6,7,8] This limitation stems from the fact that the light in the blue-green part of the spectrum used for excitation of conventional VSDs has a sub-millimeter attenuation length [9,10]. Accurate coordinate detection requires capture of the early stages of the excitation when the voltage-dependent signal is less than 0.1% from the overall fluorescence All these factors impose significant constraints on the bandwidth, dynamic range, and fidelity of the optical detectors and data acquisition system. We compare the coordinates of the stimulation site with the optically-derived coordinates of the excitation origin
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