Imaging electrical excitation inside the myocardial wall

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.