High-resolution high-speed synchronous epifluorescence imaging of cardiac activation

Abstract

An optical imaging technique with high spatial and temporal resolution was developed to record fractional changes in laser-induced epifluorescence associated with the cardiac transmembrane potential during and after the application of monophasic point stimuli. The technique takes advantage of the repeatability of the recorded events, and uses a synchronized laser strobing mechanism to overcome the speed limitation inherent to slow-scan charge-coupled device cameras, and achieves an effective frame rate of 500 frames/s at a spatial resolution of 100ϫ100 pixels in a single frame with a pixel resolution of 75 m. The signal-to-noise ratio can be improved with boxcar averaging. Patterns of virtual cathode and anode with distinctive regions of simultaneous depolarization and hyperpolarization during stimulation are demonstrated with stimuli applied to the resting myocardium of an isolated rabbit heart. The technique described in this article provides a powerful tool for investigating repeatable dynamics in the function of electrically active tissue.

Preventing ventricular fibrillation by flattening cardiac restitution

“…The optical mapping system used in the present study has been described in detail (17). The tissues were stained for 20 min with 1-2 M pyrimidine 4-(2-(6-(dibutylamino)-2-naphthalenyl)-1-(3-sulfopropyl) hydroxide (di-4-ANEPPS, Molecular Probes) added to the Tyrode's solution.…”

The Potential of Dual Camera Systems for Multimodal Imaging of Cardiac Electrophysiology and Metabolism

“…The use of rapid switching of different illumination wavelengths gated to individual image frames for high-frame-rate, i.e ., time-domain multiplexing of multiple metabolic signals, is useful if the excitation spectra do not overlap. The ability of an acousto-optic modulator to control high-speed illumination of the heart has already been demonstrated for older, low-speed CCD cameras (61, 62). An alternative would be to use LEDs of different colors whose pulsed excitation is interleaved and synchronized with the camera frames.…”

A Phased-Array Stimulator System for Studying Planar and Curved Cardiac Activation Wavefronts

“…Figure 3 shows an overview of the phased-array stimulator and an early implementation of the optical recording system [16]. The operator first selects the orientation of the desired planar wave front to be created, and specifies the parameters into the LabView™ emulator.…”

“…The imaging system uses a cooled CCD camera with a 50 mm f1.8 objective lens and a 5 W argon laser, as described in detail elsewhere [16]. An acousto-optic modulator (AOM) was used to strobe the laser illumination of the heart to provide a shorter effective exposure time than would be possible with the intrinsic shutter speed of the camera.…”

“…To acquire a sequence of 100 × 100 pixel images of a 7.5 × 7.5 mm field of view on the heart separated by intervals of 1 to 3 ms, we used 3 × 3 binning of a 300 × 300 pixel region and boxcar signal averaging for signal-to-noise enhancement [16].…”