Simultaneous optical mapping of transmembrane potential and wall motion in isolated, perfused whole hearts

Abstract

Abstract. Optical mapping of cardiac propagation has traditionally been hampered by motion artifact, chiefly due to changes in photodetector-to-tissue registration as the heart moves. We have developed an optical mapping technique to simultaneously record electrical waves and mechanical contraction in isolated hearts. This allows removal of motion artifact from transmembrane potential (V m ) recordings without the use of electromechanical uncoupling agents and allows the interplay of electrical and mechanical events to be studied at the whole organ level. Hearts are stained with the voltage-sensitive dye di-4-ANEPPS and ring-shaped markers are attached to the epicardium. Fluorescence, elicited on alternate frames by 450 and 505 nm light-emitting diodes, is recorded at 700 frames/ per second by a camera fitted with a 605 ± 25 nm emission filter. Marker positions are tracked in software. A signal, consisting of the temporally interlaced 450 and 505 nm fluorescence, is collected from the pixels enclosed by each moving ring. After deinterlacing, the 505 nm signal consists of V m with motion artifact, while the 450 nm signal is minimally voltage-sensitive and contains primarily artifacts. The ratio of the two signals estimates V m . Deformation of the tissue enclosed by each set of 3 rings is quantified using homogeneous finite strain. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

Comparison of Intensity-based B-splines and Point-to-Pixel Tracking Techniques for Motion Reduction in Optical Mapping

“…MAs manifest both as phase artifacts due to uncorrected registration and as a modulation of the signal of interest caused by different mechanisms including heterogeneities in dye distribution [3,4] or excitation light intensity [5], as well as changes in tissue volume [6,7].…”

“…Although many alternatives based on post-processing techniques have been proposed to address this issue [3][4][5][6] none of them has become widely accepted. Among previously proposed algorithms, image registration techniques [3,4,5,6] have generated a great interest, since only these methods account for phase errors. However, comprehensive evaluation of these techniques may be bias due to heterogeneous results and technical setups.…”

Toward microendoscopy-inspired cardiac optogeneticsin vivo: technical overview and perspective

“…High-resolution CCD cameras and EMCCD cameras have been popular for use in optical mapping [5][6][7][30][31][32][33][34][37][38][39][40]127,128,144 and microendoscopy due to their high-spatiotemporal resolution. EMCCD cameras take advantage of avalanche processes to perform the on-chip electron multiplication to enhance SNRs, have higher frame rates, and improved quantum efficiency.…”

“…The two key classes of fast response indicators are voltage (potentiometric) and calcium probes; examples of these indicators can be seen in Table 1. For in vitro voltage sensing, the styryl dyes di-4-ANEPPS, di-8-ANEPPS, and RH-237 undergoing spectral shifts that vary linearly with voltage changes have been used extensively in optical mapping [5][6][7]30,31,35,38,40,127,128 and other cardiac imaging systems. [12][13][14][15]44,[46][47][48] However, these potentiometric dyes are inherently inefficient.…”

“…The development of high-speed cameras, such as charged coupled device (CCD) cameras and more recently electron multiplying CCD (EMCCD) cameras, has allowed the tracking of more intricate waveforms in tissues [25][26][27] and whole hearts. [28][29][30][31][32][33][34][35] Temporal resolutions can be increased without sacrificing spatial resolution by using methods such as temporal pixel multiplexing, where pixel exposure times are offset allowing temporal information to be embedded into the image without adjusting the intrinsic frame rate of the camera. 36 This method has been employed to perform 250-Hz Ca 2þ imaging of rat cardiomyocytes using a 10-Hz megapixel CCD camera and a digital micromirror device to perform the transient illumination of subregions of the detector.…”