Optical mapping

Abstract: Cardiac optical mapping has proven to be a powerful technology for studying cardiovascular function and disease. The development and scientific impact of this methodology are well-documented. Because of its relevance in cardiac research, this imaging technology advances at a rapid pace. Here, we review technological and scientific developments during the past several years and look toward the future. First, we explore key components of a modern optical mapping set-up, focusing on: (1) new camera technologies; (2) powerful light-emitting-diodes (from ultraviolet to red) for illumination; (3) improved optical filter technology; (4) new synthetic and optogenetic fluorescent probes; (5) optical mapping with motion and contraction; (6) new multiparametric optical mapping techniques; and (7) photon scattering effects in thick tissue preparations. We then look at recent optical mapping studies in single cells, cardiomyocyte monolayers, atria, and whole hearts. Finally, we briefly look into the possible future roles of optical mapping in the development of regenerative cardiac research, cardiac cell therapies, and molecular genetic advances.

Abstract: Unique Properties of Optical Action Potentials. Introduction: Optical mapping with voltage-sensitive dyes has made it possible to record cardiac action potentials with high spatial resolution that is unattainable by conventional techniques. Optically recorded signals possess distinct properties that differ importantly from electrograms recorded with extracellular electrodes or action potentials recorded with microelectrode techniques. Despite the growing application of optical mapping to cardiac electrophysiology, relatively little quantitative information is available regarding the characteristics of optical action potentials recorded from cardiac tissue. Methods and Results: A high-resolution optical mapping system and microelectrode techniques were used to determine the characteristics of guinea pig ventricular action potentials recorded with the voltage-sensitive dye di-4-ANEPPS. The effects of optical magnification, tissue-light interaction, sampling rate, voltage resolution, spatial resolution, and cardiac motion on action potential signal characteristics were determined. The optical action potential signal represents the relative change in transmembrance potential arising from a volume of cells, where the area of a recording site is determined by optical magnification and detector area, and the depth of recording is determined by system optics and the visible light transmission characteristics of cardiac muscle. Using photographic lenses, the depth of tissue contributing to the signal is < 250 μm. The action potential plateau and final repolarization can be accurately reconstructed from data digitized at modest sampling rates (450 to 750 Hz), since the frequency content of optical action potentials is band-limited to approximately 150 Hz. However, faster sampling rates are needed to depict the subtle details of the action potential upstroke. In addition to temporal resolution, it is essential to achieve sufficient dynamic range and voltage resolution to accurately represent the time course of membrane potential change. Voltage resolution is inversely related to the square of spatial resolution, hence, there exists an inherent trade-off between increased spatial resolution and diminished voltage resolution. Cardiac motion, which can otherwise limit spatial resolution as well as signal fidelity, can be effectively reduced using mechanical stabilization of the heart without distorting action potential characteristics. Conclusions: Optical mapping with voltage-sensitive dyes provides high-fidelity multisite action potential recording with flexible spatial resolution. When recording cardiac action potentials with voltage-sensitive dyes, the Interdependence of temporal, spatial, and voltage resolutions must be carefully considered.

Abstract: Optical mapping has become an increasingly important tool to study cardiac electrophysiology in the past 20 years. Multiple methods are used to process and analyze cardiac optical mapping data, and...

Abstract: BACKGROUNDHeterogeneities of repolarization (R) across the myocardium have been invoked to explain most reentrant arrhythmias. The measurement of refractory periods (RPs) has been widely used to assess R, but conventional electrode and extrastimulus mapping techniques have not provided reliable maps of RPs.METHODS AND RESULTSGuinea pig hearts were stained with a voltage-sensitive dye to measure fluorescence (F) action potentials (APs) from 124 sites with a photodiode array. AP duration (APD) was defined as the time between depolarization (dF/dt)max and R time points (ie, the time when AP returns to baseline or some percent thereof). However, R time points are difficult to determine because AP downstrokes are often encumbered by drifting baselines and motion artifacts, which make this definition ambiguous. In optical and microelectrode recordings, the second derivative of AP downstrokes is shown to contain an easily detected, unique local maximum. The correlation between the position of this maximum (d2F/d...