Optical Mapping

Background: Optical mapping is a technique we use to study cardiac electrophysiology.
Briefly, cardiac function is assessed by either using fluorescent dyes or intrinsic fluorescent
properties of the molecules in the heart. We routinely use voltage-sensitive fluorescent dyes
such as Di-4-ANEPPS, RH237 and Di-4-ANBDQBS that bind to the cell membrane of
cardiomyocytes. The fluorescence intensity of these dyes changes with the membrane potential.
High speed image acquisition of this optical signal from the heart gives an optical surrogate of
the cardiac action potential. Similarly, calcium indicator dyes such as Rhod2-AM is used to
record calcium transients from the heart. Additionally, NADH autofluorescence can also be
recorded using this technique as a measure of cardiac metabolic state.
Applications in the Efimov Lab: The Efimov Lab uses optical mapping techniques in many
forms ranging from single parametric-single field of view imaging to multiparametric-multiple
fields of view imaging and even panoramic approaches. Our lab is equipped with five optical
mapping systems, each specializing in specific applications: 

1. High spatial resolution (256X256 pixels) single camera imaging.
2. Dual parameter optical mapping system for voltage and calcium recordings.
3. 3D printed dual optical mapping system for voltage/calcium/NADH imaging in upright
and horizontal camera orientation.
4. Panoramic optical mapping system.
5. Four camera optical mapping system for imaging multiple cardiac surfaces
simultaneously.

A list of our recent publications using these systems can be found below.

  •  Sharon A George, Jaclyn A Brennan, Igor R Efimov. Preclinical Cardiac Electrophysiology
    Assessment by Dual Voltage and Calcium Optical Mapping of Human Organotypic Cardiac
    Slices. JoVE, 2020. PMID: 32628156.
  • Brianna Cathey, Sofian Obaid, Alexander M Zolotarev, Roman A Pryamonosov, Roman A
    Syunyaev, Sharon A George, Igor R Efimov. Open-source multiparametric optical mapping. Sci
    Rep, 2019. PMID: 30679527.
  • Christopher Gloschat,  Kedar Aras , Shubham Gupta, N. Rokhaya Faye,  Hanyu Zhang , Roman A.
    Syunyaev, Roman A. Pryamonosov, Jack Rogers, Matthew W. Kay, Igor R. Efimov. RHYTHM:
    An Open Source Imaging Toolkit for Cardiac Panoramic Optical Mapping. Sci Rep, 2018. PMID:
    29440763.
  • Kedar K. Aras, Ndeye Rokhaya Faye, Brianna Cathey, Igor R. Efimov. Critical Volume of Human
    Myocardium Necessary to Maintain Ventricular Fibrillation. Circ Arrhythm Electrophysiol,
    2018. PMID: 30376733.
  • Sharon A George, Igor R Efimov. Optocardiography: A review of its past, present, and future.
    Curr Opin Biomed Eng, 2019. PMID: 31803858.

    Open-Source Resources: The Efimov Lab also provides open source resources for optical
    mapping including analysis software and custom 3D printed optical mapping system
    components design. These resources are available at https://github.com/optocardiography.
    Rhythm 1.0: Rhythm 1.0 allows the user to display, condition and analyze optical mapping
    signals recorded as .gsd or .rsd files using MiCam Ultima and MiCam 05 cameras from
    SciMedia. This Matlab based GUI performs basic signal conditioning including filtering,
    thresholding, binning, background removal, drift correction and normalization of the recorded
    optical signals of the transmembrane potential. It also analyses the data to measure activation
    times, conduction velocity, action potential duration, phase and dominant frequency.
    Rhythm 1.2: Rhythm 1.2 is a newer version of this Matlab GUI that incorporates optical calcium
    transient data analysis in addition to transmembrane potential analysis. Rhythm 1.2 performs
    all the above mentioned signal conditioning and data analyses in addition to having the option
    to visualize and analyze upto four data files simultaneously. This also allows to identify
    simultaneously recorded signals and “link” the files for further analysis. For example, in
    multiparametric analysis, simultaneously recorded voltage and calcium signals are “linked” to
    indicate that these recordings were taken at the same time and in the same field of view.
    Additionally, Rhythm 1.2 also has the capability to perform action potential and calcium
    transient upstroke rise time analysis, calcium transient duration analysis and calcium decay
    constant determination.
    Rhythm 2.0: Rhythm 2.0 on the other hand is designed to analyze panoramic optical mapping
    data of transmembrane potential. Users can generate 3D visualizations of different sized hearts
    ranging from mouse to rabbit and project optical data onto the meshes using user-friendly
    graphical user interfaces. This is useful in viewing how signals travel throughout the heart,
    especially in arrhythmia studies.
    3D printed multiparametric system: We recently developed a 3D printed optical mapping
    system for multiparametric optical mapping with the possibility to image in the horizontal and
    upright camera orientations. With the exclusion of lens, filters, dichroic mirrors and cameras, all
    parts of this optical mapping system were custom-designed and 3D printed by our lab. The
    components of this system included optical, mechanical and perfusion parts. Optical
    components include filter cubes with adjustable and fixed dichroic mirror holders, camera
    connectors and lens holders. Mechanical components include lab jack, mechanical lifts, camera
    support cages and titling platforms to change system orientation (upright to horizontal).
    Perfusion components include baths for Langendorff heart preparations (horizontal orientation)
    as well as human slice preparations (upright orientation). All these designs (.stl files) are
    available at Github (link above).
    Contact us at paloma_amaral@gwu.edu if you have questions.