DOI: 10.5061/dryad.dz08kpsbh
title: Data from: Atypical collective oscillatory activity in cardiac tissue uncovered by optogenetics

description: Many biological processes emerge as frequency-dependent responses to
 trains of external stimuli. Heart rhythm disturbances, i.e., cardiac
 arrhythmias, are important examples as they are often triggered by
 specific patterns of preceding stimuli. In this study, we investigated how
 ectopic arrhythmias can be induced by external stimuli in cardiac tissue
 containing a localised area of depolarisation. Using optogenetic in vitro
 experiments, we systematically explored the dynamics of these arrhythmias,
 which are characterized by local oscillatory activity. Our findings reveal
 a bi-stable system, in which transitions between oscillatory ectopic
 activity and a quiescent state can be precisely controlled, i.e., by
 adjusting the number and frequency of propagating waves through the
 depolarized area, oscillations could be turned on or off. These
 frequency-dependent responses arise from collective mechanisms involving
 stable, non-self-oscillatory cells, contrasting with the typical role of
 self-oscillations in individual units within biophysical systems.
description: Raw optical mapping data were obtained using a mapping setup
 containing a 100 × 100 pixel CMOS Ultima-L camera (Scimedia, Costa Mesa,
 CA). The field of view was 16 × 16 mm, resulting in a spatial resolution
 of 160 <em>μ</em>m/pixel. For targeted illumination of
 monolayers, the setup was optically conjugated to a digitally controlled
 micro-mirror device (DMD), the Polygon 400 (Mightex Systems, Toronto, ON),
 with a high-power blue (470 nm) LED (BLS-LCS-0470-50-22-H, Mightex
 Systems). Electrical stimulation was performed by applying 10-ms-long
 rectangular electrical pulses with an amplitude of 8 V to a bipolar
 platinum electrode with a spacing of 1.5 mm between anode and cathode.
 Data was captured in .rsh and .rsd format.
description: # Data from: Atypical collective oscillatory activity in cardiac tissue
 uncovered by optogenetics Dataset DOI:
 [10.5061/dryad.dz08kpsbh](https://doi.org/10.5061/dryad.dz08kpsbh) ##
 Description of the data and file structure Neonatal rat ventricular
 myocyte (NRVM) monolayers were optically mapped using the
 voltage-sensitive dye di-4-ANBDQBS (52.5 *μ*M final concentration; ITK
 diagnostics, Uithoorn, the Netherlands). The mapping setup was based on a
 100 × 100 pixel CMOS Ultima-L camera (Scimedia, Costa Mesa, CA). The field
 of view was 16 × 16 mm, resulting in a spatial resolution of 160
 *μ*m/pixel. For targeted illumination of monolayers, the setup was
 optically conjugated to a digitally controlled micro-mirror device (DMD),
 the Polygon 400 (Mightex Systems, Toronto, ON), with a high-power blue
 (470 nm) LED (BLS-LCS-0470-50-22-H, Mightex Systems). Before starting the
 actual experiments, all monolayers were mapped during 1-Hz electrical
 point stimulation to check baseline conditions. Electrical stimulation was
 performed by applying 10-ms-long rectangular electrical pulses with an
 amplitude of 8 V to a bipolar platinum electrode with a spacing of 1.5 mm
 between anode and cathode. Only cultures with an action potential duration
 (APD) at 80% repolarization (APD~80~) below 350 *ms* and a conduction
 velocity (CV) above 18 *cm/s* were used for further experiments. Stimuli
 were applied in trains that varied in number and period. Whenever the
 outcome was reproducible three consecutive times in a single monolayer, it
 was counted as successful and included as one measurement in the total
 dataset. The constant light intensity was varied in the range of
 (0.03125-0.25 *mW /mm*^2^) to search the critical value for the bi-stable
 regime. For experiments in which the light intensity was varied the
 rectangular-shaped area of illumination was in the range of 4 × 4 to 6 × 6
 mm. The highest achievable irradiation intensity (0.3125 *mW /mm*^2^) was
 used to perform size modulation experiments. The resulting electrical
 activity was recorded for 6-24 *s* at exposure times of 6 *ms* per frame.
 ### Files and variables #### File: experimental_data_resonance-001.tar.gz
 **Description:** Contains the folders "normal resonance" (Figure
 2, Figure 4-figure supplement 1), "2 vs 4" (Figure 3) and
 "Small_pattern-resonance" (Figure 4-figure supplement 2), each
 with subfolders denoting one monolayer. Within each subfolder, different
 recordings can be found using the .rsh and .rsd file format. They always
 start with a control measurement named 1Hz. Afterwards, the file names
 exactly describe what kind of protocol is being used, either denoting an
 external wave train pacing cycle length, the number of external pulses, or
 both (becomes clear when putting the figures next to the filenames). If a
 filename mentions resonance, bifurcation, or initiation, our discovered
 phenomenon of atypical collective oscillatory activity can be seen in
 those data. The regimes where this does (not) occur are described in
 detail in our manuscript. ## Code/software The .rsh and .rsd files can be
 converted to numpy arrays using sappho, an open source software package
 from [1]. You can access/download it directly using the following
 link: [https://gitlab.com/heartkor/sappho](https://gitlab.com/heartkor/sappho). A README, installation instructions and usage examples are provided in the accompanying documentation, directly accessible via: [https://heartkor.gitlab.io/sappho/](https://heartkor.gitlab.io/sappho/). When you install the graphical user interface, you can directly select the files from your system folder and open/view them. \[1] Kabus, D., De Coster, T., de Vries, A. A., Pijnappels, D. A., & Dierckx, H. (2024). Fast creation of data-driven low-order predictive cardiac tissue excitation models from recorded activation patterns. *Computers in Biology and Medicine*, *169*, 107949.