Faculty Publications

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Publications by NITK Faculty

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Author: search.filters.author.Berg, S.Has files: No

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    Quantifying spatiotemporal complexity of cardiac dynamics using ordinal patterns
    (Institute of Electrical and Electronics Engineers Inc., 2015) Schlemmer, A.; Berg, S.; Shajahan, T.K.; Luther, S.; Parlitz, U.
    Analyzing the dynamics of complex excitation wave patterns in cardiac tissue plays a key role for understanding the origin of life-threatening arrhythmias and for devising novel approaches to control them. © 2015 IEEE.
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    Scanning and resetting the phase of a pinned spiral wave using periodic far field pulses
    (Institute of Physics Publishing helen.craven@iop.org, 2016) Shajahan, T.K.; Berg, S.; Luther, S.; Krinski, V.; Bittihn, P.
    Spiral waves in cardiac tissue can pin to tissue heterogeneities and form stable pinned waves. These waves can be unpinned by electric stimuli applied close to the pinning center during the vulnerable window of the spiral. Using a phase transition curve (PTC), we quantify the response of a pinned wave in a cardiac monolayer to secondary excitations generated electric field pulses. The PTC can be used to construct a one-dimensional map that faithfully predicts the pinned wave's response to periodic field stimuli. Based on this 1D map, we predict that pacing at a frequency greater than the spiral frequency, over drive pacing, leads to phase locking of the spiral to the stimulus, which hinders unpinning. In contrast, under drive pacing can lead to scanning of the phase window of the spiral, which facilitates unpinning. The predicted mechanisms of phase scanning and phase locking are experimentally tested and confirmed in the same monolayers that were used to obtain the PTC. Our results have the potential to help choose optimal parameters for low energy antifibrillation pacing schemes. © 2016 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
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    Mechanisms of vortices termination in the cardiac muscle
    (Royal Society, 2017) Hornung, D.; Biktashev, V.N.; Otani, N.F.; Shajahan, T.K.; Baig, T.; Berg, S.; Han, S.; Krinsky, V.I.; Luther, S.
    We propose a solution to a long-standing problem: how to terminate multiple vortices in the heart, when the locations of their cores and their critical time windows are unknown. We scan the phases of all pinned vortices in parallel with electric field pulses (E-pulses). We specify a condition on pacing parameters that guarantees termination of one vortex. For more than one vortex with significantly different frequencies, the success of scanning depends on chance, and all vortices are terminated with a success rate of less than one. We found that a similar mechanism terminates also a free (not pinned) vortex. A series of about 500 experiments with termination of ventricular fibrillation by E-pulses in pig isolated hearts is evidence that pinned vortices, hidden from direct observation, are significant in fibrillation. These results form a physical basis needed for the creation of new effective low energy defibrillation methods based on the termination of vortices underlying fibrillation. © 2017 The Authors.
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    Spiral wave unpinning facilitated by wave emitting sites in cardiac monolayers
    (Royal Society Publishing, 2019) Punacha, S.; Berg, S.; Sebastian, A.; Krinski, V.I.; Luther, S.; Shajahan, T.K.
    Rotating spiral waves of electrical activity in the heart can anchor to unexcitable tissue (an obstacle) and become stable pinned waves. A pinned rotating wave can be unpinned either by a local electrical stimulus applied close to the spiral core, or by an electric field pulse that excites the core of a pinned wave independently of its localization. The wave will be unpinned only when the pulse is delivered inside a narrow time interval called the unpinning window (UW) of the spiral. In experiments with cardiac monolayers, we found that other obstacles situated near the pinning centre of the spiral can facilitate unpinning. In numerical simulations, we found increasing or decreasing of the UW depending on the location, orientation and distance between the pinning centre and an obstacle. Our study indicates that multiple obstacles could contribute to unpinning in experiments with intact hearts. © 2019 The Author(s) Published by the Royal Society. All rights reserved.