Multiscale Determinants of Delayed Afterdepolarization Amplitude in Cardiac Tissue

Biophysical Journal
Christopher Y KoJames N Weiss

Abstract

Spontaneous calcium (Ca) waves in cardiac myocytes underlie delayed afterdepolarizations (DADs) that trigger cardiac arrhythmias. How these subcellular/cellular events overcome source-sink factors in cardiac tissue to generate DADs of sufficient amplitude to trigger action potentials is not fully understood. Here, we evaluate quantitatively how factors at the subcellular scale (number of Ca wave initiation sites), cellular scale (sarcoplasmic reticulum (SR) Ca load), and tissue scale (synchrony of Ca release in populations of myocytes) determine DAD features in cardiac tissue using a combined experimental and computational modeling approach. Isolated patch-clamped rabbit ventricular myocytes loaded with Fluo-4 to image intracellular Ca were rapidly paced during exposure to elevated extracellular Ca (2.7 mmol/L) and isoproterenol (0.25 μmol/L) to induce diastolic Ca waves and subthreshold DADs. As the number of paced beats increased from 1 to 5, SR Ca content (assessed with caffeine pulses) increased, the number of Ca wave initiation sites increased, integrated Ca transients and DADs became larger and shorter in duration, and the latency period to the onset of Ca waves shortened with reduced variance. In silico analysis using a ...Continue Reading

Citations

Apr 21, 2019·The Journal of General Physiology·Maedeh Bazmi, Ariel L Escobar
Jul 29, 2020·Circulation. Arrhythmia and Electrophysiology·Michael B LiuJames N Weiss
Feb 20, 2021·Mathematical Biosciences·Bogdan AmuzescuBeatrice Mihaela Radu

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