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. 2019 Mar 29;10:350. doi: 10.3389/fphys.2019.00350

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Copyright © 2019 Tomek, Hao, Tomková, Lewis, Carr, Paterson, Rodriguez, Bub and Herring.

This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

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Effects of norepinephrine and subsequent β-blockade. (A) The effect of norepinephrine perfusion and subsequent β-blockade on normalized alternans magnitude at high pacing frequencies (each circle is an average of normalized alternans magnitudes of the given heart over bcls of 80, 85, and 90). Asterisks represent statistical significance at the level of 0.01 (^∗∗), as assessed using the Wilcoxon signed rank test; n.s., not significant. (B) Sample alternans maps from a single recording under the three conditions (control, norepinephrine, and norepinephrine+metoprolol), with sample smoothed traces of the red-marked-pixels shown below. NAM, normalized alternans magnitude. (C) The effect of norepinephrine and subsequent β-blockade on CaTD90 (calcium transient duration, at 90% calcium recovery level) at pacing of 140 ms bcl (statistical significance assessed using the Wilcoxon signed rank test; ^∗ corresponds to p < 0.05). (D) Correlation between CaTD90 from (A) and normalized alternans magnitude at fast pacing frequencies from (C), matched by heart and condition. See Supplementary Figure S5 for a separation of (A,C) by normal and border zone.