Presenter: Emma Yi Lu
Paper: Exposure to Secondhand Smoke and Arrhythmogenic Cardiac Alternans in a Mouse Model
Authors: Zhen Wang, Lianguo Wang, Srinivas Tapa, Kent E. Pinkerton, Chao-Yin Chen, and Crystal M. Ripplinger
BACKGROUND: Epidemiological evidence suggests that a majority of deaths attributed to secondhand smoke (SHS) exposure are cardiovascular related. However, to our knowledge, the impact of SHS on cardiac electrophysiology, Ca2þ handling, and arrhythmia risk has not been studied.
OBJECTIVES: The purpose of this study was to investigate the impact of an environmentally relevant concentration of SHS on cardiac electrophysiology and indicators of arrhythmia.
METHODS: Male C57BL/6 mice were exposed to SHS . Hearts were excised and Langendorﬀ perfused for dual optical mapping with voltage- and Ca2þ-sensitive dyes.
RESULTS:At slow pacing rates, SHS exposure did not alter baseline electrophysiological parameters. With increasing pacing frequency, action potential duration (APD), and intracellular Ca2þ alternans magnitude progressively increased in all groups. At 4 and 8 wk, there were no statistical diﬀerences in APD or Ca2þ alternans magnitude between SHS and FA groups. At 12 wk, both APD and Ca2þ alternans magnitude were signiﬁcantly increased in the SHS compared to FA group (p<0 :05). SHS exposure did not impact the time constant of Ca2þ transient decay (s) at any exposure time point. At 12 wk exposure, the recovery of Ca2þ transient amplitude with premature stimuli was slightly (but nonsigniﬁcantly) delayed in SHS compared to FA hearts, suggesting that Ca2þ release via ryanodine receptors may be impaired.
CONCLUSIONS: In male mice, chronic exposure to SHS at levels relevant to social situations in humans increased their susceptibility to cardiac alternans, a known precursor to ventricular arrhythmia
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