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. Author manuscript; available in PMC: 2018 Mar 1.
Published in final edited form as: JAMA Cardiol. 2017 Mar 1;2(3):278–284. doi: 10.1001/jamacardio.2016.5303

Figure 1. Heart Rate Variability Components.

Figure 1

A, The high-frequency (HF) component, an indicator of vagal activity, was significantly decreased in the e-cigarette users compared with nonuser control individuals (mean [SEM], 46.5 [3.7] nu vs 57.8 [3.6] nu, P = .04). B and C, The low-frequency (LF) component (mean [SEM], 52.7 [4.0] nu vs 39.9 [3.8] nu, P = .03), and the LF to HF ratio (1.37 [0.19] vs 0.85 [0.18], P = .05), were significantly increased in the e-cigarette users compared with nonuser controls, consistent with sympathetic predominance. These findings were present even in the absence of recent e-cigarette use, as verified by the absence of detectable nicotine in the plasma.