Figure 1.
Illustration of ECG waves and values.
(a) Illustration of standard ECG leads: The six extremity leads (I, II, III, aVL, aVR, aVF) record voltage differences by means of electrodes placed on the limbs (left panel). The triangle shows the spatial relationships of the extremity leads, which record electrical voltages onto the frontal plane of the body. The six chest leads (V1–V6) record voltage differences by means of electrodes placed on the chest wall (right panel). The oval indicates spatial relationships of the six chest leads, which record electrical voltages transmitted onto the horizontal plane. (b) Illustration of ECG amplitude parameters used in the present study (P-, R-, RS-, and T-waves, each wave is measured from each of the twelve ECG leads in each individual). Due to the absence of a Q-wave in some individuals at some leads, the R-wave is measured with regard to the iso-electric line. (c) Illustration of ECG amplitude parameters used to calculate values (indicated in red): R-wave of III (measured from the baseline preceding the P-wave), RS-complex of aVL, T-wave of aVL, and RS-complex of the chest lead with the maximal RS amplitude (usually V3 or V2). The upper panel shows averaged ECG cycles measured from a male subject with a high
value (
90th percentile of our study population), the lower panel shows averaged ECG cycles from a male subject with a low
value (
10th percentile of our study population). Both subjects had similar body height (184 vs. 185 cm), body weigt (70 vs. 72 kg), and normal QRS axis orientation (96.23
vs. 75.24
). Note the smaller T-wave in aVL in relation to the RS-wave in aVL, and the smaller R-wave in III in relation to the RS-wave in V3, in the subject with low
value (lower panel), compared to the subject with high
value (upper panel). (d) Equation for computation of
values. Computation of the ECG amplitude parameters shown in (c) leads to an
value of 1.61 for the ECG shown in the upper, and an
value of 0.17 for the ECG shown in the lower panel of (c) (for a better readability, values are scaled by a factor
). Abbrevations:
: R-wave of lead III (measured from the baseline preceding the P-wave);
: RS-complex of aVL;
: RS-complex of the chest lead with the maximal RS amplitude;
: T- wave of aVL.
Figure 2.
Group comparisons between individuals with values above and below the median of
values.
Individuals with higher values had lower neuroticism (a), and higher positive emotion scores (b). Moreover, individuals with higher
values had lower normalized LF power, higher normalized HF power, and a lower LF/HF ratio (c). Abbrevations: LF (n.u.): low frequency power (0.04–0.15 Hz) of the HRV in normalized units; HF (n.u.): high frequency power (0.15–0.4 Hz) of the HRV in normalized units; LF/HF: ratio of low frequency power to high frequency power.
Table 1.
NEO-scores, heart rate variability values, and body characteristics (means, with SD in parentheses), separately for the group with values below and above the median of
values.
Figure 3.
(a) Result of the stepwise regression with body height as dependent variable, and ECG amplitude values as independent (predictor) variables. (b) shows the result of the stepwise regression (corrected for body height) with agreeableness as dependent variable, and ECG amplitude values, as well as body height, body weight, and body mass index as independent variables. The analogous regression for positive emotion is shown in (c).