The Effect of Emotional Valence on Ventricular Repolarization Dynamics Is Mediated by Heart Rate Variability: A Study of QT Variability and Music-Induced Emotions

Abstract

Background: Emotions can affect cardiac activity, but their impact on ventricular repolarization variability, an important parameter providing information about cardiac risk and autonomic nervous system activity, is unknown. The beat-to-beat variability of the QT interval (QTV) from the body surface ECG is a non-invasive marker of repolarization variability, which can be decomposed into QTV related to RR variability (QTVrRRV) and QTV unrelated to RRV (QTVuRRV), with the latter thought to be a marker of intrinsic repolarization variability.

Aim: To determine the effect of emotional valence (pleasant and unpleasant) on repolarization variability in healthy volunteers by means of QTV analysis.

Methods: 75 individuals (24.5 ± 3.2 years, 36 females) without a history of cardiovascular disease listened to music-excerpts that were either felt as pleasant (n = 6) or unpleasant (n = 6). Excerpts lasted about 90 s and were presented in a random order along with silent intervals (n = 6). QTV and RRV were derived from the ECG and the time-frequency spectrum of RRV, QTV, QTVuRRV and QTVrRRV as well as time-frequency coherence between QTV and RRV were estimated. Analysis was performed in low-frequency (LF), high frequency (HF) and total spectral bands.

Results: The heart rate-corrected QTV showed a small but significant increase from silence (median 347/interquartile range 31 ms) to listening to music felt as unpleasant (351/30 ms) and pleasant (355/32 ms). The dynamic response of QTV to emotional valence showed a transient phase lasting about 20 s after the onset of each musical excerpt. QTV and RRV were highly correlated in both HF and LF (mean coherence ranging 0.76-0.85). QTV and QTVrRRV decreased during listening to music felt as pleasant and unpleasant with respect to silence and further decreased during listening to music felt as pleasant. QTVuRRV was small and not affected by emotional valence.

Conclusion: Emotional valence, as evoked by music, has a small but significant effect on QTV and QTVrRRV, but not on QTVuRRV. This suggests that the interaction between emotional valence and ventricular repolarization variability is mediated by cycle length dynamics and not due to intrinsic repolarization variability.

Keywords: QT variability; emotional valence; heart rate variability; music-induced emotions; repolarization; time-frequency.

FIGURE 1

Measurement of RR and QT intervals. White and red circles identify the R-wave and the end of the T-wave, respectively. The RT interval variability was used as robust surrogate for QT variability.

FIGURE 2

QT and RR interval oscillations in one individual during the entire recording (top) and during three consecutive conditions (bottom). Dashed vertical lines represent the beginning and the end of each condition, which are separated by about 20 s pause. The type of condition is reported above the top panel. R: rest; P: pleasant music; U: unpleasant music; X: sequence of Shepard tones (not considered in statistical analysis).

FIGURE 3

QT, RR, and QTc (QT corrected for heart rate) during listening to pleasant music (P), unpleasant music (U), and rest (R). Markers represent the median values and bars span from the first to the third quartile. P-values measuring pair-wise differences are reported in bold if significant and in light gray if not significant.

FIGURE 4

Example of time-frequency representations in a representative individual. The same interval including three consecutive epochs (resting, pleasant and unpleasant conditions) shown in Figure 2 is analyzed. From top to bottom: QTV and RRV superimposed and normalized to show same amplitude, QTV and RRV time-frequency spectra, time-frequency coherence between QTV and RRV and time-frequency spectrum of QTV unrelated to RRV. R: Rest; P: Pleasant condition; U: Unpleasant condition.

FIGURE 5

QTV trends. From left to right: QTV, QTV related to RRV (QTVrRRV), and QTV unrelated to RRV (QTVrRRV). From top to bottom: instantaneous power of LF, HF, and total spectral band. Solid lines represent the mean trend across all individuals and shaded areas represent standard error. R: rest; P: pleasant condition; U: unpleasant condition.

FIGURE 6

QTV and QTV related and unrelated to RRV during listening to pleasant music (P), unpleasant music (U), and rest (R). From left to right: QTV, QTV related to RRV (QTVrRRV), and QTV unrelated to RRV (QTVrRRV). From top to bottom: mean power of LF, HF and total spectral band. Markers represent the median values and bars span from the first to the third quartile. P-values measuring pair-wise differences are reported in bold if significant and in light gray if not significant.