Shiraishi Y; Katsumata Y; Sadahiro T; Azuma K; Akita K; Isobe S; Yashima
F; Miyamoto K; Nishiyama T; Tamura Y; Kimura T; Nishiyama N; Aizawa Y;
Fukuda K; Takatsuki S.
Journal of the American Heart Association. 7(1), 2018 01 07.
BACKGROUND: It has never been possible to immediately evaluate heart rate
variability (HRV) during exercise. We aimed to visualize the real-time
changes in the power spectrum of HRV during exercise and to investigate
its relationship to the ventilatory threshold (VT).
METHODS AND RESULTS: Thirty healthy subjects (29.1+/-5.7 years of age)
and 35 consecutive patients (59.0+/-13.2 years of age) with myocardial
infarctions underwent cardiopulmonary exercise tests with an RAMP protocol
ergometer. The HRV was continuously assessed with power spectral analyses
using the maximum entropy method and projected on a screen without delay.
During exercise, a significant decrease in the high frequency (HF) was
followed by a drastic shift in the power spectrum of the HRV with a
periodic augmentation in the low frequency/HF (L/H) and steady low HF.
When the HRV threshold (HRVT) was defined as conversion from a predominant
high frequency (HF) to a predominant low frequency/HF (L/H), the VO2 at
the HRVT (HRVT-VO2) was substantially correlated with the VO2 at the
lactate threshold and VT) in the healthy subjects (r=0.853 and 0.921,
respectively). The mean difference between each threshold (0.65 mL/kg per
minute for lactate threshold and HRVT, 0.53 mL/kg per minute for VT and
HRVT) was nonsignificant (P>0.05). Furthermore, the HRVT-VO2 was also
correlated with the VT-VO2 in these myocardial infarction patients
(r=0.867), and the mean difference was -0.72 mL/kg per minute and was
CONCLUSIONS: A HRV analysis with our method enabled real-time
visualization of the changes in the power spectrum during exercise. This
can provide additional information for detecting the VT.