2020 Volume 41 Pages 331-338
Introduction: The current exercise prescription, defined by a cardiopulmonary test （CPX） for patients with cardiovascular disease, makes it difficult to offer an appropriate aerobic exercise in accordance with the patients’ daily conditions. Heart rate variability （HRV） is the beat-to-beat alterations in heart rate, which reflects the cardiac autonomic nervous activity. Therefore, we examined whether real-time analysis of HRV makes it possible to determine the ventilatory threshold during cardiac rehabilitation sessions.
Methods: A total of 25 patients （66±8 y/o, 22 males） with heart failure who underwent cardiac rehabilitation on a bicycle ergometer for 25 minutes were enrolled. The oxygen uptake （VO2） and high-frequency component （HF） quantified by the power spectral analysis of HRV reflecting the parasympathetic nervous tone, were continuously measured during the rehabilitation session. The workload was adjusted every 2 minutes so that the HF power was kept between 5 and 10. All the patients had undergone a CPX session within a week before their ventilatory threshold （VT） -VO2 determination and had the exercise intensity prescribed. We compared the VO2 during the rehabilitation session （re-VO2） to the VT-VO2 determined by the CPX.
Results: The re-VO2 reached to 95.3±12.0% （13th minute after the initiation of the exercise session） , 100.7±17.3% （17th min） , 101.5±18.0% （21th min） , and 97.7±18.3% （25th min） of the level of VT-VO2 in the second half of the exercise. The mean differences between the re-VO2 and the VT-VO2 were not statistically significant at any time point.
Conclusions: Real-time assessment of the HRV during rehabilitation could offer exercise intensity of the ventilator threshold in accordance with the condition of patients with cardiovascular diseases.
