Hypoxic exposure increases right ventricular (RV) afterload by triggering pulmonary hypertension, with consequent effects on the structure and function of the RV. Improved myocardial contractility is a critical circulatory adaptation to exercise training. However, the types of exercise that enhance right cardiac mechanics during hypoxic stress have not yet been identified. This study investigated how high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) influence right cardiac mechanics during hypoxic exercise (HE).
Hypoxic exposure increases right ventricular (RV) afterload by triggering pulmonary hypertension, with consequent effects on the structure and function of the RV. Improved myocardial contractility is a critical circulatory adaptation to exercise training. However, the types of exercise that enhance right cardiac mechanics during hypoxic stress have not yet been identified. This study investigated how high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) influence right cardiac mechanics during hypoxic exercise (HE). The young and healthy sedentary males were randomly selected to engage in either HIIT (3-min intervals at 40% and 80% of VO2 oxygen uptake reserve) or MICT (sustained 60% of VO2 oxygen uptake reserve) for 30 min/day and 5 days/week for 6 weeks or were included in a control group (CTL) that did not engage in any exercise. Right cardiac mechanics during semiupright bicycle exercise tests under hypoxic conditions (i.e., 50 watts under 12% FiO2 for 3 min) were measured using two-dimensional speckle-tracking echocardiography. The primary outcome was the change in right cardiac mechanics during semiupright bicycle exercise under hypoxic conditions (i.e., 50 watts under 12% FiO2 for 3 min) as measured by two-dimensional speckle tracking echocardiography.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
SINGLE
Enrollment
54
Subjects performed HIIT (3-min intervals at 40% and 80%VO2peak) on a bicycle ergometer for 30 min/day, 5 days/week for 6 weeks.
Subjects performed MICT (sustained 60%VO 2max) on a bicycle ergometer for 30 min/day, 5 days/week for 6 weeks.
Chang Gung University
Taoyuan District, Taiwan
The changes of right cardiac mechanics during hypoxia stress echocardiography: Strain
1. Hypoxia stress echocardiography was collected under hypoxic conditions (12% FiO2) and used two-dimensional Speckle-tracking echocardiography. 2. The resting images were acquired after the subject was placed in the aforementioned position for 10 min. 3. The exercise images were conducted using semirecumbent cycling with a 50-Watt resistance for 3 min and acquired at the third minute of cycling to ensure that subjects had reached a steady-state HR (i.e., HR changes \<10 bpm within 10 s and \<110-120 bpm). 4. A modified apical four-chamber view was used to assess 2D-STE longitudinal and radial parameters of the RV and RA. 5. The RV strain was calculated using the average peak segmental values displayed by the software using a 6-segment model.
Time frame: 8 weeks
The changes of right cardiac mechanics during hypoxia stress echocardiography: Strain rate
1. Hypoxia stress echocardiography was collected under hypoxic conditions (12% FiO2) and used two-dimensional Speckle-tracking echocardiography. 2. The resting images were acquired after the subject was placed in the aforementioned position for 10 min. 3. The exercise images were conducted using semirecumbent cycling with a 50-Watt resistance for 3 min and acquired at the third minute of cycling to ensure that subjects had reached a steady-state HR (i.e., HR changes \<10 bpm within 10 s and \<110-120 bpm). 4. A modified apical four-chamber view was used to assess 2D-STE longitudinal and radial parameters of the RV and RA. 5. The RV strain rate was calculated using the average peak segmental values displayed by the software using a 6-segment model.
Time frame: 8 weeks
Cardiopulmonary fitness
To assess cardiopulmonary fitness, cardiopulmonary exercise test (CPET) on a cycle ergometer was performed 4 days before and after the intervention. All subjects underwent exercise with a mask to measured oxygen consumption (VO2) breath by breath using a computer-based system (Master Screen CPX, Cardinal-health Germany).
Time frame: 8 weeks
The cavity diameters of RV
RV basal cavity diameter (RVD1), mid-cavity diameter (RVD2), and RV longitudinal diameter (RVD3), at end-diastole and end-systole, were evaluated in the modified apical four-chamber view.
Time frame: 8 weeks
Pulmonary vascular resistance (PVR)
Pulmonary vascular resistance (PVR) was calculated using the formula PVR = (\[tricuspid regurgitation velocity/RVOT VTI\] × 10 + 0.16) 1. Tricuspid regurgitation velocity: Doppler imaging was used to measure peak tricuspid regurgitation velocities in systolic phase. 2. The RV outflow tract (RVOT): obtained from a parasternal short-axis base view modified apical four-chamber view, and the flow immediately proximal to the pulmonary artery valve during systole was detected to calculate both maximal velocity and pulsed-wave blood velocity time integral (VTI)
Time frame: 8 weeks
RV diastolic function
Doppler imaging was used to measure peak tricuspid annular (E') and flow velocities (E) in early diastole.
Time frame: 8 weeks
Tricuspid annular plane systolic excursion (TAPSE)
Tricuspid annular plane systolic excursion (TAPSE) measures the longitudinal excursion of the tricuspid annulus in one dimension, which was measured by M-mode.
Time frame: 8 weeks
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