Dimitrios Sakellariou

Effects of exercise rehabilitation program on heart rate recovery in patients with chronic heart failure

Background Heart rate recovery (HRR1) immediately after exercise reflects parasympathetic activity, which is markedly attenuated in chronic heart failure (CHF) patients. The aim of our study was to examine both continuous and interval exercise training effects on HRR1 in these patients. Design The population study consisted of 29 stable CHF patients that participated at a rehabilitation program of 36 sessions, three times per week. Of the 29 patients, 24 completed the program. Patients were randomly assigned to interval {n = 10 [100% peak work rate (WRp) for 30 s, alternating with rest for 30 s]} and to continuous training [n = 14 (50%WRp)]. Methods All patients performed a symptom-limited cardiopulmonary exercise test on a cycle ergometer before and after the completion of the program. Measurements included peak oxygen uptake (VO2p), anaerobic threshold (AT), WRp, first degree slope of VO2 during the first minute of recovery (VO2/t-slope), chronotropic response [% chronotropic reserve (CR) = (peak HR - resting HR) × 100/(220 - age - resting HR)], HRR1 (HR difference from peak exercise to one minute after). Results After the completion of the rehabilitation program there was a significant increase of WRp, VO2p, AT and VO2/t-slope (by 30%, P=0.01; 6%, P=0.01; 10%, P=0.02; and 27%, P=0.03 respectively for continuous training and by 21%, P≤0.05; 8%, P=0.01; 6%, P=NS; and 48%, P=0.02 respectively for interval training). However, only patients exercised under the continuous training regime had a significant increase in HRR1 (15.0±9.0 to 24.0±12bpm; P=0.02) and CR (57±19 to 72±21%, P=0.02), in contrast with those assigned to interval training (HRR1: 21 ± 11 to 21 ± 8 bpm; P=NS and CR: 57 ± 18 to 59 ± 21%, P=NS). Conclusions Both continuous and interval exercise training program improves exercise capacity in CHF patients. However, continuous rather than interval exercise training improves early HRR1, a marker of parasympathetic activity, suggesting a greater contribution to the autonomic nervous system.

The effects of exercise training on the kinetics of oxygen uptake in patients with chronic heart failure.

Background Prolonged oxygen uptake kinetics (O2 kinetics), following the onset of a constant workload of exercise has been associated with a poor prognosis in patients with chronic heart failure. This study aimed to determine both continuous and interval training effects on the different O2-kinetics phases in these patients. Design Twenty-one patients (60 ± 8 years) with stable chronic heart failure participated in a 36-session exercise rehabilitation program (three times weekly). Patients were randomly assigned to interval training (n = 11; 100% of peak work rate for 30 s, alternating with 30s-rest) and to continuous training (n = 10; 50% of peak work rate). Methods Before and after the completion of the program, all patients performed both incremental symptom-limited and constant workload submaximal cardiopulmonary exercise tests. Phase I O2-kinetics was evaluated by time (t), from the start of exercise until the onset of decreased respiratory exchange ratio and phase II by the time constant (τ) of the response from the end of phase I until steady state. Results After training, there was a significant increase in peak oxygen uptake and peak work rate in both continuous (15.3 ± 4.4 vs. 16.6 ± 4.5 ml/kg per min; P=0.03 and 81.8 ± 40.1 vs. 94.7 ± 46.1 W; P=0.03) and interval training groups (14.2 ± 3.1 vs. 15.4 ± 4.2 ml/kg per min; P=0.03 and 82.5 ± 24.1 vs. 93.7 ± 30.1 W; P=0.04). Patients who underwent interval training had a significant decrease in t (39.7 ± 3.7 to 36.1 ± 6.9s; P=0.05), but not τ (59.6 ± 9.4 to 58.9 ± 8.5 s; P=ns), whereas those assigned to continuous training had a significant decrease in both t (40.6 ± 6.1 to 36.4 ± 5.4 s; P=0.01) and τ (63.3 ± 23.6 to 42.5 ± 16.7 s; P=0.03). Conclusions Exercise training improves O2 kinetics in chronic heart failure patients. Both continuous and interval training improve phase I O2-kinetics, but continuous training results in superior improvement of the phase II O2-kinetics, an indirect index of muscle oxidative capacity.

VE/VCO2 slope is associated with abnormal resting haemodynamics and is a predictor of long-term survival in chronic heart failure.

Patients with chronic heart failure (CHF) present with exercise‐induced hyperpnea, but its pathophysiological mechanism has not been thoroughly investigated. We aimed to determine the relationship between exercise‐induced hyperpnea, resting haemodynamic measurements and the validity of ventilatory response (VE/VCO2 slope) as a mortality predictor in CHF patients.

Heart Rate Recovery and Oxygen Kinetics After Exercise in Obstructive Sleep Apnea Syndrome

Patients who suffer from obstructive sleep apnea (OSA) have a decreased exercise capacity and abnormal autonomic nervous function. However, the kinetics of early oxygen (O2) and heart rate recovery (HRR) have not been described.

Cardiopulmonary Rehabilitation Enhances Heart Rate Recovery in Patients With COPD

BACKGROUND: Autonomic dysfunction is present early in the course of COPD, and is associated with adverse outcomes. We utilized heart rate recovery, a simple and validated index of autonomic balance, to investigate the effects of exercise training on autonomic dysfunction in patients with COPD. METHODS: We evaluated 45 stable subjects with COPD who participated in a 36-session exercise-based cardiopulmonary rehabilitation program. Subjects underwent maximal cardiopulmonary exercise testing at baseline and after completion of the rehabilitation program. We recorded exercise testing parameters and heart rate during rest, exercise, and recovery. Heart rate recovery was calculated as heart rate at peak exercise minus heart rate at the first minute of recovery. RESULTS: Thirty-nine subjects (age 66.3 ± 7.8 y, 90% male, body mass index 27.1 ± 4.1 kg/m2, FEV1 45.7 ± 18.7%) completed the program. In these subjects, heart rate recovery increased from 16.2 ± 8.0 beats/min to 18.4 ± 8.4 beats/min (P = .01), resting heart rate decreased from 88.0 ± 10.7 beats/min to 83.3 ± 10.5 beats/min (P = .004), and heart rate at anaerobic threshold decreased from 109.0 ± 12.5 beats/min to 105.5 ± 11.7 beats/min (P = .040). In addition, oxygen consumption (V̇O2) increased from 14.3 ± 3.7 mL/kg/min to 15.2 ± 3.8 mL/kg/min at peak exercise, and from 9.7 ± 2.4 mL/kg/min to 10.4 ± 2.6 mL/kg/min at anaerobic threshold (both P = .02), while the V̇O2/t slope increased from –0.32 ± 0.16 mL/kg/min2 to –0.38 ± 0.19 mL/kg/min2 (P = .003). Parameters of ventilatory performance improved also. CONCLUSIONS: In subjects with COPD, exercise-based rehabilitation improves heart rate recovery, modestly though, which indicates a degree of attenuated autonomic dysfunction. Exercise and muscular oxidative capacity, as expressed by V̇O2/t slope, is also improved.

New insights into the exercise intolerance of β‐thalassemia major patients

The purpose of our study was assessment of the relative contribution of the systems involved in blood gas exchange to the limited exercise capacity in patients with β‐thalassemia major (TM) using integrative cardiopulmonary exercise testing (CPET) with estimation of oxygen kinetics. The study consisted of 15 consecutive TM patients and 15 matched controls who performed spirometric evaluation, measurement of maximum inspiratory pressure (Pimax) and an incremental symptom‐limited CPET on a cycle ergometer. Exercise capacity was markedly reduced in TM patients as assessed by peak oxygen uptake (pVO2, mL/kg/min: 22.1±6.6 vs 33.8±8.3; P<0.001) and anaerobic threshold (mL/kg/min: 13.0±3.0 vs 18.7±4.6; P<0.001) compared with controls. No ventilatory limitation to exercise was noted in TM patients (VE/VCO2 slope: 23.4±3.2 vs 27.8±2.6; P<0.001 and breathing reserve, %: 42.9±17.0 vs 29.5±12.0; P<0.005) and no difference in oxygen cost of work (peak VO2/WR, mL/min W: 12.2±1.7 vs 12.2±1.5; P=NS). Delayed recovery oxygen kinetics after exercise was observed in TM patients (VO2/t slope, mL/kg/min2: 0.67±0.27 vs 0.93±0.23; P<0.05) that was significantly correlated with Pimax at rest (r: 0.81; P<0.001). The latter was also significantly correlated to pVO2 (r: 0.84; P<0.001) and inversely correlated to ferritin levels (r: −0.6; P<0.02). Exercise capacity is markedly reduced in TM patients and this reduction is highly associated with the limited functional status of peripheral muscles.