Stavros Dimopoulos

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.

Inotropic Agents Improve the Peripheral Microcirculation of Patients With End-Stage Chronic Heart Failure

BACKGROUND Skeletal muscle microcirculation impairment in patients with chronic heart failure (CHF) seems to correlate with disease severity. We evaluated the microcirculation by near-infrared spectroscopy (NIRS) occlusion technique before and after inotropic infusion. METHODS We evaluated 25 patients with stable CHF, 30 patients with end-stage CHF (ESCHF) receiving treatment with intermittent infusion of inotropic agents, and 12 healthy subjects. Thenar muscle tissue oxygen saturation (StO(2)%) was measured noninvasively by NIRS before, during, and after 3-minute occlusion of the brachial artery (occlusion technique) in all subjects and in patients with ESCHF before and after 6 hours of inotropic infusion (dobutamine and/or levosimendan) or placebo (N = 5). RESULTS Patients with ESCHF or CHF presented significantly lower StO(2)% than healthy subjects (74.5% +/- 7%, 78.6% +/- 6%, and 85% +/- 5%, respectively; P = .0001), lower oxygen consumption rate during occlusion (24.6% +/- 8%/min, 28.6% +/- 10%/min, and 38.1% +/- 11.1%/min, respectively; P = .001), and lower reperfusion rate (327% +/- 141%/min, 410% +/- 106%/min, and 480% +/- 133%/min, respectively; P = .002). After 6 hours of inotropic infusion, patients with ESCHF showed significantly increased StO(2)% (74.5% +/- 7% to 82% +/- 9%, P = .001), oxygen consumption rate (24.6% +/- 8%/min to 29.3% +/- 8%/min, P = .009), and reperfusion rate (327% +/- 141%/min to 467% +/- 151%/min, P = .001). No statistical difference was noted in the placebo group. CONCLUSION Peripheral muscle microcirculation as assessed by NIRS is impaired in patients with CHF. This impairment is partially reversed by infusion of inotropic agents in patients with ESCHF.

The addition of strength training to aerobic interval training: effects on muscle strength and body composition in CHF patients.

PURPOSE: The loss of lean muscle mass and muscle strength is a common problem in chronic heart failure (CHF) patients. Endurance training is efficient in improving patient exercise capacity. This study sought to evaluate the additional effects of strength training on muscle strength and body composition in chf patients participating in an interval training program. METHODS: Twenty consecutive, stable CHF patients participated in a rehabilitation program. Subjects were randomly assigned to aerobic (n = 10) or combined aerobic plus strength training group (n = 10). Aerobic group performed interval training on cycle ergometers. Strength training incorporated exercises for various muscle groups, including quadriceps, hamstrings, biceps brachii, and the deltoids. Both regimes were of the same duration. Body composition was evaluated by whole-body dual energy x-ray absorptiometry and quadriceps strength by the sum of the 2-repitition maximum (2-RM) test for each leg. Peak oxygen uptake ( ) and peak work load (Wpeak) as well as oxygen uptake ( ) and workload at anaerobic threshold (WAT) were evaluated by a symptom limited cardiopulmonary exercise testing. RESULTS: Concerning leg lean mass, no significant within-subjects or between-groups changes were observed (P > .05). Both groups improved in 2-RM test (P < .05), while a significant difference was observed between groups (P < .05). and and Wpeak and WAT were equally improved between training groups (P < .05). CONCLUSIONS: Combined aerobic interval and strength training induces a greater benefit than interval training alone on muscle strength in CHF patients. Adaptations other than hypertrophy, such as muscle fiber type alterations and/or neuromuscular adjustments, may account for these results.

Physical exercise improves the peripheral microcirculation of patients with chronic heart failure.

PURPOSE Patients with chronic heart failure (CHF) present with microcirculation alterations, partially attributed to endothelial dysfunction. Exercise training has been shown to induce beneficial effects in CHF patients. The aim of our study was to assess the effect of physical exercise on the microcirculation of CHF patients by near-infrared spectroscopy (NIRS). METHODS Sixteen consecutive stable CHF patients (men, n = 10; mean age = 50 ± 12 years) participated in a 3-month rehabilitation program (3 sessions per week). All patients performed symptom-limited, ramp-incremental cardiopulmonary exercise testing on a cycle ergometer before and after the completion of the program. Measurements included peak oxygen uptake (VO2peak), VO2 at anaerobic threshold (AT), and first-degree slope of VO2 during the first minute of recovery (VO2/t slope). Tissue oxygen saturation was continuously measured by NIRS at the thenar muscle during a 3-minute vascular occlusion with a pneumatic cuff (occlusion technique) before and after the rehabilitation program. RESULTS The oxygen reperfusion rate (%/min) following the release of vascular occlusion increased significantly after the rehabilitation program (450 ± 105 to 532 ± 151, P = .004) as did vascular reactivity (from 27 ± 13%/min to 39 ± 21%/min, P = .006). In addition, there was a significant increase in VO2peak and AT (from 14.3 ± 4.7 mL · kg−1 · min−1 to 16.7 ± 6.3 mL · kg−1 · min−1 and from 9.5 ± 3.6 mL · kg−1 · min−1 to 11.3 ± 4 mL · kg−1 · min−1, P = .007 and P = .012, respectively) as well as in VO2/t slope (from 0.35 ± 0.17 to 0.51 ± 0.07 mL · kg−1 · min−1, P = .005). CONCLUSIONS Peripheral microcirculation of CHF patients measured by NIRS improved after the rehabilitation program. NIRS is a noninvasive technique that could be used to evaluate the effect of rehabilitation on the peripheral microcirculation of CHF patients.

Lung sonography and recruitment in patients with early acute respiratory distress syndrome: a pilot study.

IntroductionBedside lung sonography is a useful imaging tool to assess lung aeration in critically ill patients. The purpose of this study was to evaluate the role of lung sonography in estimating the nonaerated area changes in the dependent lung regions during a positive end-expiratory pressure (PEEP) trial of patients with early acute respiratory distress syndrome (ARDS).MethodsTen patients (mean ± standard deviation (SD): age 64 ± 7 years, Acute Physiology and Chronic Health Evaluation II (APACHE II) score 21 ± 4) with early ARDS on mechanical ventilation were included in the study. Transthoracic sonography was performed in all patients to depict the nonaerated area in the dependent lung regions at different PEEP settings of 5, 10 and 15 cm H2O. Lung sonographic assessment of the nonaerated lung area and arterial blood gas analysis were performed simultaneously at the end of each period. A control group of five early ARDS patients matched for APACHE II score was also included in the study.ResultsThe nonaerated areas in the dependent lung regions were significantly reduced during PEEP increases from 5 to 10 to 15 cm H2O (27 ± 31 cm2 to 20 ± 24 cm2 to 11 ± 12 cm2, respectively; P < 0.01). These changes were associated with a significant increase in arterial oxygen partial pressure (74 ± 15 mmHg to 90 ± 19 mmHg to 102 ± 26 mmHg; P < 0.001, respectively). No significant changes were observed in the nonaerated areas in the dependent lung regions in the control group.ConclusionsIn this study, we show that transthoracic lung sonography can detect the nonaerated lung area changes during a PEEP trial of patients with early ARDS. Thus, transthoracic lung sonography might be considered as a useful clinical tool in the management of ARDS patients.

Basic principles and current applications of lung ultrasonography in the intensive care unit

Until recently, the sonographic visualization of pulmonary and pleural diseases was considered a poorly accessible method, due to the inability of sound to penetrate air‐filled lung. Despite its limitations, lung ultrasonography is becoming an important diagnostic tool in a growing number of pathological situations such as pneumonia, atelectasis, interstitial‐alveolar syndrome, pulmonary embolism, pneumothorax and pleural effusion. The low sensitivity of CXR and the difficulties of performing CT make this technique invaluable for bedside use in the intensive care unit. Lung ultrasonography is an easily repeatable and radiation‐free technique, and therefore, an attractive imaging tool for use on a daily basis, especially in the management of critically ill patients.

Impairment of Autonomic Nervous System Activity in Patients With Pulmonary Arterial Hypertension: A Case Control Study

BACKGROUND Chronotropic response to exercise (CR) and heart rate recovery (HRR) immediately after exercise are indirect indices of sympathetic and parasympathetic activity, respectively. The aim of this study was to evaluate CR and HRR in patients with pulmonary arterial hypertension (PAH) in relation to disease severity. METHODS AND RESULTS Ten PAH patients (6 females/4 males, mean age: 48+/-12 years) and 10 control subjects matched for age, gender, and body mass index (6 females/4 males, mean age: 46+/-6 years) performed a ramp incremental symptom-limited cardiopulmonary exercise test on a cycle ergometer. Main measurements included heart rate at rest (HR), CR=[(peak HR-resting HR/220-age-resting HR)x100, %], HRR(1)=HR difference from peak exercise to 1minute after, ventilatory efficiency during exercise (VE/VCO(2) slope), peak oxygen uptake (VO(2)p), and the first-degree slope of VO(2) for the first minute of the recovery period (VO(2)/t-slope). PAH patients had a significantly decreased CR (58+/-31 vs 92+/-13, %, P < .001) and HRR(1) (10+/-5 vs 29+/-6, beats/min, P < .001) as well as VO(2)p (11.9+/-3.5 vs 26.9+/-6.6, mL.kg.min) and VO(2)/t-slope (0.2+/-0.1 vs. 0.9+/-0.2, mL.kg.min(2)) compared with controls. CR and HRR(1) correlated well with VO(2)p (r=0.7; P < .001 and r=0.85; P < .001, respectively) and VO(2)/t-slope (r=0.66; P < .001 and r=0.85; P < .001, respectively) and had a significant inverse correlation with VE/VCO(2) slope (r=-0.47; P < .01 and r=-0.77; P < .001, respectively). CONCLUSIONS PAH patients present a significant impairment of CR and HRR(1) in relation to disease severity, indicating profound autonomic nervous system abnormalities.

Skeletal muscle microcirculatory abnormalities are associated with exercise intolerance, ventilatory inefficiency, and impaired autonomic control in heart failure

BACKGROUND Several skeletal muscle abnormalities have been identified in patients with chronic heart failure (CHF), including endothelial dysfunction. We hypothesized that skeletal muscle microcirculation, assessed by near-infrared spectroscopy (NIRS), is impaired in CHF patients and is associated with disease severity. METHODS Eighty-three stable patients with mild-moderate CHF (72 males, mean age 54 ± 14 years, body mass index 26.7 ± 3.4 kg/m(2)) and 8 healthy subjects, matched for age, gender and body mass index, underwent NIRS with the vascular occlusion technique and cardiopulmonary exercise testing (CPET) evaluation on the same day. Tissue oxygen saturation (StO(2), %), defined as the percentage of hemoglobin saturation in the microvasculature compartments, was measured in the thenar muscle by NIRS before, during and after 3-minute occlusion of the brachial artery. Measurements included StO(2), oxygen consumption rate (OCR, %/min) and reperfusion rate (RR, %/min). All subjects underwent a symptom-limited CPET on a cycle ergometer. Measurements included VO(2) at peak exercise (VO(2)peak, ml/kg/min) and anaerobic threshold (VO(2)AT, ml/kg/min), VE/VCO(2) slope, chronotropic reserve (CR, %) and heart rate recovery (HRR(1), bpm). RESULTS CHF patients had significantly lower StO(2) (75 ± 8.2 vs 80.3 ± 6, p < 0.05), lower OCR (32.3 ± 10.4 vs 37.7 ± 5.5, p < 0.05) and lower RR (10 ± 2.8 vs 15.7 ± 6.3, p < 0.05) compared with healthy controls. CHF patients with RR ≥9.5 had a significantly greater VO(2)peak (p < 0.001), VO(2)AT (p < 0.01), CR (p = 0.01) and HRR(1) (p = 0.01), and lower VE/VCO(2) slope (p = 0.001), compared to those with RR <9.5. In a multivariate analysis, RR was identified as an independent predictor of VO(2)peak, VE/VCO(2) slope and HRR(1). CONCLUSIONS Peripheral muscle microcirculation, as assessed by NIRS, is significantly impaired in CHF patients and is associated with disease severity.