Exercise In Chronic Heart Failure Research Articles

Respiratory gas kinetics in patients with congestive heart failure during recovery from peak exercise

BackgroundCardiopulmonary Exercise Testing (CPX) is essential for the assessment of exercise capacity for patients with Chronic Heart Failure (CHF). Respiratory gas and hemodynamic parameters such as Ventilatory Efficiency (VE/VCO2 slope), peak oxygen uptake (peak VO2), and heart rate recovery are established diagnostic and prognostic markers for clinical populations. Previous studies have suggested the clinical value of metrics related to respiratory gas collected during recovery from peak exercise, particularly recovery time to 50% (T1/2) of peak VO2. The current study explores these metrics in detail during recovery from peak exercise in CHF. MethodsPatients with CHF who were referred for CPX and healthy individuals without formal diagnoses were assessed for inclusion. All subjects performed CPX on cycle ergometers to volitional exhaustion and were monitored for at least five minutes of recovery. CPX data were analyzed for overshoot of respiratory exchange ratio (RER=VCO2/VO2), ventilatory equivalent for oxygen (VE/VO2), end-tidal partial pressure of oxygen (PETO2), and T1/2 of peak VO2 and VCO2. ResultsThirty-two patients with CHF and 30 controls were included. Peak VO2 differed significantly between patients and controls (13.5 ± 3.8 vs. 32.5 ± 9.8 mL/Kg*min−1, p < 0.001). Mean Left Ventricular Ejection Fraction (LVEF) was 35.9 ± 9.8% for patients with CHF compared to 61.1 ± 8.2% in the control group. The T1/2 of VO2, VCO2 and VE was significantly higher in patients (111.3 ± 51.0, 132.0 ± 38.8 and 155.6 ± 45.5s) than in controls (58.08 ± 13.2, 74.3 ± 21.1, 96.7 ± 36.8s; p < 0.001) while the overshoot of PETO2, VE/VO2 and RER was significantly lower in patients (7.2 ± 3.3, 41.9 ± 29.1 and 25.0 ± 13.6%) than in controls (10.1 ± 4.6, 62.1 ± 17.7 and 38.7 ± 15.1%; all p < 0.01). Most of the recovery metrics were significantly correlated with peak VO2 in CHF patients, but not with LVEF. ConclusionsPatients with CHF have a significantly blunted recovery from peak exercise. This is reflected in delays of VO2, VCO2, VE, PETO2, RER and VE/VO2, reflecting a greater energy required to return to baseline. Abnormal respiratory gas kinetics in CHF was negatively correlated with peak VO2 but not baseline LVEF.

Establishment of exercise intensity for patients with chronic heart failure equivalent to anaerobic threshold based on 6-minute walking test.

The study aimed to investigate the relationship between the aerobic exercise intensity determined by 6-minute walking distance (6MWD) and its counterpart based on anaerobic threshold (AT) in chronic heart failure (CHF) individuals for exploring suitable means for CHF exercise rehabilitation. We retrospectively analyzed data in patient with CHF, who performed cardiopulmonary exercise test (CPET) and 6-minute walking test (6MWT) uniformly. Anthropometric characteristics, left ventricular ejection fraction (LVEF), and multiple parameters of 6MWT and AT were collected. The results of the analysis revealed that the 6MWD was correlated with the AT positively [CHF group: r=0.433, heart failure with reduced ejection fraction (HFrEF) group: r=0.395, heart failure with intermediate ejection fraction (HFmEF) group: r=0.477, heart failure with preserved ejection fraction (HFpEF) group: r=0.445; all P<0.05]. The regression analysis showed that the linear equation model developed can predict exercise intensity based on AT (EIAT) by exercise intensity based on 6MWD (EI6MWD), the aerobic exercise intensity based on AT and 6MWD respectively, of CHF patients. There is a correlation between EI6MWD and EIAT. 74.6-87.4% of EI6MWD in patients with CHF is equivalent to EIAT. It is feasible to establish the aerobic exercise intensity of patients with CHF equivalent to AT based on 6MWD.

The utility of the oxygen pulse recovery as a marker of the cardiac output response to exercise in patients with chronic heart failure.

The cardiac output (CO) response to exercise is a useful marker to grade the prognosis and severity of chronic heart failure (CHF). The recovery of the oxygen pulse (OP) is a non-invasive parameter, which is related to exercise capacity in cardiac patients. However, the relation between OP recovery and the central haemodynamic response to exercise remains to be determined. We hypothesized that an impaired OP recovery is associated with a reduced CO response to exercise in CHF patients. Sixty one CHF patients performed cardiopulmonary exercise test with simultaneous measurement of CO. Impaired OP recovery was defined as an overshoot during the first minute of recovery or OP at 1-min recovery as a percentage of peak OP (OPRR ). An OP overshoot was observed in 9% (n=5) of patients. In these patients, peak CO and VO2 were significantly lower (peak CO 7.9±0.8 versus 11.2±4.3 L/min and peak VO2 14.1±4.7 versus 19.6±5.8mlmin-1 kg-1 ). Mean relative recovery of OP was 78±20%. Slow OP recovery (negative OPRR ) was seen in 13% (n=8). Peak CO and VO2 were significantly lower in the negative OPRR group (11±4 versus 8±0.7 L/min and 19.7±5.9 versus 14.6±3.7mlkgmin-1 ). There was a significant relation between OPRR and stroke volume (SV) RR (r=.57), as well as between OPRR and a-v O2 diff RR (rs =.4). An impaired OP recovery is associated with a reduced CO response to exercise and worse functional status. Therefore, the OP recovery can be used to grade the severity of CHF.

One and one is not always two: hypo- and hyper-additive effects of the chemoreflex during exercise.

One and one is not always two: hypo- and hyper-additive effects of the chemoreflex during exercise.

Physical activity and exercise in chronic heart failure

Physical activity and exercise in chronic heart failure

Association between heart rate variability and haemodynamic response to exercise in chronic heart failure

Objectives. Heart rate variability (HRV) and haemodynamic response to exercise (i.e. peak cardiac power output) are strong predictors of mortality in heart failure. The present study assessed the relationship between measures of HRV and peak cardiac power output. Design. In a prospective observational study of 33 patients (age 54 ± 16 years) with chronic heart failure with reduced left ventricular ejection fraction (29 ± 11%), measures of the HRV (i.e. R-R interval and standard deviation of normal R-R intervals, SDNN) were recorded in a supine position. All patients underwent maximal graded cardiopulmonary exercise testing with non-invasive (inert gas rebreathing) cardiac output assessment. Cardiac power output, expressed in watts, was calculated as the product of cardiac output and mean arterial blood pressure. Results. The mean RR and SDNN were 837 ± 166 and 96 ± 29 ms, peak exercise cardiac power output 2.28 ± 0.85 watts, cardiac output 10.34 ± 3.14 L/min, mean arterial blood pressure 98 ± 14 mmHg, stroke volume 91.43 ± 40.77 mL/beat, and oxygen consumption 19.0 ± 5.6 mL/kg/min. There was a significant but only moderate relationship between the RR interval and peak exercise cardiac power output (r = 0.43, p = .013), cardiac output (r = 0.35, p = .047), and mean arterial blood pressure (r = 0.45, p = .009). The SDNN correlated with peak cardiac power output (r = 0.42, p = .016), mean arterial blood arterial (r = 0.41, p = .019), and stroke volume (r = 0.35, p = .043). Conclusions. Moderate strength of the relationship between measures of HRV and cardiac response to exercise suggests that cardiac autonomic function is not good indicator of overall function and pumping capability of the heart in chronic heart failure.

NT-proBNP is a weak indicator of cardiac function and haemodynamic response to exercise in chronic heart failure.

AimsN‐terminal prohormone of brain natriuretic peptide (NT‐proBNP) plays an important role in diagnosis and management of heart failure. The aim of the present study was to assess haemodynamic response to exercise and to evaluate the relationship between NT‐proBNP, cardiac function, and exercise tolerance in chronic heart failure.Methods and resultsA single‐centre, cross‐sectional pilot study recruited 17 patients with chronic heart failure with reduced left ventricular ejection fraction (age 67 ± 7 years) and 20 healthy volunteers (age 65 ± 12 years). The NT‐proBNP was measured in the heart failure group. All participants completed maximal graded cardiopulmonary exercise stress testing coupled with gas exchange (using metabolic analyser for determination of exercise tolerance, i.e. peak O2 consumption) and continuous haemodynamic measurements (i.e. cardiac output and cardiac power output) using non‐invasive bioreactance technology. Heart failure patients demonstrated significantly lower peak exercise cardiac function and exercise tolerance than healthy controls, i.e. cardiac power output (5.0 ± 2.0 vs. 3.2 ± 1.2 W, P < 0.01), cardiac output (18.2 ± 6.3 vs. 13.5 ± 4.0 L/min, P < 0.01), heart rate (148 ± 23.7 vs. 111 ± 20.9 beats/min, P < 0.01), and oxygen consumption (24.3 ± 9.5 vs. 16.8 ± 3.8 mL/kg/min, P < 0.01). There was no significant relationship between NT‐proBNP and cardiac function at rest, i.e. cardiac power output (r = −0.28, P = 0.28), cardiac output (r = −0.18, P = 0.50), and oxygen consumption (r = −0.18, P = 0.50), or peak exercise, i.e. cardiac power output (r = 0.18, P = 0.49), cardiac output (r = 0.13, P = 0.63), and oxygen consumption (r = −0.05, P = 0.84).ConclusionsLack of a significant and strong relationship between the NT‐proBNP and measures of cardiac function and exercise tolerance may suggest that natriuretic peptides should be considered with caution in interpretation of the severity of cardiac dysfunction and functional capacity in chronic heart failure.

Exercise training has restorative potential on myocardial energy metabolism in rats with chronic heart failure.

Objective(s):Exercise training is a well-known accelerator for the treatment of chronic heart failure (CHF). The current study aimed to investigate the restorative effects of aerobic interval training (AIT) intervention on myocardial energy metabolism in CHF rats. Materials and Methods: Post-myocardial infarction (MI) heart failure animal model was established. The Sprague-Dawley rats were randomly divided into sham operation group (Sham group), CHF model group, and CHF exercise group (Exercise-CHF group). Results:Our data showed that when compared to the Sham group, the left ventricular systolic pressure (LVSP), myocardial glycogen content, and expression levels of key components of AMP-activated protein kinase (AMPK) pathway were decreased significantly (P<0.05) in the CHF-model group, while the left ventricular end diastolic pressure (LVEDP), fatty acid (FA) concentration, lactic acid content, and AMPKα phosphorylation (p-AMPKα) were increased significantly (P<0.05) in the CHF-model group. Importantly, AIT reversed these alterations induced by post-MI. Conclusion:Findings of this study demonstrated that AIT could improve the metabolic remodeling and enhance cardiac function, which may be associated with the activation of AMPK/ peroxisome proliferator activated receptor α (PPARα) and its downstream signaling pathway.

Resistance exercise in chronic heart failure: hemodynamic and metabolic adjustments

The aim of this study was to characterize hemodynamic and metabolic responses to dynamic resistance exercise in chronic heart failure patients (CHF) compared to healthy older men (CTR). We hypothesized that in controlled conditions; pharmacologically treated CHF should show the adaptations to the strength exercises similar to healthy subjects, demonstrating therefore the compatibility with the practical on field. We addressed the acute effects of dynamic resistance exercise in eight CHF patients and eleven age-matched CTRs, instrumented for expiratory gas and cardiovascular analysis. All subjects performed two series with up to twelve repetitions at 70 % of 1RM on a leg press machine. Arterial pressure and heart rate progressively increased throughout the movements and decreased on cessation, while stroke volume (Modelflow software) decreased by 30 % at the start and increased by 10 % at cessation. Cardiac output increased at cessation only. All values were lower in CHF, but the changes during the exercises were not significantly different from those of CTR. Oxygen consumption increased during the exercises and continued increasing thereafter up to 60–70 % V’O2max (absolute changes were smaller in CHF). We concluded that the response to dynamic resistance exercise is characterized by a sharp hindrance to the output of blood from the heart, which reduces stroke volume and enhances arterial pressure in CHF as well as in CTR. The simultaneous increase in heart rate kept cardiac output unaltered. The most important differences concerned a reduced metabolic response during exercise in CHF, even more evident in rest. Chronic heart failure syndrome and its treatment do not interfere with the cardiovascular responses to these kinds of physical activities. This finding can be considered a step forward in demonstrating that patients with chronic heart failure can, in controlled conditions, safely practice these essential exercises to preserve their muscle integrity.

EFFECT OF INSPIRATORY MUSCLE TRAINING ON CARDIAC PARAMETERS OF EXERCISE TOLERANCE TEST IN CHRONIC HEART FAILURE PATIENTS

Introduction: inspiratory muscle training (IMT) improves exercise capacity and ventilatory responses to exercise in chronic heart failure (CHF) patients with inspiratory muscle weakness (IMW). Aim of work: To investigate the effect of inspiratory muscle training (IMT) with comprehensive cardiac rehabilitation (CR) program (aerobic and resisted exercise training) on cardiac parameters of exercise tolerance test in chronic heart failure patients Materials and Methods: Forty eligible male patients with chronic heart failure secondary to ischemic heart disease (only thirty of them completed the study). Their ages ranged from 50-60 years old .They were randomly assigned to 6 months of aerobic exercise , resisted exercise plus IMT (n=15) or to aerobic exercise plus resisted exercise only (n=15), before and after intervention, the following measures were obtained :cardiac parameter of cardiopulmonary exercise testing ( maximum heart rate , resting heart rate ). Result: Compared aerobic exercise (AE) + IMT to AE resulted in cardiac parameters of exercise tolerance test (maximum heart rate, resting heart rate) improved similarly in the 2 groups. Conclusion: This study demonstrated that the addition of IMT to AE results in improvement in cardiac response to exercise in selected patients with CHF but with no significant difference between exercise training groups.

Abstract 17080: The Anesthetized Rat Model of Exercise Faithfully Simulates Respiratory Abnormalities in Chronic Heart Failure

Background: Abnormal respiration during exercise is one of the major manifestations and a powerful predictor of survival in chronic heart failure (CHF). There have not been proposed the appropriate animal model to investigate the mechanism of respiratory abnormalities in CHF during exercise. In this study, we developed an experimental model using anesthetized CHF rats to evaluate exercise-induced abnormal respiration and central chemoreflex control function during exercise in CHF. Methods: We used anesthetized 16 weeks old rats with/without myocardial infarction induced CHF. To mimic exercise, we induced muscle contraction by stimulating bilateral distal sciatic nerves. We recorded the respiratory change in response to sciatic nerve stimulation (SNS) with ramp (5 Hz, 0.01 Volts/sec) and step (5 Hz, 0.5 Volts) protocols. We also evaluated the change of the central chemosensitivity (ventilatory response to partial pressure of carbon dioxide in arterial blood; PaCO2) by CO2 gas inhalation (0, 3 and 5%) during exercise in normal and CHF. Results: In ramp protocol, SNS significantly increased minute ventilation (VE) in CHF to a greater extent than in that of normal (normal 155.2±27.9, CHF 211.2±48.6 mL/min, p&lt;0.01). CHF markedly steepened the VE-carbon dioxide production relationship (VE/VCO2 slope) (normal 26.8±12.7, CHF 38.5±5.9, p&lt;0.05) (Fig. 1). CHF shifted the relationship of tidal volume (TV) to respiratory rate (RR) rightward reflecting the rapid and shallow breathing during exercise (Fig. 2). The SNS-induced upward shift of the VE-PaCO2 line observed in CHF indicated that exercise-related respiratory abnormalities arise from pathophysiological change in the central chemoreflex control (Fig. 3). Conclusion: Anesthetized rat exercise model simulated respiratory abnormalities in CHF reasonably well. It will provide us an opportunity to clarify the physiological mechanisms of exercise-induced abnormal respiration in CHF.

The Relation of Respiratory Muscle Strength to Disease Severity and Abnormal Ventilation During Exercise in Chronic Heart Failure Patients.

Background:Breathlessness is a common problem in chronic heart failure (CHF) patients, and respiratory muscle strength has been proposed to play an important role in causing breathlessness in these patients.Objectives:The aim of this study was to investigate the relation between respiratory muscle strength and the severity of CHF, and the influence of respiratory muscle strength on abnormal ventilation during exercise in CHF patients.Patients and Methods:In this case series study, we assessed clinically stable CHF outpatients (N = 66, age: 57.7 ± 14.6 years). The peak oxygen consumption (peak VO2), the slope relating minute ventilation to carbon dioxide production (VE/VCO2 slope), and the slope relating tidal volume to respiratory rate (TV/RR slope) were measured during cardiopulmonary exercise testing. Respiratory muscle strength was assessed by measuring the maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP).Results:The MIP and MEP decreased significantly as the New York Heart Association functional class increased (MIP, P = 0.021; MEP, P < 0.01). The MIP correlated with the TV/RR slope (r = 0.57, P < 0.001) and the VE/VCO2 slope (r = -0.44, P < 0.001), and the MEP also correlated with the TV/RR slope (r = 0.53, P < 0.001) and the VE/VCO2 slope (r = -0.25, P < 0.040). Stepwise multiple regression analysis revealed that age and MIP were statistically significant predictors of the TV/RR and VE/VCO2 slopes (both P < 0.05).Conclusions:Respiratory muscle strength is related to the severity of CHF, and associated with rapid and shallow ventilation or excessive ventilation during exercise.

Abstract 14822: Impact of Proportional Assist Ventilation on Skeletal Muscle Reoxygenation and Central Hemodynamic During Constant Work Rate Exercise in Chronic Heart Failure

Introduction: Progressive chronic heart failure slows the recovery of microvascular oxygen delivery and utilization, which produce deleterious implications to exercise capacity. Respiratory muscle unloading can enhance the responses to exercise thereby allowing a closer matching between skeletal muscle oxygen delivery and utilization in patients with chronic heart failure (CHF). Hypothesis: We reasoned that noninvasive ventilation administered by proportional assisted ventilation (PAV) could accelerate skeletal muscle reoxygenation after high intensity exercise in CHF humans. To test this hypothesis, we conducted a study with 12 patients with stable CHF who were randomized to receive PAV or sham ventilation during high-intensity constant work exercise and compared the effects of these interventions on oxygen pulmonary (O2p), cardiac output and [[Unable to Display Character: &amp;#8710;]][deoxi-Hb+Mb] off kinetics. Methods: Twelve patients with CHF (NYHA class II and III and left ventricle ejection fraction= 26±9%) underwent two high-intensity, constant-work rate (80% peak) cycle ergometer tests receiving PAV or sham ventilation. Off-exercise kinetics of the primary component of oxygen uptake, an index of fractional oxygen extraction by near infrared spectroscopy (~[[Unable to Display Character: &amp;#8710;]][deoxy-Hb+Mb]) in the vastus lateralis) and cardiac output (QT) by impedance cardiography were assessed. Results: PAV significantly accelerated the recovery of O2p when compared with sham τ = 56±22 vs. 77±42s, respectively, p&lt;0.05). Interestingly, PAV was associated with faster fractional O2 extraction (~[[Unable to Display Character: &amp;#8710;]][deoxy-Hb+Mb] by near-infrared spectroscopy) (τ= 31±19 vs. 42±22s, respectively, p&lt;0.05) . In addition, kinetics of QT were significantly faster with PAV than sham (τ = 39±22 vs. 78±46s, respectively, p&lt;0.05). Conclusions: These data indicate that PAV has beneficial effects on recovery of muscle metabolism and central hemodynamics after high-intensity exercise in CHF patients. Financial Support: FAPESP 2009-01842-0

Essential amino acids and exercise tolerance in elderly muscle-depleted subjects with chronic diseases: a rehabilitation without rehabilitation?

Exercise intolerance remains problematic in subjects with chronic heart failure (CHF) and/or chronic obstructive pulmonary disease (COPD). Recent studies show that supplemented essential amino acids (EAAs) may exert beneficial effects on CHF/COPD physical capacity. The results from 3 investigations (2 conducted on CHF and 1 on COPD subjects) served as the basis for this paper. The 3 studies consistently showed that elderly CHF and COPD improved exercise intolerance after 1–3 months of EAA supplementation (8 g/d). In CHF exercise capacity increased 18.7% to 23% (watts; bicycle test), and 12% to 22% (meters) in 6 min walking test. Moreover, patients reduced their resting plasma lactate levels (by 25%) and improved tissue insulin sensitivity by 16% (HOMA index). COPD subjects enjoyed similar benefits as CHF ones. They increased physical autonomy by 78.6% steps/day and decreased resting plasma lactate concentrations by 23%. EAA mechanisms explaining improved exercise intolerance could be increases in muscle aerobic metabolism, mass and function, and improvement of tissue insulin sensitivity (the latter only for the CHF population). These mechanisms could be accounted for by EAA's intrinsic physiological activity which increases myofibrils and mitochondria genesis in skeletal muscle and myocardium and glucose control. Supplemented EAAs can improve the physical autonomy of subjects with CHF/COPD.

Effect of High-Intensity interval training versus moderate continuous training on 24-h blood pressure profile and insulin resistance in patients with chronic heart failure

In patients with chronic heart failure (CHF) blood pressure (BP) control, represents a relevant target of management. This study evaluated the effect of different intensities exercise training on 24-h ambulatory BP profile and insulin resistance in patients with CHF. Thirty-six CHF patients with left ventricular ejection fraction <40%, were randomized to high-intensity interval training (HIT) or moderate continuous training (MIT) for 12 weeks. HIT consisted in treadmill exercise at ~75-80% of heart rate reserve (HRR), alternated with active pauses at 45-50% of HRR. MIT consisted in continuous treadmill at ~45-60% of HRR. Peak VO2 and anaerobic threshold increased significantly with both HIT and MIT, without significant differences between the two training programs. 24-h, systolic and diastolic BP decreased with both HIT and MIT. The same occurred for day-time and night-time systolic and diastolic BP. The decrease in day-time diastolic BP was slightly but significantly greater in HIT. Both HIT and MIT induced a significant decrease in fasting glucose and insulin, whereas HOMA-IR decreased significantly only after HIT. In patients with CHF exercise training reduces BP throughout the day, without substantial differences between moderate and more vigorous exercise intensity, with a small exception for day-time diastolic BP. HIT was more effective in improving insulin resistance.

Association between mental health and physical activity in patients with chronic heart failure

Purpose: Poor mental health (MH) is common in chronic heart failure (CHF) patients. No studies have reported a relation between MH status and objectively measured physical activity (PA) in CHF patients. The study aim was to determine self-reported MH-related differences associated with PA and target values of PA for improved MH in CHF outpatients. Methods: We divided 243 CHF outpatients (mean age 57.1 years) into two groups according to MH assessed by Short Form-36 score: high-MH (≥68 points) group (n = 148) and poor-MH (<68 points) group (n = 95). Average step count (steps) and energy expenditure on PA (EE) (kcal) per day for 1 week of PA were assessed by an accelerometer and compared between groups. PA resulting in high MH was determined by the receiver-operating characteristic (ROC) analysis. Results: PA correlated positively with MH in all patients (steps: r = 0.46, p < 0.001; EE: r = 0.43, p < 0.001). After adjusting for patient characteristics, steps and EE were significantly lower in the poor-MH versus high-MH group (5020.1 ± 280.7 versus 7174.1 ± 221.5 steps, p < 0.001; 133.9 ± 10.8 versus 215.9 ± 8.4 kcal, p < 0.001). Cut-off values of 5590.8 steps and 141.1 kcal were determined as PA target values associated with improved MH. Conclusions: Poor MH status may reduce PA. Attaining PA target values may improve MH status of CHF outpatients.Implications for RehabilitationPoor mental health may negatively affect physical exercise in CHF outpatients.In particular step counts and energy expenditure are lower in those with poor mental health.It may be that focused exercise training may impact positively both on mental health and physical well being.

High-Intensity Interval Exercise in Chronic Heart Failure: Protocol Optimization

BackgroundThere are little data on the optimization of high-intensity aerobic interval exercise (HIIE) protocols in patients with chronic heart failure (CHF). Therefore, we compared acute cardiopulmonary responses to 4 different HIIE protocols to identify the optimal one. Methods and ResultsTwenty men with stable systolic CHF performed 4 different randomly ordered single HIIE sessions with measurement of gas exchange. For all protocols (A, B, C, and D) exercise intensity was set at 100% of peak power output (PPO). Interval duration was 30 seconds (A and B) or 90 seconds (C and D), and recovery was passive (A and C) or active (50% of PPO in B and D). Time spent above 85% of VO2peak and time above the ventilatory threshold were similar across all 4 HIIE protocols. Total exercise time was significantly longer in protocols with passive recovery intervals (A: 1,651 ± 347 s; C: 1,574 ± 382 s) compared with protocols with active recovery intervals (B: 986 ± 542 s; D: 961 ± 556 s). All protocols appeared to be safe, with exercise tolerance being superior during protocol A. ConclusionAmong the 4 HIIE protocols tested, protocol A with short intervals and passive recovery appeared to be superior.

The intramuscular contribution to the slow oxygen uptake kinetics during exercise in chronic heart failure is related to the severity of the condition

The mechanism for slow pulmonary O(2) uptake (Vo(2)) kinetics in patients with chronic heart failure (CHF) is unclear but may be due to limitations in the intramuscular control of O(2) utilization or O(2) delivery. Recent evidence of a transient overshoot in microvascular deoxygenation supports the latter. Prior (or warm-up) exercise can increase O(2) delivery in healthy individuals. We therefore aimed to determine whether prior exercise could increase muscle oxygenation and speed Vo(2) kinetics during exercise in CHF. Fifteen men with CHF (New York Heart Association I-III) due to left ventricular systolic dysfunction performed two 6-min moderate-intensity exercise transitions (bouts 1 and 2, separated by 6 min of rest) from rest to 90% of lactate threshold on a cycle ergometer. Vo(2) was measured using a turbine and a mass spectrometer, and muscle tissue oxygenation index (TOI) was determined by near-infrared spectroscopy. Prior exercise increased resting TOI by 5.3 ± 2.4% (P = 0.001), attenuated the deoxygenation overshoot (-3.9 ± 3.6 vs. -2.0 ± 1.4%, P = 0.011), and speeded the Vo(2) time constant (τVo(2); 49 ± 19 vs. 41 ± 16 s, P = 0.003). Resting TOI was correlated to τVo(2) before (R(2) = 0.51, P = 0.014) and after (R(2) = 0.36, P = 0.051) warm-up exercise. However, the mean response time of TOI was speeded between bouts in half of the patients (26 ± 8 vs. 20 ± 8 s) and slowed in the remainder (32 ± 11 vs. 44 ± 16 s), the latter group having worse New York Heart Association scores (P = 0.042) and slower Vo(2) kinetics (P = 0.001). These data indicate that prior moderate-intensity exercise improves muscle oxygenation and speeds Vo(2) kinetics in CHF. The most severely limited patients, however, appear to have an intramuscular pathology that limits Vo(2) kinetics during moderate exercise.

Blunted local but preserved remote vascular responses after resistance exercise in chronic heart failure

A single aerobic exercise session increases blood flow and vascular reactivity in remote vascular areas in chronic heart failure (CHF). We hypothesized that CHF patients would present increased vascular reactivity after a resistance exercise session. Ten CHF patients and 10 healthy controls participated in three experiments, on different days: (1) 25-min rest (control); (2) 25-min lower-limb resistance exercises with vascular measurements in the calf (RELL); and (3) 25-min lower-limb resistance exercises with vascular measurements in the forearm (REUL). Heart rate (HR), blood pressure (BP), forearm blood flow (FBF), and calf blood flow (CBF) were measured at baseline, immediately, and 10, 30, and 60 min after the interventions. Calf and forearm reactive hyperaemia (RH) were measured at baseline and at 10, 30, and 60 min post interventions. Mean BP was unchanged throughout the protocols in CHF patients, whereas healthy controls had postexercise reduction up to 60 and 10 min after RELL and REUL sessions, respectively. Forearm RH (30- min post exercise) indicated remote effects and was increased by 36% and 43% (p < 0.05) in CHF patients and controls, respectively. Both groups increased postexercise calf RH (local effect) up to 60 min; however, healthy controls presented larger responses compared with patients (73% vs. 39%, p < 0.05). Patients with CHF present blunted vascular responses in the exercised areas, but remote vascular reactivity responses are similar to those observed in healthy individuals, suggesting that resistance exercise may remotely contribute to vascular adaptation in nontrained vasculatures.

Influence of cardiomegaly on disordered breathing during exercise in chronic heart failure

Heart failure (HF) patients breathe with a rapid shallow pattern during exercise. This study examined the relationship between cardiac size and tachypnoeic breathing in HF patients during exercise. Thirty-seven HF patients [age = 55 ± 13 years, ejection fraction (EF) = 27 ± 10%, New York Heart Association (NYHA) class = 2.3 ± 1.2] and 42 controls (CTL) (age = 56 ± 14 years, EF = 63 ± 8%) were recruited. Participants underwent maximal exercise testing, pulmonary function testing, and chest radiography for calculation of total thoracic cavity volume (TTCV), diaphragm, heart, and lung volumes. Heart failure patients were divided into two groups: Group A = cardiac volume < median (n = 18) and Group B = cardiac volume ≥ median of the HF patients (n = 19). There was no difference between groups for TTCV (CTL = 8203 ± 1489 vs. Group A = 8694 ± 1249 vs. Group B = 8195 ± 1823 cm(3)). Cardiac volume was different between groups for both absolute (CTL = 630 ± 181 vs. Group A = 894 ± 186 vs. Group B = 1401 ± 382 cm(3), P< 0.001 for all comparisons) and %TTCV (CTL = 8 ± 2 vs. Group A = 10 ± 1 vs. Group A = 18 ± 5%, P< 0.001 for all comparisons). Similarly, total lung volume as a %TTCV was significantly different among the groups (CTL = 70 ± 4 vs. Group A = 65 ± 5 vs. Group A = 58 ± 7%, P< 0.01 for all comparisons). In HF patients, there was a trend (P = 0.10) towards an independent association between cardiac size and tidal volume (V(T)) at 75% of VO(2) peak whereas this relationship was statistically significant at VO(2) peak (P = 0.02) as patients with larger cardiac size had reduced V(T). This study demonstrates the close relationship between cardiac size and breathing pattern during exercise in HF patients. These results suggest cardiac size may pose a significant constraint on the lungs during exercise and may contribute to tachypnoeic breathing.