Are oxygen uptake kinetics in chronic heart failure limited by oxygen delivery or oxygen utilization?

Background: The delay in O2 uptake kinetics during and after submaximal physical activity (O2 onset and recovery kinetics, respectively) correlates well with the functional capacity of patients with chronic heart failure (CHF). This study examined the physiological background of this delay in moderately impaired CHF patients by comparing kinetics of cardiac output (Q?) and O2 uptake (V?O2 ). Methods: Fourteen stable CHF patients (New York Heart Association class II-III) and 8 healthy subjects, matched for age and body mass index, were included. All subjects performed a submaximal constant-load exercise test to assess O2 uptake kinetics. Furthermore, in 10 CHF patients Q? was measured by a radial artery pulse contour analysis method, which enabled the simultaneous modelling of exercise-related kinetics of Q? and V?O2 . Results: Both O2 onset and recovery kinetics were delayed in the patient group. There were no significant differences between the time constants of Q? and V?O2 during exercise-onset (62 -Ý 25- s versus 59 -Ý 28- s, p = 0.51) or recovery (61 -Ý 25- s versus 57 -Ý 20- s, p = 0.38) in the patient group, indicating that O2 delivery was not in excess of the metabolic demands in these patients. Conclusion: The delay in O2 onset and recovery kinetics in moderately impaired CHF patients is suggested to be due to limitations in O2 delivery. Therefore, strategies aimed at improving exercise performance of these patients should focus more on improvements of O2 delivery than on O2 utilization. -© 2008 Elsevier Ireland Ltd. All rights reserve

Are oxygen uptake kinetics in chronic heart failure limited by oxygen delivery or oxygen utilization?

Background: The delay in O2 uptake kinetics during and after submaximal physical activity (O2 onset and recovery kinetics, respectively) correlates well with the functional capacity of patients with chronic heart failure (CHF). This study examined the physiological background of this delay in moderately impaired CHF patients by comparing kinetics of cardiac output (Q?) and O2 uptake (V?O2 ). Methods: Fourteen stable CHF patients (New York Heart Association class II-III) and 8 healthy subjects, matched for age and body mass index, were included. All subjects performed a submaximal constant-load exercise test to assess O2 uptake kinetics. Furthermore, in 10 CHF patients Q? was measured by a radial artery pulse contour analysis method, which enabled the simultaneous modelling of exercise-related kinetics of Q? and V?O2 . Results: Both O2 onset and recovery kinetics were delayed in the patient group. There were no significant differences between the time constants of Q? and V?O2 during exercise-onset (62 -Ý 25- s versus 59 -Ý 28- s, p = 0.51) or recovery (61 -Ý 25- s versus 57 -Ý 20- s, p = 0.38) in the patient group, indicating that O2 delivery was not in excess of the metabolic demands in these patients. Conclusion: The delay in O2 onset and recovery kinetics in moderately impaired CHF patients is suggested to be due to limitations in O2 delivery. Therefore, strategies aimed at improving exercise performance of these patients should focus more on improvements of O2 delivery than on O2 utilization. -© 2008 Elsevier Ireland Ltd. All rights reserve

Skeletal muscle metabolic recovery following submaximal exercise in chronic heart failure is limited more by O2 delivery than O2 utilization

CHF (chronic heart failure) is associated with a prolonged recovery of skeletal muscle energy stores following submaximal exercise, limiting the ability to perform repetitive daily activities. However, the pathophysiological background of this impairment is not well established. The aim of the present study was to investigate whether muscle metabolic recovery following submaximal exercise in patients with CHF is limited by O2 delivery or O2 utilization. A total of 13 stable CHF patients (New York Heart Association classes II-III) and eight healthy subjects, matched for age and BMI (body mass index), were included. All subjects performed repetitive submaximal dynamic single leg extensions in the supine position. Post-exercise PCr (phosphocreatine) resynthesis was assessed by 31P-MRS (magnetic resonance spectroscopy). NIRS (near-IR spectroscopy) was applied simultaneously, using the rate of decrease in HHb (deoxygenated haemoglobin) as an index of post-exercise muscle re-oxygenation. As expected, PCr recovery was slower in CHF patients than in control subjects (time constant, 47 ± 10 compared with 35 ± 12 s respectively; P=0.04). HHb recovery kinetics were also prolonged in CHF patients (mean response time, 74±41 compared with 44±17 s respectively; P=0.04). In the patient group, HHb recovery kinetics were slower than PCr recovery kinetics (P=0.02), whereas no difference existed in the control group (P=0.32). In conclusion, prolonged metabolic recovery in CHF patients is associated with an even slower muscle tissue re-oxygenation, indicating a lower O2 delivery relative to metabolic demands. Therefore we postulate that the impaired ability to perform repetitive daily activities in these patients depends more on a reduced muscle blood flow than on limitations in O2 utilization. © The Authors Journal compilation © 2010 Biochemical Society

Skeletal muscle metabolic recovery following submaximal exercise in chronic heart failure is limited more by O2 delivery than O2 utilization

CHF (chronic heart failure) is associated with a prolonged recovery of skeletal muscle energy stores following submaximal exercise, limiting the ability to perform repetitive daily activities. However, the pathophysiological background of this impairment is not well established. The aim of the present study was to investigate whether muscle metabolic recovery following submaximal exercise in patients with CHF is limited by O2 delivery or O2 utilization. A total of 13 stable CHF patients (New York Heart Association classes II-III) and eight healthy subjects, matched for age and BMI (body mass index), were included. All subjects performed repetitive submaximal dynamic single leg extensions in the supine position. Post-exercise PCr (phosphocreatine) resynthesis was assessed by 31P-MRS (magnetic resonance spectroscopy). NIRS (near-IR spectroscopy) was applied simultaneously, using the rate of decrease in HHb (deoxygenated haemoglobin) as an index of post-exercise muscle re-oxygenation. As expected, PCr recovery was slower in CHF patients than in control subjects (time constant, 47 ± 10 compared with 35 ± 12 s respectively; P=0.04). HHb recovery kinetics were also prolonged in CHF patients (mean response time, 74±41 compared with 44±17 s respectively; P=0.04). In the patient group, HHb recovery kinetics were slower than PCr recovery kinetics (P=0.02), whereas no difference existed in the control group (P=0.32). In conclusion, prolonged metabolic recovery in CHF patients is associated with an even slower muscle tissue re-oxygenation, indicating a lower O2 delivery relative to metabolic demands. Therefore we postulate that the impaired ability to perform repetitive daily activities in these patients depends more on a reduced muscle blood flow than on limitations in O2 utilization. © The Authors Journal compilation © 2010 Biochemical Society

Does physical training increase insulin sensitivity in chronic heart failure patients?

To determine the effect of training on insulin sensitivity (IS) and how this relates to peak 02 (peak oxygen uptake) in CHF (chronic heart failure), 77 CHF patients (New York Heart Association class, II/III; men/women, 59/18; age, 60 +/- 9 years; body mass index, 26.7 +/- 3.9 kg/m(2); left ventricular ejection fraction, 26.9 +/- 8.1%; expressed as means +/- S.D.) participated in the study. Patients were randomly assigned to a training or control group (TrG or CG respectively). Sixty-one patients completed the study. Patients participated in training (combined strength and endurance exercises) four times per week, two times supervised and two times at home. Before and after intervention, anthropometry, IS (euglycaemic hyperinsulinaemic clamp) and peak 02 (incremental cycle ergometry) were assessed. Intervention did not affect IS significantly, even though IS increased by 20% in TrG and 11% in CG (not significant). Peak (V)over dot O-2 increased as a result of training (6% increase in TrG; 2% decrease in CG; P <0.05). In both groups (TrG and CG), the change in IS correlated positively with the change in peak (V)over dot O-2 (r = 0.30, P <0.05). Training resulted in an increase in peak (V)over dot O-2, but not in IS. Whether physical training actually increases IS in CHF patients remains unclear

Monitoring training progress during exercise training in cancer survivors: a submaximal exercise test as an alternative for a maximal exercise test?

OBJECTIVE: To examine the use of a submaximal exercise test in detecting change in fitness level after a physical training program, and to investigate the correlation of outcomes as measured submaximally or maximally. DESIGN: A prospective study in which exercise testing was performed before and after training intervention. SETTING: Academic and general hospital and rehabilitation center. PARTICIPANTS: Cancer survivors (N=147) (all cancer types, medical treatment completed > or =3 mo ago) attended a 12-week supervised exercise program. INTERVENTIONS: A 12-week training program including aerobic training, strength training, and group sport. MAIN OUTCOME MEASURES: Outcome measures were changes in peak oxygen uptake (Vo(2)peak) and peak power output (both determined during exhaustive exercise testing) and submaximal heart rate (determined during submaximal testing at a fixed workload). RESULTS: The Vo(2)peak and peak power output increased and the submaximal heart rate decreased significantly from baseline to postintervention (P<.001). Changes in submaximal heart rate were only weakly correlated with changes in Vo(2)peak and peak power output. Comparing the participants performing submaximal testing with a heart rate less than 140 beats per minute (bpm) versus the participants achieving a heart rate of 140 bpm or higher showed that changes in submaximal heart rate in the group cycling with moderate to high intensity (ie, heart rate > or =140 bpm) were clearly related to changes in VO(2)peak and peak power output. CONCLUSIONS: For the monitoring of training progress in daily clinical practice, changes in heart rate at a fixed submaximal workload that requires a heart rate greater than 140 bpm may serve as an alternative to an exhaustive exercise test

Diagnostic utility of combined ultrasonography and mammography in the evaluation of women with mammographically dense breasts.

To assess the diagnostic utility and additional cost of combined breast ultrasonography and mammography in the evaluation of asymptomatic women with mammographically dense breasts. Of 5108 asymptomatic women, who underwent mammography, 1754 had dense breasts (BI-RADS 3 or 4) and negative mammographic outcome. They were divided in 4 subgroups according to their age (59 yrs). Breast ultrasonography was performed immediately after mammography. Lesions detected at ultrasonography were examined cytologically/histologically. Mammograms from women, who were diagnosed carcinoma at ultrasonography, were reviewed by an external radiologist. Costs per diagnosed carcinoma and per examined woman were calculated on the basis of current regional charges. Mammographies (5108) were performed, 67 cancers were detected (cancer detection rate 13.1‰): mammography identified 55 carcinomas and ultrasonography performed in women with dense breasts identified 12 cancers (17.9% of all cancers detected, overall cancer detection rate 6.8‰). Ultrasonography identified a benign condition in 1567 out of 1754 women (89.3%) (in 925 absence of focal lesions; 438 simple cysts; 56 ductal ectasia; 148 benign solid lesions); 97 complex cysts, 52 lesions that could not be differentiated as liquid or solid lesions, and 38 solid lesions suspicious for malignancy in the remaining 187 out of 1754 patients (10.7%). Cytology/histology confirmed carcinoma in 12 women (overall biopsy rate 26.2‰, benign biopsy rate 19.4‰). The additional costs were: € 6,123.45 per detected cancer, € 41.89 per examined woman. Breast ultrasonography immediately after mammography in women with dense breasts is useful to avoid diagnostic delays and inconvenient medico-legal implications even though this procedure involves increased costs