Comparison of three methods to identify the anaerobic threshold during maximal exercise testing in patients with chronic heart failure.

OBJECTIVE: Exercise training efficiently improves peak oxygen uptake (V˙O2peak) in patients with chronic heart failure. To optimize training-derived benefit, higher exercise intensities are being explored. The correct identification of anaerobic threshold is important to allow safe and effective exercise prescription. DESIGN: During 48 cardiopulmonary exercise tests obtained in patients with chronic heart failure (59.6 ± 11 yrs; left ventricular ejection fraction, 27.9% ± 9%), ventilatory gas analysis findings and lactate measurements were collected. Three technicians independently determined the respiratory compensation point (RCP), the heart rate turning point (HRTP) and the second lactate turning point (LTP2). Thereafter, exercise intensity (target heart rate and workload) was calculated and compared between the three methods applied. RESULTS: Patients had significantly reduced maximal exercise capacity (68% ± 21% of predicted V˙O2peak) and chronotropic incompetence (74% ± 7% of predicted peak heart rate). Heart rate, workload, and V˙O2 at HRTP and at RCP were not different, but at LTP2, these parameters were significantly (P < 0.0001) higher. Mean target heart rate and target workload calculated using the LTP2 were 5% and 12% higher compared with those calculated using HRTP and RCP, respectively. The calculation of target heart rate based on LTP2 was 5% and 10% higher in 12 of 48 (25%) and 6 of 48 (12.5%) patients, respectively, compared with the other two methods. CONCLUSIONS: In patients with chronic heart failure, RCP and HRTP, determined during cardiopulmonary exercise tests, precede the occurrence of LTP2. Target heart rates and workloads used to prescribe tailored exercise training in patients with chronic heart failure based on LTP2 are significantly higher than those derived from HRTP and RCP.

Impact of exercise testing mode on exercise parameters in patients with chronic heart failure.

AIM: To verify the impact of testing mode on maximal, sub-maximal parameters and on cardiopulmonary exercise test (CPET) derived prognostic markers in patients with chronic heart failure (CHF). METHOD: 55 patients (age 60.3 years ±11.1) with CHF (ejection fraction 26 %±8) underwent a maximal CPET on a bicycle and on a treadmill, in a random order, within one week. Maximal, sub-maximal parameters and CPET derived prognostic markers were compared. RESULTS: VO(2)peak and VO(2)peak corrected for lean body mass were significantly higher on treadmill compared to bicycle (+11%, p < 0.0001). This was also the case for the following sub-maximal parameters; heart rate, workload and VO(2) at ventilatory anaerobic threshold and VO(2) at the respiratory compensation point (RCP). In contrast, both VE/VCO(2) slopes (start to RCP and start to end test) were similar. Time to 1/2 VO(2)peak was longer and circulatory power was higher on the treadmill compared to exercise testing on the bicycle. CONCLUSION: The results of the present study suggest that the mode of exercise testing significantly affects absolute values for VO(2)peak but does not greatly impact the prognostic utility of the VE/VCO(2) slope in patients with moderate to severe CHF. Besides the consequences of these findings in terms of prognostication, testing mode should be taken into consideration when exercise prescription is based on VO(2)peak.

Red cell distribution width as a marker of impaired exercise tolerance in patients with chronic heart failure.

AIMS: Exercise intolerance predicts mortality in patients with chronic heart failure (CHF). Recently, increased red cell distribution width (RDW) has emerged as an additional powerful predictor of poor outcome. We investigated the relationship between RDW and exercise capacity in patients with CHF. In addition, the association between training-induced improved maximal aerobic capacity (VO(2)peak) and RDW was studied. METHODS AND RESULTS: Stable and optimally treated CHF patients (n = 118) with a left ventricular ejection fraction (LVEF) <40% were included. RDW and cardiopulmonary exercise testing were obtained at baseline and after 6 months of exercise training (n = 71) or a sedentary lifestyle (n = 47). At baseline, log[RDW] was inversely related to VO(2)peak (P = 0.003), independently of disease severity [LVEF, New York Heart Association class, N-terminal pro brain natriuretic peptide (NT-proBNP)] and haemoglobin. Exercise training was associated with a decrease in RDW compared with controls (P < 0.0001 for interaction), independent of baseline VO(2)peak, haemoglobin, and NT-proBNP levels. The change in RDW after 6 months was significantly related to the change in VO(2)peak (r= -0.248, P = 0.009). CONCLUSIONS: Higher RDW is independently related to impaired exercise capacity in CHF patients. Increased VO(2)peak following exercise training relates to the observed changes in RDW. Whether increased RDW is a marker of impaired exercise tolerance, or plays a pathophysiological role in impaired oxygen transport, deserves further investigation.

Exercise training improves function of circulating angiogenic cells in patients with chronic heart failure.

Alterations in circulating angiogenic cells (CAC) and endothelial progenitor cells (EPC), known to contribute to endothelial repair, could explain the reversal of endothelial function in response to exercise training. Moreover, training-induced vascular remodeling might affect the acute response of EPC and CAC following a single exercise bout. We studied the impact of exercise training on CAC function and numbers of CD34(+)/KDR(+) EPC in patients with chronic heart failure (CHF) and we assessed the effect of acute exercise on CAC and EPC in sedentary and trained patients. Twenty-one sedentary CHF patients underwent 6-month exercise training and were compared to a non-trained control group (n = 17) and 10 healthy age-matched subjects. At baseline and follow-up, flow-mediated dilation was assessed and graded exercise testing (GXT) was performed. Before and immediately after GXT, CAC migratory capacity was assessed in vitro and circulating CD34(+)/KDR(+) EPC were quantified using flow cytometry. At baseline, CAC migration was significantly impaired in sedentary CHF patients but normalized acutely after GXT. Training corrected endothelial dysfunction, which coincided with a 77% increase in CAC migration (P = 0.0001). Moreover, the GXT-induced improvement detected at baseline was no longer observed after training. Numbers of CD34(+)/KDR(+) EPC increased following 6-month exercise training (P = 0.021), but were not affected by GXT, either prior or post-training. In conclusion, the present findings demonstrate for the first time that exercise training in CHF reverses CAC dysfunction and increases numbers of CD34(+)/KDR(+) EPC, which is accompanied by improvement of peripheral endothelial function. The acute exercise-induced changes in CAC function wane with exercise training, suggesting that repetitive exercise bouts progressively lead to functional endothelial repair.

Maintaining physical fitness of patients with chronic heart failure: a randomized controlled trial.

BACKGROUND: We aimed to compare the effects of three different training advices, after 1 year, following a 6 months supervised cardiac rehabilitation period in patients with chronic heart failure (CHF). METHODS: Sixty-nine CHF patients were randomized, at the end of their rehabilitation period, either to usual care (UC) or to UC and controlled home training (HT), prolonged supervised training (ST) or preferred training (PT). Treadmill cardio-pulmonary exercise testing was performed before rehabilitation, postrehabilitation and thereafter at 3-month intervals during the 1-year follow-up. submaximal exercise capacity [Oxygen consumption and workload at the respiratory compensation point (VO2RCP, WattRCP) and submaximal workload (SMW) efficiency (SMW/HR) at 70% of the initial maximal workload] was chosen as a primary endpoint, because health status in CHF patients depends largely on their ability to perform activities at a submaximal level. RESULTS: After 6 months of rehabilitation, the four groups (UC, HT, ST and PT) were comparable with regard to cardiac rehabilitation-derived benefit, both at the submaximal and maximal level. Although exercise capacity during follow-up declined in both UC and HT patients, ST and especially PT patients maintained and even improved VO2peak and VO2RCP. However, only PT patients managed to maintain or even increase submaximal (WattRCP and SMW/HR ratio) workload (P=0.045 and <0.0001 for interaction, respectively). Ventilatory-derived prognostic markers during treadmill cardio pulmonary exercise testing evolved similarly in the four subgroups. CONCLUSION: This study suggests that engagement in physical training of their own choice (PT), might be the optimal training modality for maintaining physical capacity in CHF patients.

Exercise acutely reverses dysfunction of circulating angiogenic cells in chronic heart failure.

AIMS: Recruitment of endothelial progenitor cells (EPCs) and enhanced activity of circulating angiogenic cells (CACs) might explain the benefits of exercise training in reversing endothelial dysfunction in chronic heart failure (CHF) patients. We studied baseline EPC numbers and CAC function and the effect of a single exercise bout. METHODS AND RESULTS: Forty-one CHF patients (mild, n = 22; severe, n = 19) and 13 healthy subjects were included. Migratory activity of CACs was evaluated in vitro and circulating CD34+ and CD34+/KDR+ (EPC) cells were quantified by flow cytometry before and after cardiopulmonary exercise testing (CPET). Circulating stromal cell-derived factor-1alpha (SDF-1alpha) and vascular endothelial growth factor (VEGF) concentrations were measured. Both CAC migration as well as CD34+ cell numbers were significantly reduced in CHF, whereas CD34+/KDR+ cells were not different from controls. Endothelial dysfunction was related to impaired CAC migration (r = 0.318, P = 0.023). Cardiopulmonary exercise testing improved CAC migration in severe (+52%, P < 0.005) and mild CHF (+31%, P < 0.005), restoring it to levels similar to controls. Following CPET, SDF-1alpha increased in healthy controls and mild CHF (P < 0.005). Vascular endothelial growth factor, CD34+, and CD34+/KDR+ cell numbers remained unchanged. CONCLUSION: The present findings reveal a potent stimulus of acute exercise to reverse CAC dysfunction in CHF patients with endothelial dysfunction.

Combined endurance-resistance training vs. endurance training in patients with chronic heart failure: a prospective randomized study.

AIMS: This study was designed to compare the effects of combined endurance-resistance training (CT) with endurance training (ET) only on submaximal and maximal exercise capacity, ventilatory prognostic parameters, safety issues, and quality of life in patients with chronic heart failure (CHF). METHODS AND RESULTS: Fifty-eight CHF patients (NYHA class II-III) were randomized either to 6 months CT [n = 28, 58 years, left ventricular ejection fraction (LVEF) 26%, VO(2)peak 18.1 mL/kg/min] or ET (n = 30, 59 years, LVEF 23%, VO(2)peak 21.3 mL/kg/min). The increase in steady-state workload (P = 0.007) and the decrease in heart rate at SSW (P = 0.002) were significantly larger in CT- compared with ET-trained patients. Maximal exercise capacity (i.e. VO(2)peak, maximal workload) and work-economy (Wattmax/VO(2)peak) evolved similarly. VO(2)peak halftime was reduced following CT (P = 0.001). Maximal strength in upper limbs increased significantly (P < 0.001) in favour of the CT group. CT also had a beneficial effect on health-related quality of life, i.e. 60% of CT-trained patients vs. 28% of ET-trained patients reported a decrease in cardiac symptoms (OR = 3.86, 95% CI 1.11-12.46, P = 0.03). There were no differences with regard to improved LVEF, evolution of left ventricular dimensions, nor outcome data (mortality and cardiovascular hospital admissions during follow-up). CONCLUSION: In CHF patients, CT had a more pronounced effect on submaximal exercise capacity, muscle strength, and quality of life. The absence of unfavourable effects on left ventricular remodelling and outcome parameters is reassuring and might facilitate further implementation of this particular training modality.