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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.

Background: Left ventricular assist devices (LVADs) have been used as an effective therapeutic option in patients with advanced heart failure, either as a bridge to transplantation, as destination therapy, or in some patients, as a bridge to recovery., Objectives: This study evaluated whether patients undergoing an LVAD bridge-to-recovery protocol can achieve cardiac and physical functional capacities equivalent to those of healthy controls., Methods: Fifty-eight male patients-18 implanted with a continuous-flow LVAD, 16 patients with LVAD explanted (recovered patients), and 24 heart transplant candidates (HTx)-and 97 healthy controls performed a maximal graded cardiopulmonary exercise test with continuous measurements of respiratory gas exchange and noninvasive (rebreathing) hemodynamic data. Cardiac function was represented by peak exercise cardiac power output (mean arterial blood pressure × cardiac output) and functional capacity by peak exercise O 2 consumption., Results: All patients demonstrated a significant exertional effort as demonstrated with the mean peak exercise respiratory exchange ratio >1.10. Peak exercise cardiac power output was significantly higher in healthy controls and explanted LVAD patients compared with other patients (healthy 5.35 ± 0.95 W; explanted 3.45 ± 0.72 W; LVAD implanted 2.37 ± 0.68 W; and HTx 1.31 ± 0.31 W; p < 0.05), as was peak O 2 consumption (healthy 36.4 ± 10.3 ml/kg/min; explanted 29.8 ± 5.9 ml/kg/min; implanted 20.5 ± 4.3 ml/kg/min; and HTx 12.0 ± 2.2 ml/kg/min; p < 0.05). In the LVAD explanted group, 38% of the patients achieved peak cardiac power output and 69% achieved peak O 2 consumption within the ranges of healthy controls., Conclusions: The authors have shown that a substantial number of patients who recovered sufficiently to allow explantation of their LVAD can even achieve cardiac and physical functional capacities nearly equivalent to those of healthy controls., (Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.)

Objectives: The objective of the study is to determine cardiac autonomic control in patients undergoing assessment for and/or LVAD therapy., Methods: Heart rate variability (HRV) was measured in 17 explanted LVAD, 17 implanted LVAD and 23 NYHA III-IV classified chronic heart failure (CHF) patients and ten healthy matched controls under three conditions: supine free breathing, standing and supine controlled breathing. Five measures of HRV were assessed: mean R-R interval (mR-R), high frequency (HF) and low frequency (LF) spectral power, LF in normalised units (LFnu), and LF to HF (LF:HF) ratio., Results: Repeat measures ANOVA showed significant (p < 0.05) differences in HRV between all three conditions within groups. Lower values were observed in CHF for LF(in log natural units) compared with explanted patients (-1.4 [95% CI -2.6 to -0.7], p = 0.04) and controls (-2.1 [-3.5 to -0.7], p = 0.001) and for LF:HF compared with implanted patients under paced breathing conditions (z = -2.7, p = 0.007) and controls in standing (z = -2.9, p = 0.004) and paced breathing conditions (z = -2.3, p = 0.02). However, no significant differences were seen between explanted, implanted and control groups under any condition., Conclusions: Patients implanted with an LVAD and explanted from a LVAD following myocardial recovery demonstrate a more normal dynamic response to autonomic stimuli and have a lower HRV risk profile compared to CHF patients., (© 2013.)

Cardiac power output is a direct measure of overall cardiac function that integrates both flow- and pressure-generating capacities of the heart. The present study assessed the reproducibility of cardiac power output and other more commonly reported cardiopulmonary exercise variables in patients with chronic heart failure. Metabolic, ventilatory and non-invasive (inert gas re-breathing) central haemodynamic measurements were undertaken at rest and near-maximal exercise of the modified Bruce protocol in 19 patients with stable chronic heart failure. The same procedure was repeated 7 days later to assess reproducibility. Cardiac power output was calculated as the product of cardiac output and mean arterial pressure. Resting central haemodynamic variables demonstrate low CV (coefficient of variation) (ranging from 3.4% for cardiac output and 5.6% for heart rate). The CV for resting metabolic and ventilatory measurements ranged from 8.2% for respiratory exchange ratio and 14.2% for absolute values of oxygen consumption. The CV of anaerobic threshold, peak oxygen consumption, carbon dioxide production and respiratory exchange ratio ranged from 3.8% (for anaerobic threshold) to 6.4% (for relative peak oxygen consumption), with minute ventilation having a CV of 11.1%. Near-maximal exercise cardiac power output and cardiac output had CVs of 4.1 and 2.2%, respectively. Cardiac power output demonstrates good reproducibility suggesting that there is no need for performing more than one cardiopulmonary exercise test. As a direct measure of cardiac function (dysfunction) and an excellent prognostic marker, it is strongly advised in the assessment of patients with chronic heart failure undergoing cardiopulmonary exercise testing.

Aim: Exercise-derived variables have been used in the assessment of functional capacity and prognosis in patients with chronic heart failure. The aim of this study was to assess the relationship between cardiac pumping capability represented by peak cardiac power output and peak oxygen consumption, anaerobic threshold, ventilatory efficiency slope, and peak circulatory power in patients undergoing the 'Harefield Protocol'., Methods and Results: Haemodynamic and gas exchange measurements were undertaken during a graded treadmill exercise test. They were performed on 54 patients-18 implanted with left ventricular assist devices (LVADs), 16 explanted (recovered), and 20 moderate-to-severe heart failure patients. Peak oxygen consumption was only highly correlated with peak cardiac power output in explanted LVAD (r = 0.85, P< 0.01), but not in implanted LVAD and heart failure patients (r = 0.55 and 0.53, P< 0.05). The anaerobic threshold was only modestly correlated with peak cardiac power output in heart failure and explanted (r = 0.46 and 0.54, P< 0.05) and weakly in implanted LVAD patients (r = 0.37, P< 0.05). Peak cardiac power output was well correlated with peak circulatory power in LVAD explanted and implanted (r = 0.82, P< 0.01; r = 0.63, P< 0.01) but not in heart failure patients (r = 0.31, P> 0.05). Ventilatory efficiency slope was only moderately correlated with peak cardiac power output in LVAD-explanted patients (r = -0.52, P< 0.05)., Conclusion: Exercise-derived prognostic indicators demonstrate limited capacity in reflecting cardiac pumping capability in patients treated with LVADs and should therefore be used with caution in interpretation of cardiac organ function.

Background: The use of the HeartMate II continuous-flow left ventricular assist device (LVAD) improves survival, quality of life and functional capacity of patients with advanced heart failure. However, no study so far has shown the benefits of these devices for cardiac function during peak exercise., Objective: To assess cardiac and exercise performance in patients implanted with the HeartMate II LVAD under two settings: (i) optimal device support and (ii) reduced device support., Methods: Twelve patients implanted with a HeartMate II LVAD performed a graded cardiopulmonary exercise test with respiratory gas exchange and non-invasive (rebreathing) haemodynamic measurements. After a 4 h resting period, patients performed an additional cardiopulmonary exercise test with reduced LVAD support (pump speed was reduced from optimal 9000-9600 to 6000 revs/min)., Results: In response to reduced HeartMate II LVAD support, resting cardiac power output and cardiac output decreased by 21% and 13%, respectively. Also at reduced device support, peak exercise cardiac power output was 39% lower (1.40+/-0.50 vs 2.31+/-0.58 W; p<0.05), peak cardiac output 30% lower (8.6+/-2.5 vs 12.2+/-2.1 l/min; p<0.05) and mean blood pressure 13% lower (74.3+/-14.9 vs 85.4+/-15.4 vs mm Hg; p<0.05). Exercise capacity was also diminished with 23% lower peak oxygen consumption (14.1+/-5.3 vs 18.2+/-4.5 ml/kg/min; p<0.05) and an 18% shorter exercise duration (516+/-119 vs 628+/-192 s; p<0.05)., Conclusion: It has been shown for the first time that the HeartMate II LVAD can confer both resting and peak cardiac functional benefits to patients with end-stage heart failure, thus improving exercise capacity.

Peak cardiac power output (CPO), as a direct measurement of overall cardiac function, has been shown to be a most powerful predictor of prognosis for patients with chronic heart failure. The present study assessed CPO and exercise performance in patients implanted with a left ventricular assist device (LVAD), those explanted due to myocardial recovery, and those with moderate to severe heart failure. Hemodynamic and respiratory gas exchange measurements were undertaken at rest and at peak graded exercise. These were performed in 54 patients-20 with moderate to severe heart failure, 18 with implanted LVADs, and 16 with explanted LVADs. At rest there was a nonsignificant difference in CPO among groups (p >0.05). Peak CPO was significantly higher in the explanted LVAD than in the heart failure and implanted LVAD groups (heart failure 1.90 +/- 0.45 W, implanted LVAD 2.37 +/- 0.55 W, explanted LVAD 3.39 +/- 0.61 W, p <0.01) as was peak cardiac output (heart failure 9.1 +/- 2.1 L/min, implanted LVAD 12.4 +/- 2.2 L/min, explanted LVD 14.6 +/- 2.9 L/min, p <0.01). Peak oxygen consumption was higher in the explanted LVAD than in the heart failure and implanted LVAD groups (heart failure 15.8 +/- 4.1 ml/kg/min, implanted LVAD 19.8 +/- 5.8 ml/kg/min, explanted LVAD 28.2 +/- 5.0 ml/kg/min, p <0.05) as was anaerobic threshold (heart failure 11.2 +/- 1.9 ml/kg/min, implanted LVAD 14.7 +/- 4.9 ml/kg/min, explanted LVAD 21.4 +/- 5.0 ml/kg/min, p <0.05). In conclusion, peak CPO differentiates well during cardiac restoration using LVADs and emphasizes the benefits of this therapy. CPO has the potential to be a key physiologic marker of heart failure severity and can guide management of patients with LVAD.

Background: Patients with chronic heart failure have a reduced quality of life due in part to their limited range of physical activity and independence., Objectives: The paper examines whether a physical activity 'lifestyle' intervention, based on motivational interviewing, will improve quality of life at five months from baseline, compared with conventional treatment., Methods: Sixty older patients with chronic heart failure were randomly assigned to either a 'standard care', 'motivational interviewing' or 'both' treatment groups for five months in 2002. The primary outcome measures were the Medical Outcomes Short Form-36 Health Survey, the disease-specific Minnesota Living with Heart Failure questionnaire and the Motivation Readiness for Physical Activity scale., Results: There were non-significant differences between the groups at baseline for age, coronary risk factors, severity of chronic heart failure, ejection fraction, specific laboratory tests, length of hospitalisation, medication and social support. Following treatment there was a significant increase (p<0.05) for three of the dimensions of the health survey in the 'motivational interviewing' group. All groups improved their scores (p<0.05) on the heart failure questionnaire. Over the five month period there was a general trend towards improvements in self-efficacy and motivation scores., Conclusions: This study has demonstrated that a 'motivational interviewing' intervention, incorporating behaviour change principles to promote physical activity, is effective in increasing selected aspects of a general quality of life questionnaire and a disease-specific quality of life questionnaire. Thus a 'motivational interviewing' approach is a viable option compared with traditional exercise programming. It is important to test these motivational interviewing interventions more widely, especially to match individuals to treatments.

Classic risk factors for mortality due to chronic heart failure (CHF), such as low left ventricular ejection fraction, NYHA functional stage, and increased heart rate perform well in the prediction of death from pump failure. The prediction of sudden cardiac death (SCD) remains somewhat problematic. Numerous studies have analyzed the potential contribution heart rate variability (HRV) can make to risk assessment in CHF. The aim of this review was to summarize the literature and identify the role HRV might play in identifying mode of death, as well as overall mortality risk. In studies where all-cause mortality or cardiac events were the clinical end point(s), global and slow oscillatory measures of HRV were the strongest risk predictors. In the fewer studies that used SCD as an end point, the strongest risk factors were HRV measures of short-term oscillations and sympathovagal interaction. We concluded from these findings that different HRV measurements predict different modes of death in CHF.Additionally, further studies using short-term analysis of HRV and non-linear analyses are warranted. Furthermore, studies with multiple end points, which clearly delineate pump failure from SCD, may be useful to identify more clearly the role HRV measures can play in the prediction of SCD.

In patients with cardiac failure, bioreactance-based cardiac output (CO) monitoring provides a valid non-invasive method for assessing cardiac performance during exercise. The purpose of this study was to evaluate the efficacy of this technique during strenuous exercise in healthy, trained individuals. Fourteen recreational cyclists, mean (SD) age of 34 (8) years and relative peak oxygen uptake of (VO(2)) 56 (6) ml kg(-1) min(-1), underwent incremental maximal exercise testing, whilst CO was recorded continuously using a novel bioreactance-based device (CO(bio)). The CO(bio) was evaluated against relationship with VO(2), theoretical calculation of arterial-venous oxygen difference (C(a - v) O(2)) and level of agreement with an inert gas rebreathing method (CO(rb)) using a Bland-Altman plot. Bioreactance-based CO measurement was practical and straightforward in application, although there was intermittent loss of electrocardiograph signal at high-intensity exercise. At rest and during exercise, CO(bio) was strongly correlated with VO(2) (r = 0.84; P < 0.001), however, there was evidence of systematic bias with CO(bio) providing lower values than CO(rb); mean bias (limits of agreement) -19% (14.6 to -53%). Likewise, calculated (C(a - v) O(2)) was greater when determined using CO(bio) than CO(rb) (P < 0.001), although both devices provided values in excess of those reported in invasive studies. Bioreactance-based determination of CO provides a pragmatic approach to the continuous assessment of cardiac performance during strenuous exercise in trained individuals. Our findings, however, suggest that further work is needed to refine the key measurement determinants of CO using this device to improve measurement accuracy in this setting. [ABSTRACT FROM AUTHOR]