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Objective The present study assessed agreement between resting cardiac output estimated by inert gas rebreathing (IGR) and thermodilution methods in patients with heart failure and those implanted with a left ventricular assist device (LVAD). Methods and Results Hemodynamic measurements were obtained in 42 patients, 22 with chronic heart failure and 20 with implanted continuous flow LVAD (34 males, aged 50 ± 11 years). Measurements were performed at rest using thermodilution and IGR methods. Cardiac output derived by thermodilution and IGR were not significantly different in LVAD (4.4 ± 0.9 L/min vs 4.7 ± 0.8 L/min, P = .27) or patients with heart failure (4.4 ± 1.4 L/min vs 4.5 ± 1.3 L/min, P = .75). There was a strong relationship between thermodilution and IGR cardiac index (r = 0.81, P = .001) and stroke volume index (r = 0.75, P = .001). Bland–Altman analysis showed acceptable limits of agreement for cardiac index derived by thermodilution and IGR, namely, the mean difference (lower and upper limits of agreement) for patients with heart failure –0.002 L/min/m2 (–0.65 to 0.66 L/min/m2), and –0.14 L/min/m2 (–0.78 to 0.49 L/min/m2) for patients with LVAD. Conclusions IGR is a valid method for estimating cardiac output and should be used in clinical practice to complement the evaluation and management of chronic heart failure and patients with an LVAD.

PURPOSE To assess the agreement between cardiac output estimated by two-dimensional echocardiography and bioreactance methods at rest and during dobutamine stress test in heart failure patients with preserved left ventricular ejection fraction (HFpEF). METHODS Hemodynamic measurements were assessed in 20 stable HFpEF patients (12 females; aged 61 ± 7 years) using echocardiography and bioreactance methods during rest and dobutamine stress test at increment dosages of 5, 10, 15, and 20 μg/kg/min until maximal dose was achieved or symptoms and sign occurred, that is, chest pain, abnormal blood pressure elevation, breathlessness, ischemic changes, or arrhythmia. RESULTS Resting cardiac output and cardiac index estimated by bioreactance and echocardiography were not significantly different. At peak dobutamine stress test, cardiac output and cardiac index estimated by echocardiography and bioreactance were significantly different (7.06 ± 1.43 vs 5.71 ± 1.59 L/min, P

Diagnostic tools available to support general practitioners diagnose heart failure (HF) are limited.(i) Determine the feasibility of the novel cardiac output response to stress (CORS) test in suspected HF patients, and (ii) Identify differences in the CORS results between (a) confirmed HF patients from non-HF patients, and (b) HF reduced (HFrEF) vs HF preserved (HFpEF) ejection fraction.Single centre, prospective, observational, feasibility study. Consecutive patients with suspected HF (N = 105; mean age: 72 ± 10 years) were recruited from specialized HF diagnostic clinics in secondary care. The consultant cardiologist confirmed or refuted a HF diagnosis. The patient completed the CORS but the researcher administering the test was blinded from the diagnosis. The CORS assessed cardiac function (stroke volume index, SVI) noninvasively using the bioreactance technology at rest-supine, challenge-standing, and stress-step exercise phases.A total of 38 patients were newly diagnosed with HF (HFrEF, n = 21) with 79% being able to complete all phases of the CORS (91% of non-HF patients). A 17% lower SVI was found in HF compared with non-HF patients at rest-supine (43 ± 15 vs 51 ± 16 mL/beat/m2, P = 0.02) and stress-step exercise phase (49 ± 16 vs 58 ± 17 mL/beat/m2, P = 0.02). HFrEF patients demonstrated a lower SVI at rest (39 ± 15 vs 48 ± 13 mL/beat/m2, P = 0.02) and challenge-standing phase (34 ± 9 vs 42 ± 12 mL/beat/m2, P = 0.03) than HFpEF patients.The CORS is feasible and patients with HF responded differently to non-HF, and HFrEF from HFpEF. These findings provide further evidence for the potential use of the CORS to improve HF diagnostic and referral accuracy in primary care.Heart failure (HF) is a global pandemic affecting 26 million people worldwide with an estimated 1 million people in the United Kingdom. Accurate early diagnosis of HF and the initiation of evidence-based treatment is essential to reduce morbidity and mortality and the associated burden on healthcare. As there are no state-of-the-art approaches, early diagnosis is challenging and often inaccurate, as initial signs and symptoms are nonspecific. We have developed an innovative test, named CORS (cardiac output response to stress test), to help general practitioners identify HF, which uses a method similar to an electrocardiogram and measures heart function at rest and during short step exercise. We recruited suspected HF patients from specialist HF diagnostic clinics in secondary care to complete the CORS test. We successfully demonstrated that 79% of patients with newly diagnosed HF (n = 38) and 91% of non-HF patients (n = 67) were able to complete all phases of the CORS test. Our findings demonstrate that newly diagnosed HF patients are able to complete this test, which provides further evidence for the potential use of the CORS test to improve HF diagnostic and referral accuracy in primary care.

Objectives: The aim of the present study was to assess the validity and trending ability of the bioreactance method in estimating cardiac output at rest and in response to stress in advanced heart failure patients and heart transplant candidates. Design: This was a prospective single-center study. Setting: This study was conducted at the heart transplant center at the Freeman Hospital, Newcastle upon Tyne, UK. Participants: Eighteen patients with advanced chronic heart failure due to reduced left ventricular ejection fraction (19 ± 7%), and peak oxygen consumption 12.3 ± 3.9 mL/kg/min. Interventions: Participants underwent right heart catheterization using the Swan-Ganz catheter. Measurements and Main Results: Cardiac output was measured simultaneously using thermodilution and bioreactance at rest and during active straight leg raise test to volitional exertion. There was no significant difference in cardiac index values obtained by the thermodilution and bioreactance methods (2.26 ± 0.59 v 2.38 ± 0.50 L/min, p > 0.05) at rest and peak straight leg raise test (2.92 ± 0.77 v 3.01 ± 0.66 L/min, p > 0.05). In response to active leg raise test, thermodilution cardiac output increased by 22% and bioreactance by 21%. There was also a strong relationship between cardiac outputs from both methods at rest (r = 0.88, p < 0.01) and peak straight leg raise test (r = 0.92, p < 0.01). Cartesian plot analysis showed good trending ability of bioreactance compared with thermodilution (concordance rate = 93%) Conclusions: `Cardiac output measured by the bioreactance method is comparable to that from the thermodilution method. Bioreactance method may be used in clinical practice to assess hemodynamics and improve management of advanced heart failure patients undergoing heart transplant assessment.

Background Physical activity plays an important role in the prevention of cardio-metabolic diseases. The present study evaluated the effect of habitual physical activity on body composition, peak oxygen consumption, cardiac and metabolic function. Methods This was a retrospective study. Data was collected between February 2014 and November 2015. Thirty-six healthy women (age 50±16 years) were stratified according to daily number of steps into low- ( 12500 steps/day, n=19). All participants underwent body composition assessment, oral glucose tolerance test and non-invasive gas-exchange and haemodynamic (bioreactance) measurements at rest and in response to maximal graded cardiopulmonary exercise test. Results The high active group averaged 16280±3205 steps/day and the low active group averaged 6285±943 steps/day (difference p=0.00). High-active women (vs. low active) demonstrated significantly lower body weight (62.1±12.3 vs. 71.2±9.1 kg, p=0.02), body fat (27.2±9.1 vs 37.7±6.4 %, p=0.00), but increased lean body mass (72.8±9.1 vs. 62.3±6.4 %, p=0.00). Peak oxygen consumption was significantly higher in high- versus low active women (2.0±0.5 vs. 1.5±0.2 l/min, p=0.00). There were no significant differences between the groups in fasting- and 2-hour glucose levels (4.9±0.6 vs. 4.8±0.5, p=0.45 and 4.8±1.3 vs. 5.5±1.4 mmol/L, p=0.16) haemodynamic measures of cardiac function including cardiac power output, cardiac output, stroke volume and arterial blood pressure at rest and in response to exercise stress test (p>0.05). Conclusions Increased levels of habitual physical activity improve body composition and peak oxygen consumption but appears to have limited effect cardio-metabolic function in middle-aged women.

SummaryPurpose This study assessed the agreement between cardiac output estimated by inert gas rebreathing and bioreactance methods at rest and during exercise. Methods Haemodynamic measurements were assessed in 20 healthy individuals (11 females, nine males; aged 32 ± 10 years) using inert gas rebreathing and bioreactance methods. Gas exchange and haemodynamic data were measured simultaneously under rest and different stages (i.e. 30, 60, 90, 120, 150 and 180 W) of progressive graded cardiopulmonary exercise stress testing using a bicycle ergometer. Results At rest, bioreactance produced significantly higher cardiac output values than inert gas rebreathing (7·8 ± 1·4 versus 6·5 ± 1·7 l min−1, P = 0·01). At low-to-moderate exercise intensities (i.e. 30–90 W), bioreactance produced significantly higher cardiac outputs compared with rebreathing method (P

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.

The present study evaluated reproducibility of the inert gas rebreathing method to estimate cardiac output at rest and during cardiopulmonary exercise testing. Thirteen healthy subjects (10 males, 3 females, ages 23–32 years) performed maximal graded cardiopulmonary exercise stress test using a cycle ergometer on 2 occasions (Test 1 and Test 2). Participants cycled at 30-watts/3-min increments until peak exercise. Hemodynamic variables were assessed at rest and during different exercise intensities (i. e., 60, 120, 150, 180 watts) using an inert gas rebreathing technique. Cardiac output and stroke volume were not significantly different between the 2 tests at rest 7.4 (1.6) vs. 7.1 (1.2) liters min−1, p=0.54; 114 (28) vs. 108 (15) ml beat−1, p=0.63) and all stages of exercise. There was a significant positive relationship between Test 1 and Test 2 cardiac outputs when data obtained at rest and during exercise were combined (r=0.95, p

Aim The present study assessed the effect of high intensity interval training on cardiac function during prolonged submaximal exercise in patients with type 2 diabetes. Methods Twenty-six patients with type 2 diabetes were randomized to a 12 week of high intensity interval training (3 sessions/week) or standard care control group. All patients underwent prolonged (i.e. 60 min) submaximal cardiopulmonary exercise testing (at 50% of previously assess maximal functional capacity) with non-invasive gas-exchange and haemodynamic measurements including cardiac output and stroke volume before and after the intervention. Results At baseline (prior to intervention) there was no significant difference between the intervention and control group in peak exercise oxygen consumption (20.3 ± 6.1 vs. 21.7 ± 5.5 ml/kg/min, p = 0.21), and peak exercise heart rate (156.3 ± 15.0 vs. 153.8 ± 12.5 beats/min, p = 0.28). During follow-up assessment both groups utilized similar amount of oxygen during prolonged submaximal exercise (15.0 ± 2.4 vs. 15.2 ± 2.2 ml/min/kg, p = 0.71). However, cardiac function i.e. cardiac output during submaximal exercise decreased significantly by 21% in exercise group (16.2 ± 2.7–12.8 ± 3.6 L/min, p = 0.03), but not in the control group (15.7 ± 4.9–16.3 ± 4.1 L/min, p = 0.12). Reduction in exercise cardiac output observed in the exercise group was due to a significant decrease in stroke volume by 13% (p = 0.03) and heart rate by 9% (p = 0.04). Conclusion Following high intensity interval training patients with type 2 diabetes demonstrate reduced cardiac output during prolonged submaximal cardiopulmonary exercise testing. Ability of patients to maintain prolonged increased metabolic demand but with reduced cardiac output suggests cardiac protective role of high intensity interval training in type 2 diabetes. Trial registration ISRCTN78698481. Registered 23 January 2013, retrospectively registered.

Purpose To determine parameters of exercise intolerance in a group of patients with HeartWare Ventricular Assist Device(HVAD) compared to a group of heart failure(HF)patients Methods This was a single-centre parallel prospective group-study.Echocardiograms,right heart catheterisation(RHC) and cardiopulmonary exercise tests were performed in 42patients admitted for a heart transplant assessment between August2017 and October2018:20 belonged to the HVAD group and 22 to the HF group Results HVADpatients had a better exercise capacity than HFpatients, although no significant differences were noted(14.0±5.0ml/kg/min vs 11.3±3.9ml/kg/min, p=0.06).To determine exercise tolerance,both HVAD and HFgroups were subdivided into 2 groups based on the median peakVO2.The table shows the comparison between preserved and non-preserved exercise tolerance in HF and HVADpatients. In the HVAD group,all resting RHC pressures were significantly lower in the preserved exercise capacity group.However,in HFpatients there were no statistically significant differences between both subgroups in right-sided pressures,but Thermodilution exercise-induced change in cardiac output(ΔCO) and cardiac index(ΔCI) was significantly higher in the patients with preserved exercise tolerance.In the HVADgroup the right ventricle was significantly larger in the reduced exercise tolerance subgroup.Patients with lower peakVO2 had more significant tricuspid regurgitation.Nevertheless,in HFpatients none of the echocardiographic parameters were related to the exercise capacity Conclusion Right-sided parameters in the echocardiogram and RHC pressures discriminate between preserved and non-preserved exercise capacity in HVADpatients,but not in HFpatients.In these last patients only ΔCO and ΔCI were statistically correlated with peak exercise oxygen consumption.

BackgroundPrimary care physicians lack access to an objective cardiac function test during diagnostic testing for suspected heart failure.AimTo determine the role of the novel Cardiac Output Response to Stress (CORS) test in the current diagnostic pathway for heart failure and the opportunities and challenges to potential implementation in primary care.MethodQualitative study using semi-structured in-depth interviews which were audiorecorded and transcribed verbatim. Data from the interviews were analysed thematically using an inductive approach. Fourteen healthcare professionals (six males, eight females) from primary (GPs, nurses, healthcare assistants, and practice managers) and secondary care (consultant cardiologists) participated.ResultsFour themes relating to opportunities and challenges surrounding the implementation of the new diagnostic technology were identified. These reflected that adoption of CORS test would be an advantage to primary care but the test had barriers to implementation which include establishment of clinical utility, suitability for immobile patients, and cost implication to GP practices.ConclusionThe development of a simple non-invasive clinical test to accelerate the diagnosis of heart failure in primary care maybe helpful to reduce unnecessary referrals to secondary care. The CORS test has the potential to serve this purpose however, factors such as cost-effectiveness, diagnostic accuracy, and seamless implementation in primary care have to be fully explored.

BackgroundWe developed a simple non-invasive Cardiac Output Response to Stress (CORS) Test to improve diagnosis and monitoring of heart failure in primary care.AimThe aim of the present study was to assess test-retest reproducibility of the CORS test.MethodThirty-two healthy volunteers (age, 64±10, female n=18) were recruited. Cardiac output was measured continuously using bioreactance method in supine and standing position, and during a two 3-min stages of a step-exercise protocol (10 and 15 steps per minute) using a 15-cm height bench. The CORS test was performed twice i.e. Test 1 and Test 2.ResultsCardiac output and stroke volume were not significantly different between the two tests at supine (6.2±1.4 versus 6.3±1.7 L/min, P = 0.84; 102±24 versus 108±32 ml/beat, P = 0.36), standing (5.7±2.1 versus 5.7±1.9 L/min, P = 0.99; 82±32 versus 83±29 ml/beat, P = 0.93), stage one step-exercise (8.5± 1.8 versus 8.2±1.9 L/min, P = 0.56; 104±26 versus 104±27 ml/beat, P = 0.99) and stage two step-exercise (9.9±1.7 versus 9.6±2.0 L/min, P = 0.51; 109±29 versus 111±26 ml/beat, P = 0.76). There was a significant positive relationship between Test 1 and Test 2 cardiac outputs (r=0.92, PConclusionThe CORS test demonstrates acceptable reproducibility and can potentially be used in primary care to identify and monitor heart failure.

AIMS: Primary care physicians lack access to an objective cardiac function test. This study for the first time describes a novel cardiac output response to stress (CORS) test developed to improve diagnosis and monitoring of heart failure in primary care and investigates its reproducibility. METHODS AND RESULTS: Prospective observational study recruited 32 consecutive primary care patients (age, 63 ± 9 years; female, n = 18). Cardiac output was measured continuously using the bioreactance method in supine and standing positions and during two 3 min stages of a step-exercise protocol (10 and 15 steps per minute) using a 15 cm height bench. The CORS test was performed on two occasions, i.e. Test 1 and Test 2. There was no significant difference between repeated measures of cardiac output and stroke volume at supine standing and Stage 1 and Stage 2 step exercises (all P > 0.3). There was a significant positive relationship between Test 1 and Test 2 cardiac outputs (r = 0.92, P = 0.01 with coefficient of variation of 7.1%). The mean difference in cardiac output (with upper and lower limits of agreement) between Test 1 and Test 2 was 0.1 (-1.9 to 2.1) L/min, combining supine, standing, and step-exercise data. CONCLUSIONS: The CORS, as a novel test for objective evaluation of cardiac function, demonstrates acceptable reproducibility and can potentially be implemented in primary care.