Exercise performance, haemodynamics, and respiratory pattern do not identify heart failure patients who end exercise with dyspnoea from those with fatigue

Non-Invasive Cardiac Output Measurement Using Inert Gas Rebreathing Method during Cardiopulmonary Exercise Testing-A Systematic Review

BACKGROUND

The use of inert gas rebreathing for the non-invasive cardiac output measurement has produced measurements comparable to those obtained by various other methods. However, there are no guidelines for the inert gas rebreathing method during a cardiopulmonary exercise test (CPET). In addition, there is also a lack of specific standards for assessing the non-invasive measurement of cardiac output during CPET, both for healthy patients and those suffering from diseases and conditions.

AIM

This systematic review aims to describe the use of IGR for a non-invasive assessment of cardiac output during cardiopulmonary exercise testing and, based on the information extracted, to identify a proposed CPET report that includes an assessment of the cardiac output using the IGR method.

METHODS

This systematic review was conducted by PRISMA (Preferred Reporting Items for Systematic Reviews and Meta Analyses) guidelines. PubMed, Web of Science, Scopus, and Cochrane Library databases were searched from inception until 29 December 2022. The primary search returned 261 articles, of which 47 studies met the inclusion criteria for this review.

RESULTS AND CONCLUSIONS

This systematic review provides a comprehensive description of protocols, indications, technical details, and proposed reporting standards for a non-invasive cardiac output assessment using IGR during CPET. It highlights the need for standardized approaches to CPET and identifies gaps in the literature. The review critically analyzes the strengths and limitations of the studies included and offers recommendations for future research by proposing a combined report from CPET-IGR along with its clinical application.

Cardiac output changes during exercise in heart failure patients: focus on mid-exercise

Aims

Peak exercise oxygen uptake (VO₂) and cardiac output (CO) are strong prognostic indexes in heart failure (HF) but unrelated to real‐life physical activity, which is associated to submaximal effort.

Methods and results

We analysed maximal cardiopulmonary exercise test with rest, mid‐exercise, and peak exercise non‐invasive CO measurements (inert gas rebreathing) of 231 HF patients and 265 healthy volunteers. HF patients were grouped according to exercise capacity (peak VO₂ < 50% and ≥50% pred, Groups 1 and 2). To account for observed differences, data regarding VO₂, CO, stroke volume (SV), and artero‐venous O₂ content difference [ΔC(a‐v)O₂] were adjusted by age, gender, and body mass index. A multiple regression analysis was performed to predict peak VO₂ from mid‐exercise cardiopulmonary exercise test and CO parameters among HF patients. Rest VO₂ was lower in HF compared with healthy subjects; meanwhile, Group 1 patients had the lowest CO and highest ΔC(a‐v)O₂. At mid‐exercise, Group 1 patients achieved a lower VO₂, CO, and SV [0.69 (interquartile range 0.57–0.80) L/min; 5.59 (4.83–6.67) L/min; 62 (51–73) mL] than Group 2 [0.94 (0.83–1.1) L/min; 7.6 (6.56–9.01) L/min; 77 (66–92) mL] and healthy subjects [1.15 (0.93–1.30) L/min; 9.33 (8.07–10.81) L/min; 87 (77–102) mL]. Rest to mid‐exercise SV increase was lower in Group 1 than Group 2 (P = 0.001) and healthy subjects (P < 0.001). At mid‐exercise, ΔC(a‐v)O₂ was higher in Group 2 [13.6 (11.8–15.4) mL/100 mL] vs. healthy patients [11.6 (10.4–13.2) mL/100 mL] (P = 0.002) but not different from Group 1 [13.6 (12.0–14.9) mL/100 mL]. At peak exercise, Group 1 patients achieved a lower VO₂, CO, and SV than Group 2 and healthy subjects. ΔC(a‐v)O₂ was the highest in Group 2. At multivariate analysis, a model comprising mid‐exercise VO₂, carbon dioxide production (VCO₂), CO, haemoglobin, and weight predicted peak VO₂, P < 0.001. Mid‐exercise VO₂ and CO, haemoglobin, and weight added statistically significantly to the prediction, P < 0.050.

Conclusions

Mid‐exercise VO₂ and CO portend peak exercise values and identify severe HF patients. Their evaluation could be clinically useful.

How Patients With Heart Failure Perform Daily Life Activities

Background:

Cardiopulmonary exercise test and 6-minute walking test are frequently used tools to evaluate physical performance in heart failure (HF), but they do neither represent activities of daily living (ADLs) nor fully reproduce patients’ symptoms. We assessed differences in task oxygen uptake, both as absolute value and as percentage of peak oxygen consumption (peakVO 2 ), ventilation efficiency (VE/VCO 2 ratio), and dyspnea intensity (Borg scale) in HF and healthy subjects during standard ADLs and other common physical actions.

Methods:

Healthy and HF subjects (ejection fraction <45%, stable conditions) underwent cardiopulmonary exercise test. All of them, carrying a wearable metabolic cart, performed a 6-minute walking test, two 4-minute treadmill exercises (at 2 and 3 km/h), and ADLs: ADL1 (getting dressed), ADL2 (folding 8 towels), ADL3 (putting away 6 bottles), ADL4 (making a bed), ADL5 (sweeping the floor for 4 minutes), ADL6 (climbing 1 flight of stairs carrying a load).

Results:

Sixty patients with HF (age 65.2±12.1 years; ejection fraction 30.4±6.7%, peakVO 2 14.2±4.0 mL/[min·kg]) and 40 healthy volunteers (58.9±8.2 years, peakVO 2 28.1±7.4 mL/[min·kg]) were enrolled. For each exercise, patients showed higher VE/VCO 2 ratio, percentage of peakVO 2 , and Borg scale value than controls, while absolute values of task oxygen uptake and exercise duration were lower and higher, respectively, in all activities, except for treadmill (fixed execution time and intensity). Differently from Borg Scale data, metabolic values and exercise time length changed in parallel with HF severity, except for ADL duration in very short (ADL3) and composite (ADL1) activities. Borg scale values correlated with percentage of peakVO 2 .

Conclusions:

During ADLs, patients self-regulated activities in parallel with HF severity by decreasing intensity (VO 2 ) and prolonging the effort.

RETRACTED: Down-regulated microRNA-195-5p and up-regulated CXCR4 attenuates the heart function injury of heart failure mice via inactivating JAK/STAT pathway

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. Concern was raised about the integrity of the images in Figure 6, which appear to contain suspected image duplications, as detailed here: https://pubpeer.com/publications/A31DE9EEF13ED6B88BCC86A9CAC8D9 and here: https://docs.google.com/spreadsheets/d/1r0MyIYpagBc58BRF9c3luWNlCX8VUvUuPyYYXzxWvgY/edit#gid=262337249. Most of these image duplications involve either pasting portions of one image into another, or rotating/flipping the image. Numerous additional suspected image duplications were detected within Figures 2A and 7A. The journal requested the corresponding author comment on these concerns and provide the raw data. The authors did not respond to this request and therefore the Editor-in-Chief decided to retract the article.

Carotid chemoreflex and muscle metaboreflex interact to the regulation of ventilation in patients with heart failure with reduced ejection fraction

Synergism among reflexes probably contributes to exercise hyperventilation in patients with heart failure with reduced ejection fraction (HFrEF). Thus, we investigated whether the carotid chemoreflex and the muscle metaboreflex interact to the regulation of ventilation ( V ˙ E ) in HFrEF. Ten patients accomplished 4-min cycling at 60% peak workload and then recovered for 2 min under either: (a) 21% O2 inhalation (tonic carotid chemoreflex activity) with legs' circulation free (inactive muscle metaboreflex); (b) 100% O2 inhalation (suppressed carotid chemoreflex activity) with legs' circulation occluded (muscle metaboreflex activation); (c) 21% O2 inhalation (tonic carotid chemoreflex activity) with legs' circulation occluded (muscle metaboreflex activation); or (d) 100% O2 inhalation (suppressed carotid chemoreflex activity) with legs' circulation free (inactive muscle metaboreflex) as control. V ˙ E , tidal volume (VT ) and respiratory frequency (fR ) were similar between each separated reflex (protocols a and b) and control (protocol d). Calculated sum of separated reflexes effects was similar to control. Oppositely, V ˙ E (mean ± SEM: Δ vs. control = 2.46 ± 1.07 L/min, p = .05) and fR (Δ = 2.47 ± 0.77 cycles/min, p = .02) increased versus control when both reflexes were simultaneously active (protocol c). Therefore, the carotid chemoreflex and the muscle metaboreflex interacted to V ˙ E regulation in a fR -dependent manner in patients with HFrEF. If this interaction operates during exercise, it can have some contribution to the HFrEF exercise hyperventilation.

Exercise performance, haemodynamics, and respiratory pattern do not identify heart failure patients who end exercise with dyspnoea from those with fatigue

AIMS

The two main symptoms referred by chronic heart failure (HF) patients as the causes of exercise termination during maximal cardiopulmonary exercise testing (CPET) are muscular fatigue and dyspnoea. So far, a physiological explanation why some HF patients end exercise because of dyspnoea and others because of fatigue is not available. We assessed whether patients referring dyspnoea or muscular fatigue may be distinguished by different ventilator or haemodynamic behaviours during exercise.

METHODS AND RESULTS

We analysed exercise data of 170 consecutive HF patients with reduced left ventricular ejection fraction in stable clinical condition. All patients underwent maximal CPET and a second maximal CPET with measurement of cardiac output by inert gas rebreathing at peak exercise. Thirty-eight (age 65.0 ± 11.1 years) and 132 (65.1 ± 11.4 years) patients terminated CPET because of dyspnoea and fatigue, respectively. Haemodynamic and cardiorespiratory parameters were the same in fatigue and dyspnoea patients. VO₂ was 10.4 ± 3.2 and 10.5 ± 3.3 mL/min/kg at the anaerobic threshold and 15.5 ± 4.8 and 15.4 ± 4.3 at peak, in fatigue and dyspnoea patients, respectively. In fatigue and dyspnoea patients, peak heart rate was 110 ± 22 and 114 ± 22 beats/min, and VE/VCO₂ and VO₂ /work relationship slopes were 31.2 ± 6.8 and 30.6 ± 8.2 and 10.6 ± 4.2 and 11.4 ± 5.5 L/min/W, respectively. Peak cardiac output was 6.68 ± 2.51 and 6.21 ± 2.55 L/min (P = NS for all).

CONCLUSIONS

In chronic HF patients in stable clinical condition, fatigue and dyspnoea as reasons of exercise termination do not highlight different ventilatory or haemodynamic patterns during effort.