Dynamic trend of lung fluid movement during exercise in heart failure: From lung imaging to alveolar-capillary membrane function

BACKGROUND

In chronic heart failure (HF), exercise-induced increase in pulmonary capillary pressure may cause an increase of pulmonary congestion, or the development of pulmonary oedema. We sought to assess in HF patients the exercise-induced intra-thoracic fluid movements, by measuring plasma brain natriuretic peptide (BNP), lung comets and lung diffusion for carbon monoxide (DLCO) and nitric oxide (DLNO), as markers of hemodynamic load changes, interstitial space and alveolar-capillary membrane fluids, respectively.

METHODS AND RESULTS

Twenty-four reduced ejection fraction HF patients underwent BNP, lung comets and DLCO/DLNO measurements before, at peak and 1 h after the end of a maximal cardiopulmonary exercise test. BNP significantly increased at peak from 549 (328-841) to 691 (382-1207, p < 0.0001) pg/mL and almost completely returned to baseline value 1 h after exercise. Comets number increased at peak from 9.4 ± 8.2 to 24.3 ± 16.7, returning to baseline (9.7 ± 7.4) after 1 h (p < 0.0001). DLCO did not change significantly at peak (from 18.01 ± 4.72 to 18.22 ± 4.73 mL/min/mmHg), but was significantly reduced at 1 h (16.97 ± 4.26 mL/min/mmHg) compared to both baseline (p = 0.0211) and peak (p = 0.0174). DLNO showed a not significant trend toward lower values 1 h post-exercise.

CONCLUSIONS

Moderate/severe HF patients have a 2-step intra-thoracic fluid movement with exercise: the first during active exercise, from the vascular space toward the interstitial space, as confirmed by comets increase, without any effect on diffusion, and the second, during recovery, toward the alveolar-capillary membrane, clearing the interstitial space but worsening gas diffusion.

Taking a walk on the heart failure side: comparison of metabolic variables during walking and maximal exertion

AIMS

Although cardiopulmonary exercise testing (CPET) is the gold standard to assess exercise capacity, simpler tests (i.e., 6-min walk test, 6MWT) are also commonly used. The aim of this study was to evaluate the relationship between cardiorespiratory parameters during CPET and 6MWT in a large, multicentre, heterogeneous population.

METHODS

We included athletes, healthy subjects, and heart failure (HF) patients of different severity, including left ventricular assist device (LVAD) carriers, who underwent both CPET and 6MWT with oxygen consumption measurement.

RESULTS

We enrolled 186 subjects (16 athletes, 40 healthy, 115 non-LVAD HF patients, and 15 LVAD carriers). CPET-peakV̇O2 was 41.0 [35.0-45.8], 26.2 [23.1-31.0], 12.8 [11.1-15.3], and 15.2 [13.6-15.6] ml/Kg/min in athletes, healthy, HF patients, and LVAD carriers, respectively (P < 0.001). During 6MWT they used 63.5 [56.3-76.8], 72.0 [57.8-81.0], 95.5 [80.3-109], and 95.0 [92.0-99.0] % of their peakV̇O2, respectively. None of the athletes, 1 healthy (2.5%), 30 HF patients (26.1%), and 1 LVAD carrier (6.7%), reached a 6MWT-V̇O2 higher than their CPET-peakV̇O2. Both 6MWT-V̇O2 and walked distance were significantly associated with CPET-peakV̇O2 in the whole population (R2 = 0.637 and R2 = 0.533, P ≤ 0.001) but not in the sub-groups. This was confirmed after adjustment for groups.

CONCLUSIONS

The 6MWT can be a maximal effort especially in most severe HF patients and suggest that, in absence of prognostic studies related to 6MWT metabolic values, CPET should remain the first method of choice in the functional assessment of patients with HF as well as in sport medicine.

Symptomatic post COVID patients have impaired alveolar capillary membrane function and high VE/VCO2

BACKGROUND

Post COVID-19 syndrome is characterized by several cardiorespiratory symptoms but the origin of patients' reported symptomatology is still unclear.

METHODS

Consecutive post COVID-19 patients were included. Patients underwent full clinical evaluation, symptoms dedicated questionnaires, blood tests, echocardiography, thoracic computer tomography (CT), spirometry including alveolar capillary membrane diffusion (DM) and capillary volume (Vcap) assessment by combined carbon dioxide and nitric oxide lung diffusion (DLCO/DLNO) and cardiopulmonary exercise test. We measured surfactant derive protein B (immature form) as blood marker of alveolar cell function.

RESULTS

We evaluated 204 consecutive post COVID-19 patients (56.5 ± 14.5 years, 89 females) 171 ± 85 days after the end of acute COVID-19 infection. We measured: forced expiratory volume (FEV1) 99 ± 17%pred, FVC 99 ± 17%pred, DLCO 82 ± 19%, DM 47.6 ± 14.8 mL/min/mmHg, Vcap 59 ± 17 mL, residual parenchymal damage at CT 7.2 ± 3.2% of lung tissue, peakVO2 84 ± 18%pred, VE/VCO2 slope 112 [102-123]%pred. Major reported symptoms were: dyspnea 45% of cases, tiredness 60% and fatigability 77%. Low FEV1, Vcap and high VE/VCO2 slope were associated with persistence of dyspnea. Tiredness was associated with high VE/VCO2 slope and low PeakVO2 and FEV1 while fatigability with high VE/VCO2 slope. SPB was fivefold higher in post COVID-19 than in normal subjects, but not associated to any of the referred symptoms. SPB was negatively associated to Vcap.

CONCLUSIONS

In patients with post COVID-19, cardiorespiratory symptoms are linked to VE/VCO2 slope. In these patients the alveolar cells are dysregulated as shown by the very high SPB. The Vcap is low likely due to post COVID-19 pulmonary endothelial/vasculature damage but DLCO is only minimally impaired being DM preserved.

Activities of daily living in heart failure patients and healthy subjects: when the cardiopulmonary assessment goes beyond traditional exercise test protocols

Heart failure (HF) patients traditionally report dyspnoea as their main symptom. Although the cardiopulmonary exercise test (CPET) and 6 min walking test are the standardized tools in assessing functional capacity, neither cycle ergometers nor treadmill maximal efforts do fully represent the actual HF patients' everyday activities [activities of daily living (ADLs)] (i.e. climbing the stairs). New-generation portable metabolimeters allow the clinician to measure task-related oxygen intake (VO2) in different scenarios and exercise protocols. In the last years, we have made considerable progress in understanding the ventilatory and metabolic behaviours of HF patients and healthy subjects during tasks aimed to reproduce ADLs. In this paper, we describe the most recent findings in the field, with special attention to the relationship between the metabolic variables obtained during ADLs and CPET parameters (i.e. peak VO2), demonstrating, for example, how exercises traditionally thought to be undemanding, such as a walk, instead represent supramaximal efforts, particularly for subjects with advanced HF and/or artificial heart (left ventricular assist devices) wearers.

The alveolar-capillary unit in the physiopathological conditions of heart failure: identification of a potential marker

In this review, we describe the structure and function of the alveolar-capillary membrane and the identification of a novel potential marker of its integrity in the context of heart failure (HF). The alveolar-capillary membrane is indeed a crucial structure for the maintenance of the lung parenchyma gas exchange capacity, and the occurrence of pathological conditions determining lung fluids accumulation, such as HF, might significantly impair lung diffusion capacity altering the alveolar-capillary membrane protective functions. In the years, we found that the presence of immature forms of the surfactant protein-type B (proSP-B) in the circulation reflects alterations in the alveolar-capillary membrane integrity. We discussed our main achievements showing that proSP-B, due to its chemical properties, specifically binds to high-density lipoprotein, impairing their antioxidant activity, and likely contributing to the progression of the disease. Further, we found that immature proSP-B, not the mature protein, is related to lung abnormalities, more precisely than the lung function parameters. Thus, to the list of the potential proposed markers of HF, we add proSP-B, which represents a precise marker of alveolar-capillary membrane dysfunction in HF, correlates with prognosis, and represents a precocious marker of drug therapy.

Dysregulation of ventilation at day and night time in heart failure

Heart failure (HF) is characterized by an increase in ventilatory response to exercise of multifactorial aetiology and by a dysregulation in the ventilatory control during sleep with the occurrence of both central and obstructive apnoeas. In this setting, the study of the ventilatory behaviour during exercise, by cardiopulmonary exercise testing, or during sleep, by complete polysomnography or simplified nocturnal cardiorespiratory monitoring, is of paramount importance because of its prognostic value and of the possible effects of sleep-disordered breathing on the progression of the disease. Moreover, several therapeutic interventions can significantly influence ventilatory control in HF. Also, rest daytime monitoring of cardiac, metabolic, and respiratory activities through specific wearable devices could provide useful information for HF management. The aim of the review is to summarize the main studies conducted at Centro Cardiologico Monzino on these topics.

Integration of a body sensor network of wearable devices for cardio-respiratory monitoring

Wearable devices represent a non-invasive tool to monitor cardio-respiratory parameters. This paper presents a telemedicine platform constituted of four wireless units. Three wearable inertial measurement units monitor the respiratory-related excursions of the thorax and of the abdomen with respect to a reference unit (positioned on the lower back), through which respiratory rate and normalized tidal volume are extracted. The fourth unit is a reflectance wrist-worn pulse oximeter. To validate the system, 20 healthy volunteers (12 men) participated in a protocol designed to induce desaturation conditions and subsequent changes in the respiratory pattern by means of rebreathing. The results were evaluated against two different gold standards (SenTec for pulse oximetry and Cardiopulmonary Exercise Testing machine for all units) with Bland-Altman analyses. The resulting biases for the oxygen saturation comparison between the device to be validated and the SenTec and CPET systems are -0.90% and -2.68% respectively, with agreement intervals equal to [-6.37, 4.57] and [-9.00, 3.63]. Regarding the respiratory rate comparison with respect to the CPET system, the bias is -0.01 bpm with a [-11.36, 11.35] agreement interval.Clinical Relevance-This paper provides a validation of an integrated non-invasive wearable system for cardio-respiratory monitoring to be used outside of clinical settings and during the daily life of patients.

Influence of exertional oscillatory breathing and its temporal behavior in patients with heart failure and reduced ejection fraction

BACKGROUND

Exertional oscillatory breathing (EOV) represents an emerging prognostic marker in heart failure (HF) patients, however little is known about EOV meaning with respect to its disappearance/persistence during cardiopulmonary exercise test (CPET). The present single-center study evaluated EOV clinical and prognostic impact in a large cohort of reduced ejection fraction HF patients (HFrEF) and, contextually, if a specific EOV temporal behavior might be an addictive risk predictor.

METHODS AND RESULTS

Data from 1.866 HFrEF patients on optimized medical therapy were analysed. The primary cardiovascular (CV) study end-point was cardiovascular death, heart transplantation or LV assistance device (LVAD) implantation at 5-years. For completeness a secondary end-point of total mortality at 5- years was also explored. EOV presence was identified in 251 patients (13%): 142 characterized by EOV early cessation (Group A) and 109 by EOV persistence during the whole CPET (Group B). The entire EOV Group showed worse clinical and functional status than NoEOV Group (n = 1.615) and, within the EOV Group, Group B was characterized by a more severe HF. At CV survival analysis, EOV patients showed a poorer outcome than the NoEOV Group (events 27.1% versus 13.1%, p < 0.001) both unpolished and after matching for main confounders. Instead, no significant differences were found between EOV Group A and B with respect to CV outcome. Conversely the analysis for total mortality failed to be significant.

CONCLUSIONS

Our analysis, albeit retrospective, supports the inclusion of EOV into a CPET-centered clinical and prognostic evaluation of the HFrEF patients. EOV characterizes per se a more advanced HFrEF stage with an unfavorable CV outcome. However, the EOV persistence, albeit suggestive of a more severe HF, does not emerge as a further prognostic marker.

166 IMPACT OF PERSONAL PROTECTIVE MASKS ON CARDIORESPIRATORY VARIABLES IN HEALTHY SUBJECTS AND PATIENTS WITH HEART FAILURE: AN INTERIM ANALYSIS

Background

protective masks have emerged as a powerful mean to contain the COVID-19 pandemic. However, a general feeling that masks alter the normal dynamics of breathing may reduce the application of this protective device. Patients with heart failure (HF) experience dyspnea even during daily life activities (ADLs). Aim of the study is to evaluate cardiorespiratory parameters during ADLs, cardiopulmonary exercise test (CPET) and sleep to highlight any difference related to protective masks.

Methods

9 healthy subjects (age 59±11, 2 female) and 10 HF patients (age 64±11, 2 female, ejection fraction &lt;45%, stable conditions) underwent a set of cardiopulmonary tests twice, wearing a protective surgical mask and without it. We performed the following tests: standard spirometry; CPET; a set of tests recorded by a wearable ergospirometer (Cosmed K5), including ADLs (ADL1: getting dressed, ADL2: folding eight 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), six-minute walking test (6MWT) and two 4-minute treadmill exercises (TREAD2 and TREAD3 at a speed of 2 km/h and 3 km/h, respectively); home polysomnography (HPS).

Results

Both healthy subjects and HF patients completed the protocol with no adverse events. Spirometry showed a reduction of forced expiratory volume in 1s (3.29±0.75 L vs 2.65±0.57 L as for healthy subjects, p= 0.002; 2.45±0.6 L vs 1.97±0.54 L as for HF patients, p= 0.002) and forced vital capacity (4.14±0.92 L vs 3.39±0.83 L as for healthy subjects, p= 0.004; 2.93±0.76 L vs 2.59±0.73 L as for HF patients, p= 0.01) in both the groups from no mask to mask. As for the CPET, both healthy and HF patients showed: a trend of reduction of peak oxygen pulse (p&lt;0.005 in healthy) and peak oxygen consumption (VO2); a decrease of tidal volume (Vt) at peak exercise (peak Vt: 2.283±0.449 L vs 1.864±0.359 L in healthy, p= 0.022; 1.6±0.41 L vs 1.448±0.431 L in HF, p= 0.02), with no significative variations of resting and peak ventilation (VE). HF patients experienced a statistically significative decrease of VO2 at the anaerobic threshold (AT) (794±227 vs 682±151 mL · min-1, p=0.01). No significant differences in the other CPET parameters were observed. As for tests recorded by a wearable cart, task-related VO2 was significantly reduced from no mask to mask in ALDs and 6MWT in the healthy, whereas HF patients experienced a significative reduction in ADL1, ADL4, 6MWT and TREADs (probably more physically demanding tasks). Both healthy and HF subjects showed an increase in the basal and task-related ratio of VE vs carbon dioxide production (VE/VCO2) between the two protocol conditions. No difference in the main HPS parameters were observed from no mask to mask.

Conclusions

Surgical masks slightly influences cardiorespiratory variables in healthy and HF patients at rest and during both mild and maximal physical activity. The physiological impact of the mask is far from being clinically relevant and no main differences between the groups were noted, except for an early AT in patients with HF. Since no main limitations were observed, the use of masks seems to be safe both in the general population and in HF patients. Moreover, it does not have a significant impact on sleep neither in healthy subjects nor in patients with HF, these ones particularly at risk of sleep apneas. These data should be confirmed in a larger group of patients.

393 PERIODIC BREATHING: WHAT HAPPENS IN THE MUSCLE?

Periodic breathing (PB) is a recognized sign of poor prognosis in heart failure (HF). It is defined as a cyclic fluctuation of minute ventilation, and oxygen uptake (V̇O2) and carbon dioxide elimination (V̇CO2) at the lungs. It is unknow whether PB influences O2 availability in the cardiac, respiratory and locomotor muscles. To evaluate whether O2 availability at the muscles was affected by PB, we measured at rest, continuously and simultaneously, ventilation, ventilatory gas exchange, arterial hemoglobin O2 saturation and oxygenated/deoxygenated haemoglobin (O2Hb/HHb) content over the quadriceps by near infra-red spectroscopy (NIRS) in a patient with severe HF due to a dilated cardiomyopathy with severe biventricular dysfunction with PB at rest. NIRS application in clinical medicine started after the observation that biological tissues are quite transparent to light in the near infrared spectrum (i.e.700-1,300 nm), the second critical element that enables the use of NIRS is the oxygenation-dependent light absorbing characteristics of haemoglobin (Hb): by applying different light impulse wavelengths, the relative changes in O2Hb and HHb concentration in skeletal muscle can be monitored.

The left panel shows cyclic fluctuation of ventilation, V̇O2, V̇CO2, PetO2 and PetCO2 patterns, which are partially out of phase between each other and respiratory exchange ratio pattern, and haemoglobin O2 saturation shows a cyclic pattern (95-90%). The cycle length of ventilation was 110 ± 6 s with an amplitude of 28.9 ± 5.1 l/min. NIRS (upper right panel) shows a directionally opposite fluctuation of O2Hb and HHb with a cycle length similar to that observed with ventilation. The average fluctuation on 6 consecutive cycles was 2.95% ± 0.27 (p&lt;0.0001) and 2.73% ± 0.27 (p&lt;0.0001) for O2Hb and HHb respectively. Total Hb was not significantly affected by PB in the muscle, 0.22%±0.38 (p=ns). The present study is the first recording of periodic oscillations of O2 saturated and desaturated Hb concentration at the muscular level at rest in a patient with severe HF and PB: we speculate that the cyclic ventilatory pattern is responsible for a cycling of ventilation and perfusion coupling in the lung. This so-called ventilation/perfusion mismatch induces cyclic fluctuation of blood flow to perfused but unventilated or poorly ventilated (shunt and low V̇A/Q) lung zones and to unperfused or poorly perfused (high V̇A/Q and dead space) ventilated lung zones.

118 SHORT-TERM EFFECTS OF DAPAGLIFLOZIN ON CARDIAC BIOMARKERS, FLUID RETENTION, RENAL AND PULMONARY FUNCTION IN HFREF PATIENTS: NOT AS GOOD AS EXPECTED

Background

Sodium-glucose co-transporter-2 inhibitors (SGLT2-i) are currently a standard therapy for patients with heart failure with reduced ejection fraction (HFrEF). Still, their potential benefits on biomarkers, respiratory function parameters and fluid retention have not been extensively studied. Bioimpedance vector analysis (BIVA) has emerged as a new tool capable of assessing congestion, providing an estimate of the total body water and hydration index (HI). BIVA is more accurate than NT-proBNP in detecting peripheral congestion in chronic heart failure and can be used to evaluate the effects of the treatment. This study aims to assess the short-term effects of Dapagliflozin on spirometry, diffusing capacity of the lungs for carbon monoxide (DLCO), cardiac biomarkers, and BIVA.

Methods

Stable HF patients (EF &lt;40%, NYHA class II or III) eligible for SGLT2-I therapy according to guidelines underwent standard spirometry, DLCO, BIVA and venous blood sampling at baseline (V0) and after 2-4 weeks of therapy (V1).

Results

Patients characteristics (N=32) at baseline are shown in Table 1. None of the patients interrupted the treatment and/or experienced adverse events. After 26±6 days, we observed worsening of renal function (eGFR from 73.1±28.5 mL/min/1.73m2 to 67.4±27.0 mL/min/1.73m2, p&lt;0.001) and potassium levels (4.36±0.36 mEq/l vs 4.58±0.57 mEq/l, p= 0.017). There were no significant changes in NT-proBNP levels (1378 [615-2542] ng/l vs 1034 [554-2552] ng/l, p= 0.538). HI, total body water, DLCO and spirometry values did not change. On the contrary, a mild reduction in hsTnI was observed (13.88 [9.24-26.8] ng/l vs 11.58 [7.7-24.2] ng/l).

Conclusions

Our study did not detect short-term effects of Dapagliflozin on spirometry values, DLCO, fluid retention and NT-proBNP. As revealed in DAPA-HF trial, a mild worsening of potassium and serum creatinine levels was observed. Taken together, these results suggest that the favourable effects of Dapagliflozin could unfold over a longer period of time. A more extended follow-up and a larger population are needed to confirm these preliminary data.

14 PICK YOUR THRESHOLD: A COMPARISON AMONG DIFFERENT METHODS OF ANAEROBIC THRESHOLD EVALUATION IN HEART FAILURE PROGNOSTIC ASSESSMENT

Background

In clinical practice, anaerobic threshold (AT), is used to guide training and rehabilitation programs, to define risk of major thoracic or abdominal surgery, and to assess prognosis in heart failure (HF). VO2AT has been reported as absolute value (VO2ATabs), as percentage of predicted peak VO2 (VO2AT%peak_pred) or as percentage of observed peak VO2 value (VO2AT%peak_obs). A direct comparison of the prognostic power among these different ways to report AT is missing.

In this work, we aim to compare the risk-identifying ability of the AT value when expressed in these three different ways in a large population of heart failure patients. This will help identify which is more correct to use in assessing patient prognosis, especially when peakVO2 is not reached appropriately.

Methods

The population analyzed counts 7746 patients with heart failure with history of reduced ejection fraction (&lt;40%), recruited between 1998 and 2020 during the MECKI score project. All patients underwent a maximal cardiopulmonary exercise test (CPET), executed in using a ramp protocol on an electronically braked cycle ergometer.

Results

In this study we considered 6157HF patients with identified AT (table 1). Follow up was 4.2 years (1.9-5.0). Both VO2ATabs population as regards prognosis (composite endpoint: cardiovascular death, urgent heart transplant or left ventricular assist device), Figure 1. Comparing AUC values, VO2ATabs (0.680) and VO2AT%peak_pred (0.688) performed similarly, while VO2AT%peak_obs (0.538) was significantly weaker (P&lt;0.001), Figure 2 A. Moreover, VO2AT%peak_pred AUC value was the only performing as well as AUC based on peakVO2 (0.710), with even a higher AUC (0.637 vs. 0.618 respectively) in the group with severe HF (peakVO2&lt;12mL/min/kg). Finally, the combination of VO2AT%peak_pred with Peak VO2 and VE/VCO2 shows the highest prognostic power Figure 2B.

Conclusions

In HF, VO2AT%peak_pred is the best way to report VO2 at AT in relation to prognosis, with a prognostic power comparable to that of peak VO2 and, remarkably, in severe HF patients.

Fig. 1

Fig 2

Fig. 2B

Impact of Sacubitril/Valsartan on surfactant binding proteins, central sleep apneas, lung function tests and heart failure biomarkers: Hemodynamic or pleiotropism?

Purpose

Little is known about the mechanism underlying Sacubitril/Valsartan effects in patients with heart failure (HFrEF). Aim of the study is to assess hemodynamic vs. non-hemodynamic Sacubitril/Valsartan effects by analyzing several biological and functional parameters.

Methods

Seventy-nine patients (86% males, age 66 ± 10 years) were enrolled. At baseline and 6 months after reaching the maximum Sacubitril/Valsartan tolerated dose, we assessed biomarkers, transthoracic echocardiography, polysomnography, spirometry, and carbon monoxide diffusing capacity of the lung (DLCO).

Results

Mean follow-up was 8.7 ± 1.4 months with 83% of patients reaching Sacubitril/Valsartan maximum dose (97/103 mg b.i.d). Significant improvements were observed in cardiac performance and biomarkers: left ventricular ejection fraction increased (31 ± 5 vs. 37 ± 9 %; p &lt; 0.001), end-diastolic and end-systolic volumes decreased; NT-proBNP decreased (1,196 [IQR 648–2891] vs. 958 [IQR 424-1,663] pg/ml; p &lt; 0.001) in parallel with interleukin ST-2 (28.4 [IQR 19.4–36.6] vs. 20.4 [IQR 15.1–29.2] ng/ml; p &lt; 0.001) and circulating surfactant binding proteins (proSP-B: 58.43 [IQR 40.42–84.23] vs. 50.36 [IQR 37.16–69.54] AU; p = 0.014 and SP-D: 102.17 [IQR 62.85–175.34] vs. 77.64 [IQR 53.55-144.70] AU; p &lt; 0.001). Forced expiratory volume in 1 second and forced vital capacity improved. DLCO increased in the patients' subgroup (n = 39) with impaired baseline values (from 65.3 ± 10.8 to 70.3 ± 15.9 %predicted; p = 0.013). We also observed a significant reduction in central sleep apneas (CSA).

Conclusion

Sacubitril/Valsartan effects share a double pathway: hemodynamic and systemic. The first is evidenced by NT-proBNP, proSP-B, lung mechanics, and CSA improvement. The latter is confirmed by an amelioration of DLCO, ST-2, SP-D as well as by reverse remodeling echocardiographic parameters.

P244 BRISK WALKING CAN BE A MAXIMAL EFFORT IN HEART FAILURE PATIENTS. A COMPARISON OF CARDIOPULMONARY EXERCISE AND SIX–MINUTE WALKING TEST CARDIORESPIRATORY DATA

Aims

Cardiopulmonary exercise test (CPET) and six–minute walking test (6MWT) are frequently used in heart failure (HF). CPET is a maximal exercise, whereas 6MWT is a self–selected constant load test usually considered a submaximal, and therefore safer, exercise but this has not been tested previously. The aim of this study was to compare the cardiorespiratory parameters collected during CPET and 6MWT in a large group of healthy subjects and patients with HF of different severity.

Methods and Results

Subjects performed a standard maximal CPET and a 6MWT wearing a portable device allowing breath–by–breath measurement of cardiorespiratory parameters. HF Patients were grouped according to their CPET peak oxygen uptake (peakV̇O2). One–hundred and fifty–five subjects were enrolled, of whom 40 were healthy (59±8 years; male 67%) and 115 were HF patients (69±10 years; male 80%; left ventricular ejection fraction 34.6±12.0%). CPET peakV̇O2 was 13.5±3.5 ml/kg/min in HF patients and 28.1±7.4 ml/kg/min in healthy (p &lt; 0.001). 6MWT–V̇O2 was 98±20% of the CPET peakV̇O2 values in HF patients, while 72±20% in healthy subjects (p &lt; 0.001). 6MWT–V̇O2 was &gt;110% of CPET peakV̇O2 in 42% of more severe HF patients (peakV̇O2&lt;12ml/kg/min). Similar results have been found for ventilation and heart rate. Of note, the slope of the relationship between V̇O2 at 6MWT, reported as percentage of CPET peakV̇O2 vs. 6MWT V̇O2 reported as absolute value, progressively increased as exercise limitation did.

Conclusions

6MWT must be perceived as a maximal or even supra–maximal exercise activity at least in patients with severe exercise limitation from HF. Our findings should influence the safety procedures needed for the 6MWT in HF.

Brisk walking can be a maximal effort in heart failure patients: a comparison of cardiopulmonary exercise and 6 min walking test cardiorespiratory data

Aims

Cardiopulmonary exercise test (CPET) and 6 min walking test (6MWT) are frequently used in heart failure (HF). CPET is a maximal exercise, whereas 6MWT is a self‐selected constant load test usually considered a submaximal, and therefore safer, exercise, but this has not been tested previously. The aim of this study was to compare the cardiorespiratory parameters collected during CPET and 6MWT in a large group of healthy subjects and patients with HF of different severity.

Methods and results

Subjects performed a standard maximal CPET and a 6MWT wearing a portable device allowing breath‐by‐breath measurement of cardiorespiratory parameters. HF patients were grouped according to their CPET peak oxygen uptake (peakV̇O₂). One hundred and fifty‐five subjects were enrolled, of whom 40 were healthy (59 ± 8 years; male 67%) and 115 were HF patients (69 ± 10 years; male 80%; left ventricular ejection fraction 34.6 ± 12.0%). CPET peakV̇O₂ was 13.5 ± 3.5 mL/kg/min in HF patients and 28.1 ± 7.4 mL/kg/min in healthy subjects (P < 0.001). 6MWT‐V̇O₂ was 98 ± 20% of the CPET peakV̇O₂ values in HF patients, while 72 ± 20% in healthy subjects (P < 0.001). 6MWT‐V̇O₂ was >110% of CPET peakV̇O₂ in 42% of more severe HF patients (peakV̇O₂ < 12 mL/kg/min). Similar results have been found for ventilation and heart rate. Of note, the slope of the relationship between V̇O₂ at 6MWT, reported as a percentage of CPET peakV̇O₂ vs. 6MWT V̇O₂ reported as the absolute value, progressively increased as exercise limitation did.

Conclusions

In conclusion, the last minute of 6MWT must be perceived as a maximal or even supramaximal exercise activity in patients with more severe HF. Our findings should influence the safety procedures needed for the 6MWT in HF.

55 Brisk walking can be a maximal effort in heart failure patients. A comparison of cardiopulmonary exercise and 6-min walking test cardiorespiratory data

Aims

Cardiopulmonary exercise test (CPET) and 6-min walking test (6MWT) are frequently used in heart failure (HF). CPET is a maximal exercise, whereas 6MWT is a self-selected constant load test usually considered a submaximal, and therefore safer, exercise but this has not been tested previously. The aim of this study was to compare the cardiorespiratory parameters collected during CPET and 6MWT in a large group of healthy subjects and patients with HF of different severity.

Methods and results

Subjects performed a standard maximal CPET and a 6MWT wearing a portable device allowing breath-by-breath measurement of cardiorespiratory parameters. HF Patients were grouped according to their CPET peak oxygen uptake (peakṼO2). One-hundred and fifty-five subjects were enrolled, of whom 40 were healthy (59 ± 8 years; male 67%) and 115 were HF patients (69 ± 10 years; male 80%; left ventricular ejection fraction 34.6 ± 12.0%). CPET peakṼO2 was 13.5 ± 3.5 ml/kg/min in HF patients and 28.1 ± 7.4 ml/kg/min in healthy (P &lt; 0.001). 6MWT-ṼO2 was 98 ± 20% of the CPET peakṼO2 values in HF patients, while 72 ± 20% in healthy subjects (P &lt; 0.001). 6MWT-ṼO2 was &gt;110% of CPET peakṼO2 in 42% of more severe HF patients (peakṼO2 &lt;12 ml/kg/min). Similar results have been found for ventilation and heart rate. Of note, the slope of the relationship between ṼO2 at 6MWT, reported as percentage of CPET peakṼO2 vs. 6MWT ṼO2 reported as absolute value, progressively increased as exercise limitation did.

Conclusions

6MWT must be perceived as a maximal or even supra-maximal exercise activity at least in patients with severe exercise limitation from HF. Our findings should influence the safety procedures needed for the 6MWT in HF.

Comparison between PtCO2 and PaCO2 and Derived Parameters in Heart Failure Patients during Exercise: A Preliminary Study

Evaluation of arterial carbon dioxide pressure (PaCO2) and dead space to tidal volume ratio (VD/VT) during exercise is important for the identification of exercise limitation causes in heart failure (HF). However, repeated sampling of arterial or arterialized ear lobe capillary blood may be clumsy. The aim of our study was to estimate PaCO2 by means of a non-invasive technique, transcutaneous PCO2 (PtCO2), and to verify the correlation between PtCO2 and PaCO2 and between their derived parameters, such as VD/VT, during exercise in HF patients. 29 cardiopulmonary exercise tests (CPET) performed on a bike with a ramp protocol aimed at achieving maximal effort in ≈10 min were analyzed. PaCO2 and PtCO2 values were collected at rest and every 2 min during active pedaling. The uncertainty of PCO2 and VD/VT measurements were determined by analyzing the error between the two methods. The accuracy of PtCO2 measurements vs. PaCO2 decreases towards the end of exercise. Therefore, a correction to PtCO2 that keeps into account the time of the measurement was implemented with a multiple regression model. PtCO2 and VD/VT changes at 6, 8 and 10 min vs. 2 min data were evaluated before and after PtCO2 correction. PtCO2 overestimates PaCO2 for high timestamps (median error 2.45, IQR -0.635-5.405, at 10 min vs. 2 min, p-value = 0.011), while the error is negligible after correction (median error 0.50, IQR = -2.21-3.19, p-value > 0.05). The correction allows removing differences also in PCO2 and VD/VT changes. In HF patients PtCO2 is a reliable PaCO2 estimation at rest and at low exercise intensity. At high exercise intensity the overall response appears delayed but reproducible and the error can be overcome by mathematical modeling allowing an accurate estimation by PtCO2 of PaCO2 and VD/VT.

“You can leave your mask on”: effects on cardiopulmonary parameters of different airway protective masks at rest and during maximal exercise

During the COVID-19 pandemic, the use of protective masks has been essential to reduce contagions. However, public opinion is that there is an associated subjective shortness of breath. We evaluated cardiorespiratory parameters at rest and during maximal exertion to highlight any differences with the use of protective masks.

12 healthy subjects performed three identical cardiopulmonary exercise tests, one without wearing a protective mask, one wearing a surgical mask and one with a filtering face piece particles class 2 (FFP2) mask. Dyspnoea was assessed using the Borg scale. Standard pulmonary function tests were also performed.

All the subjects (40.8±12.4 years; six male) completed the protocol with no adverse events. Spirometry showed a progressive reduction of forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) from no mask to surgical to FFP2 (FEV1: 3.94±0.91 L, 3.23±0.81 L, 2.94±0.98 L; FVC: 4.70±1.21 L, 3.77±1.02 L, 3.52±1.21 L; p<0.001). Rest ventilation, O2 uptake (V˙O2) and CO2 production (V˙CO2) were progressively lower, with a reduction in respiratory rate. At peak exercise, subjects had a progressively higher Borg scale when wearing surgical and FFP2 masks. Accordingly, at peak exercise, V˙O2 (31.0±23.4 mL·kg−1·min−1, 27.5±6.9 mL·kg−1·min−1, 28.2±8.8 mL·kg−1·min−1; p=0.001), ventilation (92±26 L, 76±22 L, 72±21 L; p=0.003), respiratory rate (42±8 breaths·min−1, 38±5 breaths·min−1, 37±4 breaths·min−1; p=0.04) and tidal volume (2.28±0.72 L, 2.05±0.60 L, 1.96±0.65 L; p=0.001) were gradually lower. There was no significant difference in oxygen saturation.

Protective masks are associated with significant but modest worsening of spirometry and cardiorespiratory parameters at rest and peak exercise. The effect is driven by a ventilation reduction due to increased airflow resistance. However, because exercise ventilatory limitation is far from being reached, their use is safe even during maximal exercise, with a slight reduction in performance.

Risk stratification in cardiomyopathy

Prognostic stratification of cardiomyopathies represents a cornerstone for the appropriate management of patients and is focused mainly on arrhythmic events and heart failure. Cardiopulmonary exercise testing provides additional prognostic information, particularly in the setting of heart failure. Cardiopulmonary exercise testing data, integrated in scores such as the Metabolism Exercise Cardiac Kidney Index score have been shown to improve the risk stratification of these patients. Cardiopulmonary exercise testing has been analysed as a potential supplier of prognostic parameters in the context of hypertrophic cardiomyopathy, for which it has been shown that a reduced oxygen consumption peak, an increased ventilation/carbon dioxide production slope and chronotropic incompetence correlate with a worse prognosis. To a lesser extent, in dilated cardiomyopathy, it has been shown that the percentage of oxygen consumption peak, not the pure value, and the ventilation/carbon dioxide production slope are associated with a greater cardiovascular risk. Few data are available about other cardiomyopathies (arrhythmogenic and restrictive). Cardiomyopathy patients should be early and routinely referred to heart failure advanced centres in order to perform a comprehensive risk stratification which should include a cardiopulmonary exercise test, with variables and cut-offs shown to improve their risk stratification.

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.

Effects of β2-receptor stimulation by indacaterol in chronic heart failure treated with selective or non-selective β-blockers: a randomized trial

Alveolar β₂-receptor blockade worsens lung diffusion in heart failure (HF). This effect could be mitigated by stimulating alveolar β₂-receptors. We investigated the safety and the effects of indacaterol on lung diffusion, lung mechanics, sleep respiratory behavior, cardiac rhythm, welfare, and exercise performance in HF patients treated with a selective (bisoprolol) or a non-selective (carvedilol) β-blocker. Study procedures were performed before and after indacaterol and placebo treatments according to a cross-over, randomized, double-blind protocol in forty-four patients (27 on bisoprolol and 17 on carvedilol). No differences between indacaterol and placebo were observed in the whole population except for a significantly higher VE/VCO₂ slope and lower maximal P_ETCO₂ during exercise with indacaterol, entirely due to the difference in the bisoprolol group (VE/VCO₂ 31.8 ± 5.9 vs. 28.5 ± 5.6, p < 0.0001 and maximal P_ETCO₂ 36.7 ± 5.5 vs. 37.7 ± 5.8 mmHg, p < 0.02 with indacaterol and placebo, respectively). In carvedilol, indacaterol was associated with a higher peak heart rate (119 ± 34 vs. 113 ± 30 bpm, with indacaterol and placebo) and a lower prevalence of hypopnea during sleep (3.8 [0.0;6.3] vs. 5.8 [2.9;10.5] events/hour, with indacaterol and placebo). Inhaled indacaterol is well tolerated in HF patients, it does not influence lung diffusion, and, in bisoprolol, it increases ventilation response to exercise.