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.

Exploring the Prognostic Performance of MECKI Score in Heart Failure Patients with Non-Valvular Atrial Fibrillation Treated with Edoxaban

INTRODUCTION

Risk stratification in heart failure (HF) is essential for clinical and therapeutic management. The Metabolic Exercise test data combined with Cardiac and Kidney Indexes (MECKI) score is a validated prognostic model for assessing cardiovascular risk in HF patients with reduced ejection fraction (HFrEF). From the validation of the score, the prevalence of HF patients treated with direct oral anticoagulants (DOACs), such as edoxaban, for non-valvular atrial fibrillation (NVAF) has been increasing in recent years. This study aims to evaluate the reliability of the MECKI score in HFrEF patients treated with edoxaban for NVAF.

MATERIALS AND METHODS

This study included consecutive outpatients with HF and NVAF treated with edoxaban (n = 83) who underwent a cardiopulmonary exercise test (CPET). They were matched by propensity score with a retrospective group of HFrEF patients with NVAF treated with vitamin K antagonists (VKAs) from the MECKI score registry (n = 844). The study endpoint was the risk of cardiovascular mortality, urgent heart transplantation, or Left Ventricle Assist Device (LVAD) implantation.

RESULTS

Edoxaban patients were treated with a more optimized HF therapy and had different clinical characteristics, with a similar MECKI score. After propensity score, 77 patients treated with edoxaban were successfully matched with the MECKI-VKA control cohort. In both groups, MECKI accurately predicted the composite endpoint with similar area under the curves (AUC = 0.757 vs. 0.829 in the MECKI-VKA vs. edoxaban-treated group, respectively, p = 0.452). The two populations' survival appeared non-significantly different at the 2-year follow-up.

CONCLUSIONS

this study confirms the prognostic accuracy of the MECKI score in HFrEF patients with NVAF treated with edoxaban, showing improved predictive power compared to VKA-treated patients.

Exercise oscillatory ventilation: the past, present, and future

Exercise oscillatory ventilation (EOV) is a fascinating event that can be appreciated in the cardiopulmonary exercise test and is characterized by a cyclic fluctuation of minute ventilation, tidal volume, oxygen uptake, carbon dioxide production, and end-tidal pressure for oxygen and carbon dioxide. Its mechanisms stem from a dysregulation of the normal control feedback of ventilation involving one or more of its components, namely, chemoreflex delay, chemoreflex gain, plant delay, and plant gain. In this review, we intend to breakdown therapeutic targets according to pathophysiology and revise the prognostic value of exercise oscillatory ventilation in the setting of heart failure and other diagnoses.

Beyond VO2: the complex cardiopulmonary exercise test

Cardiopulmonary exercise test (CPET) is a valuable diagnostic tool with a specific application in heart failure (HF) thanks to the strong prognostic value of its parameters. The most important value provided by CPET is the peak oxygen uptake (peak VO2), the maximum rate of oxygen consumption attainable during physical exertion. According to the Fick principle, VO2 equals cardiac output (Qc) times the arteriovenous content difference [C(a-v)O2], where Ca is the arterial oxygen and Cv is the mixed venous oxygen content, respectively; therefore, VO2 can be reduced both by impaired O2 delivery (reduced Qc) or extraction (reduced arteriovenous O2 content). However, standard CPET is not capable of discriminating between these different impairments, leading to the need for 'complex' CPET technologies. Among non-invasive methods for Qc measurement during CPET, inert gas rebreathing and thoracic impedance cardiography are the most used techniques, both validated in healthy subjects and patients with HF, at rest and during exercise. On the other hand, the non-invasive assessment of peripheral muscle perfusion is possible with the application of near-infrared spectroscopy, capable of measuring tissue oxygenation. Measuring Qc allows, by having haemoglobin values available, to discriminate how much any VO2 deficit depends on the muscle, anaemia or heart.

Effects of sacubitril/valsartan on exercise capacity: a prognostic improvement that starts during uptitration

PURPOSE

Sacubitril/valsartan is a mainstay of the treatment of heart failure with reduced ejection fraction (HFrEF); however, its effects on exercise performance yielded conflicting results. Aim of our study was to evaluate the impact of sacubitril/valsartan on exercise parameters and echocardiographic and biomarker changes at different drug doses.

METHODS

We prospectively enrolled consecutive HFrEF outpatients eligible to start sacubitril/valsartan. Patients underwent clinical assessment, cardiopulmonary exercise test (CPET), blood sampling, echocardiography, and completed the Kansas City Cardiomyopathy Questionnaire (KCCQ-12). Sacubitril/valsartan was introduced at 24/26 mg b.i.d. dose and progressively uptitrated in a standard monthly-based fashion to 97/103 mg b.i.d. or maximum tolerated dose. Study procedures were repeated at each titration visit and 6 months after reaching the maximum tolerated dose.

RESULTS

Ninety-six patients completed the study, 73 (75%) reached maximum sacubitril/valsartan dose. We observed a significant improvement in functional capacity across all study steps: oxygen intake increased, at peak exercise (from 15.6 ± 4.5 to 16.5 ± 4.9 mL/min/kg; p trend = 0.001), while minute ventilation/carbon dioxide production relationship reduced in patients with an abnormal value at baseline. Sacubitril/valsartan induced positive left ventricle reverse remodeling (EF from 31 ± 5 to 37 ± 8%; p trend < 0.001), while NT-proBNP reduced from 1179 [610-2757] to 780 [372-1344] pg/ml (p trend < 0.0001). NYHA functional class and the subjective perception of limitation in daily life at KCCQ-12 significantly improved. The Metabolic Exercise Cardiac Kidney Index (MECKI) score progressively improved from 4.35 [2.42-7.71] to 2.35% [1.24-4.96], p = 0.003.

CONCLUSIONS

A holistic and progressive HF improvement was observed with sacubitril/valsartan in parallel with quality of life. Likewise, a prognostic enhancement was observed.

Does moderate hyperkalemia influence survival in HF? Insights from the MECKI score data base

BACKGROUND

The prognostic role of moderate hyperkalemia in reduced ejection fraction (HFrEF) patients is still controversial. Despite this, it affects the use of renin-angiotensin-aldosterone system inhibitors (RAASi) with therapy down-titration or discontinuation.

OBJECTIVES

Aim of the study was to assess the prognostic impact of moderate hyperkalemia in chronic HFrEF optimally treated patients.

METHODS AND RESULTS

We retrospectively analyzed MECKI (Metabolic Exercise test data combined with Cardiac and Kidney Indexes) database, with median follow-up of 4.2 [IQR 1.9-7.5] years. Data on K⁺ levels were available in 7087 cases. Patients with K⁺ plasma level ≥ 5.6 mEq/L and < 4 mEq/L were excluded. Remaining patients were categorized into normal >4 and < 5 mEq/L (n = 4826, 68%) and moderately high ≥5.0 and ≤ 5.5 mEq/L (n = 496, 7%) K⁺. Then patients were matched by propensity score in 484 couplets of patients. MECKI score value was 7% [IQR 3.1-14.1%] and 7.3% [IQR 3.4-15%] (p = 0.678) in patients with normal and moderately high K⁺ values while cardiovascular mortality events at two years follow-up were 41 (4.2%) and 33 (3.4%) (p = 0.333) in each group respectively.

CONCLUSIONS

Moderate hyperkalemia does not influence patients' outcome in a large cohort of ambulatory HFrEF patients.

Is red distribution width a valid tool to predict impaired iron transport in heart failure?

Background

Impaired iron transport (IIT) is a form of iron deficiency (ID) defined as transferrin saturation (TSAT) < 20% irrespective of serum ferritin levels. It is frequently observed in heart failure (HF) where it negatively affects prognosis irrespective of anaemia.

Objectives

In this retrospective study we searched for a surrogate biomarker of IIT.

Methods

We tested the predictive power of red distribution width (RDW), mean corpuscular volume (MCV) and mean corpuscular haemoglobin concentration (MCHC) to detect IIT in 797 non-anaemic HF patients.

Results

At ROC analysis, RDW provided the best AUC (0.6928). An RDW cut-off value of 14.2% identified patients with IIT, with positive and negative predictive values of 48 and 80%, respectively. Comparison between the true and false negative groups showed that estimated glomerular filtration rate (eGFR) was significantly higher (p = 0.0092) in the true negative vs. false negative group. Therefore, we divided the study population according to eGFR value: 109 patients with eGFR ≥ 90 ml/min/1.73 m², 318 patients with eGFR 60-89 ml/min/1.73 m², 308 patients with eGFR 30-59 ml/min/1.73 m² and 62 patients with eGFR < 30 ml/min/1.73 m². In the first group, positive and negative predictive values were 48 and 81% respectively, 51 and 85% in the second group, 48 and 73% in the third group and 43 and 67% in the fourth group.

Conclusion

RDW may be seen as a reliable marker to exclude IIT in non-anaemic HF patients with eGFR ≥60 ml/min/1.73 m².

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.

871 AN ADVANCED BREATHING DISORDER IN HEART FAILURE: IS THERE AN OVERLAP THROUGH EXERCISE OSCILLATORY VENTILATION AND CHEYNE-STOKES RESPIRATION? A CASE REPORT

Case summary

A 60-year-old man, normal-weighted, former smoker with a known non obstructive hypertrophic cardiomyopathy (HCM), severe mitral and tricuspid regurgitation and permanent atrial fibrillation was hospitalized for decompensated heart failure (recent worsening of exertional dyspnoea and appearance of lower limbs oedema). At the admission the ECG documented a permanent AF with normal average heart rate (66 rpm). Blood tests showed only a mildly elevation of BNP (497 pg/ml). Before the valvular repair surgery patient completed the diagnostic work-up with spirometry and cardiopulmonary exercise testing (CPET). The spirometry showed a mixed disorder predominantly obstructive (FEV1 1.8 L/min, 51% of predicted value), consistent with COPD. Also DLCO was moderately reduced. CPET documented a severe reduction in functional capacity (VO2 peak/Kg 9.2 ml/Kg/min, 32% of predicted value, Watt at peak 61), clear signs of cardiac and pulmonary vascular limitation (VO2 Work Slope 7.1, VE/VCO2 Slope 45). Interestingly, during the entire duration of the effort there were an exercise oscillatory ventilation (EOV). Instead, cardiopulmonary registration at rest showed an advanced oscillatory breathing disorder with regular long phases of apnea (average duration of 40 sec). Apnea phases were diurnal and were associated with desaturation at pulsossimetry (SpO2 93-92%).

This rest breathing disorder consisted with the definition of Cheyne-Stokes respiration. Of note, the patient had no previous history of OSAS or central sleeping disorder.

Discussion

Cheyne-Stokes respiration (CSR) is historically considered as a central sleeping disorder, particularly common in patients with heart failure with reduced ejection fraction (HFrEF) with a wide prevalence range between 16% up to 50%. It is also well known its negative prognostic value as it highly impairs quality of life and increases cardiac mortality. Recently, in HFrEF patients emerged that CSR could be also diurnal and sometimes associated to EOV.

The peculiarity of this clinical case lies firstly in the fact that we clearly documented a possible overlap through EOV and CSR, respectively seen as exerctional and rest advanced breathing disorders. Secondly, CSR was previously reported predominantly in case of LVEF &lt; 40%, but this patient had a non obstructive HCM without systolic disfunction (LVEF was 63%). This suggest that CSR and EOV could have the same pathophysiology pathway, with a continuum through each other, regardless the model of HF (reduced vs preserved ejection fraction).

Keywords: Cardiopulmonary Exercise Testing, Exercise Oscillatory Ventilation, Cheyne-Stokes Breathing, Heart Failure, Hypertrophic Cardiomyopathy.

841 ASSOCIATION BETWEEN CARDIORESPIRATORY SYMPTOMS AND LUNG FUNCTION IN PATIENTS WITH LONG-COVID SIGNS

Background

Many patients recovered from COVID-19 infection present a variety of symptoms which limits overall quality of life, as reduced exercise performance, dysfunctional breathing, cough, dyspnea, weakness and anxiety. This condition has been named long COVID. The origin of this symptomatology is still unclear. This study has the aim to analyse the relation between symptoms and respiratory function, focusing on the alveolar capillary membrane.

Methods

Consecutive patients with long COVID 19 symptoms after 6 months were included. Patients underwent full clinical evaluation, laboratory tests, echocardiography, thoracic CT scan, spirometry including alveolar capillary membrane diffusion by means of 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 capillary function. A questionnaire allowed to evaluate symptoms.

Results

We evaluated 204 post COVID-19 patients (age 56.5±14.5 y, 89 females (44%), BMI 25.7±4.0, 6% active smokers) referring to our hospital 171±85 days after the end of acute COVID-19 infection (Fig. 1). None of spirometry data was associated with long COVID 19 referred symptoms. SPB was not associated to differences in any of the referred symptoms. Subjects with lower capillary volume (VCap) have more frequently dyspnea, tiredness, fatigability and hair loss (Fig.2). CT scan lung damage correlated with SPB and membrane diffusion but not with VCap, exercise performance or VE/VCO2 slope.

The strongest correlation of SPB were with lung parenchyma damage and Vcap.

Conclusions

Our data suggest that a relevant reduction of alveolar capillary membrane function plays a central role in the long COVID cardiorespiratory symptoms.

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

848 SACUBITRIL/VALSARTAN IMPROVES EXERCISE PERFORMANCE IN PATIENTS WITH REDUCED EJECTION FRACTION: A DOSE AND TIME DEPENDENT EFFECT

Background

Sacubitril/Valsartan therapy has become a cornerstone of heart failure with reduced ejection fraction (HFrEF) pharmacological therapy due to its positive prognostic impact. However, conflicting results have emerged on the effects of sacubitril/valsartan on exercise performance assessed by cardiopulmonary exercise test (CPET).

Aim of the study

The aim of this study was to prospectively evaluate the effects of sacubitril/valsartan on prognostically significant CPET parameters in a larger population of HFrEF patients at different drug doses.

Methods

We prospectively enrolled HFrEF outpatients eligible to start sacubitril/valsartan according to 2016 ESC Guidelines in 3 Heart Failure Units. Patients underwent CPET at baseline (before sacubitril/valsartan treatment), after 1, 2, 3 months (respectively after a month taking the 24/26–49/51–97/103mg doses), and 6 months after the maximum tolerated dose was reached (end-study). The subjective impression of disease-related limitation was assessed using the 12-item Kansas City Cardiomyopathy Questionnaire (KCCQ).

Results

113 patients were enrolled (age 64.5±9.7, 81% males). Peak oxygen intake (peakVO2) improved at each step from 15.0±4.5 mL/min/kg at baseline to 16.5±4.9 mL/min/kg at end study visit, corresponding to 61.5±16.0 and 67.9±17.4% of predicted, respectively (p&lt;0.05). Minute ventilation/carbon dioxide production relationship (VE/VCO2 slope) reduced from 39.6±5.5 to 35.9±7.1 (p = 0.005) in the 39 patients (42%) with pathological VE/VCO2≥34 at baseline. KCCQ improved significantly since the first visit with an overall summary score increase from 47.9±11.1 to 52.6±9.8 (p&lt;0.001).

Conclusions

These findings suggest that sacubitril/valsartan benefits on exercise capacity are immediately evident at the lowest dose and progressively improve as the dose increases.

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.

When Outcomes Diverge: Age and Cardiovascular Risk as Determinants of Mortality and ICU Admission in COVID-19

Background: Hospital mortality and admission to the Intensive Care Unit (ICU) are markers of disease severity in COVID-19 patients. Cardiovascular co-morbidities are one of the main determinants of negative outcomes. In this study we investigated the impact of cardiovascular co-morbidities on mortality and admission to the ICU in first-wave COVID-19 patients. Methods: A multicenter, retrospective, cohort study. A total of 1077 patients were analyzed for mortality and ICU admission. Cardiovascular risk factors were explored as determinants of the outcomes after correction for other confounders. Results: In the multivariable model, after correction for age, only a history of heart failure remained independently associated (p = 0.0013) with mortality (hazard ratio 2.22, 95% confidence interval 1.37 to 3.62). Age showed a mortality risk increase of 8% per year (hazard ratio 1.08, 95% confidence interval 1.05 to 1.10, p = 0.001). The transition from ward to the ICU had, as a single determinant, the age, but in a reversed fashion (hazard ratio 0.96, 95% confidence interval 0.94 to 0.98, p = 0.0002). Conclusions: Once adjusted for the main determinant of mortality (age) heart failure only remained independently associated with mortality. Admission to the ICU was less likely for elderly patients. This may reflect the catastrophic impact of the first wave of COVID-19 pandemic in terms of ICU bed availability in Lombardy, leading to a selection process for ICU admission.

Exercise oxygen pulse kinetics in patients with hypertrophic cardiomyopathy

OBJECTIVES

Reduced cardiac output (CO) has been considered crucial in symptoms' genesis in hypertrophic cardiomyopathy (HCM). Absolute value and temporal behaviour of O₂-pulse (oxygen uptake/heart rate (VO₂/HR)), and the VO₂/work relationship during exercise reflect closely stroke volume (SV) and CO changes, respectively. We hypothesise that adding O₂-pulse absolute value and kinetics, and VO₂/work relationship to standard cardiopulmonary exercise testing (CPET) could help identify more exercise-limited patients with HCM.

METHODS

CPETs were performed in 3 HCM dedicated clinical units. We retrospectively enrolled non-end-stage consecutive patients with HCM, grouped according to left ventricle outflow tract obstruction (LVOTO) at rest or during Valsalva manoeuvre (72% of patients with LVOTO <30; 10% between 30 and 49 and 18% ≥50 mm Hg). We evaluated the CPET response in HCM focusing on parameters strongly associated with SV and CO, such as O₂-pulse and VO₂, respectively, considering their absolute values and temporal behaviour during exercise.

RESULTS

We included 312 patients (70% males, age 49±18 years). Peak VO₂ (percentage of predicted), O₂-pulse and ventilation to carbon dioxide production (VE/VCO₂) slope did not change across LVOTO groups. Ninety-six (31%) patients with HCM presented an abnormal O₂-pulse temporal behaviour, irrespective of LVOTO values. These patients showed lower peak systolic pressure, workload (106±45 vs 130±49 W), VO₂ (21.3±6.6 vs 24.1±7.7 mL/min/kg; 74%±17% vs 80%±20%) and O₂-pulse (12 (9-14) vs 14 (11-17) mL/beat), with higher VE/VCO₂ slope (28 (25-31) vs 27 (24-31)) (p<0.005 for all). Only 2 patients had an abnormal VO₂/work slope.

CONCLUSION

None of the frequently used CPET parameters, either as absolute values or dynamic relationships, were associated with LVOTO. Differently, an abnormal temporal behaviour of O₂-pulse during exercise, which is strongly related to inadequate SV increase, correlates with reduced functional capacity (peak and anaerobic threshold VO₂ and workload) and increased VE/VCO₂ slope, identifying more advanced disease irrespectively of LVOTO.

53 Exercise oxygen kinetic in hypertrophic cardiomyopathy: results from a multicentre cardiopulmonary exercise testing study

Aims

Reduced cardiac output (CO) has been considered crucial in symptoms’ genesis in hypertrophic cardiomyopathy (HCM). We evaluated the cardiopulmonary exercise testing (CPET) response in HCM focusing on parameters strongly associated with stroke volume (SV) and cardiac output (CO), such as oxygen uptake (VO2) and O2-pulse, considering both their absolute values and temporal behaviour during physical exercise.

Methods and results

We enrolled 312 non-end stage HCM patients, divided according to left ventricle outflow tract obstruction (LVOTO) at rest or during Valsalva manoeuver (72% with LVOTO &lt; 30; 10% between 30 and 49; and 18% ≥50 mmHg). Peak VO2 (percent of predicted), O2-pulse, and ventilation to carbon dioxide production (VE/VCO2) slope did not change across LVOTO groups. Ninety-six (31%) HCM patients presented an abnormal O2-pulse temporal behaviour, irrespective of LVOTO values. These patients showed lower peak systolic pressure, workload (106 ± 45 vs. 130 ± 49 W), VO2 (74 ± 17% vs. 80 ± 20%) and O2-pulse (12 [9–14] vs. 14 [11–17]ml/beat), with higher VE/VCO2 slope (28 [25–31] vs. 27 [24–31]) (P &lt; 0.005 for all). Only two patients had an abnormal VO2/work slope.

Conclusions

None of CPET parameters, either as absolute values or dynamic relationships, were associated with LVOTO. Differently, an abnormal O2-pulse exercise behaviour, which is strongly related to inadequate SV during exercise, correlates with reduced functional capacity (peak and anaerobic threshold VO2 and workload) and increased VE/VCO2 slope, helping identifying more advanced disease irrespectively of LVOTO. Adding O2-pulse kinetics evaluation to standard CPET could lead to a potential incremental benefit in terms of HCM prognostic stratification and, then, therapeutic management.

Rest and exercise oxygen uptake and cardiac output changes 6 months after successful transcatheter mitral valve repair

Aims

Changes in peak exercise oxygen uptake (VO₂) and cardiac output (CO) 6 months after successful percutaneous edge‐to‐edge mitral valve repair (pMVR) in severe primary (PMR) and functional mitral regurgitation (FMR) patients are unknown.

The aim of the study was to assess the efficacy of pMVR at rest by echocardiography, VO₂ and CO (inert gas rebreathing) measurement and during cardiopulmonary exercise test with CO measurement.

Methods and results

We evaluated 145 and 115 patients at rest and 98 and 66 during exercise before and after pMVR, respectively.

After successful pMVR, significant reductions in MR and NYHA class were observed in FMR and PMR patients. Cardiac ultrasound showed reverse remodelling (left ventricular end‐diastolic volume from 158 ± 63 mL to 147 ± 64, P < 0.001; ejection fraction from 51 ± 15 to 48 ± 14, P < 0.001; pulmonary artery systolic pressure (PASP) from 43 ± 13 to 38 ± 8 mmHg, P < 0.001) in the entire population. These changes were significant in PMR (n = 62) and a trend in FMR (n = 53), except for PASP, which decreased in both groups. At rest, CO and stroke volume (SV) increased in FMR with a concomitant reduction in arteriovenous O₂ content difference [ΔC(a‐v)O₂]. Peak exercise, CO and SV increased significantly in both groups (CO from 5.5 ± 1.4 L/min to 6.3 ± 1.5 and from 6.2 ± 2.4 to 6.7 ± 2.0, SV from 57 ± 19 mL to 66 ± 20 and from 62 ± 20 to 69 ± 20, in FMR and PMR, respectively), whereas peak VO₂ was unchanged and ΔC(a‐v)O₂ decreased.

Conclusions

These data confirm pMVR‐induced clinical improvement and reverse ventricular remodelling at a 6‐month analysis and show, in spite of an increase in CO, an unchanged exercise performance, which is achieved through a ‘more physiological’ blood flow distribution and O₂ extraction behaviour. Direct rest and exercise CO should be measured to assess pMVR efficacy.

Minute ventilation/carbon dioxide production in chronic heart failure

In chronic heart failure, minute ventilation (V'_E) for a given carbon dioxide production (V'_CO2 ) might be abnormally high during exercise due to increased dead space ventilation, lung stiffness, chemo- and metaboreflex sensitivity, early metabolic acidosis and abnormal pulmonary haemodynamics. The V'_E versus V'_CO2 relationship, analysed either as ratio or as slope, enables us to evaluate the causes and entity of the V'_E/perfusion mismatch. Moreover, the V'_E axis intercept, i.e. when V'_CO2 is extrapolated to 0, embeds information on exercise-induced dead space changes, while the analysis of end-tidal and arterial CO₂ pressures provides knowledge about reflex activities. The V'_E versus V'_CO2 relationship has a relevant prognostic power either alone or, better, when included within prognostic scores. The V'_E versus V'_CO2 slope is reported as an absolute number with a recognised cut-off prognostic value of 35, except for specific diseases such as hypertrophic cardiomyopathy and idiopathic cardiomyopathy, where a lower cut-off has been suggested. However, nowadays, it is more appropriate to report V'_E versus V'_CO2 slope as percentage of the predicted value, due to age and gender interferences. Relevant attention is needed in V'_E versus V'_CO2 analysis in the presence of heart failure comorbidities. Finally, V'_E versus V'_CO2 abnormalities are relevant targets for treatment in heart failure.

“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.

Roles of periodic breathing and isocapnic buffering period during exercise in heart failure

In heart failure, exercise - induced periodic breathing and end tidal carbon dioxide pressure value during the isocapnic buffering period are two features identified at cardiopulmonary exercise testing strictly related to sympathetic activation. In the present review we analysed the physiology behind periodic breathing and the isocapnic buffering period and present the relevant prognostic value of both periodic breathing and the presence/absence of the identifiable isocapnic buffering period.

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.

Do rebreathing manoeuvres for non-invasive measurement of cardiac output during maximum exercise test alter the main cardiopulmonary parameters?

Background

Inert gas rebreathing has been recently described as an emergent reliable non-invasive method for cardiac output determination during exercise, allowing a relevant improvement of cardiopulmonary exercise test clinical relevance. For cardiac output measurements by inert gas rebreathing, specific respiratory manoeuvres are needed which might affect pivotal cardiopulmonary exercise test parameters, such as exercise tolerance, oxygen uptake and ventilation vs carbon dioxide output (VE/VCO2) relationship slope.

Method

We retrospectively analysed cardiopulmonary exercise testing of 181 heart failure patients who underwent both cardiopulmonary exercise testing and cardiopulmonary exercise test+cardiac output within two months (average 16 ± 15 days). All patients were in stable clinical conditions (New York Heart Association I–III) and on optimal medical therapy.

Results

The majority of patients were in New York Heart Association Class I and II (78.8%), with a mean left ventricular ejection fraction of 31 ± 10%. No difference was found between the two tests in oxygen uptake at peak exercise (1101 (interquartile range 870–1418) ml/min at cardiopulmonary exercise test vs 1103 (844–1389) at cardiopulmonary exercise test-cardiac output) and at anaerobic threshold. However, anaerobic threshold and peak heart rate, peak workload (75 (58–101) watts and 64 (42–90), p < 0.01) and carbon dioxide output were significantly higher at cardiopulmonary exercise testing than at cardiopulmonary exercise test+cardiac output, whereas VE/VCO2 slope was higher at cardiopulmonary exercise test+cardiac output (30 (27–35) vs 33 (28–37), p < 0.01).

Conclusion

The similar anaerobic threshold and peak oxygen uptake in the two tests with a lower peak workload and higher VE/VCO2 slope at cardiopulmonary exercise test+cardiac output suggest a higher respiratory work and consequent demand for respiratory muscle blood flow secondary to the ventilatory manoeuvres. Accordingly, VE/VCO2 slope and peak workload must be evaluated with caution during cardiopulmonary exercise test+cardiac output.

Diabetic Cardiomyopathy: Definition, Diagnosis, and Therapeutic Implications

A strict bidirectional relationship exists between diabetes mellitus and heart failure. Diabetic cardiomyopathy is a specific cardiac manifestation of patients with diabetes characterized by left ventricular hypertrophy and diastolic dysfunction in the early phase up to overt heart failure with reduced systolic function in the advanced stages. The pathogenesis of this condition is multifactorial and recognizes as main promoting factors the presence of insulin resistance and hyperglycemia. Diabetic cardiomyopathy exerts a negative prognostic impact in affected patients and no target treatments are currently available. More efforts are needed to better define the diagnostic and therapeutic approach in this specific setting.

Sacubitril/valsartan can improve exercise performance in systolic chronic heart failure patients: a case report

OBJECTIVE

The cardiopulmonary exercise test (CPET) provides functional prognostic parameters for patients with chronic heart failure (CHF), such as peak volume of oxygen (VO₂) and minute ventilation/carbon dioxide production (VE/VCO₂) slope. Sacubitril/valsartan (LCZ696) has been recently approved for CHF patients as it reduces cardiovascular (CV) deaths and hospitalization for heart failure (HF). However, the potential beneficial effects of this therapy on exercise performance have been poorly investigated to date.

CASE PRESENTATION

We present a 64 year old woman with systolic HF (New York Heart Association [NYHA] class III, ejection fraction 35%) due to moderate/severe aortic and tricuspid regurgitation and pulmonary hypertension. The patient had several co-morbidities and a history of CV surgery (mitral valve replacement due to bacterial endocarditis). In November 2016, a CPET was performed in stable clinical conditions, showing severe cardiogenic limitation with signs of pulmonary hypertension (peak VO₂ 46% of predicted, VE/VCO₂ slope 36.5). According to current guidelines, an angiotensin-converting enzyme inhibitor was replaced with sacubitril/valsartan (24/26 mg for 2 weeks and then increased to 49/51 mg) without any other change in medical therapy. At 2 months, CPET showed improvement in exercise performance (peak VO₂ 61%, VE/VCO₂ slope 26.9). Echocardiographic parameters also showed mild improvement, whereas renal function remained unchanged. Thus, the dose of sacubitril/valsartan was increased to 97/103 mg.

CONCLUSIONS

We present a case of a systolic HF patient successfully treated with sacubitril/valsartan who showed a rapid improvement of exercise performance at CPET.

Heart rate during exercise: mechanisms, behavior, and therapeutic and prognostic implications in heart failure patients with reduced ejection fraction

Exercise intolerance is a typical manifestation of patients affected by heart failure with reduced ejection fraction (HFrEF); however, the relationship among functional capacity, mortality, and exercise-induced heart rate response during exercise remains unclear in either sinus rhythm or atrial fibrillation subjects. Heart rate increase during incremental load exercise has a typical pattern in normal subjects, whereas it is commonly compromised in HFrEF patients, mainly due to the imbalance of the autonomic nervous system. In the present review, we aim to describe the behavior of heart rate during exercise in normal subjects and in HFrEF patients in sinus rhythm and atrial fibrillation, understanding and explaining the mechanism leading to a different exercise performance and functional limitation. Moreover, the role of chronotropic incompetence and the need of standardizing the cutoff criteria are also discussed in order to clarify the clinical importance, the prognostic relevance, and the potential therapeutic implications of this condition. Looking into the relative contribution and interaction of heart rate response during exercise might represent an important issue to guide individualized therapeutic interventions and prognostic assessment in HFrEF patients.