Download HF Patients - Circulation: Heart Failure

Circulating Plasma Surfactant Protein Type B as Biological Marker
of Alveolar-Capillary Barrier Damage in Chronic Heart Failure.
RUNNING TITLE: Surfactant Protein B in Chronic Heart Failure.
AUTHORS: Magrì Damiano1,2, MD, Brioschi Maura1, PhD, Banfi Cristina1, PhD, Schmid Jean
Paul 3, MD, Palermo Pietro1, MD, Contini Mauro1, MD, Apostolo Anna1, MD, Bussotti Mauro1,
MD, Tremoli Elena1,4, PhD, Sciomer Susanna2, MD, Cattadori Gaia1, MD, Fiorentini Cesare1, MD
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and Agostoni Piergiuseppe1,5, MD, PhD.
1
Centro Cardiologico Monzino-IRCCS, Istituto di Cardiologia, Università di Milano -Milan-Italy;
2
Unità Operativa Complessa di Cardiologia, Azienda Ospedaliera Sant’Andrea, Università degli
Studi di Roma “La Sapienza”, Italy
3
Swiss Cardiovascular Center Bern, Cardiovascular Prevention & Rehabilitation, Bern University
Hospital, and University of Bern, Bern, Switzerland.
4
Department of Pharmacological Science, University of Milan, Milan, Italy.
5
Division of Pulmonary and Critical Care Medicine, University of Washington -Seattle-WA.
Address for correspondence:
Piergiuseppe Agostoni,
Centro Cardiologico Monzino, IRCCS,
Istituto di Cardiologia, Università di Milano,
via Parea 4, 20138 Milano.
Tel +39 02 58002299; Fax +39 02 58002283
E-mail: [email protected]
TOTAL WORD COUNT: 4940
SUBJECTS CODE: [110]
1
ABSTRACT
Background- Surfactant protein B (SPB) is needed for alveolar gas exchange. SPB is
increased in the plasma of heart failure (HF) patients with a concentration that is higher when HF
severity is highest. The aim of the current study was to evaluate the relationship between plasma
SPB and both alveolar-capillary diffusion at rest and ventilation vs. carbon dioxide production
(VE/VCO2) during exercise.
Methods and Results- Eighty chronic consecutive HF patients and 20 healthy controls were
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evaluated but the required quality for procedures was only reached by 71 HF patients and 19
healthy controls. Each subject underwent pulmonary function measurements, including lung
diffusion (DLCO) and membrane diffusion (DM), and maximal cardiopulmonary exercise test.
Plasma SPB was measured by immunoblotting. In HF patients SPB values were higher [4.5(11.1)
vs 1.6(2.9), p= 0.0006, median and 25-75th interquartile], while DLCO (19.7±4.5 vs 24.6±6.8
mL/mmHg/min, p< 0.0001, mean±SD) and DM (28.9±7.4 vs 38.7±14.8, p< 0.0001) were lower.
Peak oxygen consumption (VO2) and VE/VCO2 slope were 16.2±4.3 vs 26.8±6.2 ml/kg/min (p<
0.0001) and 29.7±5.9 and 24.5±3.2 (p< 0.0001) in HF and controls, respectively. In the HF
population, univariate analysis showed a significant relationship between plasma SPB and DLCO,
DM, peak VO2 and VE/VCO2 slope (p< 0.0001 for all). On multivariable logistic regression analysis
DM (beta: −0.54, SE: 0.018, p< 0.0001), peak VO2 (beta: −0.53, SE: 0.036, p= 0.004) and VE/VCO2
slope (beta: 0.25, SE: 0.026, p= 0.034) were independently associated with SPB.
Conclusion- Circulating plasma SPB levels are related to alveolar gas diffusion, overall
exercise performance and efficiency of ventilation showing a link between alveolar-capillary barrier
damage, gas exchange abnormalities and exercise performance in HF.
Key-words: chronic heart failure, surfactant protein B, lung diffusion, cardiopulmonary
exercise test, alveolar-capillary barrier damage.
2
INTRODUCTION
Lung function abnormalities are part of the chronic heart failure (HF) syndrome, as both
lung mechanics and gas exchange are impaired.1-4 As regards gas exchange, alveolar capillary
diffusion limitation in HF has been suggested as a prognostic marker,5 a target for therapy6,7 and
also as a limiting factor for exercise performance.8-10 In humans alveolar gas exchange is measured
in terms of total lung diffusion for carbon monoxide (DLCO) and specific membrane diffusion
capacity (DM).11,12
In HF, gas exchange abnormalities are associated with anatomical changes in the alveolarDownloaded from http://circheartfailure.ahajournals.org/ by guest on June 18, 2017
capillary membrane, which include reduction in the number of the alveolar-capillary units,
interstitial fibrosis, local thrombosis and an increase in cellularity.13,14,15 Recently an increased
circulating plasma level of surfactant protein B (SPB) has been reported, with SPB that is higher
when HF severity is highest.16 The mature form of SPB plays a crucial role in the formation and
stabilization of pulmonary surfactant film,17,18 so that the presence of SPB in the plasma may be a
biological marker for alveolar-capillary barrier damage.16,19,20 However, no data are available as
concerns a correlation between SPB and lung diffusion, both total DLCO and membrane specific
DM. Moreover, it is unknown whether or not SPB correlates with peak oxygen consumption (VO2),
and, more intriguing, with exercise-derived parameters related, even if just partially, to
ventilation/perfusion mismatch, such as the slope of the linear relationship between ventilation (VE)
and production of carbon dioxide (VCO2). Indeed, both peak VO2 and VE vs. VCO2 slope are
altered in HF and, notably, are prognosis predictors that are independently related to each other.21-25
The current study was therefore designed to evaluate the circulating plasma SPB level in HF
patients and in healthy controls and its relationship with alveolar-capillary diffusion abnormalities
at rest and with ventilation/perfusion mismatch during exercise.
3
METHODS
Study population
One hundred subjects were evaluated consecutively: 80 chronic HF (42 ischemic and 38
non-ischemic dilated cardiomyopathy) patients and 20 healthy control subjects. Patients belong to a
group of individuals regularly followed at our HF unit, while controls were recruited from hospital
staff. Study inclusion criteria for patients were NYHA functional class I to III, optimized,
individually tailored drug treatment, stable clinical conditions for at least 2 months,
capability/willingness to perform a maximal or near maximal cardiopulmonary exercise test
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(CPET), absence of a clinical history and/or documentation of pulmonary embolism or primary
valvular heart disease, pericardial disease, severe obstructive lung disease, primitive or occupational
lung disease, anaemia (Hb< 11 g/dL), renal failure (serum creatinine > 2.0 mg/dL), significant
peripheral vascular disease, exercise-induced angina, ST changes, or severe arrhythmias. All
patients have recently (<1 month) performed an echocardiographic evaluation.
The investigation was approved by the local ethics committee and subjects signed a written
informed consent before participating in the study. The Authors had full access to and take full
responsibility for the integrity of the data. All Authors have read and agree to the manuscript as
written.
Specimen handling and assays
After 15 minutes of resting condition and immediately before the pulmonary function and
lung diffusion measurements, a venous blood sample was taken, collected in citratre tubes and
centrifuged at 3000 rpm at 4°C; the plasma was frozen at -80°C for blind batch analysis.
In order to resolve low molecular weight proteins precisely, equal amounts of plasma
proteins (50 μg) were separated by one dimensional SDS-PAGE on 15% polyacrylamide gels using
a Tris-Tricine buffer system in non reducing conditions.26 Gels were electrophoretically transferred
to nitrocellulose at 60 V for 2 h. Immunoblotting on transferred samples was performed as follows:
blocking in 5% w/v non-fat milk in Tris-buffered saline (100 mM TrisHCl, pH 7.5, 150 mM NaCl)
4
containing 0.1% Tween 20 (TBS-T) for 1 h at room temperature; overnight incubation at 4°C with
primary antibody against SP-B (rabbit anti-human SP-B H300, Santa Cruz Biotecnology) diluted to
1:200 in 5% w/v non-fat milk in TBS-T; incubation with secondary goat anti-rabbit antibody
conjugated with horseradish peroxidase (Bio-Rad) at 1:1000 for 1 h. Bands were visualized by
enhanced chemiluminescence using the ECL kit (Amersham Corp.) and acquired using a
densitometer (GS800 Biorad). In each analysis a plasma sample was loaded as a control for
normalization. Bands detected by ECL were quantified by densitometry of the exposed film, using
the image analysis software QuantityOne (version 4.5.2) from Biorad. Results obtained as a ratio of
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band volume after local background subtraction versus the volume of the sample used for
normalization are expressed as an arbitrary unit. The inter-assay variation coefficient was
12.1±2.9%.
Pulmonary function and lung diffusion
Immediately before CPET, all subjects enrolled were evaluated using standard pulmonary
function tests, which included DLCO. Forced expiratory volume in 1 s (FEV1) and lung vital
capacity (VC) were measured according to the American Thoracic Society standard criteria, using
the predicted values of Quajer et al.27,28 We considered a FEV1/VC ratio less than 60% as indicative
of a severe obstructive ventilatory defect. DLCO was measured with the intra-breath expiratory flow
technique (Vmax29C, Sensor Medics, Yorba Linda, CA, USA).11 DM was calculated applying the
Roughton and Forster method.12 For this purpose, subjects inspired gas mixtures containing 0.3%
CH4, 0.3% CO, with three different oxygen fractions equal to 20, 40, and 60%, respectively, and
balanced with nitrogen.
Cardiopulmonary exercise test
A maximal symptom-limited CPET was performed on an electronically braked
cycloergometer (Ergometrics-800, SensorMedics, USA), with the subject wearing a nose clip and
breathing through a mass flow sensor (Vmax29C, Sensor Medics, Yorba Linda, CA, USA)
connected to a saliva trap. A personalized ramp exercise protocol was chosen, aiming at a test
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duration of 10±2 min. The exercise was preceded by 5 min of resting breath-by-breath gas exchange
monitoring and by a 3 min unloaded warm-up. A 12-lead ECG, blood pressure and heart rate were
also recorded. CPET were self-terminated by the subjects when they claimed that they had achieved
the maximal effort. However, we considered as maximal exercise only tests in which the respiratory
exchange ratio (VCO2/VO2) was above 1.05.
All tests were executed and evaluated by two expert readers blinded to plasma SPB values.
The anaerobic threshold (AT) was identified by V-slope analysis of VO2 and VCO2 and confirmed
by specific behaviour of O2 (VE/VO2) and CO2 (VE/VCO2) ventilatory equivalents and end-tidal
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pressure of O2 and of CO2. The end of the isocapnic buffering period was identified when VE/VCO2
increased and end-tidal pressure of CO2 decreased.29 The relation between VE vs. VCO2 was
calculated as the slope of the linear relationship between VE and VCO2 from one minute after the
beginning of loaded exercise to the end of the isocapnic buffering period.30
Statistical Analysis
Unless otherwise indicated all data is expressed as mean ± SD. Data non-normally
distributed are given as median and interquartile range [75th percentile-25th percentile]. Categorical
variables were compared with χ2 test while ANOVA followed, when ANOVA main effect was
significant, by two sample t-test was used to compare the general characteristics and other
continuous data in the study groups. Kruskal-Wallis and Mann-Whitney U test were used for
comparison between data with non-linear distribution. Statistical analysis was also performed by
subdividing patients into four groups according to DM (A: >30 ml/mmHg/min; B: 25 to 30
ml/mmHg/min; C: 20 to 25 ml/mmHg/min; D: < 20 ml/mmHg/min), according to the Weber
classification,21 which is based on peak VO2 (A: >20 ml/min/kg; B: 16 to 20 ml/min/kg; C: 12 to 16
ml/min/kg; D: < 12 ml/kg/min) and according a cut-off value of 34 for the relationship between VE
and VCO2 (A: < 34; B ≥ 34).24
Because plasma SPB values showed a non-linear distribution, Spearman’s correlation was used to
disclose possible correlations between this protein and clinical, echocardiographic, pulmonary and
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CPET findings. After transforming SPB values into the natural logarithm, multivariable linear
regression analysis with stepwise selection of variables (age, gender, NYHA functional class,
LVEF, VC, FEV1, DLCO, DM, peak VO2 % of predicted, ml/min, ml/kg/min, VO2 at AT, peak
VCO2, peak VE, VE/VCO2 slope) was used to disclose predictors independently associated with
circulating SPB values. To avoid distorted estimates of the effect, Spearman’s correlation and linear
regression analysis was limited to the heart failure population.
A p value < 0.05 was considered as statistically significant. All tests were two-sided. The
SAS software (v. 8.02, SAS Institute Inc., Cary, NC, USA) was used to perform all analyses.
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RESULTS
Of the 100 cases evaluated for this study only 90 subjects met the study inclusion/exclusion
criteria and were therefore analyzed; we excluded 9 patients and 1 control subject resulting in 71
chronic HF patients (38 ischemic and 33 non-ischemic dilated cardiomyopathy) and 19 healthy
control subjects effectively enrolled. Four patients were excluded because of the presence of a
severe obstructive lung disease, 2 patients because of a poor compliance to DLCO techniquemeasurements and 3 patients and 1 healthy control because they performed an exercise judged as
not-maximal according to the low respiratory quotient reached. General characteristics of the two
study groups, including patients’ left ventricular ejection fraction, are reported in table 1. Patients
with HF and control subjects were well matched with respect to age and gender (table 1). Treatment
in HF patients included ACE-inhibitors/AT1 blockers in 64 cases, betablockers in 63 cases,
diuretics in 40 cases, antialdosteronic drug in 36 cases, amiodarone in 18 cases, digoxin in 8 cases,
antiplatelet in 29 cases and anticoagulant in 19 cases.
Patients with HF showed a significantly lower lung VC and FEV1 than control subjects,
while there was no difference in FEV1/VC ratio (table 2). DLCO, either as absolute values or as
percentage of predicted and DM were significant lower in patients than in controls (table 2).
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Exercise performance was significantly reduced in patients with HF, as demonstrated by the
lower peak workload, peak VO2 and VO2 at AT reached and by the higher values of VE/VCO2
slope (table 2 and 3).
Plasma SPB, which is detectable in the 3 predominant forms with molecular mass
ranging from 17 to 42 kDa (figure 1), was 4.5 (11.1) and 1.6 (2.9) arbitrary units (p= 0.0006,
median and 25-75th interquartile range) in HF patients and controls, respectively. Analyzing only
the HF population, SPB values were significantly related to peak VO2, VE/VCO2 slope and DM
(figures 2, 3 and 4). This finding was also confirmed by circulating plasma levels of SPB
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categorized accordingly to peak DM, VO2, and VE/VCO2 slope classification (table 3). Significant
Spearman’s correlation coefficients between plasma SPB and some measured parameters (DLCO,
DM, peak VO2, VE/VCO2 slope) are reported in table 4. Using multivariable logistic regression
analysis, DM (beta: −0.55, standard error: 0.018, p< 0.0001), peak VO2 (beta: −0.344, standard error:
0.036, p= 0.004) and VE/VCO2 slope (beta: 0.25, standard error: 0.026, p= 0.034) were
independently associated with circulating SPB values.
DISCUSSION
This study confirms that circulating SPB values are increased in HF patients, and that
patients with most severe HF have the highest values of SPB. It also shows, for the first time, that
SPB values are directly related to alveolar gas diffusion damage.
Surfactant-specific proteins, synthesized almost exclusively by type II alveolar cells,
represent a minor but necessary fraction of the surfactant.17,18 Inside type II alveolar cells SPB
undergoes complex proteolithic processing, changing from a larger form to the mature active form
of SPB (8-kDa).18 Physiologically the mature form of surfactant protein B plays a critical role in
formation and stabilization of pulmonary surfactant films and, indeed, the deficiency of SPB leads
to a lethal respiratory distress syndrome.31 The hydrophilic precursors of SPB, weighing 17 to 42kDa, more easy detectable in the blood than the small hydrophobic 8-kDa mature form, have been
8
reported increased in the plasma of HF patients, suggesting alveolar cell wall leak and, in all
likelihood, cell death.16,19 It has been suggested that SPB increase in HF patients is due to an acute,
although transient, increase in pulmonary microvascular pressure (Pmv) such as that observed during
an acute cardiogenic edema.19,20 The increase in pulmonary microvascular pressure leads to a
mechanical disruption of the alveolar-capillary barrier with an increased leakage of SPB into the
bloodstream, owing to the large concentration gradient (1500:1) between alveolar cells and blood.
Specifically, it has been demonstrated that circulating plasma SPB levels were higher in the most
severe HF patients, as suggested by NYHA classification and HF hospitalization rate.16 The present
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data confirm that SPB values are increased in HF even in subjects in stable clinical conditions such
ours who, according to study inclusion criteria, had been clinically stable for at least 2 months.
Therefore, albeit a significant SPB increase is reasonable during a transient increase of Pmv, it is
also possible that alveolar cell disruption participates in the chronic dynamic remodeling of the
alveolar capillary membrane in HF patients, which is characterized by progressive reduction in the
number of the alveolar-capillary units, increase of interstitial fibrosis and cellularity as well as local
thrombosis.13-15 Indeed, albeit we have not carried out repeated SPB measurements in the same
subject, our data are consistent with the concept of a constant SPB flow into the circulation due to
chronic remodelling of the alveolar-capillary membrane and suggest SPB as a possible biological
marker for chronic alveolar-capillary damage.
Lung function abnormalities are well known in chronic HF and data observed in the present
population, both in terms of lung mechanics and gas exchange impairment, are similar to those
previously reported by various groups.1-4 Furthermore, it is well known that lung diffusion
impairment is one of the possible causes of exercise limitation in chronic HF.10 Indeed, in the
presence of alveolar-capillary membrane damage the oxygen gradient across the alveolar-capillary
membrane, the ∆(A-a)O2, increases particularly when oxygen flow has to increase, for example
during exercise.10 However, the amount of ∆(A-a)O2 at rest and how fast the ∆(A-a)O2 increases
during exercise is related to resting lung diffusion and to how lung diffusion changes during
9
exercise.10 Furthermore an upper limit of the ∆(A-a)O2 seems to exist, so that all-in-all these
observations explain the link between exercise limitation and gas exchange impairment in HF
patients. A similar link between exercise capacity and lung diffusion applies to elite athletes.32
Accordingly, HF patients with lowest lung diffusion capacity are those with the lowest ability to
perform exercise at altitude, where alveolar gas diffusion is also limited by the reduced air pO2.10 It
is of note that both DLCO and DM are strongly related to SPB values but that DM is the parameter
which, under multivariable analysis, remains related to SPB. Indeed DM is the specific alveolarcapillary membrane resistance while DLCO, besides being influenced by DM, is also influenced by
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the capillary volume which is the amount of blood participating in gas exchange during the DLCO
measurement.
Exercise performance is usually evaluated in terms of oxygen consumption during
exercise.21,22 However, during the last decade, it has become evident that other parameters obtained
from an exercise study are useful for exercise performance evaluation in HF, more specifically the
VE vs. VCO2 relationship.22-25 The relationship between VE and VCO2 has been evaluated as the
ratio of VE and VCO2 at anaerobic threshold,33 as the lowest ratio recorded during exercise34 or as
the slope of VE vs VCO2 throughout the entire exercise35 or, more physiologically, from the
beginning of exercise up to the end of the iso-capnic buffing period,24 as was the case in the present
study. Regardless of the methods used for calculation, the relationship between VE and VCO2
reflects the efficiency of ventilation. It is of note that VE vs. VCO2 relationship is a prognosis
predictor for HF independent of peak VO2, and, in reality, the combined use of peak VO2 and VE
vs. VCO2 has a stronger ability to predict prognosis in HF patients than both parameters taken
individually.22 Interestingly, on multivariable analysis, both peak VO2 and VE/VCO2 slope were
correlated to SPB, again suggesting the physiological link between anatomical damage of the
alveolar-capillary membrane and ventilation efficiency as well as overall exercise performance.
The present is the first demonstration of a link between anatomical alveolar-capillary
damage, as inferable by circulating plasma SPB values, and functional alveolar-capillary damage,
10
as inferable by lung diffusion parameters, and efficiency of ventilation abnormalities and overall
exercise performance in HF. However, the correlation between circulating plasma SPB levels and
functional changes of the respiratory pattern in HF patients needs to be further studied. It is likely,
but up to now unproved, that an increase wedge pressure might contribute to both SPB increase
through an alveolar-capillary membrane damage and to ventilation/perfusion mismatch, as inferable
from VE/VCO2 slope analysis. At present, no clinical application of plasma SPB is known but a
possible clinical role of SPB can be foreseen. Indeed, up to now, we cannot evaluate whether or not
treatment capable of effecting DLCO, influences the anatomy of the alveolar capillary membrane. It
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is probable that, in the future, it will be possible to differentiate between a functional effect, for
example active solute transport mechanisms,6,36 and an anatomical effect on the alveolar capillary
membrane, such as reduction of alveolar-capillary membrane remodeling rate. In other words it
might be possible to evaluate whether a drug acts on alveolar-capillary membrane function,
anatomy or both. Indeed, the present physiological interpretation of the effect of HF drugs acting on
the alveolar-capillary membrane seems to indicate that drugs such as ACE-inhibitors6 and βblockers37 act on the active transport mechanisms, while antialdosteronic drugs7 have an effect on
the anatomy of the alveolar capillary membrane. These are just working ideas which need to be
evaluated, but they represent a new way of looking at alveolar-capillary membrane remodeling and
function in HF.
CONFLICT OF INTEREST DISCLOSURES:
NONE
11
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36. Mutlu GM, Dumasius V, Burhop J, McShane PJ, Meng FJ, Welch L, Dumasius A,
Mohebahmadi N, Thakuria G, Hardiman K, Matalon S, Hollenberg S, Factor P.
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37. Agostoni PG, Contini M, Cattadori G, Apostolo A, Sciomer S, Bussotti M, Palermo P,
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15
Table 1. General characteristics and plasma SPB values of the two study groups.
HF Patients
Healthy Controls
N= 71
N= 19
P values
62/9
16/3
NS
Age, years
59 ± 13
59 ± 11
NS
BMI, kg/m2
26.9 ± 3.4
24.5 ± 2.2
.004
NYHA class
1.9 ± 0.8
1 ± 0.0
< .0001
33 ± 7
-
-
Male/Female
LVEF, %
Data are expressed as mean ± SD. BMI: body mass index; SPB: surfactant protein type B; LVEF:
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left ventricular ejection fraction; NYHA: New York Heart Association.
16
Table 2. Pulmonary function and CPET data in the two study groups.
HF Patients
Healthy Controls
N= 71
N= 19
P values
VC, % of predicted
92 ± 13
111 ± 13
< .0001
FEV1, % of predicted
85 ± 12
106 ± 12
< .0001
FEV1/VC
73 ± 8
76 ± 6
NS
DLco, ml/mmHg/min
19.7 ± 4.5
24.6 ± 6.8
< .0001
DLco, % of predicted
72 ± 13
90 ± 11
< .0001
DM, mL/mmHg/min
28.9 ± 7.4
38.7 ± 14.8
< .0001
97 ± 37
162 ± 48
< .0001
Peak VO2, ml/min
1300 ± 425
1947 ± 620
< .0001
Peak VO2, ml/kg/min
16.2 ± 4.3
26.8 ± 6.2
< .0001
VO2 at AT, ml/kg/min
10.2 ± 5.5
16.1 ± 3.0
< .0001
Peak VCO2, ml
1484 ± 474
2365 ± 759
< .0001
Peak VE, l/min
54 ± 13
78 ± 27
< .0001
VE/VCO2 Slope
29.7 ± 5.9
24.5 ± 3.2
< .0001
Pulmonary function data
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CPET data
Peak Workload, Watts
Data are expressed as mean ± SD. VC: lung vital capacity; FEV1: forced expiratory volume; DLco:
lung diffusion for carbon monoxide; DM: membrane diffusion capacity; VO2: oxygen consumption;
AT: anaerobic threshold; VCO2: carbon dioxide production; VE: ventilation.
17
Table 3. SPB values categorized accordingly to DM, peak VO2 and VE/VCO2 slope classification.
DM
Controls
Classification
Class A
Class B
Class C
Class D
(> 30
(> 25 to 30
(≤ 20 to 25
(< 20
P Anova
ml/mmHg/min) ml/mmHg/min) ml/mmHg/min) ml/mmHg/min)
N.
19
26
21
17
7
1.6 (2.3)
1.6 (3.7)
6.2 (10.9)
8.9 (17.1)
11.9 (15.8)
Controls
Class A
Class B
Class C
Class D
(> 20
(> 16 to 20
(≥ 12 to 16
(< 12
ml/min/kg)
ml/min/kg)
ml/min/kg)
ml/kg/min)
19
15
18
27
11
SPB, au
1.6 (2.3)
1.5 (1.8)
3.2 (7.4)
7.9 (11.2)
12.7 (18.2)
VE/VCO2 Slope
Controls
SPB, au
Peak VO2
Classification
N.
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Class A
Class B
(< 34)
(≥ 34)
19
56
15
1.6 (2.3)
3.0 (6.9)
13.6 (15.0)
Classification
N.
SPB, au
< .0001
P Anova
< .0001
P Anova
< .0001
SPB values are reported as median and, between brackets, the interquartile range [75th percentile 25th percentile]. N: number of subjects. Au: arbitrary units.
18
Table 4. Spearman’s correlations between SPB-Total, lung diffusion and CPET parameters in the
heart failure population.
SPB
DLCO
DM
Peak VO2
VE/VCO2 Slope
SPB
--
– 0.37
– 0.51
– 0.48
+ 0.55
DLCO
--
--
+ 0.78
+ 0.51
– 0.40
DM
--
--
--
+ 0.50
– 0.55
Peak VO2
--
--
--
--
– 0.67
All correlation coefficient reported are significant with p < .0001. See table 2 and 3 for
abbreviations.
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19
Figure Legends
Figure 1. Example of SPB analysis’ results obtained by immunoblotting technique in an
healthy control and in four HF patients with different membrane diffusion capacity (DM) values.
Figure 2. Relationship between circulating plasma SPB and DM values in the entire study
population (r value refers to Spearman’s correlation in heart failure population only). Normal
subjects are shown, for completeness, with bold symbols.
Figure 3. Relationship between circulating plasma SPB and peak VO2 values in the entire
study population (r value refers to Spearman’s correlation in heart failure population only). Normal
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subjects are shown, for completeness, with bold symbols.
Figure 4. Relationship between circulating plasma SPB and VE/VCO2 slope values in the
entire study population (r value refers to Spearman’s correlation in heart failure population only).
Normal subjects are shown, for completeness, with bold symbols.
20
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Circulating Plasma Surfactant Protein Type B as Biological Marker of Alveolar-Capillary
Barrier Damage in Chronic Heart Failure
Damiano Magrì, Maura Brioschi, Cristina Banfi, JeanPaul Schmid, Pietro Palermo, Mauro
Contini, Anna Apostolo, Maurizio Bussotti, Elena Tremoli, Susanna Sciomer, Gaia Cattadori,
Cesare Fiorentini and Piergiuseppe Agostoni
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Circ Heart Fail. published online March 30, 2009;
Circulation: Heart Failure is published by the American Heart Association, 7272 Greenville Avenue, Dallas, TX
75231
Copyright © 2009 American Heart Association, Inc. All rights reserved.
Print ISSN: 1941-3289. Online ISSN: 1941-3297
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