Evaluation of Right Ventricular Function in Patients With COPD
Yosuke Tanaka MD PhD, Mitsunori Hino MD PhD, Kyoichi Mizuno MD PhD,
and Akihiko Gemma MD PhD
BACKGROUND: Pulmonary hypertension is an independent risk factor for death in patients with
COPD. Current prognostic models of COPD do not include sufficient indicators of right ventricular
(RV) function to enable accurate assessment of changes in RV function over time. The aim of the
present study was to test the hypothesis that it would be useful to include noninvasive markers of
RV function in the routine assessment and prognostic models of early stage COPD with or without
pulmonary hypertension. METHODS: We reviewed the clinical records of 49 male subjects who
had COPD but no other conditions that might affect physical status or prognosis, who underwent
cardiac ultrasonography. Various echocardiographic parameters of pulmonary circulation and RV
function were compared with indices of physical status and prognosis. RESULTS: The Medical
Research Council dyspnea score was higher in subjects with echocardiographic findings suggestive
of pulmonary hypertension than those without (mean ⴞ SD 3.17 ⴞ 1.23 vs 2.26 ⴞ 0.81, P ⴝ .02).
RV ejection time, RV isovolumetric relaxation time, RV isovolumetric contraction time ⴙ RV
isovolumetric relaxation time, and RV total ejection isovolume index differed significantly between
subjects with echocardiographic findings suggestive of pulmonary hypertension and those without.
The RV total ejection isovolume index was strongly correlated with the MRC score (P < .001), and
was significantly correlated with the overall survival rate (hazard ratio 5.31, 95% CI 1.91–14.77)
and hospital-free survival rate (hazard ratio 3.26, 95% CI 1.48 –7.16). CONCLUSIONS: It may be
valuable to add assessment of RV function to the routine evaluation of physical status in patients
with COPD. Key words: chronic obstructive respiratory disease; right ventricular function; echocardiography; pulmonary hypertension; heart failure; circulation. [Respir Care 2013;58(5):816 –823. © 2013
Daedalus Enterprises]
Introduction
COPD is well known to cause systemic effects. Discrepancies are often observed between the physical status
Drs Tanaka and Hino are affiliated with the Department of Respiratory
Medicine, Chiba-Hokusoh Hospital, Nippon Medical School, Chiba, Japan. Dr Mizuno is affiliated with the Division of Cardiology; and
Dr Gemma is affiliated with the Division of Pulmonary Medicine, Infectious Diseases, and Oncology, Department of Internal Medicine, Nippon Medical School, Bunkyo-ku, Tokyo, Japan.
The authors have disclosed no conflicts of interest.
Correspondence: Yosuke Tanaka MD PhD, Department of Respiratory
Medicine, Chiba-Hokusoh Hospital, Nippon Medical School, 1715 Kamagari, Inzai, Chiba 270-1694, Japan.
DOI: 10.4187/respcare.01856
816
of COPD patients and the results of routine tests such as
pre and post exercise blood gas analysis and pulmonary
function tests.1 Classification of the severity of COPD
according to the Global Initiative for Obstructive Lung
Disease (GOLD) classification is based on the degree of
air-flow obstruction (percent-of-predicted FEV1). This classification is limited, as it does not include other important
factors such as exercise tolerance, comorbidities, and complications.1 Physical status is affected by various factors,
including impairment of ventilation and gas exchange, hypoxia, and impairment of pulmonary circulation.1 For this
reason, assessment of the severity of COPD often uses a
combination of assessment tools, such as the BODE index
(body mass index, air-flow obstruction, dyspnea, and exercise capacity), the St George’s Respiratory Questionnaire (SGRQ), and the 36-item Medical Outcomes Study
Short Form questionnaire (SF-36).2,3 None of these indices
include an assessment of pulmonary artery pressure or
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right ventricular (RV) load. However, some studies have
reported that pulmonary hypertension (PH) is an independent risk factor for death in patients with COPD.4,5 Early
changes in RV function have been reported in clinically
stable COPD patients with no evidence of PH.6 If a noninvasive and easily available marker of RV function is
included in prognostic models of COPD, RV overload
may be detected even in patients with mild or absent elevation of pulmonary artery pressure.
Some studies have reported the assessment of RV function and pulmonary artery pressure by Doppler echocardiography.7-15 These studies recommended using the total
ejection isovolume (TEI) index as a noninvasive method
to assess RV function in patients with PH.7,8 Several studies have reported on the use of the TEI index to assess RV
function, but these studies included only patients with severe pulmonary arterial hypertension, old tuberculosis, or
connective tissue disease.7,9,11 The TEI index has not been
used as a marker of RV function in prognostic models of
COPD.
At our institution, echocardiography with a focus on
pulmonary artery pressure and the TEI index is performed
routinely on COPD patients, to check for PH and to detect
any other cardiac conditions that may affect activities of
daily living (ADLs).
Based on the assumption that COPD leads to reduced
RV compliance and changes in RV function before pulmonary artery pressure begins to rise, we hypothesized
that it would be useful to include markers of RV function
in the routine assessment and prognostic models of early
stage COPD, with or without PH. Such a marker of RV
function should be clinically feasible and noninvasive. We
used the data available at our institution to retrospectively
compare the TEI index with the physical status and prognosis of COPD patients.
Methods
The clinical records of all male patients with COPD
who were admitted to our hospital from April 2000 to
March 2005 were reviewed to identify those who underwent routine echocardiography during this time period and
did not require any change in their treatment regimen for
at least 3 months before and 3 months after echocardiography. The diagnosis of COPD was in accordance with the
criteria established by the American Thoracic Society. We
included only men in this study because the assessment of
physical status is affected by symptoms such as respiratory
distress, which may be affected by hormonal changes in
women.16-26 Patients were excluded from the analysis if
any condition other than COPD that might affect ADLs,
such as arrhythmia, changes in left ventricular (LV) function, or intervertebral disc herniation, was observed from
the time of echocardiography until the end of the analysis
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PATIENTS WITH COPD
QUICK LOOK
Current knowledge
Pulmonary hypertension is an independent risk factor
for death in patients with COPD. The available prognostic models for COPD do not include indicators of
right ventricular (RV) function for assessing RV function over time.
What this paper contributes to our knowledge
There were strong correlations between COPD-associated RV dysfunction and prognosis, and difficulty with
activities of daily living. COPD may cause RV dysfunction in the absence of pulmonary hypertension.
COPD assessment guidelines should include assessment
of pulmonary hypertension and RV function.
period in March 2011. Patients were also excluded if they
required psychotropic medication, a change in medication
dose for more than 4 weeks, or a change in any medication
that may affect hemodynamic function, such as theophylline, steroids, diuretics, digitalis, or antihypertensive agents,
as these could affect assessment of the progression of
COPD. An increase in diuretic medication was allowed if
it was required to treat congestion resulting from worsening PH. These selection criteria were set because this study
aimed to evaluate the usefulness of additional assessment
of RV function, compared with the usual assessments undertaken in patients with COPD.
At our institution, all patients with COPD routinely underwent echocardiography in addition to standard chest
x-ray and pulmonary function tests, unless they explicitly
refused. All echocardiography measurements were performed at rest, and were performed by the same staff using
the same equipment throughout the study period. Subjects
were evaluated for respiratory failure, physical status, hospital-free survival, and overall survival. Physical status
was assessed using the Medical Research Council (MRC)
dyspnea scale.27 Treatment of COPD was limited to that
recommended by the American Thoracic Society guidelines for COPD,1 ensuring that arterial oxygen saturation
did not fall below 90% during ADLs. This study was
approved by the medical ethics committee of Nippon Medical School.
Echocardiographic Examination
Complete 2-dimensional, pulsed-wave, color-flow echocardiography was performed using an ultrasound machine
(Sonos 1000, Hewlett-Packard, Palo Alto, California), as
previously described.7,9-11,14,28-33
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Statistical Analysis
Values are expressed as mean ⫾ standard deviation. All
comparisons between groups were performed using the
Mann-Whitney U test. Correlations were investigated using Spearman rank correlation test. Survival analysis was
performed using the Cox proportional hazards model. In
all analyses, P ⬍ .05 was considered significant. All statistical analyses were performed using statistics software
(JMP 6.03, SAS Institute, Cary, North Carolina).
Fig. 1. Schema of color Doppler echocardiographic measurements.
A: Interval between the cessation of tricuspid in-flow and the start
of the next tricuspid in-flow. B: Interval between the R wave and
the cessation of right ventricular (RV) out-flow. C: Interval between
the R wave and the start of tricuspid in-flow. RV out-flow acceleration time (AcT) is the interval between the start of RV out-flow
and peak velocity. Ejection time (ET) is the interval of RV out-flow,
measured from the start to the end of the RV out-flow Doppler
velocity profile below the baseline. Tricuspid closing to opening
time is the interval between the end and start of the tricuspid
in-flow Doppler velocity profile above the baseline, shown as A.
Mean values were obtained by averaging at least 5 beats. Interval
A from the cessation to the start of tricuspid forward flow was
calculated as the sum of isovolumetric contraction time (ICT, calculated as A – ET – IRT), ET, and isovolumetric relaxation time
(IRT, calulated as C – B). The interval measured by subtracting ET
from A was calculated as ICT ⫹ IRT. The total ejection isovolume
(TEI) index, which is a systolic and diastolic myocardial performance index, was calculated as (A – ET)/ET. The other parameters
(IRT, ICT, and ICT/ET) were determined according to the method
of Tei et al.9
The right heart circulation was assessed as follows. Color
Doppler flow imaging was used to detect and semi-quantify pulmonary and tricuspid valve regurgitation. The tricuspid in-flow velocity was recorded from the apical
4-chamber view with the pulsed-wave Doppler sample volume positioned at the tip of the tricuspid leaflets during
diastole. The RV out-flow tract velocity was recorded from
the parasternal short-axis view with the pulsed-wave Doppler sample volume positioned just below the pulmonary
valve.
Doppler Measurements
All measurements for the assessment of RV function
were performed according to the methods previously reported7,9-11 (Fig. 1). Mean values were obtained by averaging at least 5 beats. RV out-flow acceleration time and
tricuspid regurgitation velocity were measured to determine if there was any evidence of PH. Results were considered to be suggestive of PH when the tricuspid regurgitation velocity was ⬎ 2.8 m/s without pulmonary valve
stenosis,8,34 when PA acceleration time was ⬍ 90 ms, or
when PA acceleration time/PA ejection time was
⬍ 0.3.14,15,35 All measurements were made at end-expiration.
818
Results
Of the 241 COPD patients who attended our hospital
from April 2000 to March 2005, 53 met the inclusion
criteria for this study. Patients were excluded for the following reasons: 33 had cardiac disease that affected ADLs,
such as LV dysfunction, 26 had unstable COPD, 11 had
dementia, 18 had cerebral disease that impaired ADLs, 24
had arrhythmia including atrial fibrillation, 15 had other
conditions with affected ADLs such as intervertebral disc
herniation, 23 had pulmonary disease other than COPD, 5
were taking psychotropic medication, and 9 could not attend the hospital on a regular basis. Twenty-four of these
patients met at least 2 exclusion criteria. Four additional
patients were excluded later because they developed cardiac disease that might have resulted in LV dysfunction on
effort during the analysis period (the time from echocardiography to March 2011). None of the remaining 49 patients had conditions other than COPD that might have
affected ADLs.
Table 1 shows the clinical characteristics of the study
population. There were no significant differences in age,
height, body weight, or pulmonary function indices between subjects with findings suggestive of PH and those
without. Physical status assessed by the MRC dyspnea
score was significantly worse in subjects with findings
suggestive of PH (P ⫽ .02).
Table 2 shows the Doppler echocardiographic parameters in subjects with and without findings suggestive of
PH. Except for isovolumetric contraction time, these parameters were all significantly different between the 2
groups. Even though physical status assessed by the MRC
dyspnea score and several color Doppler echocardiographic
parameters differed significantly between the groups, there
was overlap between groups in all of these indices. These
findings differ from the data reported in previous studies
of subjects with severe PH.9-11 As a result, none of the
indices could be used to distinguish the 2 groups of subjects in this study, indicating that RV functional disorder
may occur even in the absence of PH.
Figure 2 shows a significant correlation between the
TEI index and the MRC dyspnea score. The results presented in Table 1 and Figure 2 indicate that the pulmonary
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Table 1.
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PATIENTS WITH COPD
Clinical Characteristics of the Study Population
Male/female, no.
Age, y
Height, cm
Weight, kg
MRC dyspnea score
FEV1/FVC
%FEV1/%FVC
TLC, L
DLCO, mL/min/mm Hg
DLCO/predicted DLCO
PaO2, mm Hg
Pulmonary
Hypertension
No Pulmonary
Hypertension
30/0
71.73 ⫾ 5.98
162.46 ⫾ 8.18
57.44 ⫾ 11.70
3.17 ⫾ 1.23
42.71 ⫾ 13.98
49.29 ⫾ 21.66
5.99 ⫾ 1.33
12.40 ⫾ 6.87
86.21 ⫾ 43.60
74.64 ⫾ 18.17
19/0
72.21 ⫾ 5.87
163.40 ⫾ 8.20
56.55 ⫾ 7.93
2.26 ⫾ 0.81
48.87 ⫾ 14.56
65.97 ⫾ 30.61
5.68 ⫾ 1.27
11.99 ⫾ 6.36
83.35 ⫾ 37.52
78.20 ⫾ 11.38
P
All Subjects
.86
.45
.88
.02
.18
.058
.32
.88
.69
.18
49/0
71.92 ⫾ 5.88
162.82 ⫾ 7.88
57.10 ⫾ 10.32
2.82 ⫾ 1.17
45.10 ⫾ 14.38
55.76 ⫾ 26.50
5.87 ⫾ 1.30
12.26 ⫾ 6.62
30 ⫾ 40.99
75.78 ⫾ 16.15
⫾ Values are mean ⫾ SD.
MRC ⫽ Medical Research Council
TLC ⫽ total lung capacity
DLCO ⫽ diffusing capacity of the lung for carbon monoxide
Table 2.
Color Doppler Echocardiographic Results
RV ejection time, ms
RV isovolumetric contraction time, ms
RV isovolumetric relaxation time, ms
Isovolumetric contraction time ⫹ isovolumetric
relaxation time, ms
Total ejection isovolume index
Pulmonary
Hypertension
No Pulmonary
Hypertension
P*
All subjects
229 ⫾ 50.5
48.5 ⫾ 26.3
98.3 ⫾ 44.4
145 ⫾ 51.4
294 ⫾ 37.7
38.8 ⫾ 21.9
66.0 ⫾ 22.4
100.2 ⫾ 32.9
⬍ .001
.30
.01
.001
225.19 ⫾ 55.71
45.07 ⫾ 24.99
87.07 ⫾ 41.01
127.61 ⫾ 49.87
0.68 ⫾ 0.45
0.35 ⫾ 0.14
.002
0.55 ⫾ 0.40
Values are mean ⫾ SD.
* Via Mann-Whitney U test.
RV ⫽ right ventricular
Fig. 2. Correlation between total ejection isovolume (TEI) index
and MRC dyspnea score in subjects with COPD (Spearman rank
correlation test). The correlation is significant.
circulation affects the physical status of COPD subjects,
especially the limitation of ADLs. No other parameters
were significantly correlated with the MRC dyspnea score.
RESPIRATORY CARE • MAY 2013 VOL 58 NO 5
Figure 3 and Table 3 show hospital-free and overall survival analyzed by the Cox proportional hazards model.
Backward stepwise selection, including age, height, weight,
total lung capacity (TLC), FEV1/FVC, percent-of-predicted
FEV1, and TEI index, showed that percent-of-predicted
FEV1, FEV1/FVC, TEI index, and height were correlated
with hospital-free survival. As the correlation coefficient
between FEV1/FVC and percent-of-predicted FEV1 was
high, correlation was assessed separately among age, height,
weight, TLC, FEV1/FVC, and TEI index, and among age,
height, weight, TLC, percent-of-predicted FEV1, and TEI
index. TEI index and height were shown to be independently correlated with hospital-free survival. Backward
stepwise selection, including age, height, weight, TLC,
percent-of-predicted FEV1, FEV1/FVC, and TEI index,
showed that TEI index and height were correlated with
overall survival. Analyses using body mass index instead
of height and weight showed that body mass index was not
correlated with hospital-free or overall survival. Further
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PATIENTS WITH COPD
Fig. 3. Cumulative survival versus (A) hospital-free survival days and (B) overall survival days (via Cox proportional hazards model) in
49 subjects. For hospital-free survival days (A), backward stepwise selection included age, height, weight, percent-of-predicted FEV1,
FEV1/FVC, total lung capacity (TLC), and total ejection isovolume (TEI) index. Only TEI index (P ⫽ .003) and height (P ⫽ .03) were correlated
with hospital-free survival days. For overall survival days (B), backward stepwise selection included age, height, weight, percent-ofpredicted FEV1, FEV1/FVC, TLC, and TEI index. Only TEI index (P ⬍ .001) and height (P ⬍ .03) were related to overall survival. TEI index
and height were independently correlated with hospital-free and overall survival. The other factors were were not correlated with hospitalfree or overall survival. Analysis using body mass index instead of height and weight showed that body mass index was not associated with
hospital-free or overall survival.
Table 3.
Survival Versus Total Ejection Isovolume Index Category*
Hospital-free survival days
TEI index
Height
Overall survival days
TEI index
Height
Coefficient
SD
Coefficient/SD
Chi-square
1.18
0.08
0.40
0.04
2.94
2.23
8.62
4.96
1.67
0.10
0.52
0.05
3.20
2.22
10.25
4.91
Exp
(coefficient)
95% CI of Exp
(coefficient)
.003
.03
3.26
1.09
1.48–7.16
1.01–1.17
⬍ .001
.03
5.31
1.11
1.91–14.77
1.01–1.21
P
* These data correspond to Figure 3.
TEI ⫽ total ejection isovolume
analysis showed that TEI index and height were independently correlated with overall survival. The TEI index
showed an especially high correlation with both hospitalfree survival (P ⫽ .003) and overall survival (P ⬍ .001).
These results indicate that the TEI index may be a useful
marker of RV function to include in prognostic models of
COPD. RV dysfunction as determined by the TEI index
may provide an indication of disease progression and clarify the effects of COPD on ADLs.
Discussion
In 2005 it was reported that severe PH was associated
with reduced survival of COPD patients.4,5 However, no
studies have included assessment of RV function in the
evaluation of the physical status of COPD patients with
absent or very early PH. The present study found that
820
MRC dyspnea scores were significantly correlated with
the TEI index and several echocardiographic parameters,
but not with pulmonary function indices. The TEI index
was also significantly correlated with overall and hospitalfree survival. These data strongly suggest that assessment
of RV function using the TEI index is very useful for
assessing the physical status and prognosis of patients with
COPD.
We evaluated exertional dyspnea using the MRC dyspnea score. In patients with COPD, exercise capacity is
limited by PH, muscular fatigue of the lower extremities,
and pulmonary dysfunction. Exercise test results do not
correlate well with the results of pulmonary circulation or
function tests. Some reports have indicated that the anaerobic threshold can be noninvasively determined by analysis of expiratory gas.36,37 This is difficult in patients with
COPD, however, because the responses that increase ven-
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tilatory volume at the anaerobic threshold are limited, the
increase in carbon dioxide production is delayed because
the PaCO2 tends to increase during exercise, and the respiratory pattern is disturbed.36,37 The characteristic ventilatory responses at the anaerobic threshold and maximum
oxygen uptake are therefore difficult to measure.
Various methods are currently used to evaluate the physical status of COPD patients, including the 6-min walk
test, New York Heart Association functional class, SF-36,
BODE index, and SGRQ.2,3 We could not use these methods in the present analysis because of the retrospective
nature of the study. The GOLD classification may not be
an ideal method for evaluation of the physical status of
COPD patients because it is mostly based on the degree of
air-flow limitation,1 and does not account for the effects of
other systemic conditions. However, the MRC dyspnea
score has been reported to be as useful as the SGRQ or
Chronic Respiratory Questionnaire as a measure of disability in patients with COPD.27 The MRC dyspnea score
was therefore used in this study to evaluate the physical
status of COPD patients, and more detailed evaluation of
the physical status was not possible.
Nevertheless, the TEI index showed good correlation
with the MRC dyspnea score, suggesting that if a more
detailed physical status score was used, an even stronger
correlation may have been found between physical status
and the TEI index. The severity of dyspnea and the effect
of dyspnea on ADLs depend on factors such as musculoskeletal build, heart rate, and cardiac disease causing LV
dysfunction at rest or on effort. Patients with LV dysfunction on effort associated with cor pulmonale8,16,37 were
included because this condition results from RV dysfunction.38-41 Other underlying conditions that may have resulted in LV diastolic dysfunction were excluded. It should
be noted that the TEI index is not affected by heart rate.9
Our results confirmed that the arterial oxygen saturation
did not fall below 90% in any patients during ADLs.
The strict exclusion criteria of this study resulted in
inclusion of ⬍ 25% of the COPD patients treated at our
institution. The present data suggest that RV dysfunction
associated with COPD, as assessed by the TEI index, markedly affected ADLs, with or without findings suggestive of
PH. The TEI index was highly correlated with the MRC
dyspnea score and the prognosis of COPD patients.
Our results showed that the TEI index was an independent prognostic factor in COPD. Height was also correlated with prognosis in patients with COPD, whereas age,
weight, FEV1/FVC, percent-of-predicted FEV1, and TLC
were not. Failure to detect any association between age,
weight, FEV1/FVC, percent-of-predicted FEV1, and TLC
and the prognosis of COPD patients may be partly explained by the highly homogeneous study population. Some
of these factors might have shown correlations with prognosis if the exclusion criteria had been relaxed. However,
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PATIENTS WITH COPD
relaxation of the exclusion criteria was not possible in this
study, for the reasons described above.
This study has a number of limitations. Many of the
subjects had a good overall physical status, because they
were all out-patients in a stable condition. All hemodynamic parameters were assessed by echocardiography only,
which has limited accuracy, compared with invasive methods such as catheterization. The prevalence of echocardiography findings suggestive of PH in this study was higher
than the reported prevalence of PH on invasive hemodynamic assessment in patients with severe emphysema requiring lung-volume-reduction surgery.42 This may reflect
aspects of this cohort that are not generalizable, and reinforces the need for our observations to be repeated and
validated. Even though echocardiography has a relatively
poor ability to accurately diagnose PH in individual cases,34
the MRC dyspnea score was significantly different between the groups with and without findings suggestive of
PH. The percent-of-predicted diffusing capacity of the lung
for carbon monoxide was slightly higher in the group with
findings suggestive of PH than the group without, but this
difference was not significant. This may be due to the
method of assessing PH in this study, as well as the nature
of percent-of-predicted DLCO, which, unlike FEV1/FVC or
percent-of-predicted FEV1, is substantially affected by the
subject’s breathing effort.
Another limitation was the small sample size, this being
a single-center study including only male subjects, the
majority of whom were elderly. Subject numbers were
limited by the inclusion of only those who were in a stable
condition requiring no changes in their treatment regimens
within 3 months of echocardiography, and the exclusion of
patients with any condition other than COPD that might
have affected their ADLs. The study showed that the MRC
dyspnea score was correlated with PH, and the RV TEI
index was correlated with the MRC dyspnea score. To our
knowledge, this is the first study demonstrating that the
TEI index is correlated with survival independently of
factors such as the severity of COPD, TLC, and age.
We also compared the clinical characteristics between
subjects with a TEI index ⬍ 0.28 and those with a TEI
index ⱖ 0.28; the score of 0.28 was selected as the cutoff
because the normal RV TEI index is 0.28 ⫾ 0.04.7,9 In this
analysis the difference in MRC dyspnea score between the
2 groups was significant (P ⫽ .04). By contrast, the other
parameters listed in Table 4, including percent-of-predicted
FEV1, DLCO, and percent-of-predicted DLCO, were not significantly different. However, because there were fewer
subjects with a TEI index ⬍ 0.28 than subjects with a TEI
index ⱖ 0.28, this cutoff value may be too low for subjects
with COPD in routine clinical settings, which likely biased
the results. When we repeated the analysis by classifying
subjects according to RV TEI index ⬍ 0.40 or ⱖ 0.40,
there were significant differences between the 2 groups for
821
EVALUATION
Table 4.
OF
RIGHT VENTRICULAR FUNCTION
Total Ejection Isovolume Index
Category
n
Age, y
Height, cm
Weight, kg
MRC dyspnea score
FEV1/FVC
TLC, L
PaO2, mm Hg
ⱖ 0.28
12
70.17 ⫾ 7.02
162.55 ⫾ 7.48
61.12 ⫾ 7.96
2.33 ⫾ 1.23
52.03 ⫾ 15.90
5.45 ⫾ 0.90
81.06 ⫾ 9.73
37
72.49 ⫾ 5.45
162.91 ⫾ 8.10
55.79 ⫾ 10.75
2.98 ⫾ 1.12
42.85 ⫾ 13.31
6.01 ⫾ 1.39
77.47 ⫾ 18.60
P
.87
.74
.06
.04
.06
.25
.19
⫾ Values are mean ⫾ SD.
MRC ⫽ Medical Research Council
TLC ⫽ total lung capacity
MRC dyspnea score, FEV1/FVC, and percent-of-predicted
FEV1. These findings may be inevitable when evaluating
RV function in subjects with COPD. Considering these
findings, the RV TEI index is a highly sensitive marker for
RV function in prognostic models of COPD, because a
strong correlation was observed only with the TEI index in
analyses of specific indices including MRC dyspnea score,
hospital-free survival, and overall survival.
These results indicate that further large-scale studies
using a more accurate assessment method for PH are warranted, to achieve a more detailed assessment of the RV
dysfunction associated with COPD, to further investigate
whether RV dysfunction mirrors the early decline in pulmonary function or occurs later secondary to pulmonary
failure, and to determine whether echocardiography can
provide additional useful measurements.
Conclusions
The results of this study demonstrate a strong correlation between RV dysfunction associated with COPD and
ADLs and prognosis of COPD patients, as expected. However, no marker of RV function that can be used in daily
clinical practice is currently available. Our results may
lead to further studies, and hopefully to inclusion of an
assessment of both PH and RV function in the guidelines
for COPD assessment. In the present study there was an
overlap in all parameters between patients with findings
suggestive of PH and those without, unlike data from previous studies of patients with severe PH.8-10 This indicates
that COPD may result in RV dysfunction without apparent
PH.
ACKNOWLEDGMENTS
We thank Professor Chuwa Tei, Department of Cardiovascular, Respiratory, and Metabolic Medicine, Graduate School of Medicine, Kagoshima
822
PATIENTS WITH COPD
University, Kagoshima, Japan; Peter D Wagner MD, Division of Pulmonary and Critical Care Medicine, University of California, San Diego;
and Richard L ZuWallack MD, Pulmonary Diseases, Saint Francis Hospital and Medical Center, Hartford, Connecticut, for their helpful advice.
Clinical Characteristics Versus Total Ejection Isovolume
Index Category
⬍ 0.28
IN
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