Download Vectorcardiographic Detection of Early Hemodynamic Abnormalities

Vectorcardiographic Detection of Early
Hemodynamic Abnormalities in Chronic
Obstructive Pulmonary Disease*
John R. Wilson,
Robert
John J. Picken,
The
M.D.; Ulysses G. Mason, III,
C. Bahler,
M.D., F.C.C.P.;
M.D., F.C.C.P.;
Edward
and Gerald
ability of the vectorcardiogram
M.D.;
H. Chester,
M.D.,
L. Baum, M.D.,
to detect
mild
F.C.C.P.;
F.C.C.P.
± 10.7 percent) or group 3 ( 1 7 . 8 ± 14.8 percent). Sixty-
circulatory abnormalities in patients with chronic ob-
five percent (13) of the 2 0 patients with hemodynamic
structive pulmonary disease (COPD) is unclear. There-
abnormalities had rightward terminal QRS forces of 15
fore, vectorcardiographic changes were correlated with
percent or more, whereas only 8 percent (one) of the
hemodynamic measurements made at rest and during
12 patients with normal hemodynamic data had such
supine exercise in 3 2 patients with COPD and no clini-
forces of 15 percent or more. The mean of the right-
cal or electrocardiographic evidence of right ventricu-
ward terminal QRS forces in 2 7 age-matched normal
lar hypertrophy. Twelve patients had normal hemody-
subjects was 5.0 ±
namic data (group 1), nine had abnormal hemodynamic
had forces of 15 percent or more. We conclude that
data only during exercise (group 2 ) , and 1 1 had abnor-
hemodynamic abnormalities are frequent
mal hemodynamic
exercise
with COPD and no clinical evidence of right ventricu-
(group 3 ) . The extent of rightward terminal QRS forces
lar hypertrophy and that the vectorcardiogram provides
noted on the vectorcardiogram was significantly less in
an indirect method of detecting these abnormalities.
data at rest and during
5.4 percent, and only one subject
in patients
group 1 (5.5 + 8.7 percent) than in either group 2 ( 1 9 . 0
T T e m o d y n a m i c abnormalities of the pulmonary circulation are found in over 50 percent of the
Based on these correlations, we identified a simple
vectorcardiographic
criterion
for
detecting
mild
patients with chronic obstructive pulmonary disease
hemodynamic abnormalities of the pulmonary circu-
(COPD).
lation in patients with C O P D .
1 - 8
These abnormalities
range from nor-
mal resting hemodynamics with abnormal circulatory responses to exercise "
1
monary
hypertension.
4
The
to severe resting pulclinical
examination,
MATERIALS AND METHODS
Ambulatory patients with C O P D and a forced expiratory
volume in one second ( F E V - J that was 7 5 percent or less
of the predicted value were identified by reviewing data from
pulmonary function tests and clinical records at Cleveland
Metropolitan General Hospital and Cleveland Veterans Administration Hospital. Patients with intrinsic heart disease,
hypertension, clinical signs of pulmonary hypertension, or
prior episodes of respiratory failure were excluded. Thirtytwo patients agreed to participate in this study. Written
informed consent was obtained. Twenty of these patients
were also part of a multidisciplinary study on the treatment
of C O P D .
1 2
electrocardiogram,
9
and vectorcardiogram
10,11
usu-
ally allow detection of those patients with moderate or severe pulmonary hypertension;
however,
the detection of patients with mild hemodynamic
abnormalities presently requires cardiac catheterization.
T h e purpose of this study was to determine if the
vectorcardiogram can also identify this latter group
of patients. By comparing hemodynamic and vectorcardiographic
data
in
a
group
of
patients
with
C O P D , we found that a single vectorcardiographic
measurement, the extent of rightward terminal QRS
forces, correlated with hemodynamic measurements.
* F r o m the Departments of Medicine, Cleveland Metropolitan
General Hospital, the Veterans Administration Hospital,
and Case Western Reserve University School of Medicine,
Cleveland.
Supported in part by grant 1 3 - P - 5 5 3 2 4 / 5 from the Social
and Rehabilitation Services of the US Department of Health,
Education, and Welfare.
Manuscript received August 7; revision accepted February 1.
Reprint requests: Dr. Bahler, Cleveland
Metropolitan
General Hospital, Cleveland
44109
160
1 3
Twelve-lead E C G s and vectorcardiograms using the Frank
lead system were obtained. E a c h patient also underwent
right heart catheterization on the same day or within a few
days of the vectorcardiogram. Therapy with all medications
was discontinued a minimum of 2 4 hours prior to hemodynamic study. At catheterization, the mean pulmonary arterial
pressure, the pulmonary capillary pressure, and the cardiac
output (indicator-dilution method with either indocyanine
green or iced saline solution as the indicator) were measured
at rest and again during the final minute of three to seven
minutes of supine exercise on a bicycle ergometer set at
between 1 5 0 and 3 0 0 kilopond • meters. Total pulmonary
resistance was calculated as the mean pulmonary arterial
WILSON ET AL
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CHEST, 76: 2, AUGUST, 1979
pressure divided by the cardiac output, and the pulmonary
vascular resistance was calculated as the mean pulmonary
arterial pressure minus the mean pulmonary capillary wedge
pressure divided by the cardiac output. The E C G s were
reviewed using the following criteria for right ventricular
hypertrophy: ( 1 ) S j - Q pattern; ( 2 ) right axis deviation of
1 0 0 " or more; ( 3 ) Sj-S^Sg pattern; and ( 4 ) R/S ratio of
one or less in leads V or V .
Right ventricular hypertrophy was considered to be present if two criteria were
met.T h e vectorcardiograms were classified into five types of
horizontal loops, as shown in Figure 1A. T h e maximum QRS
vector, the half-area QRS vector, the posterior/anterior ratio
of millivolts, and the percentage of area of e a c h quadrant were
measured on all horizontal and inferior loops as described
previously. Only the extent of rightward terminal QRS
forces was found to correlate with the hemodynamic m e a surements. This report will be confined to a discussion of this
variable.
The rightward terminal QRS force was calculated by using
a plastic grid to measure the percentage area in both the right
posterior quadrant in the horizontal loop and in the right
inferior quadrant in the frontal loop ( s h a d e d areas, Fig I B ) .
The rightward terminal QRS force was defined as the greater
of these two measurements.
The patients were divided into the following three groups
based on the hemodynamic findings: ( 1 ) group 1, normal
mean pulmonary arterial pressure or normal total pulmonary
resistance both at rest and during exercise; ( 2 ) group 2,
normal mean pulmonary arterial pressure or normal total
pulmonary resistance at rest, with clearly elevated values for
either or both with exercise; and ( 3 ) group 3, elevated mean
pulmonary arterial pressure and total pulmonary resistance
both at rest and during exercise.
The normal value for resting mean pulmonary arterial
pressure is 15 mm Hg (range, 10 to 18 mm H g ) and for
resting total pulmonary resistance is 2 . 5 6 ± 0.64 u n i t s . '
During modest levels of exercise, the mean pulmonary arterial pressure normally rises to 2 0 mm Hg (range, 15 to 2 9
3
5
6
1 4
11
1 5
mm H g ) , while the total pulmonary resistance remains unchanged or decreases slightly.
Normal subjects over 6 0
years of age may have mild elevations in total pulmonary
resistance during e x e r c i s e .
Criteria for the detection of abnormal hemodynamics were
evaluated using the following two f o r m u l a s : ( 1 ) sensitivity
equals the true-positives divided by the sum of the truepositives plus the false-negatives times 100; and ( 2 ) specificity equals the true-negatives divided by the sum of the
false-positives plus the true-negatives times 100.
F o r comparison, vectorcardiograms obtained from 27 agematched normal subjects were also analyzed for the extent of
the rightward terminal QRS force. None of these subjects had
smoked more than five years or within the past 15 years, and
no subject had clinical or electrocardiographic evidence of
cardiac or pulmonary disease. Statistical analysis was performed using standard least-squares methods for linear
regression and Student's nonpaired f - t e s t .
17
1 9
20
21
22
RESULTS
The characteristics of the 32 patients are noted in
the following tabulation, showing the mean values
(with ranges in parentheses):
Age, yr
51(37-69)
F E V , / (percent predicted)
47 ( 1 8 - 7 5 )
Arterial oxygen pressure ( P a 0 ) , m m H g
2
73 (54-98)
Arterial carbon dioxide tension ( P a C O , ) , m m H g 3 5 ( 2 8 - 4 9 )
Electrocardiographic data
Frontal-plane QRS axis, degrees
Frontal-plane P axis, degrees
S wave in lead V , m V
6
66(30-130)
70(59-90)
0.12(0-7)
1 6
F I G U R E 1. A (top), F i v e types of horizontal loops. Loops of
types 1, 2, and 3 are oriented posteriorly, while types 4 and 5
have anterior orientation. B (bottom),
Method for determining rightward terminal QRS forces. These were defined as
greater of following two measurements: ( 1 ) percentage area
in right posterior quadrant (horizontal l o o p ) ; and ( 2 ) percentage area in right inferior quadrant (frontal l o o p ) .
One patient had an R / S ratio of less than one in lead
Ve, and one patient had an S1-Q3 pattern. No patient had a Q R S duration exceeding 110 msec or
electrocardiographic evidence of right ventricular
hypertrophy. The results of catheterization and
vectorcardiographic analysis are shown in Table 1
and Figures 2 and 3. There was no statistical difference in the mean age, Pa02, or F E V i among the
three hemodynamic groups.
Loops of types 1, 2, 3, 4, and 5 were found in 15, 8,
3, 1, and 5 patients, respectively. An initial anterior
rightward (septal) force of greater then 10 msec
was found in only 17 patients (53 percent). There
was no correlation between hemodynamic variables
and either the absence of a normal septal force or
the type of vectorcardiographic loop.
There was no correlation between terminal rightward Q R S forces and hemodynamic data when all
32 patients were considered; however, in patients
with posteriorly oriented horizontal loops (types 1
to 3 ) , there was a linear correlation between terminal rightward Q R S forces and the mean pulmonary
arterial pressure during exercise (r = 0.54; P <
0.01) (Fig 4 ) and the total pulmonary vascular
CHEST, 76: 2, AUGUST, 1979
VCG DETECTION OF EARLY ABNORMALITIES IN COPD
Type I
Type
Type
2
3
14
iZ
Type
Horizontal
4
Loop
Type
5
Frontal
Loop
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161
Table
1—Hemodynamic and Vectorcardiographic
Group 1
Group 2
Group 3
50
52
52
F E V i , percent
51 + 18
51 ± 1 5
40 + 16
P a 0 , mm Hg
Rest
Exercise**
77 ± 1 3
72 ± 9
72 ± 8
71 ± 7
71 ± 7
62 + 10
Data
Age,
yr
Pulmonary capillary
wedge pressure,
mm Hg
Rest
Exercise
T o t a l pulmonary
resistance, units f
Rest
Exercise
Resting
50
Exercise
Normal
Normal
range
mean
cn 4 0
2
Pulmonary arterial
pressure, mm Hg
Rest
Exercise
60
Data*
T"
_1_
CZ
t
E
-—
16±3
24 ± 3
17±3
34 ± 4
23 ± 4
40 ± 8
30
\<
|o- 2 0
10
7±2
11 ± 3
7±2
14±2
10 + 4
18 + 7
0
Groupl
( n = 12)
2.71+0.54
2.72 ± 0 . 4 8
T e r m i n a l rightward
Q R S forces, percent 5.5 ± 8.7
3.19 ± 0 . 4 6
4.30 ± 1 . 0 3
4.16±0.84
5.25 ± 1 . 2 0
19.0±10.7
17.8 ± 1 4 . 8
* T a b l e values are means ± S D .
**Obtained in only six patients in each group.
fArbitrary units, where total pulmonary resistance equals
mean pulmonary arterial pressure divided by cardiac
output.
resistance during exercise (r = 0.41; P < 0.05) but
not with resting mean pulmonary arterial pressure,
resting total pulmonary resistance, or pulmonary
vascular resistance. When only patients with type-1
loops were considered, the correlation between the
rightward terminal QRS force and both the mean
pulmonary arterial pressure during exercise and the
total pulmonary resistance during exercise (r = 0.70;
P < 0.01) was improved.
Regardless of the configuration of the loops, vectorcardiograms in group 1 had significantly less terminal rightward QRS force (5.5 ± 8.7 percent) (P
< 0.01) than either group 2 (19.0 ± 10.7 percent)
or group 3 (17.8 ± 14.8 percent). Eighty-five percent ( 1 7 ) of the 20 patients with hemodynamic
abnormalities had rightward terminal QRS forces of
5 percent or more, and 65 percent ( 1 3 ) had such
forces of 15 percent or more. In contrast, only 25
percent (three) of the 12 patients with normal
hemodynamic data had a rightward terminal QRS
force of 5 percent or more, and only 8 percent (one)
had a rightward terminal QRS force of 15 percent or
more.
When the presence of a rightward terminal QRS
force of 5 percent or more was used to identify
patients with abnormal hemodynamics, 85 percent
of the patients in groups 2 and 3 were properly
identified, with a specificity of 75 percent. By using a
Group H
( n = 9)
Group IE
( n • II)
F I G U R E 2. Mean pulmonary arterial pressure ( P A ) at rest
and during supine exercise for three groups.
rightward terminal QRS force of 15 percent or more
to identify these patients, the sensitivity dropped to
65 percent, although the specificity increased to 92
percent. In the 26 patients with loops of types 1 to 3,
these same criteria were more sensitive, although the
specificity remained approximately the same. In
these 26 patients, when the criterion of a rightward
terminal QRS force of 5 percent or more was used,
80
Resting
Exercise
7
8
c
o
in
5
0
Normal
range
Normal
mean
6 0
50
o>
DC
r5
c
o
4.0
E
r> 3 . 0
Q_
0
0
Groupl
Groupl
GroupIU.
(n=l2)
(n-9)
(n=ll)
F I G U R E 3. Total pulmonary resistance at rest and during
supine exercise is expressed in arbitrary units ( U ) , where
total pulmonary resistance equals mean pulmonary arterial
pressure divided by cardiac output.
162 WILSON ET AL
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CHEST, 76: 2, AUGUST, 1979
saturation correlated with hemodynamic data, although a trend toward a lower Pa02 during exercise
was noted in group 3.
These observations suggest that the development
of right ventricular hypertrophy in COPD can begin
at a time when resting pulmonary hemodynamics
and arterial oxygenation are both relatively normal.
Apparently, an abnormal increase in right ventricular work, even if it is only during exertion, is sufficient to bring about mild hypertrophy.
60
,—,
50
O)
X
E
£•
<
0-
40
•
30
</)
u
L_
0)
X
20
Hi
0
'0
10
20
30
40
50
60
Rightward Terminal Forces (%)
FIGURE 4 . Correlation of rightward terminal Q R S forces with
mean pulmonary arterial pressure (PA) during exercise. Open
circles indicate type -1 loops; solid circles indicate loops of
types 2 and 3 ( n = 2 6 ; r = 0 . 5 4 ; P < 0 . 0 1 ) .
the sensitivity was 94 percent, and the specificity
was 70 percent; when the criterion of a rightward
terminal QRS force of 15 percent or more was used,
the sensitivity was 81 percent, and the specificity
was 90 percent.
The ages of the 27 normal subjects (range, 34 to
59 years) did not differ significantly from the patients. Only one subject had a rightward terminal
QRS force of 15 percent or more, and the mean (5.0
± 5.4 percent) was comparable to group 1.
DISCUSSION
This study demonstrates that the vectorcardiogram offers a simple noninvasive method of detecting mild hemodynamic abnormalities in patients
with COPD. By superimposing a plastic grid over a
patient's horizontal-plane and frontal-plane vectorcardiographic loops, the extent of terminal rightward QRS forces is easily calculated. Based on the
measured value for such forces and the criteria outlined previously, one can determine the likelihood
that a patient has abnormalities of the pulmonary
circulation.
The basis for this increased workload is an abnormal increase in pulmonary arterial pressure during exercise, rather than any excessive increase in
cardiac output. Why there is an abnormal exertional
increase in pressure is unclear. Previous investigators
have demonstrated that hypoxia, hypercapnia, and
acidosis are partially responsible for elevation of the
pulmonary arterial pressure during exercise in patients with moderate to severe pulmonary hypertension; - ' * however, it is unlikely that the pulmonary
hypertension during exertion seen in our patients,
particularly in those in group 2, was due to such
chemical stimuli, since we observed only minimal
changes in Pa02, PaC02, and pH during exercise in
most of the patients.
1
5 2
It is also unlikely that left ventricular dysfunction
was responsible for the pulmonary hypertension.
Although several patients did have an elevated pulmonary capillary pressure during exercise, none of
the patients had any clinical or electrocardiographic
evidence of left ventricular disease, and none had an
elevated pulmonary capillary pressure at rest. Furthermore, an exercise-induced increase in pulmonary capillary pressure has been observed in many
patients with C O P D . This increase is thought to
be due to mechanical factors related to the pulmonary disease. " For example, Lim and Brownlee
demonstrated a good correlation between pulmonary
capillary pressure and intraesophageal pressure during exercise in patients with COPD, thus demonstrating that the marked fluctuation in intrathoracic pressures commonly observed in patients with COPD
clearly influences the observed pressures in the pulmonary circulation.
3,4
25
27
5
In our patients, these abnormalities could not be
anticipated with either resting arterial blood gas
levels or pulmonary function tests. Although significant correlations between the mean pulmonary
arterial pressure and both the arterial oxygen saturation ' and the F E V i
have been reported,
such correlations are obtained only when patients
with moderate to severe pulmonary hypertension
are included in the group under study. In our patients, neither the F E V i nor the resting oxygen
Regardless of the actual stimulus to the pulmonary hypertension, it is clear from our study that the
vectorcardiogram is more sensitive than originally
thought to mild abnormalities of the pulmonary circulation.
Previous investigators correlated the vectorcardiogram with the resting pulmonary arterial pressure in patients with COPD and known pulmonary
hypertension or clinically suspected right ventricular hypertrophy. Our study extends the use of
the vectorcardiogram to a group of patients with
CHEST, 76: 2, AUGUST, 1979
VCG DETECTION OF EARLY ABNORMALITIES IN COPD 163
9
13
23
2 S
10
11
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COPD in whom abnormalities of the pulmonary
circulation were not known to be present and confirms that the presence of a rightward terminal Q R S
force of 15 percent or more is a sensitive and specific
indicator of abnormal pulmonary hemodynamics.
W e have also shown that in patients without
marked pulmonary hypertension, vectorcardiographic changes correlated more closely with exertional
than with resting hemodynamic measurements. Consequently, correlation of the vectorcardiogram with
only resting hemodynamic data will underestimate
the ability of the vectorcardiogram to detect hemodynamic abnormalities.
This apparent sensitivity of the vectorcardiogram
to altered pulmonary hemodynamics makes it necessary to exclude smokers from a "normal" population
when defining the normal vectorcardiogram. Inclusion of some smokers with subclinical COPD and
associated abnormalities of the pulmonary circulation could bias the data. This is supported by the
rarity of an increased rightward terminal Q R S force
in our age-matched control group.
In conclusion, mild hemodynamic abnormalities
are frequently present in patients with COPD and
no clinical evidence of pulmonary hypertension. The
vectorcardiogram appears to provide an effective
noninvasive method of detecting these abnormalities. Moreover, it appears that the extent of the
rightward terminal Q R S force may represent a more
sensitive index of excessive right ventricular work
than do resting hemodynamic measurements. Therefore, the vectorcardiogram may offer a sensitive
method of detecting patients who are at risk to
develop cor pulmonale and of following the effects
of therapeutic methods, such as long-term therapy
with supplemental oxygen, that are used to reduce
right ventricular work.
A C K N O W L E D G M E N T : W e thank Dr. Charles Duncan,
who greatly assisted in the initial aspects of the study.
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CHEST, 76: 2, AUGUST, 1979
VCG DETECTION OF EARLY ABNORMALITIES IN COPD
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165