Download Echocardiographic Determination of Contraction and

CONTRACTION AND RELAXATION OF LV WALL/Goldberg et al.
hypertensive subjects. Circulation 59: 623, 1979
12. Henry WL, Bonow RO, Borer JS, Ware JH, Kent KM,
Redwood DR, McIntosh CL, Morrow AG, Epstein SE: Observations on the optimum time for operative intervention for aortic regurgitation. I. Evaluation of aortic valve replacement in
symptomatic patients. Circulation 61: 471, 1980
13. Henry WL, Bonow RO, Rosing DR, Epstein SE: Observations
1061
on the optimum time for operative intervention for aortic
regurgitation I I. Serial echocardiographic evaluation of asymptomatic patients. Circulation 61: 484, 1980
14. Henry WL, Bonow RO, Borer JS, Kent KM, Ware JH,
Redwood DR, Itscoitz SB, McIntosh CL, Morrow AG, Epstein
SE: Evaluation of aortic valve replacement in patients with
valvular aortic stenosis. Circulation 61: 814, 1980
Echocardiographic Determination of Contraction and
Relaxation Measurements of the Left Ventricular
Wall in Normal Subjects and Patients
with Muscular Dystrophy
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STANLEY J. GOLDBERG, M.D., LINDA FELDMAN, CYNTHIA REINECKE,
LAWRENCE Z. STERN, M.D., DAVID J. SAHN, M.D., AND HUGH D. ALLEN, M.D.
SUMMARY Boys with Duchenne's muscular dystrophy (DMD) usually have a cardiomyopathy
characterized by fibrosis of the epicardial half of the left ventricle. This cardiomyopathy is difficult to detect by
noninvasive techniques. We report a technique that evaluates incremental left ventricular posterior wall
thickening and thinning. High-quality left ventricular posterior wall echoes in 24 boys with DMD and 32 controls were recorded at chordal level two times 1 year apart. Endocardial and epicardial echoes and a timing
ECG were digitized and analyzed by minicomputer. Left ventricular wall amplitudes were determined at standardized temporal increments during contraction and relaxation. To compare with this left ventricular assessment technique, systolic ejection times, shortening fraction and mean velocity of circumferential fiber shortening (Vcf) were also computed in the standard way. Mean year-to-year changes were minor. Mean Vcf, the
ratio of preejection period to left ventricular ejection time and shortening fraction during the first year were
statistically similar to those of the controls. Shortening fraction decreased slightly during the second year and
became significantly different from the control, but remained within the normal range. Left ventricular wall
thickness and cavity size were significantly less in boys with DMD than in controls. Therefore, we had to normalize incremental wall thickness to determine if any significant difference occurred. To do this, we evaluated
the percentage of maximal wall thickness which occurred at a given percent of systole and diastole. Using this
technique, it was shown that thickening during systole was a nearly linear process with respect to time in both
groups. However, relaxation was significantly different between the groups. Relaxation was found to be an
alinear process, and most thinning occurred in the first 40% of diastole. The major finding of this investigation
was that the left ventricular wall of boys with DMD thinned at a slower rate than that of normal subjects. This
new technique appears to be sensitive and demonstrates subtle changes in the left ventricular posterior wall.
THE CARDIAC PATHOLOGY of Duchenne's
muscular dystrophy (DMD) has been described in
only a few patients. Detailed gross and microscopic
analyses of 15 hearts of affected boys showed that left
ventricular fibrosis and/or dilation was present in
94%.1` The results (table 1) indicate that left ventricular fibrosis was usually localized to the epicardial
half of the left ventricular free wall and usually occurred in a diffuse distribution. In 27%, fibrotic
changes were localized to the posterior basal area of
the heart. The fibrosis is not similar to that observed in
From the Departments of Pediatrics and Neurology, University
of Arizona Health Sciences Center, Tucson, Arizona.
Address for correspondence: Stanley J. Goldberg, M.D., Department of Pediatrics (Cardiology), University of Arizona Health
Sciences Center, Tucson, Arizona 85724.
Received November 8, 1979; revision accepted April 4, 1980.
Circulation 62, No. 5, 1980.
myocardial infarction, for in DMD, normal muscle
cells are intermixed with fibrotic areas.
Although death in some patients with DMD results
from congestive cardiac failure, frank cardiac
decompensation is a relatively uncommon feature in
the early or middle stage of the disease.5 However,
electrocardiographic evidence of cardiac abnormality
is frequently found in children younger than 5 years of
age.6 Thus, DMD provides a model of mild cardiomyopathy that progresses to a more severe form in
the second decade.7 8
The purpose of our investigation was to develop a
method for evaluating the cardiomyopathy found in
DMD patients. Previous investigations have shown
that conventional echocardiographic measurements of
myocardial function, such as velocity of circumferential fiber shortening (Vcf), shortening fraction, ejection fraction and stroke index, have been normal or
ClIRCULATION
1062
TABLE 1. Combined Data from Examination of Gross Specimensl-'-Duchenne's Mluscular Dystrophy Pathology.
(15 reported cases)
Heart size
Increased
47
Normal
33( /o
Unstated
20%/o
Fibrosis
Epicardial-half generalized
Posterobasal
Type unspecified
None
47%
27%,
20c '
6%,6
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Other areas (1 each)
Septal
Right ventricle
Papillary
Coronary
only slightly decreased in DMD.8 9 Most of these
global measurements of myocardial function
evaluated cyclic changes in left ventricular dimension
or time intervals,8 9 hut did not directly evaluate the
involved portion of the heart, the left ventricular
posterior wall. Kovick and co-workers'0 evaluated the
left ventricular wall and determined that DMD
patients have abnormalities of systolic and diastolic
velocity. They determined this by drawing a tangent to
the endocardial surfaces and measuring the slope of
that tangent to determine velocity. Although their
observation was important, the measurement did not
take into account the fact that varying degrees of epipericardial separation might influence this measurement or the problems of tangent construction. Ahmad
and co-workers9 repeated the study of Kovick et al.'0
and failed to confirm the systolic change, and concluded that the reduced maximal diastoli-c endocardial
velocity may reflect overall movement of the heart
within the thorax rather than a functional cardiac abnormality.9
In this investigation, we report a method that
separates total cardiac motion from changes in wall
thickness that occur in systole and diastole. Our
results demonstrate that the left ventricular posterior
wall (LVPW) in DMD fails to thin rapidly during
early diastole.
Methods
The study group included 24 boys with DMD, ages
2-24 years, followed in our DMD clinic, who had
varying degrees of progressive muscular dystrophy.
To a maximal extent, all other neurologic diagnoses
had been ruled out. Confirmatory information for the
presence of DMD consisted of family history, muscle
biopsy, elevated creatine phosphokinase and an abnormal ECG.6 All had muscular weakness and in most
instances the weakness was severe. All had been
followed serially with muscle-testing analysis.
VOL 62, No 5, NOVEMBER 1980
The control group consisted of normal subjects in
the same age range as the DMD boys. None was
known to have neuromuscular or cardiac disease.
These boys were unrelated friends of the families or
other randomly selected volunteers.
For boys with DMD and controls, height, weight
and blood pressure were obtained. For those with
DMD only, an ECG was obtained if one had not been
previously performed in the Duchenne's clinic. A standard echocardiogram was obtained for each participant and this was repeated 1 year later. Equipment for
echocardiography consisted of a Smith Kline 20A
echograph modified to have increased receiver gain by
altering the receiver card circuitry. A switched-gain
circuit was installed after the description of Griffith
and Henry.'1 Recording was accomplished on a
Honeywell 1856 recorder at a recording speed of 50 or
100 cm/sec. Time mark accuracy was verified with a
stopwatch. A chest wall equivalent of electrocardiographic lead II was recorded for timing reference.
If the QRS was isoelectric in this lead, another lead
was selected. A variety of ultrasonic transducers,
ranging in frequency from 2.25-5 MHz with crystal
sizes of 6-12 mm, was used. After a standard echocardiogram was recorded, the LVPW was reexamined at
the level of the chordae, and the posterior left ventricular wall image was then electronically expanded
so that the septum was at the top of the oscilloscope
screen and the LVPW was at the bottom. The objective was to enlarge the left ventricular posterior wall to
improve tracing accuracy (fig. IA). An acceptable
wall was defined as one in which the plane of the beam
was appropriate and the endocardial and epicardial
surfaces were seen as continuous. We also required
that the epicardium was imaged separately from the
pericardium. After each tracing was obtained, it was
assigned a random six-number sequence to eliminate
any future analysis bias.
Standard Measurements
The left ventricular internal dimension (LVID) and
LVPW were measured according to suggested criteria
in end-systole (s) and end-diastole (d)."1 All measurements were made from leading edge to leading
edge. Left ventricular ejection time (LVET) for the
mean Vcf calculation was obtained from aortic valve
tracings recorded at R-R intervals matched to those of
the ventricular dimensions under analysis. Vcf was
computed as: LVID(d)-LVID(s)/LVID(d) X
LVET. 13 Shortening fraction was computed as
LVID(d)-LVID(s)/LVID(d).'4 Left ventricular systolic time ratio was computed as: Preejection period
(PEP)/LVET. PEP was measured as the time from
the first inscription of the QRS to the first opening
motion of the aortic valve. LVET was measured as the
time from the initial opening of the aortic valve until
aortic leaflet recoaptation."1
Computer Analysis of LVPW Wall Tracing
The endocardium and epicardium of the expanded
LVPW were manually traced with an ultrasonic
CONTRACTION AND RELAXATION OF LV WALL/Goldberg et al.
1063
FIGUREE 1. (A) An expanded section of left ventricular
pos terior wall (L VPW). The septum is partially visible at the
top of the panel and the endocardium and pericardium are
clearly visible, particularly in the left complex. Pieces of
chordae are noted. (B) An example of a wall thickness plot
for one beat. The QRS initial deflection is at the origin and
end of the trace. Numbers on the x-axis refer to a given percent of contraction or relaxation.
:.LVPW
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ME,
25
75 100 1020
40
CONTRACTION AT RELAXATION AT
% TIME
% TIME
TIME TO
TIME TO
No CONTRACTION S% RELAXATION
digitizing pen interfaced to a Wang 600 computer. The
onset of the QRS was digitized for each complex to
act as a time marker. The program accepted only
epicardial measurements that occurred at exactly the
same time as the previously digitized endocardial
points. One hundred twenty-eight points were allocated for each cardiac cycle. Wall thickness was determined by subtracting endocardial from epicardial
distance between each pair of points. Then an X-Y
plotter drew a reconstruction of the original wall as a
check and a continuous LVPW thickness from subtraction data. The computer then subdivided the X
axis first into systolic and diastolic time, and then into
quartiles and deciles for each phase (fig. IB). At the
quartiles and deciles of time, the Y value, wall
thickness, was automatically determined. The standardized beginning of systole was the initial deflection
of the QRS complex. End-systole was defined from
the wall thickness graph as the peak of wall thickness.
This was initially verified experimentally by comparing the time between the onset of the QRS and aortic
coaptation and the time from the QRS onset to the
peak of wall thickness. The times were found to be
identical in 12 subjects - five normals and seven with
DMD, and thereafter the wall graph alone was used
for identification of end-systole.
Repeatability for Wall Trace Evaluation
Repeatability was tested by: (1) having different individuals trace the same complex of the same tracing;
(2) comparing the values of traces of different complexes of the same record; (3) comparing values of
tracings of the same individual recorded on different
days; and (4) comparing values of all participants obtained from tracings one year apart.
Two-dimensional Evaluation
To rule out the possibility that we might have
selected an isolated affected segment of the wall for
evaluation that differed from the rest of the ventricle,
we performed two-dimensional echocardiography to
observe for akinetic or dyskinetic segments. Examination was performed with a Toshiba SSH lOA phasedarray or an electronically focused, high-resolution
prototype 3-MHz scanner. The left ventricle was
evaluated in three planes: long axis, short axis and
apical.'6' 17 The short axis was evaluated at the level of
1064
CIRCULATION
the anterior mitral valve leaflet, the area in which both
leaflets were visible, the chordal level and the papillary
level. The long axis was then evaluated from the standard precordial position and from the four-chamber
apical position. The transducer was rotated to
progressively evaluate as much myocardial wall as
possible. Images were reviewed after the method of
Rogers et al. to observe for akinesis or dyskinesis.'8
Data Handling
Data were dealt with exclusively by the six-digit
numbers. The code was broken only after the computer formed the groups and analyzed the data.
Statistics
For reproducibility, analysis of variance techniques
or paired t ratio was used as applicable, depending
upon the number of groups and group size. For comDownloaded from http://circ.ahajournals.org/ by guest on June 14, 2017
parison of controls and DMD patients, unpaired t
ratio was used. A linear correlation technique was
used to compare variables for the two groups.
Results
Two sets of data, separated by 1 year, were obtained
for 26 boys with DMD and 32 controls. Two DMD
traces were excluded because of inadequate record
quality, leaving 24 adequate pairs of records.
Anthropometric Data
Although ages of the patients and their controls
statistically similar, normal subjects were a mean
of 1 1 kg heavier and 15 cm taller than DMD patients.
The height of many DMD patients was inaccurate
because of severe skeletal deformities, usually
kyphoscoliosis. In many patients, we used length from
heel to head measured while the boy was lying down.
Mean calculated body surface area was 0.48 m2
smaller in boys with DMD, but this number is
probably falsely low because of the kyphoscoliosis.
were
VOL 62, No 5, NOVEMBER 1980
Vital Signs
Heart rate was significantly faster in DMD than in
controls (p < 0.05), but no significant year-to-year
variability occurred in either group (table 2). Blood
pressure was statistically similar for both groups.
Vcf
The Vcf was statistically similar for controls and
DMD patients (table 2). Statistical similarity
remained after Vcf was corrected for heart rate after
the data of Hirschleiter et al.19
Ratio of PEP/LVET
The ratio was statistically similar for controls and
DMD patients (table 2).
Shortening Fraction
Comparison of controls and DMD boys indicated
that mean shortening fraction was similar in year 1,
but was slightly but significantly lower (p < 0.05) in
year 2 for DMD patients compared with year 2 controls (table 2). However, the mean of both groups fell
within the previously described normal range. 14
Cavity Size
LVID in systole and diastole was less in boys with
DMD than in controls (p < 0.05) (table 3). Although
the decrement might appear greater than could be accounted for on the basis of body size differences,20
such a comparison is unwarranted, for the body surface area in these DMD boys is more speculative than
known, because accurate heights were not obtainable.
Wall Thickness During the Cardiac Cycle
The thickness of the wall
was
measured in milli-
meters at 25%, 50%, 75% and 100% of systolic time,
and 10%, 20%, 40% and 100% of diastolic time (table
4). Systolic divisions were initially selected arbitrarily
TABLE 2. Comparison of Velocity of Circumnferential Fiber Shortening, Preejection Period/Left Ventricular
Ejection Time, Shortening Fraction, and Heart Rate for Normal Subjects and for Duchenne's Muscular Dystrophy
Patients for Years 1 and 2
Control year Control year DMD year
DMD year
1
1
2
2
(n= 32)
(n= 24)
(n= 32)
(n= 24)
Significance
Vcf
1.6
0.34
1.5 0.33
1.6
0.35
1.5 0.42
0.29
0.09
0.28 0.09
0.29
0.08
0.30
0.07
PEP/LVET
0.35 0.04
0.35 0.04
0.33 0.07
0.31
0.06
a
Shortening fraction
81.1
Heart rate
14.8
78.3
14.3 101.9
13.0 104.3
12.0
a, b
Values are mean * SD.
Differences between the means for controls year 1 and year 2 and differences between the means for
DMD patients year 1 and year 2 were not significant.
a = p < 0.05 between the means for controls year 2 and DMD patients year 2.
b = p < 0.05 between the means for controls year 1 and DMD patients year 1.
Abbreviations: Vcf = velocity of circumferential fiber shortening; PEP/LVET = ratio of preejection
period to left ventricular ejection time; DMD = Duchenne's muscular dystrophy.
CONTRACTION AND RELAXATION OF LV WALL/Goldberg et al.
1065
TABLE 3. Comparison of Means for Raw Standard Echocardiographic Measurements of Controls and Duchenne's
Muscular Dystrophy Patients
Control year
1
(n 32)
Control year
2
(n= 32)
DM1) year
1
(n 24)
DMD year
2
(n= 24)
Significance
LVIDd
42.6 5.3
43.8 6.0
36.2 3.8
37.3 3.0
a, b
LVIDs
27.7 4.2
28.6 4.3
24.2 4.1
26.0 4.0
a, b
LVPWd
6.1
1.2
6.3 i 1.1
4.8
1.3
5.0 1.3
a, b
LVPWs
11.9 2.1
12.0 1.8
8.7 2.0
9.0 + 1.8
a, b
Values are mean - SD.
Differences between the means for controls year 1 and year 2 and differences between the means for
DMD patients year 1 and year 2 were not significant.
a = p < 0.05 between the means for controls year 1 and DMD patients year 1.
b = p < 0.05 between the means for controls year 2 and 1)MD patients year 2.
Abbreviations: LVIDd = left ventricular internal dimension at end-diastole; LVIDs = left ventricular
internal dimension at end-systole; LVPWd = left venitricular wall thickness at end-diastole; LVPWs = left
ventricular posterior wall thickness at end-systole; l)MI) = Duchenne's muscular dystrophy.
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and retained when it became apparent that systolic
thickening progressed linearly. As diastolic thinning
occurs rapidly, diastolic divisions were selected to
track this event. The 100% diastolic measurement is
identical to conventional LVPW thickness at enddiastole, and 100% systolic thickness is identical to
conventional maximal thickness of the left ventricular
wall. These data demonstrated that during the 1-year
interval between examinations, the wall, for each time
interval, increased in end-diastolic measurement for
both groups 1-10%. This increase was almost certainly due to growth and in several timed measurements the change was significant at the p < 0.05
level. However, wall thicknesses at any time interval
were significantly less (p < 0.05) for boys with DMD
than for normals (fig. 2, table 4). In boys with DMD,
end-diastolic thickness increased 82% and in normal
subjects it increased 92%. The difference between the
two groups, for this measurement, was not statistically significant.
The absolute thicknesses of the two groups were
different, so we had to evaluate the percent thickening
during systole and percent thinning during diastole at
a percent of systolic or diastolic time. When this was
done, the contraction was a nearly linear process for
both groups. In year 1, boys with DMD demonstrated
26% thickening at 25% time, 53% thickening at 50%
time, and 78% at 75% time. For normals, the mean
values at 25%, 50%, and 75% were 31%, 48%, and
77%. Thus, for both groups, thickening proceeded
similarly and linearly (table 5, fig. 3).
Relaxation was an alinear process. As an example,
for the normal group in year 1, 31% of relaxation occurred within the first 10% of diastole, 68% occurred
at the end of 20% of diastole, and 87% occurred when
diastole was 40% completed. For each time range,
boys with DMD demonstrated slower relaxation rates.
Relaxation proceeded at a significantly slower
(p < 0.05) rate of 22%, 51%, and 80% for 10%, 20%,
and 40% of diastolic time, respectively (table 5, fig. 3).
TABLE 4. Comparison of Means and Standard Deviations for Wail Thickness at a Percent of Systolic and Diastolic Time
Control year Control year
DMD year
DMD year
1
1
2
2
Wall thickness
(n = 24)
(n = 24)
(n = 32)
(n = 32)
(mm) at
Significance
6.0
1.6
8.1
1.2
1.5
7.3
5.8
1.5
25% S time
a, b, c
7.1
1.6
6.9
1.8
8.8 v 1.7
9.7
1.5
50% S time
a, b, c
8.1
1.8
11.0
1.9
1.9
1.7
7.8
b, c
10.5
75% S time
1.8
2.0
9.0
2.1
8.7
11.9
12.0
1.8
a, b, c
100%o S time
2.0
1.7
7.8
7.8
10.0
2.0
10.0
1.7
b, c
10% D time
1.6
1.6
6.8
b, c
6.6
8.0 - 1.4
7.8
1.5
20% D time
5.9
1.8
1.4
1.4
7.0 - 1.1
5.5
6.8
b, c
40% D time
1.3
5.0
1.3
4.8
6.1
1.2
6.3 - 1.1
b, c
100% D time
Differences between the means for DMD patients year 1 and year 2 were not significant.
a = p < 0.05 between the means for controls year 1 and 2.
b = p < 0.05 between the means for controls year 1 and DMD patients year 1.
c = p < 0.05 between the means for controls year 2 and DMD9patients year 2.
Abbreviations: S = systolic; D = diastolic; DMD = Duchenne's muscular dystrophv.
1066
CIRCULATION
VOL 62, No 5, NOVEMBER 1980
12
11
*
CONTROL
P< .05
9
FIGURE 2. Change (in mm) in wall
thickness for systole (left) and diastole
(right). The dashed line represents controls
and the solid line represents boys with
Duchenne's muscular dystrophy (DMD).
The cross-hatched lines indicate that the
difference between means for a time period
7
5
4
3
2
50
25
75
Downloaded from http://circ.ahajournals.org/ by guest on June 14, 2017
% TIME SYSTOLE
is significant (p < 0.05).
m
10)
80
100
% TIME DIASTOLE
Difference in relaxation could also be noted by merely
observing the wall thickness tracings. Figure 4
demonstrates four randomly selected normal tracings. All curves showed biphasic relaxation, and this
configuration was a uniform characteristic of the normal group. The initial phase of relaxation is rapid wall
thinning followed by a slower phase. The lower panel
of this figure demonstrates four types of relaxation
curves found for boys with DMD. The least common
(lower left) was a normal curve. Most had tracings
similar to those in the middle two panels. Both panels
show slowing of wall thinning during relaxation. The
left middle trace shows two recognizable phases of
thinning, but the right middle example demonstrates a
single slow phase in diastole. Older patients, who had
more severe muscular dystrophy, had traces that were
similar to the right lower tracing. In these subjects
contraction started longer after the QRS, wall
thickness increased less, and diastole had a single very
slow non-phasic slope.
Wall Tracing Repeatability
Wall tracings results were shown to be highly
repeatable by repeat tracing of the same and different
complexes on a given record and by evaluating the
results of tracings obtained 1 year apart (fig. 4).
Correlation of Age, Size, Heart Rate and Blood Pressure
to Contraction and Relaxation Measurements
Low-level (r = 0.28 to 0.60) but significant correlations (p < 0.05) were found between measurements obtained at a percent of systolic or diastolic time, and age, weight, height and body surface
area. Heart rate showed a very weak (r = -0.34 to
-0.49) negative, but significant (p < 0.05) correlation
to contraction and relaxation measurements. Despite
the statistical significance of the correlations, the level
of correlation was too low to be of clinical importance.
TABLE 5. Comparison of Percent Contraction at a Percent of Systolic and Diastolic Time
Control year
Control year
1
(n = 32)
2
(n
32)
DMD year
1
(n = 24)
31.2
8.1
48.3 f12.5
76.9
9.9
31.7
60.3
82.8
7.7
7.2
5.3
26.2
53.1
78.0
DMD year
2
(n = 24)
Significance
% contraction at
25%oS time
50'% S time
75%:,S time
12.2
14.6
i
12.8
27.0
54.3
79.0
11.4
11.7
10.1
% relaxation at
1QC D time
31.9
11.6
34.0
16.5
22.3
13.8
31.0
19.6
20% D time
68.4
17.9
68.2
16.9
51.4 i23.5
55.0 - 23.2
40% D time
87.7
11.5
86.0
10.3
80.1
14.0
16.1
75.7
Differences between the means for DMD patients year 1 and year 2 were not significant.
p < 0.05 between the means for controls year 1 and 2.
p < 0.05 between the means for controls year 2 and DMD patients year 2.
p < 0.05 betweeni the means foi controls year 1 and DMD patients year 1.
Abbreviations: S = systolic; D = diastolic; DMD = Duchenne's muscular dystrophy.
a
b
=
=
c =
a, b
a
c
b,
c
b,
c
CONTRACTION AND RELAXATION OF LV WALL/Goldberg et al.
1067
100
------*
COM
X9 P<.05
950
I-
40
El
20
FIGURE 3. Data offigure 2, normalized by
plotting the percent of thickening or thinning at a percent of systolic or diastolic
time. Boys with Duchenne's muscular
dystrophy (DMD) and normal subjects
thicken linearly in systole. However,
diastole shows a slower rate of thinning in
DMD than normal (p < 0.05).
10
25
75
50
20
100
%SYSTOLIC TIME
40
60
60
1W)
% DIASTOLIC TIME
NORMALS
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1
cm except
an
noted
~~~~~.31
1
DUCHENNES
FIGURE 4. The top four tracings were randomly selected from the normal group and
the bottom panel shows traces for
Duchenne's muscular dystrophy patients.
Each trace starts and stops at the onset of a
QRS. See text for detailed interpretation.
Abbreviation: MN mainly normal;
SR = slow relaxation, LR = loss of
biphasic relaxation; Tt = increased time
from QRS until contraction.
=
/
.51
MN
1
SR
.
SR, LR
SR,LR9T+
Interpretation of Two-dimensional Echocardiogram
Two-dimensional echocardiograms did not reveal
detectable left ventricular akinesis or dyskinesis in any
patient.
Discussion
The unique feature of this investigation is the use of
digitized LVPW echocardiograms to demonstrate that
a major component in the Duchenne's cardiomyopathy is inability to thin normally during diastole.
The heart in DMD has received considerable attention. One of the earliest findings was an abnormal
electrocardiographic pattern in approximately 90% of
affected boys.6 This was characterized by an increased
net R-S, RSR' or polyphasic R in lead V,. Deep T
waves were also found in the left precordium. However, the ECG is not indicative of the state of the
disease or myocardial involvement.8 Tachycardia is
usually present. The size of the heart on radiograph is
variable and may be difficult to interpret because of
severe skeletal deformities.8
The most common techniques for evaluating
myocardial function rely on changes in the left ventricular cavity. Although cavity size and a change in
cavity during the cardiac cycle would be expected to
reflect, in part, the state of the myocardium, these
cavity sizes are clearly affected by numerous factors,
only one of which is myocardial function. None-
theless, with these techniques, marked depression in
myocardial function can usually be separated from
normal function,22 but subtle or perhaps even moderate structural changes may go undetected. In a similar manner, systolic time intervals are a function of
many variables,23 but may not detect subtle changes in
the myocardium in children. Perhaps it is not surprising that these indicators are normal in DMD.
Evaluation of LVPW by M-mode echocardiography is not simple, and this is probably why it has
been infrequently evaluated. However, Kovick and coworkers'0 and Ahmad et al.9 found diastolic endocardial velocity (DEVM) to be the most sensitive
method for detecting the abnormality in DMD.
However, DEVM is a problematic measurement.
Most important, it neglects the fact that the myocardium separates from the pericardium to a variable extent in systole. This epi-pericardial separation was
found in 100% of our patients and its detection is principally a function of meticulous techniques and axial
resolution. Axial resolution, in this instance, is complicated because the distance between the transducer
and the area of interest is maximal in studying the epipericardial separation of the posterior wall. At this
depth, the signal-to-noise ratio of the echograph is at
its lowest for cardiac examination. The magnitude of
the separation is not apparent in the figures of Kovick
and co-workers or those of Ahmad and coworkers.9' 1' We could record the separation by in-
1068
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creasing the echocardiographic receiver gain in each
stage of the receiver board. We also increased the
dynamic range of the echograph with switch gain."
The latter appears to be more important than the
former. Observation of tracings leads to the suspicion
that the larger the epi-pericardial space, the greater
would be the DEVM; the reverse also seems true. Factors that govern the size of the space are unclear. It
could result from motion of the entire heart within the
pericardium, heart size, the amount of pericardial
fluid, or from all these factors. Perhaps DEVM is also
affected by heart rate, as cardiac motion might be expected to be decreased if the stroke index were smaller
due to tachycardia. Patients with DMD did have
relative tachycardia and this could have been a factor
in those slopes. The technique that we present makes
no assumptions regarding the total cardiac motion,
for tracing both sides of the left ventricular wall
cancels the effect of cardiac motion and permits
evaluation of cyclic thickening and thinning. Further,
the technique of Kovick and co-workers requires
drawing the best tangent to a moving wall.'0 This can
be very difficult, for the wall is both thinning and moving, each at a different rate. The technique we present
does not require construction of tangents. The
repeatability studies for the presented technique show
a high degree of reproducibility. The problem with the
presented technique is obtaining very high quality
recordings, and such a recording requires considerably
more time, effort, knowledge of the equipment, and to
an extent, equipment modification.
Our technique makes two major assumptions. The
first is common to all echocardiographic work, and
proposes that returned echoes come from structures
that are perpendicular to the ultrasonic beam and that
the myocardium of the left ventricular posterior wall
is relatively uniform in thickness if the operator takes
care not to image the papillary muscles. Since few
nonperpendicular echoes return to the transducer, or if
they do return to the transducer, they appear as weak
echoes, the first part of the first assumption is
probably true. Pathologic examination of the free wall
of the left ventricle shows that it is generally of similar
thickness from just below the mitral ring to near the
papillary muscle. This is important, for a different
portion of the left ventricular wall is imaged at each
instant, since the left ventricle has motion in all three
axes, and, in effect, passes by the motionless
transducer.24 This portion of the first assumption,
although not frequently discussed, is common to all
echographic work. The second assumption is more
specific to this investigation and concerns the
possibility that the area of the left ventricular wall that
was examined was not a representative section, as it
could have been mainly a fibrous area or alternatively,
the only contractile area of an otherwise fibrotic wall.
To deal with this question, we performed twodimensional echocardiographic examinations of
DMD patients. The left ventricle was imaged in cross
section from the apex and in long axis. This examination did not define areas of akinesis or hypokinesis.
Failure to find such areas suggested that our sample
VOL 62, No 5, NOVEMBER 1980
site selected for M-mode study was reasonable.
However, the value of such observation is limited
because we could not rule out subtle systolic, or more
important, diastolic events.
Our investigation shows that thickening of the left
ventricular wall in DMD and normals proceeds as a
linear or nearly linear function. Diastole has two
phases in normal subjects: a rapid thinning phase that
occupies about the first 40% of diastole and a slow
phase that lasts until slightly after the inscription of
the QRS complex. Although rarely a normal pattern
occurs in DMD, the most common pattern was one of
decreased rate of wall thinning. Decreased rate of
relaxation is probably related to fibrosis. Kovick and
co-workers'0 suggested that since fragmented sarcoplasmic reticulum isolated from DMD skeletal
muscle accumulates calcium more slowly than does
fragmented sarcoplasmic reticulum isolated from normal muscles, the slow uptake of calcium may be accompanied by slow relaxation in DMD. Ahmad et al.9
suggested that reduced DEVM may reflect reduced
overall movement of the heart in the thorax rather
than functional cardiac abnormality.9 Cardiac motion
may be a major factor in DEVM, so this conclusion
may be partially appropriate. However, the present
study shows that the abnormal diastolic thinning is not
a function of cardiac motion because effects of cardiac
motion are, in effect, canceled by the procedure. Accordingly, the abnormal diastolic thinning of the left
ventricle appears to be the major impairment that
could be detected by the echocardiographic technique
of this study.
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Echocardiographic determination of contraction and relaxation measurements of the left
ventricular wall in normal subjects and patients with muscular dystrophy.
S J Goldberg, L Feldman, C Reinecke, L Z Stern, D J Sahn and H D Allen
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Circulation. 1980;62:1061-1069
doi: 10.1161/01.CIR.62.5.1061
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