Download Mean Velocity of Fiber Shortening

Mean Velocity of Fiber Shortening
A Simplified Measure of Left Ventricular
Myocardial Contractility
By JOEL S. KARLINER, M.D., JAMES H. GAULT, M.D., DWAIN ECKBERG, M.D.,
CHARLES B. MULLINS, M.D.,
AND JOHN
Ross,
JR.,
M.D.
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SUMMARY
Previously it was shown that left ventricular (LV) myocardial contractility can be
assessed from the instantaneous relation between velocity of fiber shortening and
maximum LV wall tension (VcF at max T). Such analysis is complex, requiring
frame-by-frame correlation of LV dimensions with pressure, and a simpler approach
was sought. In 50 patients the mean velocity of circumferential fiber shortening
(mean VCF), determined from the systolic excursion of the LV internal minor equator
obtained by cineangiography, was compared with instantaneous tension-velocity relations. In 13 subjects without LV disease, VeF at max T averaged 1.74 + 0.31 (mean +
SD) circumferences (circ) /sec (range, 1.37-2.52); corresponding mean VCF was 1.50
0.27 circ/sec (range, 1.23-2.03). In 22 patients with LV myocardial disease VCF at
max T averaged 0.64 + 0.29 circ/sec (range, 0.12-1.27); mean VUF averaged 0.68
0.36 circ/sec (range, 0.15-1.29, P< 0.001 compared with normal subjects). Similar
results were obtained in 15 patients with valvular lesions and an abnormal VCF at
max T. Mean VCF detected impaired myocardial function in 95% of patients with
abnormal instantaneous tension-velocity relations, and in the remaining 5% the amount
of overlap between normal and abnormal mean VCF was slight. The extent of fiber
shortening and the percent shortening of the internal diameter at the minor equator
did not provide separation of normal from abnormal groups. It is concluded that the
mean velocity of fiber shortening provides a simplified method of estimating LV
contractility which: (1) requires analysis of only two frames of a cineangiogram;
(2) allows quantitative comparison of LV myocardial contractility among patients;
(3) adequately detects altered cardiac performance, even when valvular disease and
myocardial dysfunction coexist.
Additional Indexing Words:
Cineangiography
Mean circumferential fiber shortening rate
Myocardial disease
wall tension during ejection.14 The mean rate
of circumferential fiber shortening has been
estimated by indicator-dilution techniques and
used to assess ventricular function,5 6 but
comparisons with more direct methods have
not been made, and the usefulness of this
measure has remained uncertain. Since calculation of the mean rate of circumferential fiber
R ECENT investigations
have demonstrated that left ventricular contractility
in man can be quantified from cineangiograms
by relating the instantaneous velocity of fiber
shortening of the minor equator to maximum
From the Department of Medicine, Cardiovascular
Division, University of California, San Diego, 225 West
Dickinson Street, San Diego, California 92103.
Dr. Gault's present address: Milton S. Hershey
Medical Center, Hershey, Pennsylvania. Dr. Mullins'
present address: University of Texas, Southwestern
Medical School, Dallas, Texas.
Circulation, Volume XLIV, September 1971
Instantaneous tension-velocity relations
Mitral regurgitation
Supported by U. S. Public Health Service Grants
HE 12373 and HE 05846.
Received January 14, 1971; revision accepted for
publication April 14, 1971.
323
KARLINER ET AL.
324
Table 1
Pat-ients uithout Left Ventricular Disease
Diagnosis
Patient
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M.M.
W.C.
R.R.
W.M.
J.S.
E.D.
R.M.
H.D.
J.G.
C.J.
C.P.
M.C.
J.W.
Average
ASD
MS
ASD
ASD
Functional murmur
ASD
CAD
CAD
Chest wall pain
Functional murmur
MR
MR, MS
PS, AS
HR
(beats/min)
88
37
88
94
1Oa
80
61
64
60
75
84
98
102
Arterial P (mm Hg)
Dias.
Sys.
113
110
137
116
140
116
124
140
114
136
120
126
120
70
60
86
71
80
38
77
78
64
72
68
80
60
LVEDP
(mm Hg)
cl
(liters/min/M2)
9
9
8
8
7
9
7
8
12
8
14
16
6
2.60
3.23
3.88
2.33
5.37
3.09
2.5
3.2
2.5
3.8
2.8
2.6
3.86
3.21
EF
ED internal
circ (cm)
13.9
14.6
16.2
14.5
0.59
0.59
0.60
0.77
0.64
0.72
0.65
0.65
12.9
14.7
19.1
17.4
20.0
17.5
32.2
19.0
13.6
17.5
Abbreviations: HR = heart rate; LV = left ventricular; ED -end-diastolic; P pressure; CI- cardiac index; circ =
circumference; EF = ejection fraction; Sys. = systolic; Dias. = diastolic; ASD = atrial septal defect; MS = mitral stenosis;
CAD = coronary artery disease; PS = pulmonic stenosis; MR = mitral regurgitation; AS = aortic stenosis; VcF = velocity
of circumferential fiber shortening; max T = maximum tension.
shortening by angiography is much simpler
than derivation of the instantaneous forcevelocity relation and could be determined
readily from left ventriculograms performed
for routine diagnostic purposes, it seemed of
importance to assess its usefulness and limitations. Accordingly, the present study compares
the instantaneous rate of fiber shortening at
maximum wall tension with the mean rate of
circumferential fiber shortening of the left
ventricle. Studies were performed in patients
with normal left ventricular performance, with
various degrees of left ventricular dysfunction,
and with associated valvular lesions.
Methods
Fifty patients, 7 to 62 years of age, were
studied during diagnostic left heart catheterization. Their diagnoses are listed in tables 1-3. The
first group consisted of 13 patients in whom
mechanical performance of the left ventricle was
considered to be normal. Tension-velocity data in
six of these subjects have been reported previously.' The entire group included four patients with
atrial septal defect, one with mitral stenosis, one
with minimal aortic stenosis (difference in left
ventricular-aortic peak systolic pressure, 6 mm
Hg), two with mitral regurgitation (regurgitant
fractions of 0.30 and 0.47, respectively), two
with coronary artery disease but without wall
motion abnormalities on ventriculography, two
with functional heart murmurs, and one patient
with atypical chest pain who had normal
coronary arteriograms. Eleven of these patients
had normal hemodynamic values (table 1), and
in two patients the left ventricular end-diastolic
pressures were slightly elevated (14 and 16 mm
Hg).7
A second group was composed of 22 patients
who had left ventricular myocardial disease.
Twelve had idiopathic cardiomyopathy, two had
idiopathic left ventricular hypertrophy, five had
coronary artery disease, and three had abnormal
left ventricular performance associated with
mitral stenosis (pressure differences across the
mitral valve ranging from 10 to 19 mm Hg)
(table 2). In one patient complete heart block
had recently developed with a ventricular rate of
40 beats/min. The remaining 21 patients had
sinus rhythm with heart rates ranging from 65 to
105 beats/ min. The brachial arterial pressures
were normal in all 22 of these patients, the left
ventricular end-diastolic pressure was elevated in
14 patients, and the cardiac indices were below
normal in eight patients (<2.5 liters/min/m2).
The instantaneous tension-velocity data have
been reported previously in nine of these
patients,' and all of the 13 additional patients
had reduced tension-velocity values.
The third group consisted of 15 patients who
had valvular lesions causing mechanical overload
Circulation, Volume XLIV, September 1971
MEAN VELOCITY OF FIBER SHORTENING
Shortening of internal
circ
(cm)
(% ED)
5.7
4.5
4.8
5.1
5.5
6.9
6.2
5.3
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7.7
5.7
8.0
7.8
5.2
6.0
41.2
30.5
29.5
35.2
42.2
46.9
32.5
30.5
38.0
32.5
24.8
41.1
32.0
35.1
325
VCF (midwall) at max T
Corresponding
tension
Maximum VCF (midwall)
Corresponding
tension
(cm/sec)
(circ/sec)
(g/cm2)
(cm/sec)
(circ/sec)
(g/cm2)
31.3
24.7
30.4
37.7
36.0
36.7
32.0
46.2
37.4
37.4
32.3
41.8
23.2
34.4
2.33
1.66
271
270
23.2
23.3
1.72
409
26.6
2.42
2.71
2.63
2.52
2.50
1.78
2.21
1.51
2.03
2.28
2.15
255
175
298
178
374
189
373
163
261
30.4
30.6
28.9
32.0
33.3
32.0
34.2
30.5
41.8
22.6
30.0
1.48
1.48
1.46
1.82
2.04
1.78
2.52
1.76
1.60
1.86
1.47
2.03
1.37
1.74
330
284
417
268
230
352
178
376
191
422
208
227
265
on the left ventricle associated with reduced left
ventricular mechanical performance. Fourteen of
these subjects had a diminished instantaneous
velocity of circumferential fiber shortening at
maximum tension, and one had only a reduced
maximum instantaneous velocity of shortening.
Twelve patients had predominant mitral regurgitation, one had aortic stenosis (difference in left
ventricular-aortic peak systolic pressure, 55 mm
Hg), one had combined mitral, aortic, and
tricuspid regurgitation, and one had mitral and
aortic regurgitation (table 3). All of these
patients except the subject with aortic stenosis
had atrial fibrillation. The ventricular rates
ranged from 58 to 110 beats/min, the brachial
arterial diastolic pressures were normal in all
patients, and two patients had elevated systolic
arterial pressures. The left ventricular enddiastolic pressures at rest were elevated in seven
(> 12 mm Hg) and normal in eight patients. In
six patients the cardiac index was reduced
(< 2.5 liters/ min/M2).
Cardiac catheterization was performed in the
postabsorptive state after administration of sodium pentobarbital (100 mg) intramuscularly. A
Cournand needle was placed in the left brachial
or left radial artery. Left heart catheterization and
left ventriculography were performed by the
retrograde arterial technique, by transseptal
puncture,8 or by introduction of a catheter into
the left heart via an atrial septal defect. In some
patients the left ventricle was made visible by
injection of contrast material proximal to the left
ventricle through a catheter introduced into the
left atrium by transseptal puncture, via an atrial
septal defect, or through a catheter in the
pulmonary artery.
Circulation, Volume XLIV, September 1971
261
375
299
Mean VCF (endocardial
surface)
(circ/sec)
(cm/sec)
21.3
18.0
1.54
1.23
20.6
19.1
25.3
1.27
20.1
35.4
22.1
31.9
35.5
61.5
30.0
22.6
28.0
1.32
1.96
1.39
1.85
1.27
1.60
2.03
1.38
1.32
1.34
1.50
The patient was positioned in the right anterior
oblique projection (21 patients), or in the supine
position (29 patients). In midinspiration 45 to 75
ml of radiographic contrast material* was injected
over 2 to 3 sec with a power syringe while
cineangiograms were exposed at 60 frames/sec
(21 patients) or 75 frames/sec (27 patients) on
35 mm cineangiographic film. Two patients had
cineangiograms exposed at 200 frames/sec on 16
mm film. During the cineangiogram the brachial
arterial pressure and an appropriate ECG lead
were recorded at 200 mm/sec on a photographic
recorder. The cinetrace systemt was used to
identify end-diastole in 21 patients, while in 29
subjects electronic pulses inscribed on the
photographic recorder as each cine frame was
exposed confirmed the time of end-diastole 0.03
to 0.06 sec after the onset of the QRS complex of
the electrocardiogram. To minimize the effects of
contrast material on ventricular function, the
earliest cardiac cycles providing adequate visualization of the left ventricular chamber were
analyzed.1 9 Cardiac cycles that followed extrasystoles were not used.
Instantaneous tension velocity relations during
ejection were calculated as described previously.'
The silhouette of the left ventricular cavity was
drawn in outline, frame by frame, throughout
systole. The long axis of the left ventricle was
taken as the line from the midpoint of the mitral
or aortic valve plane to the left ventricular apex.
*Hypaque-M, 75% or 90%, or Renovist, 69% (sodium
and meglumine diatrizoates).
tElectronics for Medicine, White Plains, New
York.
326
KARLINER ET AL.
Table 2
Patients with Left Ventricular Dysfunction
Patient
Diagnosis
E.T.
A.S.
C.A.
W.L.
H.G.
W.W.
J.B.
Myo. Dis.
ASHD
Myo. Dis.
Myo. Dis.
ASHD/CHB
ASHD
ASHD
Myo. Dis.
Myo. Dis.
MS
MS
MS
Myo. Dis.
Myo. Dis.
Myo. Dis.
Myo. Dis.
Myo. Dis.
Myo. Dis.
Myo. Dis.
Myo. Dis.
Myo. Dis.
ASHD
J.M.
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L.M.
J.F.
M.S.
B.K.
R.T.
B.J.
L.E.
M.H.
C.T.
J.T.
S.D.
D.R.
J.T.
E.W.
Average
Abbreviations: Myo. Dis.
others = see table 1.
HR
(beats/min)
Arterial P (mm Hg)
Dias.
Sys.
65
87
80
102
110
55
65
140
90
90
90
128
151
100
115
131
125
94
128
128
173
116
132
205
160
140
112
224
126
57
40
90
100
69
93
84
81
60
74
90
65
105
77
68
75
69
70
68
50
65
72
100
62
76
104
80
60
96
90
76
11
2.50
2.93
2.36
1.49
1.43
3.03
8
17
25
22
21
13
16
23
12
3.19
2.61
12
3.12
2.44
3.38
2.26
3.07
2.92
2.30
5.10
3.60
23
7
28
30
14
20
4
32
15
2.97
2.37
=
myocardial disease; ASHD
1- 2
)
where P = left ventricular intracavitary pressure
in g/cm2, ri = instantaneous internal radius or
diameter in cm, L -long axis in cm, and
h = wall thickness in cm. In these computations h
and L were measured at end-diastole and endsystole, intermediate points being calculated
assuming a linear change in wall thickness and
=
arteriosclerotic heart disease; CHB
=
circ
EF
(cm)
-
19.7
17.1
0.53
0.49
0.59
0.56
0.38
0.63
0.16
0.31
0.59
0.78
0.66
0.37
26.4
26.6
21.8
22.4
23.1
17.8
26.8
17.8
16.1
17.8
18.3
21.7
16.7
25.6
22.2
18.0
19.2
17.5
28.5
2.87
2.94
2.13
10
11
ED internal
CI
(liters/min/m2)
2.75
The internal radius or diameter of the minor left
ventricular circumference was measured from
each outline drawing perpendicular to and at the
midpoint of the long axis. A curve representing
internal diameter throughout was then drawn to
fit these measurements. Wall thickness of the left
ventricle was measured from the cineangiogram
in the plane of the minor left ventricular
circumference at end-diastole and at end-systole.
Both internal dimensions and wall thickness were
corrected for X-ray magnification. Left ventricular
wall tension in g/cm2 (stress) was computed at
16.7- or 10-msec intervals throughout systole with
the aid of a digital computer as" 10
wall tension -h
56
67
65
60
87
60
LVEDP
(mm Hg)
0.45
30.2
0.50
21.4
complete heart block;
length. The instantaneous velocity of circumferential fiber shortening was computed at the midwall
as 2 7 dr/dt where r = ri + (h/2) and was
corrected for the corresponding instantaneous
midwall circumference.
The mean rate of circumferential fiber shortening in the normal group and in the patients with
left ventricular myocardial disease was defined as
the extent of shortening of the minor internal
circumference (at the midpoint of the long axis)
between end-diastole and end-ejection, divided
by the time required for shortening less 50 msec
(fig. 1). The time for shortening equalled the
product of the interval between frames and the
number of frames exposed between end-diastole
and end-ejection during each beat selected for
analysis. End-ejection was defined as the maximum inward wall excursion determined by visual
inspection of the cineangiogram. The 50 msec
value accounted for the preejection period which
averaged 48 msec in the normal subjects (range,
30-70 msec) and 55 msec in the patients with
left ventricular myocardial disease (range, 40120 msec). Use of the actual value for the
preejection period, rather than the mean value of
Circulation, Volume XLIV, September 1971
MEAN VELOCITY OF FIBER SHORTENING
Shreningornera
Shortenungcof
irternal
(%(cm)ED)
3.7
3.3
1.0
1.0
5.4
1.6
2.8
2.6
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1.1
3.3
4.1
4.0
6.2
3.6
6.0
2.0
0.6
5.6
7.8
56
7.1
5.0
3.8
18.8
19.1
3.8
3.8
24.6
7.0
12.3
14.8
4.1
18.5
25.5
22.5
33.5
16.6
35.9
7.8
2.7
31.1
40.6
31.9
24.9
16.6
18.9
Maximum VCF (midwall)
Corresponding
tension
(cm/sec)
(cire/sec)
(g/cm,)
19.3
20.5
7.8
6.8
20.3
12.0
19.6
21.5
6.6
21.0
16.7
16.7
25.8
22.0
25.8
29.8
11.9
20.4
37.7
19.5
60.9
18.5
20.9
0.93
1.11
0.26
0.23
0.94
0.48
0.81
0.93
0.22
0.92
0.97
0.92
1.43
0.89
1.49
0.98
0.46
1.11
1.78
1.04
1.87
1.01
0.94
316
234
330
351
467
377
305
137
386
190
199
212
470
257
202
257
496
225
221
207
346
249
292
50 msec, did not sharpen the distinction between
normal and abnormal patients, and for simplicity
the mean value was utilized. Since in patients
with mitral regurgitation there is no isovolumetric
contraction period, in these subjects 50 msec was
not subtracted. The mean velocity of shortening
of the internal circumference was divided by the
end-diastolic internal circumference at the minor
equator.
Under constant loading conditions (unchanged
end-diastolic volume and aortic diastolic pressure) in two sequential beats, the mean rate of
circumferential fiber shortening was reproducible
in 10 patients within 0.10 circ/sec. However,
under conditions of variable loading, such as
occur in atrial fibrillation, the mean rate of
circumferential fiber shortening might be expected to vary directly with the left ventricular enddiastolic volume. Hence in patients with atrial
fibrillation and a variable ventricular response,
either several beats must be analyzed and the
results averaged, or a beat with a cycle length
reflecting the mean heart rate should be chosen.
The latter method was employed in the present
study.
In 19 patients the dicrotic notch of the brachial
arterial pressure pulse of the beat selected for
Circulation, Volume XLIV, September 1971
327
VCF (midwall) at max T
Corresponding
tension
(cm/sec)
(circ/sec)
(g/cm2)
12.6
16.7
7.8
4.1
17.9
12.9
18.9
18.1
3.5
21.0
7.2
10.4
19.5
19.2
22.6
7.9
11.6
11.0
9.4
16.3
27.0
15.7
14.2
0.58
0.87
0.26
0.14
0.79
0.52
0.75
0 75
0.11
0.92
0.39
0.52
1.01
0.76
1.27
0.26
0.45
0.52
0.41
0.89
0.91
0.77
0.64
351
239
330
355
475
381
310
145
391
190
226
278
485
260
202
305
497
259
246
320
382
288
314
Mean VC F (endocardial
surface)
(cm/sec)
(circ/sec)
12.7
12.0
4.3
4.0
13.0
6.4
13.4
13.5
4.0
13.2
12.4
22.5
23.7
12.4
19.4
11.1
0.64
0.70
0.16
0.15
0.59
0.29
0.58
0.76
0.15
0.74
0.77
2.9
16.4
22.1
18.6
32.3
16.1
13.9
0.93
1.29
0.57
1.16
0.43
0.13
0.91
1.22
1.07
1.13
0.53
0.68
angiographic analysis could be adequately identified. The ejection time, calculated from the time
elapsed from the upstroke of the arterial pulse
contour to the dicrotic notch, correlated well with
the ejection time obtained from the angiogram, as
described above (r = 0.91). In no case did use of
the ejection time calculated from the arterial
pressure pulse alter the mean circumferential fiber
shortening rate sufficiently to change the patient's
classification from normal to abnormal or vice
versa.
In all groups, the extent of fiber shortening and
the percentage shortening of the internal diameter
of the minor equator were also analyzed and
compared.
Results
The hemodynamic data and the derived
mechanical data, expressed both in absolute
terms and normalized for left ventricular
circumference, are summarized in each group
in tables 1-3.
Comparison of Instantaneous and Mean Data
In the 13 patients without left ventricular
disease instantaneous velocity of the circum-
KARLINER ET AL.
328
Table 3
Patients w;ith Valvular Disease with Mechanical Overload and Left Ventricular Dysfunction
Patient
Diagnosis
I.K.
MiR
T.W.
i.S.
M.M.
M.it.
J.RF.
1B..C.
I).M.
J.L.
MR
J.M.
F.W.
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F.J.
M.).
l1.M.
E.W.
MR
Mit
MRt
MIt
Sys.
60
78
120
117
108
110
104
58
110
mR
MR.
M it
MR
mR.
MR
MS, AI, MI)
MIt, Al, TI
AS
rtenal P (mm Hg)
Dias.
HR
(beats/min)
94
95
77
58
59
8;?5)
73
63
82
86
85.
110
160
15
L6
132
170
184
1.31
118
11.5
94
70
67
62
70
66
70
90
75
62
86
66
52
76
50
5)s
LVEDP
(mm H g)
=
aotic insufficiency; TI
=
EF
1.9
5
8
17
2.5
1.9
8.0
4.7
7
9
1(
20
20
16
22
3.0
3.8
2.4
2.3
2.8
2.0
2.3
3.01
2.81
3.6
3.1
11
20
7
20
11
Aver.age
Abbreviations: AI
cl
(liters min/m2)
tricuspid insufficiency; others
0.52
0.65
0.43
0.46
(.55
0.5 6
01.151
(.) 1
0.70
0.54
internal
AI) cire
(cm)
19.7
18.8
21.9
17.9
22.9
22.9
20.4
37.4
22.3
29.8
44.0
26.8
19.5
27.4
14. 5
24.4
see table 1.
Figure 1
A cineangiographic film exposed in the frontal projection at end-diastole (left), and endsystole (right). The left ventricular cavity is opacified after injection of contrast material.
The long axis of the left ventricle is drawn from the midpoint of the aortic valve plane to
the apex; the minor axis is drawn perpendicular to the long axis at its midpoint. For calculation of the mean circumferential fiber shortening rate, see text.
Circulation, Volume XLIV, September 1971
MEAN VELOCITY OF FIBER SHORTENING
Shortening of internal
circ
(cm)
(% ED)
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7.1
6.7
6.3
6.2
9.1
2.0
5.4
12.0
3.5
6.6
8.8
8.2
5.2
6.3
4.0
6.5
36.0
35.6
28.7
34.6
39.7
8.7
26.5
32.1
15.7
22.1
20.0
30.6
26.7
23.0
27.6
27.2
329
Maximum VCF (midwall)
Corresponding
tension
VCF (midwall) at max T
Corresponding
tension
(cm/sec)
(circ/sec)
(g/cm2)
(cm/sec)
(circ/sec)
(g/cm2)
37.5
28.7
31.0
20.4
37.9
21.0
31.4
34.5
15.7
26.1
17.4
33.6
20.4
28.6
15.4
25.0
1.89
1.60
1.49
1.28
1.98
0.67
1.43
1.61
0.64
208
295
358
144
25.2
15.8
27.6
14.6
22.6
13.3
31.4
29.4
12.6
8.0
17.4
30.5
17.3
22.3
15.4
20.2
1.14
0.761.04
0.80
0.91
0 56
1.43
1.31
0.51
0.42
0.79
1.07
0.80
0.80
1.00
0.89
262
350
404
251
299
551
274
279
232
305
505
227
267
345
374
328
1.29
0.82
1.16
1.06
1.04
1.10
1.27
213
516
274
275
231
290
487
224
242
343
297
293
Mean VCF (endocardial
surface)
(circ/sec)
(cm/sec)
21.3
17.4
18.9
19.6
24.8
16.7
15.8
34.3
10.9
25.3
26.7
21.6
20.0
18.5
16.6
20.6
1.08
0.93
0.86
1.09
1.08
0.73
0.77
0.92
0.49
0.85
0.61
0.81
1.00
0.68
1.15
0.87
ferential fibers (VCF) at maximum wall
tension averaged 1.74 + 0.31 (mean + SD)
circumferences/sec (range, 1.37-2.52). In
the 22 subjects with myocardial disease and in
the 14 patients with left ventricular overload
due to valvular disease with impaired left
ventricular performance, these values averaged 0.64 ± 0.29 (range, 0.11-1.27), and
0.89 + 0.27 (range, 0.42-1.43) circumferences / sec, respectively (fig. 2). Determination
of VCF at maximum tension provides almost
complete separation of patients with normal
left ventricular performance from those with
impaired left ventricular function (fig. 2,
tables 1-3).
In the normal subjects the maximum
instantaneous velocity of circumferential fiber
shortening (max VCF) was 2.15 ± 0.36 circumferences/sec (range, 1.51-2.71). In the
subjects with myocardial disease max VWF
was 0.94 ± 0.43 circumferences/sec (range,
0.22-1.87), and in patients with valvular
disease and left ventricular dysfunction it
was 1.27 + 0.39 circumferences/ sec (range,
0.64-1.98). Although the mean value for
each of the latter groups differed significantly
from that of the normal subjects (P < 0.001),
considerable overlap with the normal group
occurred (fig. 3).
Circulation, Volume XLIV, September 1971
3..Un
CL)
*
F(I)
0
uJ 2.0 _
0
crz
LLJ
Eu
1.0 _
A
1-
A
i
Un-
y - 0035 + 1014x
A
*
A
U-
C->)
r = 0.83
p < 0.001
As
A
A
2.0
1.0
0
MEAN
VCF
3.0
( circ/sec )
Figure 2
Comparison of the instantaneous velocity of circumferential fiber shortening (VCF) at maximum tension
(max T) with mean VCF. Both are expressed in circumferences (circ)/sec. Overlap between normal and
abnormal groups occurred in only three patients.
* = no LV disease; A = LV disease without mechanical overload; m = valvular disease with mechanical
overload and LV dysfunction.
KARLINER ET AL.
330
MAXIMUM VCF
NO LV
D1S
-
CIRC/SEC
PERCENT
NO LV DIS.
LV DIS.
VALVULAR DIS
NO MECH. OVER- - MECH. OVER
LOAD
LOAD
* LV DYSFUNCTION
i
INTERNAL CIRCUMFERENCE
A
LV DIS.
NO MECH. OVERLOAD
MEAN VCF - CM/SEC
VALVULAR IRS.
MECH. OVER-
NO
LOAD
*
LV DYSFlRCTION
60
LV DIR.
LV DIS.
NO
VALVOLAR
DIR.
OVER- MECH OVERMECHLOAD
LOAD
*LV DRYFUNCTION
40
40
_
.
300
a
30
.
l41h
A
20
A
200
.
A
.A
A
10-
10
0.
+.S
0
0
P'
001
pV '
p
00
< .001
p' .02
0-
p'
.0I
Figure 3
Downloaded from http://circ.ahajournals.org/ by guest on June 18, 2017
(Left) Maximum velocity of circumferential fiber shortening (VCF), expressed in circ/sec, is
plotted on the vertical axis in patients with normal LV function, in subjects with impaired
LV performance, and in patients with valvular disease and mechanical LV overload. Considerable overlap is apparent. Horizontal bars indicate the mean values for each group.
(Center) Extent of circumferential shortening expressed as percent of end-diastolic circumference, is plotted on the vertical axis in the same three groups of patients. Considerable
overlap, especially in the patients with valvular disease, is apparent. (Right) Mean velocity
of circumferential fiber shortening (VCF), expressed in circ/sec, is plotted on the vertical
axis in the three groups. Unless mean VcF is normalized for end-diastolic circumference,
considerable overlap among groups occurs.
In the 13 patients with normal left ventricular performance the mean velocity of circumferential fiber shortening (mean VCF) averaged 1.50-0.27 circumferences/sec (range,
1.23-2.03). This value differed significantly
(P < 0.001) from that of the patients with left
ventricular myocardial disease in whom mean
VCF averaged 0.68 + 0.36 circumferences/sec
(range, 0.13-1.29). The mean value in the
patients with valvular disease causing left
ventricular overload and impaired left ventricular performance was 0.87 + 0.19 circumferences/sec (range, 0.49-1.15), which also
differed significantly from that of the normal
group (P < 0.001). A small degree of overlap
with the control subjects occurred in only two
patients with left ventricular disease, while no
overlap occurred in the patients with valvular
disease (fig. 2).
Extent of Circumferential Fiber Shortening
Total systolic excursion of the internal
minor equator averaged 6.0 1.14 cm (range,
4.5-8.0) in the normal group. Mean values in
the patients with myocardial disease and
valvular disease with left ventricular dysfunction were 3.79 + 2.05 cm (range, 1.0-7.8)
and 6.49 2.37 cm (range, 2.0-12.0) respectively. The difference from the normal subjects was significant only in the subjects with
myocardial disease (P <00.01). Overlap with
the normal group occurred in eight patients
with left ventricular myocardial disease and in
12 subjects with valvular lesions (tables 1-3).
Percent Shortening of the Internal Diameter
In the normal patients the extent of
shortening at the midwall averaged 35.1 + 6.0%
(range, 24.8-46.9). In the patients with
myocardial disease this value was 18.9 11.1%
(range, 3.8-40.6) and was significantly smaller than in the normal group (P < 0.001).
Overlap occurred in four patients (fig. 3). In
the subjects with valvular lesions and impaired left ventricular performance the average extent of shortening at the equator of the
left ventricle averaged 27.2 + 8.0% (range,
8.7-39.7). Although the mean value differed
significantly from the control group (P < 0.02),
overlap occurred in 11 patients (fig. 3).
Circulation, Volume XLIV, September 1971
MEAN VELOCITY OF FIBER SHORTENING
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Discussion
Determination of instantaneous tension-velocity relations provides a sensitive means of
comparing the level of the ventricular contractile state among patients.1- However, such
analysis is tedious, requiring frame-by-frame
measurement of ventricular dimensions, accurate estimations of changes in ventricular wall
thickness, and high fidelity left ventricular
pressure recordings. Computer facilities are
desirable for the necessary calculations. For
these reasons, mechanical analysis of ventricular function has remained largely a research
procedure.
In the present study, the angiographically
derived mean rate of circumferential fiber
shortening has been compared directly with
the more complex mechanical indices of
ventricular performance. The results indicate
that estimation of the mean rate of circumferential fiber shortening provides a relatively
simple and satisfactory method of measuring
left ventricular performance, even when valvular and myocardial defects coexist. Quantitative comparison of left ventricular performance among patients is also possible, since
velocity is divided by end-diastolic circumference and expressed per unit of circumferential
length, a term analogous to muscle lengths per
second in the isolated muscle.' Neither the
extent of shortening (expressed as a percentage of the end-diastolic circumference) nor
the mean velocity of circumferential fiber
shortening, expressed in cm/sec, allowed consistent differentiation from the normal values
(fig. 3).
There are few published studies of the
mean rate of fiber shortening in man.5' 6, 11
Those in which indicator-dilution techniques
were employed5' 6 were based on a spheroidal
left ventricular model which may underestimate the extent and velocity of shortening of
most of the cardiac fibers in the normal
ventricle.' Support for this contention is found
in the present study in which the mean rate of
fiber shortening of the minor left ventricular
equatorial axis in normal subjects was 27.9
cm/sec, while values of 13.4 cm/sec (Gorlin et
al.5) and 15.2 cm/sec (Wileken6) have been
Circulation, Volume XLIV, September 1971
331
reported in patients without left ventricular
disease by indicator-dilution methods.
Bristow et al. used angiographic techniques
similar to those employed in the present study
to measure mean rate of circumferential fiber
shortening in patients with coronary artery
disease.'2 In five control subjects the value for
mean VCF was 1.09 circumferences/sec and
for 15 patients with coronary disease, 0.91
circumferences/sec.12 The means were not
significantly different, but 10 of the 15 patients
with coronary artery disease had mean rates of
circumferential shortening below the lowest
normal value. In addition, there is a discrepancy between the average value for mean VCF
reported by Bristow et al. in five normal
subjects (1.09 circumferences/sec) 12 and our
own finding of an average of 1.50 circumferences/sec. A variety of factors, including size
of the control group, and the more rapid rate
of filming in the present investigation, which
allowed more precise definition of end-diastole
and end-ejection, may help to explain this
difference. Moreover, Bristow et al. did not
subtract the preejection period from the total
time required for shortening. The diameter
change that occurs in normal subjects prior to
aortic valve opening averages only 1 mm."
Subtraction of the preejection period of 50
msec, during which this small diameter
change occurs, from the time that elapses
between the end-diastolic and the end-ejection
cine frames, yields a mean rate of circumferential fiber shortening which is considerably
greater. When the preejection period was not
taken into account in our normal subjects, the
average value obtained for mean VCF was 1.28
circumferences/sec, a figure that was closer to
that of Bristow et al.12 but that produced
considerable overlap with patients in whom
left ventricular performance was impaired. It
should be emphasized, however, that in
patients with mitral regurgitation the preejection period should not be subtracted, since
considerable circumferential fiber shortening
occurs in such patients prior to aortic valve
opening.'1
Four patients in the study of Bristow et al.
with a borderline or low mean VCF had a
KARLINER ET AL.
332
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normal ejection fraction,12 suggesting that
mean VCF is a more sensitive indicator of
impaired contractility than the ejection fraction.13' 14 This finding is in agreement with the
present study in which there were five patients
with left ventricular myocardial disease and
normal ejection fractions who had borderline
low or abnormal values for VCF (table 2).
Of the 14 patients with regurgitant valvular
lesions accompanied by reduced left ventricular performance, three had a normal ejection
fraction (table 3). In 12 of these patients, the
extent of circumferential fiber shortening was
normal, and in 10 the percent shortening of
the internal diameter was normal. These data
are in accord with experimental observations
that suggest that a normal ejection fraction
may occur in the presence of valvular regurgitation despite impairment of the contractile
state.'5 In addition, it is clear that other
measures of external left ventricular performance, such as the extent and the percentage
of fiber shortening during ejection, do not
provide an adequate description of muscle
function, especially in the presence of regurgitant valvular lesions, in which considerable
reduction in impedance to ventricular ejection
may occur.
It is
of the
to recognize that calculation
circumferential fiber shortening
rate in the plane of the minor left ventricular
circumference may not reflect other regional
areas of impaired or normal cardiac function
which may occur in patients with coronary
artery disease. However, it is possible to
measure the mean rate of fiber shortening in
more than one circumferential plane. For sequential studies, such as in patients who
have undergone coronary surgical procedures,
quadrisection of the long axis by three chords
appears to be a satisfactory method of assessing serial changes in dyskinetic areas.16
Although patients with impaired left ventricular performance tended to have larger
end-diastolic dimensions than normal, use of
end-diastolic circumference appeared to be a
practical and simple method of normalization
for ventricles of different size. That the use of
necessary
mean
the end-diastolic circumference did not introduce a systematic error is suggested by the
fact that one patient with normal left
ventricular performance and mitral regurgitation had a somewhat enlarged end-diastolic
circumference (32.2 cm, table 1), while 11
patients with left ventricular myocardial disease without mechanical overload and four
patients with abnormal left ventricular performance and a mechanical overload had a
normal left ventricular end-diastolic circumference ( < 20 cm, tables 2 and 3). Moreover,
use of a "mean" ventricular circumference,
derived by subtracting one-half the total
amount of circumferential fiber shortening
from the end-diastolic circumference, did not
sharpen the distinction between patients with
normal and abnormal left ventricular performance.
A major advantage of this technique is its
suitability for use in the usual diagnostic
cardiac catheterization laboratory. Only two
single-plane angiographic frames must be
drawn, the tedium of planimetry is obviated,
and no estimate of wall thickness is required.
Correction for X-ray magnification, although
utilized in the present study, is unnecessary
because the result can be expressed as
circumferences/sec. Since the equatorial diameter, which is the only dimension measured, generally lies in the center of the X-ray
beam where distortion is minimal, correction
for the latter also is unnecessary. In the
present study, measurements were made in
the right anterior oblique, frontal and lateral
projections, indicating that patient position
probably also is unimportant for accurate
results. Finally, it has recently been demonstrated that contrast material does not exert an
important influence on ventricular contractility provided that early beats are selected for
analysis,9 thereby further validating the use of
angiographic methods in the assessment of left
ventricular performance.
References
1. GAULT JH, Ross J JR, BRAUNWALD E: Contractile
state of the left ventricle in man. Circ Res 22:
451, 1968
Circulation. Volume XLIV, September 1971
MEAN VELOCITY OF FIBER SHORTENING
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2. ECKBERG DL, BoucHARD RJ, GAULT JH: Left
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3. GAULT JH, KAHAN R, BoucHAw R, KARLINER
JS, Ross J JR: Comparison of maximal
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333
9. BoucHARD RJ, KARLINER JS, GAULT JH: Effect
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10. TIMOSHENKO S, WINOWSKY-KREGER S: Theory
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E: Is the ejection fraction an index of myocardial contractility? Cardiologica 53: 1, 1968
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Mean Velocity of Fiber Shortening: A Simplified Measure of Left Ventricular
Myocardial Contractility
JOEL S. KARLINER, JAMES H. GAULT, DWAIN ECKBERG, CHARLES B.
MULLINS and JOHN ROSS, JR.
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Circulation. 1971;44:323-333
doi: 10.1161/01.CIR.44.3.323
Circulation is published by the American Heart Association, 7272 Greenville Avenue, Dallas, TX
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Copyright © 1971 American Heart Association, Inc. All rights reserved.
Print ISSN: 0009-7322. Online ISSN: 1524-4539
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