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Doppler signal and interval measurements in the fetal dog
Doppler signal and interval measurements in the fetal dog RICHARD
L.
BERTRAM
D.
Bethesda,
BERNSTINE, LITT,
CAPTAIN
(MC)
USN
A.M.
Maryland
A study of the has been made to the phase of the signals and The use of the successful.
duration of the Doppler signals* and intervals between these signals in the dog fetus. Analysis of these measured parameters in reference the cardiac cycle in which they occur has been made; the variation in intervals being greater from fetus to fetus than within a single fetus. signals or intervals to predict the length of systole or diastole was not
PREVIOUS REPORTS~~~ have indicated the efficiency of ultrasound utilizing the D oppler principle to detect fetal heart action. Studies in the adult39 4 and the fetus5 have suggested the periods of cardiac activity responsible for the various Doppler signals. A recent study5 reported associations of the Doppler signals with electrocardiogram, and carotid artery pressure curves in animal fetuses. The present report extends these observations to include the interrelationships of the Doppler signals and the intervals be-
tween them to each other and to the part of the cardiac cycle during which they occur. The duration of each signal and interval was examined to establish a mean value and standard deviation. Material
and
methods
Eleven term, mongrel bitches were surgically explored. The operative details are described in a previous article.5 A single fetus was studied from each maternal animal. During the recording of the electrocardiogram and ultrasonic Doppler study of the fetal heart, the uterus remained entirely within the abdomen and was covered with hot saline sponges. No significant change in deep body temperature was noted during the period of study. Nor were gross fluctuations in the rate or rhythm of the fetal heart noted. The Doppler signals were recorded on magnetic tape and were sampled for 3, onesecond random periods for each minute of tape. The study samples were obtained by 2 methods: in the first instance, photographs were taken from the oscilloscope face upon which portions of the tape were displayed (Fig. 1) ; in the other method, contour plots* were obtained of one-second segments of the
From the Bureau of Medicine and Surgery, Navy Department, Research Task No. MROO5.19-0004. The opinions or assertions contained herein are the private ones of the authors and are not to be construed as oficial or reflecting the views of the Navy Department or the Naval service at large. The experiments reported herein were conducted according to the principles enunciated in “Guide for Laboratory Animal Facilities and Care.” *The following abbreviations will be used throughout the article: Dl = first Doppler signal; 02 = second Doppler signal; 03 = third Doppler signal; D4 = fourth Doppler signal; 01-02 = interval between first and second Doppler signals; 02-03 = interval between second and third Doppler signals; D3-D4 = interval between third and fourth Dopgler signals; 04-01 = interval between fourth and first (next cycle) Doppler signals.
*Signatection
893
Company.
894
Bernstine
and Litt
Amer.
March 15, 1970 J. Obstet. Gynec.
Fig. 1, A and B. Upper line represents the Doppler signal; the lower line, electrocardiogram. Each is labeled according to the description in the text of the article. The Doppler intervals are not labeled but may be easily observed.
tape (Fig. 2). both methods were utilized for analysis of recordings from a single fetus. The time duration for each signal and interval between signals was determined manually. A total of 1,474 to 1,617 observations were made in the 11 fetuses. The observations were obtained by examining 150 cardiac cycles in each fetus. The observations of all the Doppler signals in a single fetus under study varied from 134 to 147 in this group. The range in observations reported is due to the difficulty in some instances to identifying all parts of the Dopper signals. In instances where all component parts of the Doppler signals were not evident, this cycle was not included in the statistical analysis.
Results Figs. 3 and 4 present the length of each Doppler signal and interval (expressed in milliseconds) according to the frequency of its observation. This frequency is presented as a percentage of the total group studied (all animals). Table I presents the mean value and standard deviation for the measured DoppIer signals and the intervals between them. The results for the entire group considered as a unit are presented at the bottom of the table. A comparison has been made between the various Doppler signals, the intervals between them, and the portion of the cardiac cycle
Volume Number
106 6
Doppler
Fig. 2. Frequency
signal
analysis of the Doppler signal and electrocardiogram. Labeling from Fig. 1. There are several additional signals present in this tracing. They studied extensively and do not occur as frequently as the labeled Doppler signals.
during which they occur. An attempt has been made in this manner to estimate the length of systole or diastole from one of these measurements. The Doppler signals do not vary as greatly in duration as the intervals separating them. D3 has the shortest duration and the smallest range of observations. Dl and D2 are quite similar in duration and range of observations. D4 has the greatest variability of the Doppler signals. The Doppler intervals occurring during diastole varied greatly. D3-D4 and D4-Dl were quite similar in duration and mean values. D2-D3 represented the shortest interval and was the only interval occurring during systole.
Table gression diastole.
II presents of Doppler
and
interval
895
is unchanged have not been
a summary of the resignals to systole and
Comment No studies have been reported which examine in detail the various components of the Doppler signal in the fetus. Japanese investigators have made studies in the adult human examining the normal and abnormal hearts. They have correlated their findings with data on other cardiac functions. Additionally, they have consistently recorded Doppler signals in the range of greater than 800 cycles per second. The emphasis of their research has centered on the high frequency Doppler signal.
FRECUENCY
DlSTRlBUTKXJ FETAL
OF WPPLER
SKjNALS
Dot
P+ OCQRER
l
SIGNAL
o 2”dCOWLER
SIGNAL
l
3rd KWLER
.
4fhKPPLER
SIGNAL StGNAL
MILLISECONDS
Fig. 3. Frequency distribution the total observations made.
of the observed
Doppler
signals
is presented
as a percentage
of
Table I. Summary of duration of Doppler signals and intervals Animal
No.
1
Dl
1 01-02
(
D2
( 02-03
1
03
1 03-04
I
04
1 04-01
1
0.0402 (20.008)
0.0446 (20.008)
0.0403 (+O.OOS)
0.0155 (20.002)
0.0153 (f0.004)
0.0383 (20.008)
0.0224 (kO.005 )
0.0586 (+0.013)
2
0.0296 (kO.005)
0.0350 (tO.007)
0.0389 (kO.006)
0.0153 (+O.OOl)
0.0155 (+0.002)
0.0733 (kO.011)
0.0444 (+O.OOS)
0.0274 (20.005)
3
0.0277 (fO.004)
0.0328 (20.006)
(20.006)
0.0154 (?0.002)
0.0153 (+O.OOl)
0.0771 (?O.Oll)
0.0381 (kO.008)
0.0308 (T0.007)
4
0.0314 (+O.OOS)
0.0362 (-cO.OO’l)
0.0384 (AO.007)
0.0154 (+0.002)
0.0153 (+O.OOl j
0.0760 (AO.021)
0.0364 (?0.007)
0.0418 (?O.Qll)
5
0.0349 (+0.007)
0.0319 (kO.008)
0.0354 (tO.007)
0.0305 (+0.008)
0.0194 (20.007)
0.0827 (f0.015)
0.0248 (kO.005)
0.0271 (?0.004)
6
0.0337 (?0.007)
0.0303 (kO.005)
0.0388 (kO.007)
0.0205 (+-0.005)
0.0154 (+-0.001)
0.0773 (kO.013)
0.0341 (kO.007)
0.0436 (?O.OlO)
7
0.0363 (?0.007)
0.0373 (kO.009)
0.0427 (+0.007)
0.0235 (20.007)
0.0163 (+0.003)
0.0376 (+O.OOS)
0.0230 (20.004)
0.0472 (*O.OOS)
8
0.0345 (kO.006)
0.0406 (20.008)
0.0345 (k0.005)
0.0152 (+-0.001)
0.0153 (+o.ool)
0.0432 (kO.008)
0.0237 (kO.005)
0.0816 (20.015)
9
0.0357 (kO.006)
0.0371 (+0.007)
0.0322 (f0.005)
0.0155 (20.002)
0.0150 (fo.001)
0.0553 (+0.009)
0.0212 (?0.002)
0.0880 (+0.006)
10
0.0327 (TO.006)
0.0486 (+0.007)
0.0429 (?0.007)
0.032 1 (~0.009)
0.0202 (+0.003)
0.0635 (kO.016)
0.0467 (~0.011)
0.0421 (to.0261
11
0.0318 (ko.005)
0.0352 (f0.005)
0.0335 (+O.OOj)
0.0153 (+O.OOl)
0.0152 (+O.OOl)
0.0356 (+O.OOS)
0.0203 (20.001)
0.0696 (kO.007)
0.0336 (50.007)
0.0368 (tO.008)
0.0373 (-FO.O07)
0.0183 (20.006)
0.0159 (50.003)
0.0593 (20.002)
0.0297 (TO.011)
0.0520 (20.023)
Pooled data for all animals Values
are
expressed
as seconds.
Numbers
0.0359
in
parentheses
represent
standard
deviation.
vorllme Number
106 6
Doppler
68
FREWENCl IlXRlBUTKX4 BETWEEN DCPPLER FETAL
signal
and
interval
897
W INTMWLS SIGNALS
DOG
40
0 DI-D2 0 D2-D3
35
A D3-D4 n
zi I= 30 3 E 8
25
d 6 k
20
D4-DI
B s 15
IO
Fig. total
15
20
4. Frequency observation
25
distribution made.
30
35
of the
45
Doppler
Yoshida and associates3 have described 3 low frequency Doppler signals. The first occurs soon after the P-wave and has a duration of 70 to 120 msec. This signal corresponds to the first Doppler signal of the present study, the duration of which is 33.6 msec. The second Doppler signal described by Yoshida and associates3 occurs within 40 to 90 msec. of the beginning of the QRS complex and lasts aImost until the summit of the T-wave. In the present study, this signal corresponds in part to the second Doppler signal and to an unknown area of the immediately following cardiac cycle. The last low frequency Doppler signal described by Yoshida and associatesS begins approxrmately at the same time as the second heart sound and soon after the T-wave of the electrocardiogram. It has a duration of about 300 msec. This signal probably corresponds to the fourth Doppler signal of the present study, the duration of which is 29.7 msec.
50
intervals
55
60
65
is presented
70
as a percentage
Table II. Linear Doppler
predictor models signals and intervals
of the
for
cosfiSignal
or
interval
Linear
equation
cisnt of detesmination
Systole/D:!
y = 0.118
+0.011x
0.588
Systole/D2-D3
y =
+0.034x
0.563
Diastole/Dl
y = 0.396
+ 0.213x
0.014
Diastole/Dl-D2
y = 0.640
+ 0.203x
0.054
Diastole/DJ
y = 0.243
+ 0.223x
0.0009
Diastole/D3-D4
y = 0.451
+0.200x
0.184
Diastole/D4
y = 0.485
+0.212x
0.051
Diastole/D4-D
p = 0.336
+ 0.209x
0.120
1
The discrepancies values between the adult humans and on fetal dogs may primary difference groups evaluated.
1.118
in the observed time Japanese studies made on the reported study made lie in several areas. The is obvious in the study It should also be noted
898
Bernstine
and
Litt
that Yoshida and associates” do not describe the details for arriving at these time values. Further study should be made prior to deciding that differences do exist and of the magnitude quoted. Yoshida and associates3 and Satomura4 detailed the interval between the electromotive excitement of the myocardium (beginning of QRS complex) and the actual motion of the heart (beginning of second Doppler signal). Yoshida and associates3 described a time value for this interval of 40 to 90 msec., Satomura, one of 50 to 100 msec. In the fetus, this interval had a mean value of 17.98 msec. with a range of 15 to 35 msec. The difference in results could be partially attributed to the faster heart rate. The Japanese investigators do not discuss the time intervals (periods of no measurable Doppler shift) between Doppler signals. In the present study, the variability in the intervals D3-D4 and D4-Dl account for the differences in the length of each cardiac cycle. An attempt has been made in this study to predict the length of diastole or systole from each of the component parts of that phase of the cardiac cycle. Both the Doppler signals and the intervals between signals were
Amer.
employed. Table II presents the regression equations and coefficients of determination. The findings explain only slightly more than half of the total variation in systsle when the Dopper signal (D2) or the interval (D2-D3) is used. The results obtained by a similar process in diastole are without any success. The association represented between systole and D2, D2-D3 is greater than may be expected by chance (p > .OOl ) . A similar procedure was used, employing the logarithmic values for systole, diastole, and Doppler signals and intervals. The results were approximately the same as those described in Table II. The analysis of variance was used to evaluate whether interanimal variation during Dl-D2, D3-D4 or D4-Dl could be explained by chance. It could not, i.e., choosing a probability of 0.001, we found that this null hypothesis should be rejected for the Dl-D2 (F = 93.73), D3-D4 (F = 327.91), and D4-Dl (F = 366.07) intersignal periods. The individual animal used as its own control is a more powerful or accurate estimator than is a group of animals in estimating heart action parameters from Doppler signal data.
REFERENCES
1. 2. 3.
Bernstine, R. L., and Callagan, D. A.: AMER. J. OBSTET. GYNEC. 95: 1001, 1966. Bishop, E. H.: AMER. J. OBSTET. GYNEC. 96: 863, 1966. Yoshida, T., Mori, M., Nimura, Y., Hikita,
March 15, 1970 J. Obstet. Gym.
4.
G., Takagishi, S., Nakawishi, K., and mura, S.: Amer. Heart J. 61: 61, 1961. Satomura, S.: J. Acoust. Sot. Amer. 29:
Sato1181,
1957.
5.
Bernstine, In press.
R.
L.:
AMER.
J.
OBSTET.
GYNEC.
L.
BERTRAM
D.
Bethesda,
BERNSTINE, LITT,
CAPTAIN
(MC)
USN
A.M.
Maryland
A study of the has been made to the phase of the signals and The use of the successful.
duration of the Doppler signals* and intervals between these signals in the dog fetus. Analysis of these measured parameters in reference the cardiac cycle in which they occur has been made; the variation in intervals being greater from fetus to fetus than within a single fetus. signals or intervals to predict the length of systole or diastole was not
PREVIOUS REPORTS~~~ have indicated the efficiency of ultrasound utilizing the D oppler principle to detect fetal heart action. Studies in the adult39 4 and the fetus5 have suggested the periods of cardiac activity responsible for the various Doppler signals. A recent study5 reported associations of the Doppler signals with electrocardiogram, and carotid artery pressure curves in animal fetuses. The present report extends these observations to include the interrelationships of the Doppler signals and the intervals be-
tween them to each other and to the part of the cardiac cycle during which they occur. The duration of each signal and interval was examined to establish a mean value and standard deviation. Material
and
methods
Eleven term, mongrel bitches were surgically explored. The operative details are described in a previous article.5 A single fetus was studied from each maternal animal. During the recording of the electrocardiogram and ultrasonic Doppler study of the fetal heart, the uterus remained entirely within the abdomen and was covered with hot saline sponges. No significant change in deep body temperature was noted during the period of study. Nor were gross fluctuations in the rate or rhythm of the fetal heart noted. The Doppler signals were recorded on magnetic tape and were sampled for 3, onesecond random periods for each minute of tape. The study samples were obtained by 2 methods: in the first instance, photographs were taken from the oscilloscope face upon which portions of the tape were displayed (Fig. 1) ; in the other method, contour plots* were obtained of one-second segments of the
From the Bureau of Medicine and Surgery, Navy Department, Research Task No. MROO5.19-0004. The opinions or assertions contained herein are the private ones of the authors and are not to be construed as oficial or reflecting the views of the Navy Department or the Naval service at large. The experiments reported herein were conducted according to the principles enunciated in “Guide for Laboratory Animal Facilities and Care.” *The following abbreviations will be used throughout the article: Dl = first Doppler signal; 02 = second Doppler signal; 03 = third Doppler signal; D4 = fourth Doppler signal; 01-02 = interval between first and second Doppler signals; 02-03 = interval between second and third Doppler signals; D3-D4 = interval between third and fourth Dopgler signals; 04-01 = interval between fourth and first (next cycle) Doppler signals.
*Signatection
893
Company.
894
Bernstine
and Litt
Amer.
March 15, 1970 J. Obstet. Gynec.
Fig. 1, A and B. Upper line represents the Doppler signal; the lower line, electrocardiogram. Each is labeled according to the description in the text of the article. The Doppler intervals are not labeled but may be easily observed.
tape (Fig. 2). both methods were utilized for analysis of recordings from a single fetus. The time duration for each signal and interval between signals was determined manually. A total of 1,474 to 1,617 observations were made in the 11 fetuses. The observations were obtained by examining 150 cardiac cycles in each fetus. The observations of all the Doppler signals in a single fetus under study varied from 134 to 147 in this group. The range in observations reported is due to the difficulty in some instances to identifying all parts of the Dopper signals. In instances where all component parts of the Doppler signals were not evident, this cycle was not included in the statistical analysis.
Results Figs. 3 and 4 present the length of each Doppler signal and interval (expressed in milliseconds) according to the frequency of its observation. This frequency is presented as a percentage of the total group studied (all animals). Table I presents the mean value and standard deviation for the measured DoppIer signals and the intervals between them. The results for the entire group considered as a unit are presented at the bottom of the table. A comparison has been made between the various Doppler signals, the intervals between them, and the portion of the cardiac cycle
Volume Number
106 6
Doppler
Fig. 2. Frequency
signal
analysis of the Doppler signal and electrocardiogram. Labeling from Fig. 1. There are several additional signals present in this tracing. They studied extensively and do not occur as frequently as the labeled Doppler signals.
during which they occur. An attempt has been made in this manner to estimate the length of systole or diastole from one of these measurements. The Doppler signals do not vary as greatly in duration as the intervals separating them. D3 has the shortest duration and the smallest range of observations. Dl and D2 are quite similar in duration and range of observations. D4 has the greatest variability of the Doppler signals. The Doppler intervals occurring during diastole varied greatly. D3-D4 and D4-Dl were quite similar in duration and mean values. D2-D3 represented the shortest interval and was the only interval occurring during systole.
Table gression diastole.
II presents of Doppler
and
interval
895
is unchanged have not been
a summary of the resignals to systole and
Comment No studies have been reported which examine in detail the various components of the Doppler signal in the fetus. Japanese investigators have made studies in the adult human examining the normal and abnormal hearts. They have correlated their findings with data on other cardiac functions. Additionally, they have consistently recorded Doppler signals in the range of greater than 800 cycles per second. The emphasis of their research has centered on the high frequency Doppler signal.
FRECUENCY
DlSTRlBUTKXJ FETAL
OF WPPLER
SKjNALS
Dot
P+ OCQRER
l
SIGNAL
o 2”dCOWLER
SIGNAL
l
3rd KWLER
.
4fhKPPLER
SIGNAL StGNAL
MILLISECONDS
Fig. 3. Frequency distribution the total observations made.
of the observed
Doppler
signals
is presented
as a percentage
of
Table I. Summary of duration of Doppler signals and intervals Animal
No.
1
Dl
1 01-02
(
D2
( 02-03
1
03
1 03-04
I
04
1 04-01
1
0.0402 (20.008)
0.0446 (20.008)
0.0403 (+O.OOS)
0.0155 (20.002)
0.0153 (f0.004)
0.0383 (20.008)
0.0224 (kO.005 )
0.0586 (+0.013)
2
0.0296 (kO.005)
0.0350 (tO.007)
0.0389 (kO.006)
0.0153 (+O.OOl)
0.0155 (+0.002)
0.0733 (kO.011)
0.0444 (+O.OOS)
0.0274 (20.005)
3
0.0277 (fO.004)
0.0328 (20.006)
(20.006)
0.0154 (?0.002)
0.0153 (+O.OOl)
0.0771 (?O.Oll)
0.0381 (kO.008)
0.0308 (T0.007)
4
0.0314 (+O.OOS)
0.0362 (-cO.OO’l)
0.0384 (AO.007)
0.0154 (+0.002)
0.0153 (+O.OOl j
0.0760 (AO.021)
0.0364 (?0.007)
0.0418 (?O.Qll)
5
0.0349 (+0.007)
0.0319 (kO.008)
0.0354 (tO.007)
0.0305 (+0.008)
0.0194 (20.007)
0.0827 (f0.015)
0.0248 (kO.005)
0.0271 (?0.004)
6
0.0337 (?0.007)
0.0303 (kO.005)
0.0388 (kO.007)
0.0205 (+-0.005)
0.0154 (+-0.001)
0.0773 (kO.013)
0.0341 (kO.007)
0.0436 (?O.OlO)
7
0.0363 (?0.007)
0.0373 (kO.009)
0.0427 (+0.007)
0.0235 (20.007)
0.0163 (+0.003)
0.0376 (+O.OOS)
0.0230 (20.004)
0.0472 (*O.OOS)
8
0.0345 (kO.006)
0.0406 (20.008)
0.0345 (k0.005)
0.0152 (+-0.001)
0.0153 (+o.ool)
0.0432 (kO.008)
0.0237 (kO.005)
0.0816 (20.015)
9
0.0357 (kO.006)
0.0371 (+0.007)
0.0322 (f0.005)
0.0155 (20.002)
0.0150 (fo.001)
0.0553 (+0.009)
0.0212 (?0.002)
0.0880 (+0.006)
10
0.0327 (TO.006)
0.0486 (+0.007)
0.0429 (?0.007)
0.032 1 (~0.009)
0.0202 (+0.003)
0.0635 (kO.016)
0.0467 (~0.011)
0.0421 (to.0261
11
0.0318 (ko.005)
0.0352 (f0.005)
0.0335 (+O.OOj)
0.0153 (+O.OOl)
0.0152 (+O.OOl)
0.0356 (+O.OOS)
0.0203 (20.001)
0.0696 (kO.007)
0.0336 (50.007)
0.0368 (tO.008)
0.0373 (-FO.O07)
0.0183 (20.006)
0.0159 (50.003)
0.0593 (20.002)
0.0297 (TO.011)
0.0520 (20.023)
Pooled data for all animals Values
are
expressed
as seconds.
Numbers
0.0359
in
parentheses
represent
standard
deviation.
vorllme Number
106 6
Doppler
68
FREWENCl IlXRlBUTKX4 BETWEEN DCPPLER FETAL
signal
and
interval
897
W INTMWLS SIGNALS
DOG
40
0 DI-D2 0 D2-D3
35
A D3-D4 n
zi I= 30 3 E 8
25
d 6 k
20
D4-DI
B s 15
IO
Fig. total
15
20
4. Frequency observation
25
distribution made.
30
35
of the
45
Doppler
Yoshida and associates3 have described 3 low frequency Doppler signals. The first occurs soon after the P-wave and has a duration of 70 to 120 msec. This signal corresponds to the first Doppler signal of the present study, the duration of which is 33.6 msec. The second Doppler signal described by Yoshida and associates3 occurs within 40 to 90 msec. of the beginning of the QRS complex and lasts aImost until the summit of the T-wave. In the present study, this signal corresponds in part to the second Doppler signal and to an unknown area of the immediately following cardiac cycle. The last low frequency Doppler signal described by Yoshida and associatesS begins approxrmately at the same time as the second heart sound and soon after the T-wave of the electrocardiogram. It has a duration of about 300 msec. This signal probably corresponds to the fourth Doppler signal of the present study, the duration of which is 29.7 msec.
50
intervals
55
60
65
is presented
70
as a percentage
Table II. Linear Doppler
predictor models signals and intervals
of the
for
cosfiSignal
or
interval
Linear
equation
cisnt of detesmination
Systole/D:!
y = 0.118
+0.011x
0.588
Systole/D2-D3
y =
+0.034x
0.563
Diastole/Dl
y = 0.396
+ 0.213x
0.014
Diastole/Dl-D2
y = 0.640
+ 0.203x
0.054
Diastole/DJ
y = 0.243
+ 0.223x
0.0009
Diastole/D3-D4
y = 0.451
+0.200x
0.184
Diastole/D4
y = 0.485
+0.212x
0.051
Diastole/D4-D
p = 0.336
+ 0.209x
0.120
1
The discrepancies values between the adult humans and on fetal dogs may primary difference groups evaluated.
1.118
in the observed time Japanese studies made on the reported study made lie in several areas. The is obvious in the study It should also be noted
898
Bernstine
and
Litt
that Yoshida and associates” do not describe the details for arriving at these time values. Further study should be made prior to deciding that differences do exist and of the magnitude quoted. Yoshida and associates3 and Satomura4 detailed the interval between the electromotive excitement of the myocardium (beginning of QRS complex) and the actual motion of the heart (beginning of second Doppler signal). Yoshida and associates3 described a time value for this interval of 40 to 90 msec., Satomura, one of 50 to 100 msec. In the fetus, this interval had a mean value of 17.98 msec. with a range of 15 to 35 msec. The difference in results could be partially attributed to the faster heart rate. The Japanese investigators do not discuss the time intervals (periods of no measurable Doppler shift) between Doppler signals. In the present study, the variability in the intervals D3-D4 and D4-Dl account for the differences in the length of each cardiac cycle. An attempt has been made in this study to predict the length of diastole or systole from each of the component parts of that phase of the cardiac cycle. Both the Doppler signals and the intervals between signals were
Amer.
employed. Table II presents the regression equations and coefficients of determination. The findings explain only slightly more than half of the total variation in systsle when the Dopper signal (D2) or the interval (D2-D3) is used. The results obtained by a similar process in diastole are without any success. The association represented between systole and D2, D2-D3 is greater than may be expected by chance (p > .OOl ) . A similar procedure was used, employing the logarithmic values for systole, diastole, and Doppler signals and intervals. The results were approximately the same as those described in Table II. The analysis of variance was used to evaluate whether interanimal variation during Dl-D2, D3-D4 or D4-Dl could be explained by chance. It could not, i.e., choosing a probability of 0.001, we found that this null hypothesis should be rejected for the Dl-D2 (F = 93.73), D3-D4 (F = 327.91), and D4-Dl (F = 366.07) intersignal periods. The individual animal used as its own control is a more powerful or accurate estimator than is a group of animals in estimating heart action parameters from Doppler signal data.
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1. 2. 3.
Bernstine, R. L., and Callagan, D. A.: AMER. J. OBSTET. GYNEC. 95: 1001, 1966. Bishop, E. H.: AMER. J. OBSTET. GYNEC. 96: 863, 1966. Yoshida, T., Mori, M., Nimura, Y., Hikita,
March 15, 1970 J. Obstet. Gym.
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G., Takagishi, S., Nakawishi, K., and mura, S.: Amer. Heart J. 61: 61, 1961. Satomura, S.: J. Acoust. Sot. Amer. 29:
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Bernstine, In press.
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