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Fetal heart studies with the ultrasonic Doppler technique
Fetal heart studies with the ultrasonic Doppler technique A preliminary
RICHARD Bethesda,
study
L.
BERNSTINE,
COMMANDER
(MC)
USN
Maryland
Fetal guinea pigs and fetal dogs were examined in utero utilizing electrocardiography, ultrasonic Doppler inspection of the fetal heart, and carotid artery pressure curves (dogs only). Correlation between these parameters has established a relationship between two Doppler signals and fetal cardiac cycle. The second Doppler signal probably occurs during isometric contraction phase of the fetal ventricles, the third Doppler signal during isometric relaxation phase.
of less than 1,000 c.p.s., and usually in the range of 150 to 600 c.p.s. The significance of these signals is obscure without knowing their relationship to other measurements of the fetal cardiac cycle. In pursuit of this objective, studies were conducted on the fetal guinea pig and fetal dog. The remainder of the report concerns itself with these studies.
T H E P R E c I s E examination of the fetal heart has eluded investigators thus far. Accurate measurements of fetal heart rate have been accomplished, 1l 2 but detailing of the phases of the heart cycle still remains unsolved. The development of ultrasound and application of the Doppler principle to study of the fetal heart has offered an opportunity to widen the scope of investigation in this field. A previous report3 indicates the efficiency of this technique in establishing fetal heart action in the human. Once the uterus has become an abdominal organ, it is possible to detect fetal heart action in 98 per cent of cases of live fetuses. These Doppler signals, as recorded on magnetic tape, generally have two to four individual components. Each of these parts has a frequency From
Procedure Laparotomy was performed on the test animal at or near term. The pregnant uterus was exposed and the segment nearest to the cervix identified. Thermocouples were inserted into the muscles of the fetal buttocks and into the amniotic space. Teflon-coated steel wire was sutured in the neck and lower back of the fetus to serve as electrocardiogram leads. Ultrasonic Doppler study was made of the fetal heart. During the procedure, hot saline sponges covered the uterus to maintain body tempera-
the Bureau
of Medicine and Department, Research MROO5.19.0004.
Surgery, Navy Task
No.
The opinions or assertions contained herein are the private ones of the authors and are not to be construed as official or reflecting the views of the Navy Department or the Naval service at large.
ture.
In the case of the fetal dog, a small elliptical incision was made in the uterus over the nose of the animal. The head and neck were delivered, expanding the incision. The exposed portion of the fetal dog was retained
The experiments reported herein were conducted according to the principles enunciated in the “Guide for Laboratory Animal Facilities and Care.”
961
962
Ikcembct 1, 1968 Am. J. Obst. & Gynec.
Bernstine
Fig. 1. Ultrasonic Doppler inspection of the heart is displayed on the oscilloscope and then photographed.
Fig. line)
2. The same displayed.
study
as presented
in Fig.
Fig. The
3. Tracing of carotid artery pressure, arrows indicate the Doppler signals.
1, but
of a fetal
with
electrocardiogram,
guinea
the fetal
and
pig.
A 2 second
electrocardiogram
Doppler
from
interval
(bottom
a fetal
dog.
Volume Number
102 7
Fetal heart studies with Doppler
technique
963
The vesselwas catheterized (PE50 polyethylene) and connected to a Sanborn No. 267B pressure transducer and then to a Sanborn Model 350-3000B Carrier preamplifier. Recordings of the fetal electrocardiogram, carotid artery pressure curve, and ultrasonk Doppler inspection of the fetal heart were made simultaneously. Results
Fig. 4. Similar cate the Doppler
tracing to Fig. signals.
3. The
arrows
indi-
QRS Fig. 5. The
temporal relationships of fetal QRS complex, Doppler signals (stippled), and carotid artery pressure (arrow) curves in a dog fetus presented diagrammatically.
place by sutures or Allis clamps inserted on the uterine wall and fetal skin. A thermocouple needle was inserted beneath the skin of the exposed fetal head. A small transverse incision was made in the neck of the fetal dog below the level of the thyroid cartilage. The trachea was identified and, by means of blunt dissection, the carotid artery exposed (usually on the right side). in
Fifty-one dogs were examined utilizing ultrasonic Doppler inspection of the fetal heart and electrocardiogram. Of these, 25 dogs had the carotid artery exposed and cannulated for pressurestudies. In addition, 20 guinea pig fetuses were studied with the Doppler and electrocardiogram. The following findings are the product of these studies. Fig. 1 demonstrates the four components of the Doppler signal (2 second sample) obtained from the fetal guinea pig with the uterus intact. Although there is ample evidence of fetal heart action, further detailing of the fetal cardiac cycle is not possible. Fig. 2 represents the same study but the fetal electrocardiogram which has been recorded simultaneously is shown. Doppler signals occur consistently just prior to the QRS and after the P wave, immediately following the QRS, and at the time of the T wave of the fetal electrocardiogram. Three Doppler signalshave been observed in the same time relationship to the electrocardiogram in other speciesof animals. The significance of these signalswill be presented later. Fig. 3 depicts the carotid artery pressure curve, fetal electrocardiogram, and Doppler signals from the fetal dog. The two Doppler signals present occur prior to and following the QRS of the electrocardiogram. The second Doppler signal occupies the ascending limb of the carotid artery pressure curve. Fig. 4 demonstrates two Doppler signals occurring after the QRS complex. The first Doppler signal in this tracing (same as Doppler signal No. 2 from Fig. 3) occupies the ascending limb of the carotid artery pressure curve. The second Doppler signal in this
964
Bernstine
tracing occurs on the midportion of the descending limb of the carotid artery pressure curve. Fig. 5 presents the temporal relationships of these signals. These relationships have been derived from the visual inspections of many hours of paper recordings of these parameters in the fetal dog. Comment Bishop,4 and Bernstine and Callagan3 have reported on the clinical uses of ultrasound and the Doppler effect in obstetrics. Until the present report, no effort has been made to identify the phase of the fetal cardiac cycle when a specific Doppler signal occurs. The studies in the fetal guinea pig and more specifically in the fetal dog have yielded information which demonstrates that the second and third Doppler signals (Fig. 5) occur soon after electrical stimulation of the
ventricles. The second Doppler signal probably occurs during the isometric contraction phase of the fetal ventricles. The third Doppler signal occurs soon after the notch on the descending limb of carotid artery pressure cun;e which marks the closure of the aortic valve. This signal probably represents isometric relaxation phase diastole. Thus, the measurement of the second Doppler signal and the interval from the end of the second to the beginning of the third Doppler signal represents systole of the fetal heart. Further investigations are pursuing the study of the fetal cardiac cycle as defined by ultrasonic Doppler inspection. Establishment of “normal” time relationships between the various Doppler signals and intervals is being done. Correlation of the electrocardiogram and Doppler signals is being explored in a similar manner. fetal
REFERENCES
1. 2.
Hon, E. H.: Anesthesiology 26: 477, 1965. Caldeyro-Barcia, R., Mendez-Bauer, C., Poseiro, J. J., Escarcena, L. A., Pose, S. V., Bienian, J., Arnt, I., Gulin, L., and Althabe, 0.: In Cassels, D. E., editor: The Heart and Circulation
3. 4.
in the Newborn and Infant, New York, 1966, Grune & Stratton, Inc., pp. 7-36. Bernstine, R. L., and Callagan, D. A.: AM. J. OBST. & GYNEC. 95: 1001, 1966. Bishop, E. H.: J. Internat. Fed. Gynec. Obst. 4: 190, 1966.
RICHARD Bethesda,
study
L.
BERNSTINE,
COMMANDER
(MC)
USN
Maryland
Fetal guinea pigs and fetal dogs were examined in utero utilizing electrocardiography, ultrasonic Doppler inspection of the fetal heart, and carotid artery pressure curves (dogs only). Correlation between these parameters has established a relationship between two Doppler signals and fetal cardiac cycle. The second Doppler signal probably occurs during isometric contraction phase of the fetal ventricles, the third Doppler signal during isometric relaxation phase.
of less than 1,000 c.p.s., and usually in the range of 150 to 600 c.p.s. The significance of these signals is obscure without knowing their relationship to other measurements of the fetal cardiac cycle. In pursuit of this objective, studies were conducted on the fetal guinea pig and fetal dog. The remainder of the report concerns itself with these studies.
T H E P R E c I s E examination of the fetal heart has eluded investigators thus far. Accurate measurements of fetal heart rate have been accomplished, 1l 2 but detailing of the phases of the heart cycle still remains unsolved. The development of ultrasound and application of the Doppler principle to study of the fetal heart has offered an opportunity to widen the scope of investigation in this field. A previous report3 indicates the efficiency of this technique in establishing fetal heart action in the human. Once the uterus has become an abdominal organ, it is possible to detect fetal heart action in 98 per cent of cases of live fetuses. These Doppler signals, as recorded on magnetic tape, generally have two to four individual components. Each of these parts has a frequency From
Procedure Laparotomy was performed on the test animal at or near term. The pregnant uterus was exposed and the segment nearest to the cervix identified. Thermocouples were inserted into the muscles of the fetal buttocks and into the amniotic space. Teflon-coated steel wire was sutured in the neck and lower back of the fetus to serve as electrocardiogram leads. Ultrasonic Doppler study was made of the fetal heart. During the procedure, hot saline sponges covered the uterus to maintain body tempera-
the Bureau
of Medicine and Department, Research MROO5.19.0004.
Surgery, Navy Task
No.
The opinions or assertions contained herein are the private ones of the authors and are not to be construed as official or reflecting the views of the Navy Department or the Naval service at large.
ture.
In the case of the fetal dog, a small elliptical incision was made in the uterus over the nose of the animal. The head and neck were delivered, expanding the incision. The exposed portion of the fetal dog was retained
The experiments reported herein were conducted according to the principles enunciated in the “Guide for Laboratory Animal Facilities and Care.”
961
962
Ikcembct 1, 1968 Am. J. Obst. & Gynec.
Bernstine
Fig. 1. Ultrasonic Doppler inspection of the heart is displayed on the oscilloscope and then photographed.
Fig. line)
2. The same displayed.
study
as presented
in Fig.
Fig. The
3. Tracing of carotid artery pressure, arrows indicate the Doppler signals.
1, but
of a fetal
with
electrocardiogram,
guinea
the fetal
and
pig.
A 2 second
electrocardiogram
Doppler
from
interval
(bottom
a fetal
dog.
Volume Number
102 7
Fetal heart studies with Doppler
technique
963
The vesselwas catheterized (PE50 polyethylene) and connected to a Sanborn No. 267B pressure transducer and then to a Sanborn Model 350-3000B Carrier preamplifier. Recordings of the fetal electrocardiogram, carotid artery pressure curve, and ultrasonk Doppler inspection of the fetal heart were made simultaneously. Results
Fig. 4. Similar cate the Doppler
tracing to Fig. signals.
3. The
arrows
indi-
QRS Fig. 5. The
temporal relationships of fetal QRS complex, Doppler signals (stippled), and carotid artery pressure (arrow) curves in a dog fetus presented diagrammatically.
place by sutures or Allis clamps inserted on the uterine wall and fetal skin. A thermocouple needle was inserted beneath the skin of the exposed fetal head. A small transverse incision was made in the neck of the fetal dog below the level of the thyroid cartilage. The trachea was identified and, by means of blunt dissection, the carotid artery exposed (usually on the right side). in
Fifty-one dogs were examined utilizing ultrasonic Doppler inspection of the fetal heart and electrocardiogram. Of these, 25 dogs had the carotid artery exposed and cannulated for pressurestudies. In addition, 20 guinea pig fetuses were studied with the Doppler and electrocardiogram. The following findings are the product of these studies. Fig. 1 demonstrates the four components of the Doppler signal (2 second sample) obtained from the fetal guinea pig with the uterus intact. Although there is ample evidence of fetal heart action, further detailing of the fetal cardiac cycle is not possible. Fig. 2 represents the same study but the fetal electrocardiogram which has been recorded simultaneously is shown. Doppler signals occur consistently just prior to the QRS and after the P wave, immediately following the QRS, and at the time of the T wave of the fetal electrocardiogram. Three Doppler signalshave been observed in the same time relationship to the electrocardiogram in other speciesof animals. The significance of these signalswill be presented later. Fig. 3 depicts the carotid artery pressure curve, fetal electrocardiogram, and Doppler signals from the fetal dog. The two Doppler signals present occur prior to and following the QRS of the electrocardiogram. The second Doppler signal occupies the ascending limb of the carotid artery pressure curve. Fig. 4 demonstrates two Doppler signals occurring after the QRS complex. The first Doppler signal in this tracing (same as Doppler signal No. 2 from Fig. 3) occupies the ascending limb of the carotid artery pressure curve. The second Doppler signal in this
964
Bernstine
tracing occurs on the midportion of the descending limb of the carotid artery pressure curve. Fig. 5 presents the temporal relationships of these signals. These relationships have been derived from the visual inspections of many hours of paper recordings of these parameters in the fetal dog. Comment Bishop,4 and Bernstine and Callagan3 have reported on the clinical uses of ultrasound and the Doppler effect in obstetrics. Until the present report, no effort has been made to identify the phase of the fetal cardiac cycle when a specific Doppler signal occurs. The studies in the fetal guinea pig and more specifically in the fetal dog have yielded information which demonstrates that the second and third Doppler signals (Fig. 5) occur soon after electrical stimulation of the
ventricles. The second Doppler signal probably occurs during the isometric contraction phase of the fetal ventricles. The third Doppler signal occurs soon after the notch on the descending limb of carotid artery pressure cun;e which marks the closure of the aortic valve. This signal probably represents isometric relaxation phase diastole. Thus, the measurement of the second Doppler signal and the interval from the end of the second to the beginning of the third Doppler signal represents systole of the fetal heart. Further investigations are pursuing the study of the fetal cardiac cycle as defined by ultrasonic Doppler inspection. Establishment of “normal” time relationships between the various Doppler signals and intervals is being done. Correlation of the electrocardiogram and Doppler signals is being explored in a similar manner. fetal
REFERENCES
1. 2.
Hon, E. H.: Anesthesiology 26: 477, 1965. Caldeyro-Barcia, R., Mendez-Bauer, C., Poseiro, J. J., Escarcena, L. A., Pose, S. V., Bienian, J., Arnt, I., Gulin, L., and Althabe, 0.: In Cassels, D. E., editor: The Heart and Circulation
3. 4.
in the Newborn and Infant, New York, 1966, Grune & Stratton, Inc., pp. 7-36. Bernstine, R. L., and Callagan, D. A.: AM. J. OBST. & GYNEC. 95: 1001, 1966. Bishop, E. H.: J. Internat. Fed. Gynec. Obst. 4: 190, 1966.