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Dependency of magnetocardiographically determined fetal cardiac time intervals on gestational age, gender and postnatal biometrics in healthy pregnancies.

Van Leeuwen P, Lange S, Klein A, Geue D, Grönemeyer DH - BMC Pregnancy Childbirth (2004)

Bottom Line: Gender differences were found only for the QRS complex from the 31st week onward (p < 0.05).The influence on the P wave or QRS complex of biometric data, collected in a subgroup in whom recordings were available within 1 week of birth, did not display statistical significance.Fetal development is thus in part reflected in the CTI and may be useful in the identification of intrauterine growth retardation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biomagnetism, Research and Development Center for Microtherapy (EFMT), Universitätsstr, 142, 44799 Bochum, Germany. petervl@microtherapy.de

ABSTRACT
BACKGROUND: Magnetocardiography enables the precise determination of fetal cardiac time intervals (CTI) as early as the second trimester of pregnancy. It has been shown that fetal CTI change in course of gestation. The aim of this work was to investigate the dependency of fetal CTI on gestational age, gender and postnatal biometric data in a substantial sample of subjects during normal pregnancy. METHODS: A total of 230 fetal magnetocardiograms were obtained in 47 healthy fetuses between the 15th and 42nd week of gestation. In each recording, after subtraction of the maternal cardiac artifact and the identification of fetal beats, fetal PQRST courses were signal averaged. On the basis of therein detected wave onsets and ends, the following CTI were determined: P wave, PR interval, PQ interval, QRS complex, ST segment, T wave, QT and QTc interval. Using regression analysis, the dependency of the CTI were examined with respect to gestational age, gender and postnatal biometric data. RESULTS: Atrioventricular conduction and ventricular depolarization times could be determined dependably whereas the T wave was often difficult to detect. Linear and nonlinear regression analysis established strong dependency on age for the P wave and QRS complex (r2 = 0.67, p < 0.001 and r2 = 0.66, p < 0.001) as well as an identifiable trend for the PR and PQ intervals (r2 = 0.21, p < 0.001 and r2 = 0.13, p < 0.001). Gender differences were found only for the QRS complex from the 31st week onward (p < 0.05). The influence on the P wave or QRS complex of biometric data, collected in a subgroup in whom recordings were available within 1 week of birth, did not display statistical significance. CONCLUSION: We conclude that 1) from approximately the 18th week to term, fetal CTI which quantify depolarization times can be reliably determined using magnetocardiography, 2) the P wave and QRS complex duration show a high dependency on age which to a large part reflects fetal growth and 3) fetal gender plays a role in QRS complex duration in the third trimester. Fetal development is thus in part reflected in the CTI and may be useful in the identification of intrauterine growth retardation.

No MeSH data available.


Related in: MedlinePlus

Averaged FMCG signal FMCG signal traces from 4 selected channels of the averaged data of a recording performed in the 39th week of gestation. The vertical lines show how the signal onsets and ends were set and used to determine the cardiac time intervals. (B = magnetic field strength)
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Figure 2: Averaged FMCG signal FMCG signal traces from 4 selected channels of the averaged data of a recording performed in the 39th week of gestation. The vertical lines show how the signal onsets and ends were set and used to determine the cardiac time intervals. (B = magnetic field strength)

Mentions: In each set of data, maternal heart beats were identified by correlation to a maternal QRS signal template and the maternal PQRST signal components were then digitally averaged and subsequently subtracted from the signal traces. In the resulting traces, fetal beats were similarly identified on the basis of a representative fetal QRS signal template. Fetal PQRST courses to be averaged were chosen on the basis of a good correlation (r ≥ 0.90) to the template (generally»300 beats). In the averaged data, the onsets (or endpoints) of the P wave, QRS complex and T wave were defined as the visually identifiable first (or last) deviation from the signal's baseline in any one channel out of all channels available for evaluation [11]. Due to the low amplitude of the T wave and possible DC drift, its onsets and end were determined on the basis of identifiable changes in amplitude at appropriate latencies. All channels were displayed individually avoiding overlap and within a fixed time window (20 ms/cm) and a defined range of amplitudes (0.1–0.5 pT/cm for the P and T wave, 0.5–1.0 pT/cm for the QRS complex). The onsets and ends were independently determined by two experienced investigators and their results were compared. The final value for each time point was set accordingly: in cases of differences > 2 ms both investigators re-evaluated and corrected the results, otherwise the results were averaged. These time points were then used to calculate the duration of the CTI. We determined the consecutive, non-overlapping (disjunct) intervals as follows: P wave = Pend - Ponset, PQ interval = QRSonset - Pend, QRS complex = QRSend - QRSonset, ST segment = Tonset - QRSend and T wave = Tend - Tonset. Furthermore, the following composite CTI were determined: PR interval = P wave + PQ interval and QT interval = QRS complex + ST segment + T wave (see Figure 2). Also, the rate corrected QT interval (QTc) was calculated according to Bazett's formula [18]. In some traces, signal quality did not permit the unequivocal identification of the timing of an event and the corresponding CTI were not determined.


Dependency of magnetocardiographically determined fetal cardiac time intervals on gestational age, gender and postnatal biometrics in healthy pregnancies.

Van Leeuwen P, Lange S, Klein A, Geue D, Grönemeyer DH - BMC Pregnancy Childbirth (2004)

Averaged FMCG signal FMCG signal traces from 4 selected channels of the averaged data of a recording performed in the 39th week of gestation. The vertical lines show how the signal onsets and ends were set and used to determine the cardiac time intervals. (B = magnetic field strength)
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC411040&req=5

Figure 2: Averaged FMCG signal FMCG signal traces from 4 selected channels of the averaged data of a recording performed in the 39th week of gestation. The vertical lines show how the signal onsets and ends were set and used to determine the cardiac time intervals. (B = magnetic field strength)
Mentions: In each set of data, maternal heart beats were identified by correlation to a maternal QRS signal template and the maternal PQRST signal components were then digitally averaged and subsequently subtracted from the signal traces. In the resulting traces, fetal beats were similarly identified on the basis of a representative fetal QRS signal template. Fetal PQRST courses to be averaged were chosen on the basis of a good correlation (r ≥ 0.90) to the template (generally»300 beats). In the averaged data, the onsets (or endpoints) of the P wave, QRS complex and T wave were defined as the visually identifiable first (or last) deviation from the signal's baseline in any one channel out of all channels available for evaluation [11]. Due to the low amplitude of the T wave and possible DC drift, its onsets and end were determined on the basis of identifiable changes in amplitude at appropriate latencies. All channels were displayed individually avoiding overlap and within a fixed time window (20 ms/cm) and a defined range of amplitudes (0.1–0.5 pT/cm for the P and T wave, 0.5–1.0 pT/cm for the QRS complex). The onsets and ends were independently determined by two experienced investigators and their results were compared. The final value for each time point was set accordingly: in cases of differences > 2 ms both investigators re-evaluated and corrected the results, otherwise the results were averaged. These time points were then used to calculate the duration of the CTI. We determined the consecutive, non-overlapping (disjunct) intervals as follows: P wave = Pend - Ponset, PQ interval = QRSonset - Pend, QRS complex = QRSend - QRSonset, ST segment = Tonset - QRSend and T wave = Tend - Tonset. Furthermore, the following composite CTI were determined: PR interval = P wave + PQ interval and QT interval = QRS complex + ST segment + T wave (see Figure 2). Also, the rate corrected QT interval (QTc) was calculated according to Bazett's formula [18]. In some traces, signal quality did not permit the unequivocal identification of the timing of an event and the corresponding CTI were not determined.

Bottom Line: Gender differences were found only for the QRS complex from the 31st week onward (p < 0.05).The influence on the P wave or QRS complex of biometric data, collected in a subgroup in whom recordings were available within 1 week of birth, did not display statistical significance.Fetal development is thus in part reflected in the CTI and may be useful in the identification of intrauterine growth retardation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biomagnetism, Research and Development Center for Microtherapy (EFMT), Universitätsstr, 142, 44799 Bochum, Germany. petervl@microtherapy.de

ABSTRACT
BACKGROUND: Magnetocardiography enables the precise determination of fetal cardiac time intervals (CTI) as early as the second trimester of pregnancy. It has been shown that fetal CTI change in course of gestation. The aim of this work was to investigate the dependency of fetal CTI on gestational age, gender and postnatal biometric data in a substantial sample of subjects during normal pregnancy. METHODS: A total of 230 fetal magnetocardiograms were obtained in 47 healthy fetuses between the 15th and 42nd week of gestation. In each recording, after subtraction of the maternal cardiac artifact and the identification of fetal beats, fetal PQRST courses were signal averaged. On the basis of therein detected wave onsets and ends, the following CTI were determined: P wave, PR interval, PQ interval, QRS complex, ST segment, T wave, QT and QTc interval. Using regression analysis, the dependency of the CTI were examined with respect to gestational age, gender and postnatal biometric data. RESULTS: Atrioventricular conduction and ventricular depolarization times could be determined dependably whereas the T wave was often difficult to detect. Linear and nonlinear regression analysis established strong dependency on age for the P wave and QRS complex (r2 = 0.67, p < 0.001 and r2 = 0.66, p < 0.001) as well as an identifiable trend for the PR and PQ intervals (r2 = 0.21, p < 0.001 and r2 = 0.13, p < 0.001). Gender differences were found only for the QRS complex from the 31st week onward (p < 0.05). The influence on the P wave or QRS complex of biometric data, collected in a subgroup in whom recordings were available within 1 week of birth, did not display statistical significance. CONCLUSION: We conclude that 1) from approximately the 18th week to term, fetal CTI which quantify depolarization times can be reliably determined using magnetocardiography, 2) the P wave and QRS complex duration show a high dependency on age which to a large part reflects fetal growth and 3) fetal gender plays a role in QRS complex duration in the third trimester. Fetal development is thus in part reflected in the CTI and may be useful in the identification of intrauterine growth retardation.

No MeSH data available.


Related in: MedlinePlus