Fetal ECG: a novel predictor of atrioventricular block in anti-Ro positive pregnancies.
OBJECTIVE
Approximately 2.8% of pregnancies are Ro/La antibody positive. 3-15% of fetuses develop complete heart block (CHB). First-degree atrioventricular heart block (1 degrees AVB) is reported in a third of Ro/La fetuses but as most have a normal postnatal ECG this may reflect inadequacies of Doppler measurement techniques.


METHODS
Comparison was made between mechanical (mPR) and electrical (ePR) intervals obtained prospectively using Doppler and non-invasive fetal ECG (fECG) in 52 consecutive Ro/La pregnancies in 46 women carrying 54 fetuses in an observational study at a fetal medicine unit. 121 mPR and 37 ePR intervals were recorded in 49 Ro/La fetuses. Five were referred with CHB and excluded. ePR was measured successfully in 35/37 (94%) and mPR was measured in all cases. 1 degrees AVB was defined as PR >95% CI. Logistic regression predicted abnormal final fetal rhythm from first mPR or ePR.


RESULTS
The ePR model gave 66.7% sensitivity (6 of 8 final abnormal fetal rhythm cases were predicted correctly in fetuses >20 weeks) and 96.2% specificity. mPR gave 44.4% sensitivity (4 of 9 cases) and 88.5% specificity. Z scores for ePR (zPR) were calculated from 199 normal fetuses. The area under the receiver operator characteristic (ROC) curve was 0.88 (95% CI, 0.754 to 1.007). A cut-off of 1.65 gave a sensitivity of 87.5% and specificity of 95% for those with prolonged and normal ePR intervals, respectively.


CONCLUSIONS
zPR is better than mPR at differentiating between normal and prolonged PR intervals, suggesting that fECG is the diagnostic tool of choice to investigate the natural history and therapy of conduction abnormalities in Ro/La pregnancies.
Gardiner
Helena M
HM
Institute of Reproductive and Developmental Biology, Faculty of Medicine, Imperial College, Queen Charlotte's and Chelsea Hospital, Du Cane Road, London, W12 0HS, UK. helena.gardiner@imperial.ac.uk
Belmar
Cristian
C
Pasquini
Lucia
L
Seale
Anna
A
Thomas
Matthew
M
Dennes
William
W
Taylor
Myles J O
MJ
Kulinskaya
Elena
E
Wimalasundera
Ruwan
R
D000293:Adolescent; D000328:Adult; D000974:Antibodies, Antinuclear / Q000097:blood*; D054537:Atrioventricular Block / Q000175:diagnosis* / Q000188:drug therapy / Q000276:immunology; D015150:Echocardiography, Doppler; D004562:Electrocardiography; D004812:Epidemiologic Methods; D005260:Female; D005315:Fetal Diseases / Q000175:diagnosis* / Q000188:drug therapy / Q000276:immunology; D046128:Fetal Therapies; D005938:Glucocorticoids / Q000627:therapeutic use; D006801:Humans; D011247:Pregnancy; D016216:Ultrasonography, Prenatal / Q000379:methods
D000974:Antibodies, Antinuclear; D005938:Glucocorticoids; C035356:SS-A antibodies; C035357:SS-B antibodies