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Foetal LQTS linked to gestational age

Foetal heart rate (FHR) varies by gestational age (GA) in both normal and long QT syndrome (LQTS) foetuses. Postnatal evaluation of neonates with FHR ≤3rd percentile for GA may improve ascertainment of LQTS in foetuses, neonates, and undiagnosed family members.

Foetal LQTS is associated with complex arrhythmias including torsades de pointes and 2° atrioventricular block. Sinus bradycardia has also been associated with foetal LQTS, but little is known of this rhythm manifestation. Our purpose was to characterize the FHR/GA profile of foetal LQTS.

We ascertained foetal LQTS subjects by family history (Group 1) or foetal arrhythmia referral (Group 2). We compared FHR in LQTS subjects versus normal foetuses. To identify FHR predictors of LQTS, we calculated a bradycardia index as % of LQTS FHR recordings either ≤110 beats per minute (obstetric standard) or ≤3rd percentile for GA. Among 42 LQTS subjects, 26 were in Group 1 and 16 in Group 2.There were 536 normal foetuses.

The bradycardia index was only 15% for FHR ≤110 beats per minute, but 66% for FHR ≤3rd percentile for GA. Ten foetuses with complex arrhythmias also had severe and sustained sinus bradycardia throughout gestation. Identifying a foetal proband in Group 2 resulted in LQTS diagnosis in 9 unsuspected members of 6 families.


1. Mitchell JL, Cuneo BF, Etheridge SP, Horigome H, Weng HY, Benson DW. Fetal heart rate predictors of long QT syndrome. Circulation 2012;126:2688–95.​CIRCULATIONAHA.112.114132

Published on: January 25, 2013

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