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Published on: January 16, 2019
The beginnings of long QT syndrome
1Department of Pediatrics and Obstetrics, University of Colorado School of Medicine, Children's Hospital Colorado Heart Institute, The Colorado Institute for Maternal and Fetal Health, Aurora, Colorado, USA.
Insights
Recognizing fetal long QT syndrome (LQTS) is crucial for preventing sudden death. Specific fetal heart rhythms like bradycardia or torsades de pointes predict postnatal arrhythmias and LQTS mutations.
Area of Science:
- Cardiology
- Genetics
- Obstetrics
Background:
- Long QT syndrome (LQTS) is a genetic disorder associated with sudden cardiac death.
- LQTS can manifest in fetal life but is often unrecognized.
- Fetal LQTS poses risks for both the neonate and family members.
Purpose of the Study:
- To provide an update on the presentation and management of fetal LQTS.
- To inform perinatal cardiologists and obstetric care providers about recognizing LQTS in fetuses.
- To highlight the importance of early diagnosis and intervention for LQTS.
Main Methods:
- Review of clinical presentations of LQTS in fetal life.
- Analysis of fetal heart rate patterns and arrhythmias.
- Correlation of fetal phenotypes with postnatal outcomes and genetic mutations.
Main Results:
- Fetal LQTS is often missed due to atypical presentations, such as heart rates below the third percentile for gestational age, not meeting standard bradycardia criteria.
- Torsades de pointes (TdP) with atrioventricular block (AVB) are key indicators.
- Fetal rhythm patterns predict postnatal arrhythmias and suggest specific LQTS genotypes (e.g., KCNQ1, SCN5A, KCNH2 mutations).
Conclusions:
- Fetal bradycardia (heart rate <3rd percentile for GA) and TdP ±2° AVB are strong indicators of LQTS.
- These fetal findings predict similar postnatal rhythms and the presence of an LQTS mutation.
- Early recognition and management of fetal LQTS are life-saving.
Purpose Of Review:
The purpose of this study is to update the perinatal cardiologist and obstetrical care provider on the presentation and management of the fetus with long QT syndrome (LQTS).
Recent Findings:
LQTS is a known cause of sudden death in childhood, adolescence and young adulthood that presents during fetal life, but is often not recognized. Torsades de pointes (TdP) ±2° atrioventricular block (AVB) are not always attributed to LQTS, although the most common LQTS rhythm, a fetal heart rate of less than third percentile for gestational age (GA), is not recognized as abnormal because it does not meet the standard obstetrical criteria for bradycardia. Early recognition and appropriate treatment can be life saving for the fetus and unsuspecting LQTS family members. Fetal rhythm phenotype and postnatal QTc can predict postnatal rhythm and suggest genotype: bradycardic fetuses usually have KCNQ1 mutation, while those with TdP and/or a postnatal QTc more than 500 ms have SCN5A, KCNH2 or uncharacterized mutations.
Summary:
The fetus with repeated heart rates of less than third percentile of GA and those with TdP ±2° AVB are likely to manifest the same rhythm after birth and have an LQTS mutation.
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