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The following is a summary of “Assessment of Severity of Long QT Syndrome Phenotype and Risk of Fetal Death,” published in the November 2023 issue of Cardiology by Albertini et al.

Long QT syndrome (LQTS) has been proposed as a potential factor contributing to fetal loss due to its speculated adverse impact on placental and myometrial function. This study aimed to explore the frequency of fetal demise among pregnant women diagnosed with long QT syndrome and to examine whether those with a more severe phenotype encountered poorer fetal outcomes.

In a retrospective analysis, the authors assessed the fetal outcomes of 64 pregnancies involving 23 women diagnosed with long QT syndrome, all monitored during pregnancy within a specialized pregnancy and heart disease program. Among the 64 pregnancies, 13 (20%) ended in fetal loss, comprising 12 miscarriages (19%) and 1 stillbirth (1.6%). Initial maternal characteristics, such as age and the utilization of β‐blockers, showed no notable differences between women experiencing fetal loss and those who did not. However, it was observed that the maternal corrected QT interval (QTc) was notably longer in pregnancies ending in fetal demise compared to those resulting in live births (median, 518 ms [interquartile range (IQR), 482‐519 ms] versus 479 ms [IQR, 454–496 ms], P<0.001). 

Mothers undergoing β‐blocker treatment gave birth to babies at term with reduced birth weight compared to untreated counterparts (2973±298 g versus 3470±338 g, P=0.002). Moreover, among treated women, babies born at term to those with a QTc >500 ms exhibited significantly lower birth weights than those with a QTc <500 ms (2783±283 g versus 3084±256 g, P=0.029).

In conclusion, women diagnosed with long QT syndrome, displaying more severe phenotypes, showcased a heightened incidence of fetal demise. This was reflected in longer maternal QTc intervals during pregnancies that ended in fetal loss. Additionally, the birth weights of babies born to mothers on β‐blockers with a QTc >500 ms were notably lower, suggesting that patients with more pronounced phenotypes might encounter adverse fetal outcomes.

Source: ahajournals.org/doi/10.1161/JAHA.122.029407