Objectives: The purpose of this study was to assess the pregnancy-related cardiovascular risk in LQT1 patients. Background: Only 1 study addressed this issue in genotyped patients and reported that the highest risk is for LQT2 patients. Methods: This case-control study, performed in a cohort of patients from 22 families affected by LQT1 and all sharing the common KCNQ1-A341V mutation, involved 36 mutation carriers and 24 of their unaffected sisters for a total of 182 pregnancies. Results: There were 3 (2.6%) cardiac events (2 cardiac arrests) in the 115 LQT1 pregnancies. Because they occurred only among the 27 mothers with previous symptoms, all off-therapy, the risk for symptomatic patients is 11%, but decreases to 0 in symptomatic patients treated with beta-blockers. Carriers and control subjects did not differ for the incidence of miscarriage (10% vs. 15%). Cesarean sections (C-sections), elective or owing to fetal distress, were performed more often in carriers than in non-carriers (27% vs. 14%). Beta-blocker therapy did not influence the prevalence of fetal distress. Among the infants born to carriers, all those with fetal distress were carriers of the A341V mutation (10 of 10, 100%). Among the offspring of the carriers, 48 of 92 (52%) were mutation carriers, and of those, 15% died suddenly at age 14 ± 6 years. Conclusions: Women affected by the common KCNQ1-A341V mutation are at low risk for cardiac events during pregnancy and without excess risk of miscarriage; their infants delivered by C-section because of fetal distress are extremely likely to also be mutation carriers. Beta-blockers remain recommended. These conclusions likely apply to most LQT1 patients.
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