Abstract 9821: Fetal Rhythm Phenotype Predicts LQTS Mutation: Risk Stratification of Perinatal Long QT Syndrome
Introduction: Torsade de pointe (TdP) and/or 2° atrioventricular block (2° AVB) are signature rhythms for perinatal LQTS known for their high morbidity and mortality. We hypothesized that the clinical profile of patients with complex fetal arrhythmias might be mutation specific.
Methods: Perinatal records of subjects with LQTS exhibiting complex fetal arrhythmia were reviewed. Fetal echocardiograms, neonatal ECG and genetic testing were evaluated.
Results: We studied 11 LQTS subjects exhibiting complex fetal arrhythmias. Mutation in a known LQTS gene was identified in 9: SCN5A (5), KCNH2 (2) and KCNQ1 (2). Most mutations were de novo including 4 SCN5A-1623Q. TdP occurred in 8 cases (7 prenatal, mean gestational age=30.5 weeks). Most fetuses with TdP also had 2° AVB, but 3 cases had 2° AVB alone. TdP exhibited 2 patterns: fast (>270 bpm) and incessant or slow (<250 bpm) and intermittent. All cases with SCN5A mutation had fast-incessant TdP, while cases with KCNH2 mutations had slow-intermittent TdP. Cases with KCNQ1 mutations had 2° AVB. Fetuses with TdP were delivered earlier (33.6 weeks) than those with 2° AVB (38.5 weeks). Neonatal QTc intervals were 652 ± 42 (in utero TdP) and 507 ± 43, p=0.01 (in utero 2° AVB). Prenatal treatment was administered in 6 cases without maternal complications; 4 fetuses improved and TdP ceased in 2. Despite medical and pacemaker therapy, cardiac arrest (n=6) resulting in sudden death (n=2) were common.
Conclusion: Complex rhythm phenotypes of fetal LQTS have mutation specific features that may allow risk stratification in these high risk patients.
- © 2012 by American Heart Association, Inc.