Herberg, Ulrike

Abstract Aims In long QT syndrome (LQTS), primary prevention improves outcome; thus, early identification is key. The most common LQTS phenotype is a foetal heart rate (FHR) < 3rd percentile for gestational age (GA) but the effects of cohort, genotype, variant, and maternal β-blocker therapy on FHR are unknown. We assessed the influence of these factors on FHR in pregnancies with familial LQTS and developed a FHR/GA threshold for LQTS. Methods and results In an international cohort of pregnancies in which one parent had LQTS, LQTS genotype, familial variant, and maternal β-blocker effects on FHR were assessed. We developed a testing algorithm for LQTS using FHR and GA as continuous predictors. Data included 1966 FHRs at 7–42 weeks’ GA from 267 pregnancies/164 LQTS families [220 LQTS type 1 (LQT1), 35 LQTS type 2 (LQT2), and 12 LQTS type 3 (LQT3)]. The FHRs were significantly lower in LQT1 and LQT2 but not LQT3 or LQTS negative. The LQT1 variants with non-nonsense and severe function loss (current density or β-adrenergic response) had lower FHR. Maternal β-blockers potentiated bradycardia in LQT1 and LQT2 but did not affect FHR in LQTS negative. A FHR/GA threshold predicted LQT1 and LQT2 with 74.9% accuracy, 71% sensitivity, and 81% specificity. Conclusion Genotype, LQT1 variant, and maternal β-blocker therapy affect FHR. A predictive threshold of FHR/GA significantly improves the accuracy, sensitivity, and specificity for LQT1 and LQT2, above the infant’s a priori 50% probability. We speculate this model may be useful in screening for LQTS in perinatal subjects without a known LQTS family history.

Abstract Background In primary hyperoxaluria Type 1 (PH1), endogenous oxalate overproduction significantly elevates urinary oxalate excretion, resulting in recurrent urolithiasis and/or progressive nephrocalcinosis and often early end-stage renal disease (ESRD). In ESRD, dialysis cannot sufficiently remove oxalate; plasma oxalate (Pox) increases markedly, inducing systemic oxalate deposition (oxalosis) and often death. Interventions to reduce Pox in PH1 subjects with ESRD could have significant clinical impact. This ongoing Phase II, open-label trial aimed to evaluate whether long-term Oxabact™ (Oxalobacter formigenes, OC5, OxThera Intellectual Property AB, Sweden) lowers Pox in PH1 ESRD subjects, ameliorating clinical outcome. Methods PH1 ESRD subjects on stable dialysis regimens were examined. Subjects were administered one OC5 capsule twice daily for up to 36 months or until transplantation. Total Pox values, cardiac function and safety were evaluated. Free Pox was evaluated in a comparative non-treated PH1 dialysis group using retrospective chart reviews and analyses. Results Twelve subjects enrolled in an initial 6-week treatment phase. Following a washout of up to 4 weeks, eight subjects entered a continuation study; outcomes after 24 months of treatment are presented. After 24 months, all subjects had reduced or non-elevated Pox compared with baseline. Cardiac function improved, then stabilized. No treatment-related serious adverse events were reported. Conclusions Compared with an untreated natural control cohort, 24 months OC5 administration was beneficial to PH1 ESRD subjects by substantially decreasing Pox concentrations, and improving or stabilizing cardiac function and clinical status, without increasing dialysis frequency. OC5 was safe and well-tolerated.

Background: Long-QT syndrome (LQTS), an inherited cardiac repolarization disorder, is an important cause of fetal and neonatal mortality. Detecting LQTS prenatally is challenging. A fetal heart rate (FHR) less than third percentile for gestational age is specific for LQTS, but the sensitivity is only ≈50%. Left ventricular isovolumetric relaxation time (LVIRT) was evaluated as a potential diagnostic marker for fetal LQTS. Methods and Results: LV isovolumetric contraction time, LV ejection time, LVIRT, cycle length, and FHR were measured using pulsed Doppler waveforms in fetuses. Time intervals were expressed as percentages of cycle length, and the LV myocardial performance index was calculated. Single measurements were stratified by gestational age and compared between LQTS fetuses and controls. Receiver-operator curves were performed for FHR and normalized LVIRT (N-LVIRT). A linear mixed-effect model including multiple measurements was used to analyze trends in FHR, N-LVIRT, and LV myocardial performance index. There were 33 LQTS fetuses and 469 controls included. In LQTS fetuses, the LVIRT was prolonged in all gestational age groups ( P <0.001), as was the N-LVIRT. The best cutoff to diagnose LQTS was N-LVIRT ≥11.3 at ≤20 weeks (92% sensitivity, 70% specificity). Simultaneous analysis of N-LVIRT and FHR improved the sensitivity and specificity for LQTS (area under the curve=0.96; 95% confidence interval, 0.82–1.00 at 21–30 weeks). N-LVIRT, LV myocardial performance index, and FHR trends differed significantly between LQTS fetuses and controls through gestation. Conclusions: The LVIRT is prolonged in LQTS fetuses. Findings of a prolonged N-LVIRT and sinus bradycardia can improve the prenatal detection of fetal LQTS.