Fetal long QT syndrome manifested as atrioventricular block and ventricular tachycardia: a case report and a review of the literature

Calmodulin mutation in long QT syndrome 15 associated with congenital heart defects further complicated by a functional 2:1 atrioventricular block: Management from foetal life to postpartum

We report a long QT syndrome 15 whose diagnosis was suspected during foetal life and confirmed at birth and was associated with congenital heart disease. Genetic testing revealed a rare mutation associated with the CALM2 gene. At 23 weeks of gestation, severe foetal sinus bradycardia (∼100 bpm) was detected. In the third trimester, the foetus developed severe right ventricular hypertrophy. At birth, the electrocardiogram showed a long QT interval of 640 ms, and after 1 hour, the newborn showed functional 2:1 atrioventricular block at ventricular rate of 50 bpm. After further pharmacological therapies, epicardial wires were surgically implanted for transient pacing in VVI mode at 90 bpm. Echocardiogram showed aneurysmatic left atrial appendage, dilated right segments, hypertrophied right ventricle, ostium secundum type atrial septal defect, and muscular ventricular septal defect. At two weeks of postpartum, a permanent dual-chamber pacemaker was implanted in the DDD mode and the patient was discharged with a prescription of beta-blockers and calcium therapy.

A rare case with fetal autoimmune heart block and KNCH2 variant-induced long QT syndrome: a controversial opinion on prenatal management strategy

BACKGROUND

Among all fetal heart block patients, > 50% cases are associated with maternal autoimmune diseases, and such patients should receive treatment. However, nearly half of fetal heart block cases involve a mother with negative results following autoimmune antibody screening. A few studies have reported long QT syndrome (LQTS) can also present as a severe fetal bradycardia, which does not respond to fetal treatment. Herein, we reported a rare case of an infant who presented with high-degree autoimmune-mediated fetal atrioventricular block (AVB) with LQTS induced by a novel KCNH2 variant. This case led us to review our prenatal therapeutic strategy.

CASE PRESENTATION

A 1-year-old boy presented to our heart center having experienced syncope 5 times in the past year. He had previously presented with fetal bradycardia during the fetal stage from 27 + 3 gestational weeks. The fetal echocardiography demonstrated AVB (2:1 transmission). As the maternal autoimmune antibody results were positive, his mother had received dexamethasone treatment during pregnancy; subsequently, the fetal AVB had changed from 2:1 to 4:3 transmission with elevated ventricular beating rates. However, this patient was identified to have complete AVB after birth. The initial electrocardiogram and Holter measurements at hospital administration showed complete AVB, pleomorphic ventricular tachycardia, a prolonged QT interval (QT = 602 ms, corrected QT = 538 ms), and wide and deep inverted T-waves. Meanwhile, torsades de pointes could be observed in several transit ventricular tachycardias based on Holter monitoring review. Genetic testing revealed KCNH2 c.2483G > A variant-induced LQTS. An implantable cardioverter defibrillator device and permanent pacemaker were both considered as therapeutic alternations; his parents ultimately accepted the implantation of a permanent pacemaker.

CONCLUSIONS

For fetuses with autoimmune-mediated AVB, intrauterine treatment should still be pursued immediately. However, once the treatment outcomes are deemed unacceptable or unexpected, other genetic variant-related channelopathies should be highly suspected. If the fetus lacks a positive family history, fetal genetic testing should be recommended to improve the prognosis of such patients by introducing integrative therapeutic strategies between the prenatal and postnatal phases.

Long QT syndrome with AV Wenckebaching & bundle branch block in a neonate

We present a case of 21-day-old neonate brought with history of 3 episodes of syncope. Evaluation revealed congenital long QT syndrome associated with long cycle atypical AV Wenkebaching with a long short cycle sequence related left bundle branch aberrancy. Syncope was attributed to multiple episodes of Torsades de Pointes, necessitating emergency epicardial pacemaker implantation. In addition, child was started on oral propranolol therapy. On 2 months follow up, child was stable with no ventricular high rate episodes during pacemaker interrogation.

Clinical spectrum of fetal long QT syndrome: a single-center experience

OBJECTIVE

A considerable proportion of unexplained intrauterine fetal deaths are attributed to long QT syndrome (LQTS) susceptibility. Additionally, the estimated prevalence of LQTS in newborns is 1 in 2000. Still, prenatal diagnosis of LQTS is very rare. The aim of this study was to assess the frequency of prenatal diagnosis of LQTS at our institution, present the cases, compare our findings with the existing literature and propose a possible screening approach.

METHODS

We searched our fetal database between 2006 and 2013 for cases with suspected diagnosis of LQTS.

RESULTS

During the investigation period around 26 000 fetuses were evaluated and three cases of suspected fetal LQTS identified. Two cases of familial LQTS had no or mild intrauterine manifestation of the condition, the third fetus had a de-novo mutation with severe, early-onset disease.

CONCLUSIONS

LQTS continues to be a challenging prenatal diagnosis. In fetuses who present with complex arrhythmias, a high degree of suspicion is required, and close surveillance and timely delivery in the presence of a multidisciplinary team are necessary. For asymptomatic cases or screening purposes, routine fetal heart rate registration and detailed assessment of cases with a low for gestational age baseline may be an option.

Inherited arrhythmias: The cardiac channelopathies

Ion channels in the myocardial cellular membrane are responsible for allowing the cardiac action potential. Genetic abnormalities in these channels can predispose to life-threatening arrhythmias. We discuss the basic science of the cardiac action potential; outline the different clinical entities, including information regarding overlapping diagnoses, touching upon relevant genetics, new innovations in screening, diagnosis, risk stratification, and management. The special considerations of sudden unexplained death and sudden infant death syndrome are discussed. Scientists and clinicians continue to reconcile the rapidly growing body of knowledge regarding the molecular mechanisms and genetics while continuing to improve our understanding of the various clinical entities and their diagnosis and management in clinical setting. Two separate searches were run on the National Center for Biotechnology Information's website. The first using the term cardiac channelopathies was run on the PubMed database using filters for time (published in past 5 years) and age (birth-18 years), yielding 47 results. The second search using the medical subject headings (MeSH) database with the search terms “Long QT Syndrome” (MeSH) and “Short QT Syndrome” (MeSH) and “Brugada Syndrome” (MeSH) and “Catecholaminergic Polymorphic Ventricular Tachycardia” (MeSH), applying the same filters yielded 467 results. The abstracts of these articles were studied, and the articles were categorized and organized. Articles of relevance were read in full. As and where applicable, relevant references and citations from the primary articles where further explored and read in full.