Electrocardiographic Screening of 1-Month-Old Infants for Identifying Prolonged QT Intervals

Precision Medicine and Cardiac Channelopathies: Human iPSCs Take the Lead

Sudden cardiac death (SCD) is one of the leading causes of death worldwide, usually involving young people. SCD remains a critical public health problem accounting for 185,000-450,000 deaths annually, representing around 7%-18% of all deaths globally. As per evidence, ∼2%-54% of sudden unexpected deaths in people under the age of 35 years fail to show evidence of structural cardiac abnormalities at autopsy, making ion channelopathies the probable causes in such cases. The most generally recognized cardiac ion channelopathies with genetic testing are long QT syndrome (LQTS), Brugada syndrome (BrS), short QT syndrome (SQTS), and catecholaminergic polymorphic ventricular tachycardia (CPVT). The substantial progress in understanding the genetics of ion channelopathies in the last 2 decades has obliged the early diagnosis and prevention of SCD to a certain extent. In this review, we analyze the critical challenges and recent advancements in the identification, risk stratification, and clinical management of potentially fatal cardiac ion channel disorders. We also emphasize the application of precision medicine (PM) and artificial intelligence (AI) for comprehending the underlying genetic mechanisms, especially the role of human induced pluripotent stem cell (iPSC) based platforms to unravel the primary refractory clinical problems associated with channelopathies.

QTc Interval Reference Values and Their (Non)-Maturational Factors in Neonates and Infants: A Systematic Review

QTc interval measurement is a widely used screening tool to assess the risk of cardiac diseases, arrhythmias, and is a useful biomarker for pharmacovigilance. However, the interpretation of QTc is difficult in neonates due to hemodynamic maturational changes and uncertainties on reference values. To describe trends in QTc values throughout infancy (1 year of life), and to explore the impact of (non)-maturational changes and medicines exposure, a structured systematic review (PROSPERO CRD42022302296) was performed. In term neonates, a decrease was observed over the first week of life, whereafter values increased until two months of age, followed by a progressive decrease until six months. A similar pattern with longer QTc values was observed in preterms. QTc is influenced by cord clamping, hemodynamic changes, therapeutic hypothermia, illnesses and sleep, not by sex. Cisapride, domperidone and doxapram result in QTc prolongation in neonates. Further research in this age category is needed to improve primary screening practices and QTcthresholds, earlier detection of risk factors and precision pharmacovigilance.

The Value of Routine Tests before Pediatric Eye Surgery: A 10-Year Experience at a Tertiary Care Hospital

Background

Routine tests before ophthalmologic surgery in adult patients are no longer recommended. However, there are limited data on the utility of routine preoperative tests for children.

Aims

We aimed to describe the effect of routine preoperative tests on systemic perioperative complications by hospital discharge or by day 30 following eye surgery.

Settings and Design

This was a single-center, observational, and descriptive study.

Subjects and Methods

We examined all patients ≤ 17 years old for whom ophthalmologists consulted with anesthesiologists before eye surgery under general anesthesia in an academic teaching tertiary care hospital from January 2010 to December 2019.

Results

A total of 708 pediatric patients were analyzed. The mean patient age was 8.5 ± 4.6 years. The most frequently performed procedure was strabismus surgery in 433 patients (61.2%). Following anesthetic consultations, 15 patients (2.1%) underwent surgery postponed due to abnormalities at the physical examination. Routine tests identified that the two patients (0.3%) required additional evaluations due to elevated serum creatine kinase and electrocardiographic abnormalities. However, further examinations found that these abnormalities were unremarkable. The remaining 691 patients (97.6%) underwent surgery as scheduled. Substantial intraoperative blood loss was observed only in three patients with malignant tumors or trauma. The incidence of systemic complications was 0 (0%; 95% confidence interval, 0%-0.05%).

Conclusions

These data indicated that the development of systemic perioperative complications following pediatric ophthalmic surgery is rare. Preoperative tests should be requested only if they are clinically indicated or before potentially bleeding procedures, such as malignancy or trauma surgery.

Resuscitated Sudden Cardiac Arrest of a Neonate with Congenital LQT Syndrome-Associated Torsades de Pointes: A Case Report and Literature Review

Sudden infant death syndrome (SIDS), the most common cause of infant death in developed countries, is attributed to diverse trigger factors. Malignant cardiac dysrhythmias are potentially treatable etiologies, and congenital long QT syndrome (LQTS) is the most common cardiac ionic channelopathy confronted. β-Blockers or class Ib agents are the drugs of choice for the control of arrhythmias, and an implantable cardioverter defibrillator (ICD) should be considered for secondary prevention in survivors of lethal cardiac death. We report the case of a 4-day old neonate, later genetically confirmed as LQT type 3 (LQT3), who survived a pulseless torsades de pointes (TdP) attack and was successfully treated with propranolol, mexiletine, and ICD implantation.

School-based routine screenings of electrocardiograms for the diagnosis of long QT syndrome

Aims

School-based routine screenings of electrocardiograms (ECGs) have been performed upon admission to primary school (PS), junior high school (JHS), and high school (HS) in Japan. Though ECGs with prolonged QT intervals are occasionally found, the role of regular ECG screening tests in identifying long QT syndrome (LQTS) remains to be determined. We investigated the usefulness of the ECG screenings by comparing the results of genetic tests between students who showed QT-prolongation in the screenings and patients with LQTS.

Methods and results

We genetically screened 341 students (106 PS, 173 JHS, and 62 HS). Of these, 230 subjects showed QT-prolongation during regular screenings (S-S group), and the other 111 patients were clinically consulted with suspected LQTS by paediatricians (C-C group). Genotype–phenotype relationships were compared between the two groups. The positive rates in the genetic tests were comparable among the two groups; however, symptomatic subjects were significantly fewer in the S-S group than the C-C group (3% vs. 70%). Compared to the genotype-negative subjects, the positive subjects showed significantly longer QTc (P < 0.0001) and more frequently presented LQTS risk scores with ≥3.5 points (P < 0.0001). Lethal arrhythmic events (LAE) occurred only in the C-C group; 18 subjects experienced LAE and 83% of them were found to carry variant(s) in the LQTS-related genes.

Conclusion

The school-based ECG screenings are effective in identifying young patients with LQTS who require genetic analysis. If individuals are screened at a younger age, we can identify patients at risk earlier and provide preventative treatments.

Successful vaginal delivery in a parturient with long QT syndrome type 2 using double-catheter epidural analgesia: A CARE-compliant case report

RATIONALE

Congenital long QT syndrome (LQTS) can cause syncope or sudden death due to ventricular arrhythmia. Congenital LQTS has 3 major types, 1, 2, and 3. Life-threatening arrhythmias are triggered by emotion in patients with LQTS type 2. As patients with LQTS type 2 have a higher incidence of postnatal cardiac events, careful perinatal management especially during delivery is required. To the best of our knowledge, perinatal management of a patient with LQTS type 2 has not been properly described with consideration to its type-specific risk factors for ventricular tachyarrhythmia.

PATIENT CONCERNS

A 36-year-old pregnant woman, gravida 1, para 0, with LQTS type 2 was scheduled to undergo vaginal delivery under epidural labor analgesia in the 38th week of pregnancy. No fainting episodes were reported since she began to take 40 mg of propranolol once daily at the age of 25. Despite this, we instituted maximum preventive measures for the safety of both the parturient and the fetus to minimize the risk of maternal cardiac events throughout the perinatal period.

DIAGNOSES

She was diagnosed with LQTS type 2 by genetic testing at the age of 25.

INTERVENTIONS

Two epidural catheters were placed at levels T11-T12 and L5-S1. Injection of 0.2% ropivacaine and subsequent infusion of ropivacaine 0.1% with fentanyl (2 μg/mL) was directed through each catheter according to the stage of labor. Concurrently, landiolol, a selective and short-acting β1 receptor antagonist, was infused intravenously at a dose of 1 to 7 μg/kg/min.

OUTCOMES

The delivery proceeded uneventfully without pain. No adverse cardiac events were observed during the perinatal period.

LESSONS

Vaginal delivery under epidural labor analgesia using 2 catheters might be a viable option for maternal perinatal care and delivery of patients with LQTS type 2.

Defining the normal QT interval in newborns: the natural history and reference values for the first 4 weeks of life

AIMS

Evaluation of the neonatal QT interval is important to diagnose arrhythmia syndromes and evaluate side effects of drugs. We aimed at describing the natural history of the QT interval duration during the first 4 weeks of life and to provide reference values from a large general population sample.

METHODS AND RESULTS

The Copenhagen Baby Heart Study is a prospective general population study that offered cardiac evaluation of newborns. Eight-lead electrocardiograms were obtained and analysed with a computerized algorithm with manual validation. We included 14 164 newborns (52% boys), aged 0-28 days, with normal echocardiograms. The median values (ms, 2-98%ile) for the corrected intervals QTc (Bazett), QTc (Hodges), QTc (Fridericia), and QTc (Framingham) were 419 (373-474), 419 (373-472), 364 (320-414), and 363 (327-405). During the 4 weeks, we observed a small decrease of QTcFramingham, and an increase of QTcHodges (both P < 0.01), while QTcBazett and QTcFridericia did not change (P > 0.05). Applying published QT interval cut-off values resulted in 5-25% of the newborns having QT prolongation. Uncorrected QT intervals decreased linearly with increasing heart rate (HR). Sex and infant size did not affect the QT interval and the gestational age (GA) only showed an effect when comparing the extreme low- vs. high GA groups (≤34 vs. ≥42 weeks, P = 0.021).

CONCLUSION

During the 4 weeks QTcFramingham and QTcHodges showed minor changes, whereas QTcBazett and QTcFridericia were stable. The QT interval was unaffected by sex and infant size and GA only showed an effect in very premature newborns. Reference values for HR-specific uncorrected QT intervals may facilitate a more accurate diagnosis of newborns with abnormal QT intervals.

Artificial Intelligence-Enabled Assessment of the Heart Rate Corrected QT Interval Using a Mobile Electrocardiogram Device

BACKGROUND

Heart rate-corrected QT interval (QTc) prolongation, whether secondary to drugs, genetics including congenital long QT syndrome, and/or systemic diseases including SARS-CoV-2-mediated coronavirus disease 2019 (COVID-19), can predispose to ventricular arrhythmias and sudden cardiac death. Currently, QTc assessment and monitoring relies largely on 12-lead electrocardiography. As such, we sought to train and validate an artificial intelligence (AI)-enabled 12-lead ECG algorithm to determine the QTc, and then prospectively test this algorithm on tracings acquired from a mobile ECG (mECG) device in a population enriched for repolarization abnormalities.

METHODS

Using >1.6 million 12-lead ECGs from 538 200 patients, a deep neural network (DNN) was derived (patients for training, n = 250 767; patients for testing, n = 107 920) and validated (n = 179 513 patients) to predict the QTc using cardiologist-overread QTc values as the "gold standard". The ability of this DNN to detect clinically-relevant QTc prolongation (eg, QTc ≥500 ms) was then tested prospectively on 686 patients with genetic heart disease (50% with long QT syndrome) with QTc values obtained from both a 12-lead ECG and a prototype mECG device equivalent to the commercially-available AliveCor KardiaMobile 6L.

RESULTS

In the validation sample, strong agreement was observed between human over-read and DNN-predicted QTc values (-1.76±23.14 ms). Similarly, within the prospective, genetic heart disease-enriched dataset, the difference between DNN-predicted QTc values derived from mECG tracings and those annotated from 12-lead ECGs by a QT expert (-0.45±24.73 ms) and a commercial core ECG laboratory [10.52±25.64 ms] was nominal. When applied to mECG tracings, the DNN's ability to detect a QTc value ≥500 ms yielded an area under the curve, sensitivity, and specificity of 0.97, 80.0%, and 94.4%, respectively.

CONCLUSIONS

Using smartphone-enabled electrodes, an AI DNN can predict accurately the QTc of a standard 12-lead ECG. QTc estimation from an AI-enabled mECG device may provide a cost-effective means of screening for both acquired and congenital long QT syndrome in a variety of clinical settings where standard 12-lead electrocardiography is not accessible or cost-effective.

Early Identification of Prolonged QT Interval for Prevention of Sudden Infant Death

Introduction: Long QT syndrome is the main arrhythmogenic disease responsible for sudden death in infants, especially in the first days of life. Performing an electrocardiogram in newborns could enable early diagnosis and adoption of therapeutic measures focused on preventing lethal arrhythmogenic events. However, the inclusion of an electrocardiogram in neonatal screening protocols still remains a matter of discussion. To comprehensively analyse the potential clinical value of performing an electrocardiogram and subsequent follow-up in a cohort of newborns. Methods: Electrocardiograms were performed in 685 neonates within the first week of life. One year follow-up was performed if QTc > 450 ms identified. Comprehensive genetic analysis using massive sequencing was performed in all cases with QTc > 470 ms. Results: We identified 54 neonates with QTc > 450 ms/ <470 ms; all normalized QTc values within 6 months. Eight cases had QTc > 480 ms at birth and, if persistent, pharmacological treatment was administrated during follow-up. A rare variant was identified as the potential cause of long QT syndrome in five cases. Three cases showed a family history of sudden arrhythmogenic death. Conclusions: Our prospective study identifies 0.14% of cases with a definite long QT, supporting implementation of electrocardiograms in routine pediatric protocols. It is an effective, simple and non-invasive approach that can help prevent sudden death in neonates and their relatives. Genetic analyses help to unravel the cause of arrhythmogenic disease in diagnosing neonates. Further, clinical assessment and genetic analysis of relatives allowed early identification of family members at risk of arrhythmias helping to adopt preventive personalized measures.

A Case Report: Two Young Children with Long QT Syndrome Type-2 Diagnosed by Presymptomatic Genetic Testing

Long QT syndromes (LQTSs) can lead to sudden cardiac death, yet these syndromes are often asymptomatic and clinically undetected, despite the prolongation of the QT interval. Currently, when a disease-causing variant is identified in an individual, presymptomatic genetic testing is available and can form part of the recommended cascade testing to identify other family members at risk. We herein report the cases of two daughters who received presymptomatic genetic testing in infancy when the proband mother had been diagnosed with LQTS type 2 (LQT2; c.1171C > T, p.Q391X in KCNH2) after suffering from cardiac arrhythmia at 30 years of age. The daughters had a normal QTc interval, but they carried the same disease-causing variant as their mother. Children with family members who have genetically confirmed LQTS have a high risk of suffering from cardiac events later in life, so genetic testing is required. This poses a complex problem, as guidelines for medical intervention and follow-up systems among asymptomatic children with LQTS have yet to be established. Genetic testing should only be performed after adequate counseling to support children later in life. Individualized long-term genetic counseling is required for both parents and children at stages throughout life.

An NGS-based genotyping in LQTS; minor genes are no longer minor

Mutations in KCNQ1, KCNH2, and SCN5A are the major cause of long QT syndrome (LQTS). More than 90% of the genotyped patients have been reported to carry mutations in any of these three genes. Thanks to increasing popularity of next generation sequencer (NGS), novel CACNA1C mutations have been identified among LQTS patients without extra-cardiac phenotypes. We aimed to clarify the frequency of genotypes in LQTS patients in the era of NGS. The study comprised 160 congenital LQTS patients (71 males) registered from November 2015 to September 2018. Inclusion criteria was QTc > 460 ms and Schwartz score ≥ 3. We performed genetic analysis using target gene method by NGS and confirmed the mutations by Sanger method. The median age for genetic screening was 13 (0-68) years. Sixteen patients suffered cardiac arrest, 47 syncope, and 97 were asymptomatic. We identified genetic mutations in 111 (69.4%) patients including 6 CACNA1C (5.4% of the genotyped patients) with 4 asymptomatic patients. Five (3.1%) patients carried double mutations; three out of them with RYR2 and KCNQ1 or KCNH2. In conclusion, CACNA1C screening would be recommended even if the patient is asymptomatic to elucidate the genetic background of the LQTS patients.

Electrocardiographic Screening in the First Days of Life for Diagnosing Long QT Syndrome: Findings from a Birth Cohort Study in Germany

INTRODUCTION

Newborn sudden infant death syndrome (SIDS) has failed to decrease in the last decades, and a third of the neonatal cases occurred within the first 6 days of life. The long QT syndrome (LQTS) is a genetic disease with a prevalence of 1 in 2,000 live births and contributes to almost 10% of SIDS cases. Early identification of LQTS through electrocardiogram (ECG) screening is likely to reduce mortality.

METHODS AND RESULTS

In this ongoing prospective study we evaluated 2,251 ECGs from newborns participating in the KUNO Kids birth cohort study between July 2015 and July 2018. ECGs were recorded at a mean age of 2.0 days (IQR 0 days). The QT interval was corrected for heart rate using Bazett's formula (QTc). A QTc between 451 and 460, 461-470, and >470 ms was measured in 23 (1.0), 14 (0.6), and 62 (2.8%) participants, respectively. Fourteen neonates (0.62%) were admitted and monitored because their initial QTc was ≥500 ms. In 2 genetically analyzed participants, a mutation was found. One disease-causing for LQTS type 1 and the other of unclear significance. Cascade screening revealed affected members in both families.

CONCLUSION

A standardized neonatal ECG screening in the first days of life is able to identify neonates with a relevant transient form of prolonged QT intervals and to aid diagnosing congenital LQTS.

Epidemiology of inherited arrhythmias

The primary electrical disorders are a group of inherited cardiac ventricular arrhythmias that are a major cause of sudden cardiac death in young individuals. Inherited ventricular arrhythmias result from mutations in genes encoding cardiac ion channels or their modulatory subunits. Advances in genetic screening in the past three decades have led to the assembly of large patient cohorts with these disorders. Studies in these patients, as well as in the general population, have striven to define the prevalence of these inherited arrhythmias and the characteristics of patients with different genetic subtypes of the disease. In this Review, we provide a comprehensive update on the epidemiology of inherited ventricular arrhythmias, focusing on natural history, prevalence and patient demographics. In addition, we summarize the various founder populations (groups of individuals with a disease that is caused by a genetic defect inherited from a common ancestor) that have been identified for some of these disorders and which lead to increased prevalence in some geographical regions. To date, although numerous studies have markedly increased our understanding of the epidemiology of these disorders, demographic data, especially from non-Western countries, remain scarce. Furthermore, defining the true prevalence of these disorders remains challenging. International collaboration will undoubtedly accelerate the collection of demographic information and improve the accuracy of prevalence data.

Copenhagen Baby Heart Study: a population study of newborns with prenatal inclusion

Congenital heart diseases (CHDs) are reported in 0.8% of newborns. Numerous factors influence cardiovascular development and CHD prevalence, and possibly also development of cardiovascular disease later in life. However, known factors explain the probable etiology in only a fraction of patients. Past large-scale population-based studies have made invaluable contributions to the understanding of cardiac disease, but none recruited participants prenatally and focused on the neonatal period. The Copenhagen Baby Heart Study (CBHS) is a population-based study of the prevalence, spectrum, and prognosis of structural and functional cardiac abnormalities. The CBHS will also establish normal values for neonatal cardiac parameters and biomarkers, and study prenatal and early childhood factors potentially affecting later cardiovascular disease risk. The CBHS is an ongoing multicenter, prospective study recruiting from second trimester pregnancy (gestational weeks 18-20) (expected n = 25,000). Information on parents, pregnancy, and delivery are collected. After birth, umbilical cord blood is collected for biochemical analysis, DNA purification, and biobank storage. An echocardiographic examination, electrocardiography, and post-ductal pulse oximetry are performed shortly after birth. Infants diagnosed with significant CHD are referred to a specialist or admitted to hospital, depending on CHD severity. CBHS participants will be followed prospectively as part of specific research projects or regular clinical follow-up for CHD. CBHS design and methodology are described. The CBHS aims to identify new mechanisms underlying cardiovascular disease development and new targets for prevention, early detection, and management of CHD and other cardiac diseases presenting at birth or developing later in life.

Autonomic Function and QT Interval During Night-Time Sleep in Infant Long QT Syndrome

BACKGROUND

Sudden infant death syndrome mainly occurs during night-time sleep. Approximately 10% of cases are thought to involve infants with long QT syndrome (LQTS). Autonomic function and QT interval in night-time sleep in early infancy in LQTS infants, however, remain controversial.Methods and Results:Holter electrocardiography was performed in 11 LQTS infants before medication in early infancy, and in 11 age-matched control infants. Control infants were re-evaluated in late infancy. The power spectral density was calculated and parasympathetic activity and sympathovagal balance were obtained. Electrocardiograms of a representative hour during night-time sleep, daytime sleep, and daytime activity, were chosen and QT/RR intervals were manually measured. LQTS infants had significantly lower parasympathetic activity and higher sympathovagal balance during night-time sleep than control infants in early infancy. These autonomic conditions in early infancy were significantly depressed compared with late infancy. Corrected QT interval (QTc) during night-time sleep (490±20 ms) was significantly longer than that in daytime sleep (477±21 ms, P=0.04) or daytime activity (458±18 ms, P=0.003) in LQTS infants, and significantly longer than that during night-time sleep in controls.

CONCLUSIONS

A combination of the longest QTc and autonomic imbalance during night-time sleep in early infancy may be responsible for development of life-threatening arrhythmia in LQTS infants. Critical cases should be included in future studies.

Wolff-Parkinson-White syndrome and noncompaction in Leber's hereditary optic neuropathy due to the variant m.3460G>A

This report describes a 66-year-old Caucasian male who acutely developed severe, bilateral impairment of visual acuity at 24 years of age. Leber’s hereditary optic neuropathy (LHON) was suspected but the diagnosis was not genetically confirmed until the age of 49 years when the primary LHON mutation m.3460G>A was detected. Since onset, visual acuity had slightly improved. The family history was positive for LHON (brother, two sisters of mother, female cousin) and genetically confirmed in his brother and one aunt. Since the age of 65 years, he had experienced recurrent vertigo. His cardiological history was positive for arterial hypertension, noncompaction, myocardial thickening, intermittent right bundle-branch-block (RBBB) and Wolff-Parkinson-White (WPW) syndrome. In addition to LHON, he presented with polyneuropathy, hyperCKaemia, carotid artery occlusion, and a history of stroke. Cardiological investigations at 66 years of age revealed mildly reduced systolic function, enlarged atria, and nonsustained ventricular tachycardias. He underwent an electrophysiological investigation, but radiofrequency ablation was ruled out due to a ‘bizarre’ cardiac conduction system. Instead, an implantable cardioverter defibrillator was proposed but refused by the patient. Since the vertigo did not resolve it was attributed to polyneuropathy. This case demonstrates that LHON may be associated with noncompaction, myocardial thickening, reduced systolic function, enlarged atria, RBBB, WPW syndrome and nonsustained ventricular tachycardias. WPW syndrome in LHON may require invasive antiarrhythmic treatment.

Heart rate variability as predictive factor for sudden cardiac death

Sudden cardiac death (SCD) represents about 25% of deaths in clinical cardiology. The identification of risk factors for SCD is the philosopher's stone of cardiology and the identification of non-invasive markers of risk of SCD remains one of the most important goals for the scientific community.The aim of this review is to analyze the state of the art around the heart rate variability (HRV) as a predictor factor for SCD.HRV is probably the most analyzed index in cardiovascular risk stratification technical literature, therefore an important number of models and methods have been developed.Nowadays, low HRV has been shown to be independently predictive of increased mortality in post- myocardial infarction patients, heart failure patients, in contrast with the data of the general population.Contrariwise, the relationship between HRV and SCD has received scarce attention in low-risk cohorts. Furthermore, in general population the attributable risk is modest and the cost/benefit ratio is not always convenient.The HRV evaluation could become an important tool for health status in risks population, even though the use of HRV alone for risk stratification of SCD is limited and further studies are needed.

Environmental risk factors for sudden infant death syndrome in Japan

While the prevalence of sudden infant death syndrome (SIDS) has decreased worldwide, this decline has plateaued recently. Strategies are needed to resume the constant decrease of SIDS in Japan. A prospective electrocardiographic screening program for infants was performed between July 2010 and March 2011. Parents of 4319 infants were asked about environmental factors related to SIDS through questionnaires at a one-month medical checkup and one year. Parental awareness of prone position, smoke exposure, and breast feeding as environmental factors were 81.4 %, 69.0 %, and 47.8 %, respectively. The prevalence of laying infants exclusively in a supine position was 96.7 %. At the one-month medical checkup, smoking prevalence was 41.7 % in fathers and 2.1 % in mothers. Maternal smoking prevalence was significantly increased at one year after (p < 0.001). Multivariate regression analysis showed that risk factors for new or continued maternal smoking habits were maternal smoking habits at one month (p < 0.001), paternal smoking habits one year later (p < 0.001), and younger maternal age (p = 0.02).

CONCLUSION

Most parents already avoid laying infants in the prone position, and parental smoking is still a SIDS risk concern in Japan. Smoking cessation programs should be further implemented for parents to decrease risks of SIDS in Japan. What is Known: • The prevalence of sudden infant death syndrome (SIDS) has decreased worldwide, however, this decline has plateaued recently. What is New: • Most infants were laid sleeping in the supine position (96.7 %) and were fed breast milk or a mix of expressed milk and formula (92.7 %), and 2.1 % of mothers smoked at the one-month medical checkup. • Maternal smoking prevalence significantly increased from the one-month medical checkup to one year later, and smoking mothers were more likely to feed infants by formula rather than breast milk. • Independent risk factors for new or continued maternal smoking habits included younger maternal age, maternal smoking habits at one month, and paternal smoking habits one year later.

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.

Comorbid Epilepsy and Developmental Disorders in Congenital Long QT Syndrome With Life-Threatening Perinatal Arrhythmias

OBJECTIVES

Given the association of long QT syndrome (LQTS) and neurological disorders, we speculated that the more severe LQTS phenotype, perinatal LQTS, would exhibit more frequent comorbid neurodevelopmental anomalies than LQTS without perinatal arrhythmias (nonperinatal LQTS).

BACKGROUND

Congenital LQTS with life-threatening perinatal arrhythmias (perinatal LQTS) has a poor life prognosis.

METHODS

Twenty-one consecutive LQTS patients diagnosed before 1 year of age at our institution and 3 previously reported perinatal LQTS patients with neurological seizures were enrolled. In total, the clinical course was evaluated in 24 patients.

RESULTS

Among 21 infantile LQTS patients, 5 of 6 with perinatal LQTS (83%) were diagnosed with epilepsy and 4 (67%) with developmental disorders, but none with nonperinatal LQTS were. The total development quotient by Kinder Infant Development Scale scores was 17 to 72 (median 67) in 5 epileptic perinatal LQTS. In the 8 perinatal LQTS patients with neurological disorders, including 3 previously reported cases, epileptic seizures occurred at 2 days to 2.5 years of age and 5 had developmental disorders. Mutations in these 8 patients were located in the transmembrane loop of KCNH2, and D3/S4-S5 linker, D4/S4, or the D4/S6 segment of SCN5A.

CONCLUSIONS

A high comorbidity of neurodevelopmental anomalies was observed in perinatal LQTS. Mutations in patients with neurological comorbidities were in loci linked to LQTS with a severe cardiac phenotype. These observations indicate the possibility that neurological disorders in perinatal LQTS are manifested as neurological phenotypes associated with severe cardiac phenotypes, while we could not completely exclude another possibility that those were caused by a brain perfusion injury.

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.

Comparison of formulas for calculation of the corrected QT interval in infants and young children

OBJECTIVE

To compare 4 heart rate correction formulas for calculation of the rate corrected QT (QTc) interval among infants and young children.

STUDY DESIGN

R-R and QT intervals were measured from digital electrocardiograms. QTc were calculated with the Bazett, Fridericia, Hodges, and Framingham formulas. QTc vs R-R graphs were plotted, and slopes of the regression lines compared. Slopes of QTc-R-R regression lines close to zero indicate consistent QT corrections over the range of heart rates.

RESULTS

We reviewed electrocardiograms from 702 children, with 233 (33%) <1 year of age and 567 (81%) <2 years. The average heart rate was 122 ± 20 bpm (median 121 bpm). The slopes of the QTc-R-R regression lines for the 4 correction formulas were -0.019 (Bazett); 0.1028 (Fridericia); -0.1241 (Hodges); and 0.2748 (Framingham). With the Bazett formula, a QTc >460 ms was 2 SDs above the mean, compared with "prolonged" QTc values of 414, 443, and 353 ms for the Fridericia, Hodges, and Framingham formulas, respectively.

CONCLUSIONS

The Bazett formula calculated the most consistent QTc; 460 ms is the best threshold for prolonged QTc. The study supports continued use of the Bazett formula for infants and children and differs from the use of the Fridericia correction during clinical trials of new medications.

Rationale and objectives for ECG screening in infancy

Electrocardiographic (ECG) screening in infants and children who may be at risk of sudden cardiac death (SCD) is controversial, and both rational and emotional arguments have often been given equal weight. We all have direct experience in this field, but have different backgrounds and have expressed divergent views on this topic. We attempted to build consensus among ourselves on the basis of the available facts, in the hope of providing an unbiased review of the relevant science and policy issues in favor of or against ECG screening in infants and children. This report presents our shared view on this medically and societally important topic. Long QT syndrome (LQTS) satisfies several criteria that may make ECG screening worthwhile: it is not rare (~1 in 2000 births); ECG diagnosis is feasible and can be used to trigger appropriate genetic testing; it causes approximately 10% of cases of sudden infant death syndrome (SIDS) as well as deaths in childhood and later in life, and effective treatments are available. By stimulating cascade screening in family members, diagnosis of affected infants may also prompt identification of asymptomatic but affected individuals. Neonatal screening is cost-effective by conventional criteria, and with a corrected QT (QTc) cutoff of 460 ms in 2 different ECGs, the number of false positives is estimated to be low (~1 in 1000 births). It is our conclusion that parents of newborn children should be informed about LQTS, a life-threatening but treatable disease of significant prevalence that may be diagnosed by a simple ECG.