Prolonged QT interval and cardiac arrhythmias in two neonates: sudden infant death syndrome in one case

Two neonates with arrhythmias and the long QT syndrome are described. The arrhythmias were detected in utero and both infants were apparently well after birth. The first infant, although well, had a bradycardia for the first 9 days of life. A normal heart rate was documented at 10 days but a prolonged QT interval was not appreciated on the ECG. He was discharged from hospital but died suddenly and unexpectedly 3 days later. A post-mortem examination failed to find a cause for his death which therefore fell into the category of the sudden infant death syndrome (SIDS). A retrospective analysis of the perinatal electrocardiogram showed a probable junctional rhythm with 2:1 conduction to the ventricle; the QT interval was prolonged at 0.52 seconds (QTC = 0.63). The second infant had a QT interval of 0.52 seconds (QTC = 0.54) and frequent ventricular premature beats on a 24-hour electrocardiogram. She was treated with propranolol and remains well 2 years later. Sudden infant death has often been described in the siblings of children with the long QT syndrome and one other report described a case of SIDS which was said to have had a prolonged QT interval on the perinatal ECG. This report, however, provides unquestionable evidence, in one case, of an association between the long QT syndrome and SIDS.     

Prolonged QT interval and cardiac arrhythmias in two neonates: sudden infant death syndrome in one case.

Two neonates with arrhythmias and the long QT syndrome are described. The arrhythmias were detected in utero and both infants were apparently well after birth. The first infant, although well, had a bradycardia for the first 9 days of life. A normal heart rate was documented at 10 days but a prolonged QT interval was not appreciated on the ECG. He was discharged from hospital but died suddenly and unexpectedly 3 days later. A post-mortem examination failed to find a cause for his death which therefore fell into the category of the sudden infant death syndrome (SIDS). A retrospective analysis of the perinatal electrocardiogram showed a probable junctional rhythm with 2:1 conduction to the ventricle; the QT interval was prolonged at 0.52 seconds (QTC = 0.63). The second infant had a QT interval of 0.52 seconds (QTC = 0.54) and frequent ventricular premature beats on a 24-hour electrocardiogram. She was treated with propranolol and remains well 2 years later. Sudden infant death has often been described in the siblings of children with the long QT syndrome and one other report described a case of SIDS which was said to have had a prolonged QT interval on the perinatal ECG. This report, however, provides unquestionable evidence, in one case, of an association between the long QT syndrome and SIDS.     

Perinatal manifestations of idiopathic long QT syndrome

A neonate who had presented with sustained irregular heart rate during labor was found to have QT prolongation and repetitive polymorphic ventricular tachycardia (torsades de pointes) postnatally. Propranolol and propafenone successfully controlled the ventricular arrhythmias. Follow-up electrocardiograms and Holter records show persistent QT prolongation, bizarre T waves, and intermittent episodes of T wave alternans. On propranolol monotherapy the boy is thriving and completely free of ventricular arrhythmias. In the rare case of long QT syndrome in the neonate, early detection and therapy are mandatory to prevent ventricular arrhythmias and sudden death.     

Neonatal long QT syndrome and sudden cardiac death

Neonatal sudden cardiac death most often results from cardiac electrical diseases, cardiomyopathies, or sudden infant death syndrome. In infants without a known premortem diagnosis or abnormalities identified at autopsy, sudden infant death syndrome accounts for the vast majority of sudden deaths. Potential cardiac causes of some sudden infant death syndrome cases may include malignant brady- or tachyarrhythmias and congenital long QT syndrome. The possible mechanisms include abnormal brain stem respiratory control of arousal, dysautonomia and malignant cardiac bradyarrhythmias or tachyarrhythmias. Screening for neonatal sudden cardiac death may not be feasible, but hopefully through careful review of history, physical examination, and family health history, and judicious diagnostic testing, can the risk of cardiac sudden death be reduced. Further comprehension of the genetic basis of inherited arrhythmia disorders may help elucidate the mechanisms of arrhythmogenesis and etiologies of sudden infant death. Prevention and treatment of these disorders may also be improved through more detailed understanding of the molecular basis of cardiac electrical pathophysiology.     

Short QT Syndrome in a Pediatric Patient

Short QT syndrome (SQTS) is a recently described genetic syndrome characterized by abnormally brisk ventricular repolarization. Similar to long QT syndrome, SQTS might result in ventricular arrhythmias, syncope, and sudden death. The clinical diagnosis of SQTS is supported by the finding of an abnormally short QT interval on the resting electrocardiogram in combination with a suggestive clinical or family history. To date, few pediatric cases have been reported and the ideal therapy is unknown. We report a teenage boy who suffered a witnessed ventricular fibrillation arrest and was subsequently diagnosed with SQTS. Additional data from nine other pediatric patients diagnosed with SQTS are presented.     

Use of the newborn screening card to define cause of death in a 12-year-old diagnosed with epilepsy

Post-mortem investigation of sudden death in young people frequently reveals no overt cause for the death. Full investigation is hampered if tissue or blood is not retained for DNA analysis. We report a post mortem molecular diagnosis of long QT syndrome in a 12-year-old boy diagnosed with epilepsy who died suddenly playing sport. The DNA was extracted from an archived blood spot on his newborn screening ('Guthrie') card, which had been taken from him at 6 days of age. A missense mutation was detected in exon 5 of the KCNQ1 gene; R243C (835C > T), associated with long QT type 1. The same mutation was found in the mother (who now takes effective preventative therapy), but not in the sib who has now been reassured that she is not at risk of sudden death.     

Sudden infant death syndrome and prolongation of the QT interval

A standard lead II ECG was recorded during either the first or the fourth week of life or at both ages from 30 neonates whose sibling had died of the sudden infant death syndrome (SIDS). Electrocardiographic recordings also were obtained from 75 control neonates and from 52 adults who had had an infant who died of SIDS. The neonatal data revealed that the QT interval, corrected for heart rate (QTC), was longest during NREM (vs rapid eye movement [REM]) sleep. Furthermore, the QTC interval was longer within the fourth week than in the first week of life. However, the QTC interval of siblings of SIDS victims did not differ from that of the control infants, nor did the QT interval of parents of SIDS victims differ from published normal values. One neonate who subsequently died of SIDS did not have an abnormally long QTC interval. These data do not support the hypothesis that genetically determined prolongation of the QT interval plays a major role in SIDS.     

Cost-effectiveness and implications of newborn screening for prolongation of QT interval for the prevention of sudden infant death syndrome

OBJECTIVE: To determine the cost-effectiveness of universal and high-risk neonatal electrocardiographic (ECG) screening for QT prolongation as a predictor of sudden infant death syndrome (SIDS) risk in a theoretical group of neonates.Study design: Incremental cost-effectiveness analysis with decision analytic modeling. A hypothetical cohort of healthy, term infants was modeled, comparing options of no screening, high-risk neonate screening, and universal screening. The high-risk strategy is speculative, because no currently accepted methodology is known for identifying infants at high risk for SIDS. Given the uncertain mechanisms of association between prolonged corrected QT interval (QTc) and SIDS, analyses were repeated under different assumptions. Sensitivity analyses were also performed on all input variables for both costs and effectiveness. RESULTS: Under the assumption that neonatal electrocardiographic screening detects long QT syndrome responsive to conventional therapy, the cost-effectiveness of high-risk screening was $3403 per life year gained, whereas universal screening cost $18,465 per additional life year gained. However, if the effectiveness of SIDS therapy falls below 10%, the cost-effectiveness deteriorates to $28,376 per life year saved for the high-risk strategy and $118,900 for universal screening. The analyses were robust to a broad array of sensitivity analyses. CONCLUSIONS: The acceptability of the cost-effectiveness of neonatal electrocardiographic screening is heavily dependent on the pathophysiologic mechanism of SIDS and on the efficacy of monitoring and antiarrhythmic treatment. The nature of this association must be elucidated before routine neonatal electrocardiographic screening is warranted.     

Sudden infant death syndrome, child sexual abuse, and child development

Since the introduction of the Back to Sleep Campaigns, there has been a dramatic reduction in sudden infant death syndrome in this country. Steven Blatt and Victoria Meguid review the literature surrounding sleep position. Investigators have continued efforts to find other modifiable risk factors of sudden infant death syndrome. A prospective study of more than 33,000 neonates found a link between a prolonged QT electrocardiogram interval and sudden infant death syndrome. Also discussed are investigations seeking to explain the relationship between smoking and sudden infant death syndrome. Ann Botash, Florence Jean-Louis and Mongkae Ploy Siripornsawan review the latest thinking on genital warts and their relation to specific viral etiologies and child sexual abuse. Other symptoms and signs of sexual abuse are the focus of a number of articles that can help the practitioner care for these unfortunate children. Catherine Church reviews medication options for children diagnosed with pervasive developmental disorders or autism spectrum disorders. Finally, in this article, risperidone, fluoxetine and naltrexone are reviewed.     

CARDIOVASCULAR CAUSES FOR SUDDEN INFANT DEATH

Although sudden infant death syndrome (SIDS) is a cause for sudden infant death, other causes should be ruled out before diagnosing SIDS. Cardiac causes for sudden infant death include viral myocarditis, congential heart disease particularly congential aortic stenosis, endocardial fibroelastosis, and anomalous origin of the left coronary artery from the pulmonary artery. Other cardiac conditions that may result in sudden death include rhabdomyomas of the heart in tuberous sclerosis and conduction system disorders. The most frequent conduction system disorders resulting in sudden death include histiocytoid cardiomyopathy, congential heart block that may be associated with maternal lupus erythematosus, arrhythmogenic right ventricular dysplasia, noncompaction of the left ventricle, and long QT syndromes.     

Jervell and Lange–Nielsen Syndrome: Homozygous Missense Mutation of KCNQ1 in a Turkish Family

Long QT syndrome is one of the most common cardiac ion channel diseases, but its morbidity and mortality rate can be lessened with an early diagnosis and proper treatment. This cardiac ventricular repolarization abnormality is characterized by a prolonged QT interval and a propensity for ventricular tachycardia (VT) of the torsades de pointes type. The long QT syndrome represents a high risk for presyncope, syncope, cardiac arrest, and sudden death. Jervell and Lange–Nielsen syndrome (JLNS) is a recessively inherited form of long QT syndrome characterized by profound sensorineural deafness and prolongation of the QT interval. Findings have shown that JLNS occurs due to homozygous and compound heterozygous pathogenic variants in KCNQ1 or KCNE1. A 3.5-year-old girl presented to the hospital with recurrent syncope, seizures, and congenital sensorineural deafness. Her electrocardiogram showed a markedly prolonged QT interval, and she had a diagnosis of JLNS. The sequence analysis of the proband showed the presence of a pathogenic homozygous missense variant (c.728G>A, p.Arg243His). Heterozygous mutations of KCNQ1 were identified in her mother, father, and sister, demonstrating true homozygosity. Even with high-dose beta-blocker therapy, the patient had two VT attacks, so an implantable cardioverter defibrillator was fitted. The authors suggest early genetic diagnosis for proper management of the disease in the proband and genetic counseling for both the proband and the girl’s extended family.     

Fetal Presentation of Congenital Long QT Syndrome

Thirty-two-week prenatal ultrasound revealed a fetal heart rate of 100 bpm with decreased variability on the heart rate tracing. Echocardiogram documented normal anatomy and sinus bradycardia. Newborn electrocardiogram revealed sinus rhythm at 100 bpm with a QTc of 0.657. Follow-up electrocardiogram revealed a QTc interval of 0.568, 2:1 atrioventricular block with a ventricular rate of 60 bpm, and ventricular ectopy. The infant received a pacemaker and beta-blocker therapy. Long QT syndrome should be in the differential diagnosis of the fetus with bradycardia and decreased heart rate variability in the absence of distress. Early diagnosis allowed for preventative care in the infant and identification of family members at risk.     

Prevalence of Idiopathic Long QT Syndrome in Children with Congenital Deafness

Long QT syndrome (LQTS) is characterized by prolongation of the QT interval associated with a high risk for syncope and sudden death. Jervell and Lange-Nielsen initially described LQTS in association with congenital sensorineural deafness. We have investigated the prevalence of this syndrome in a school for deaf children, evaluating by ECG 350 congenitally deaf children with an age range of 6–19 years. The corrected QT interval (QTc) was calculated by Bazett's formula. Eight children with a QTc interval >440 ms were further studied by cardiac examination, repeat ECGs (three times), Holter monitoring, echocardiography, and exercise testing. The families were assessed for a history of syncope and deafness and underwent ECG evaluations regarding lengthened QTc interval. Among these eight children only two girls aged 14 and 15 years were diagnosed as having LQTS according to Schwartz's criteria (0.57% of the 350 deaf children; 95% confidence intervals 0, ≤p≤ 0.013). The first patient had two major criteria (QTc 483 ms and a history of syncopal attack) and one minor criteron (congenital deafness); the second also had two major criteria (QTc 613 ms and family members with LQTS) and one minor criterion (congenital deafness). Prophylactic β-blocker therapy was started in these two patients to prevent sudden death. In conclusion, this syndrome should be sought in children with syncope or a family history of it, especially those with congenital deafness.     

The congenital long QT syndrome

OBJECTIVE: The long QT syndrome (LQTS) is a disorder of the electrical system of the heart, due to dysfunction of the ion channels and involving the repolarisation process. The inherited form occurs when there is a mutation in one of the genes which encode the making of a channel. Prolongation of the QT interval renders the patient vulnerable to an arrythmia called torsade de pointes, resulting in syncope and sudden death. METHODS: Three children with the congenital long QT syndrome presented to the pediatric department, one of them also having a 2:1 atrio-ventricular block. The parents and siblings of these children were screened for the long QT syndrome with an electrocardiogram. 2D echocardiography was done to rule out structural abnormalities and audiometry for deafness. RESULTS: Four family members were identified on screening to have LQTS. Propranolol was started on all children with LQTS. The child with heart block also received a pacemaker. LQTS must be considered in all patients presenting with syncope especially if associated with deafness and/or a family history of sudden deaths in infancy or childhood. CONCLUSION: The corrected QT interval must be determined in all children with heart block since the two conditions are often associated.     

Preoperative Diagnosis of Long QT Syndrome in an Infant With Tetralogy of Fallot

Long QT syndrome is a well-described entity in infants. Its presentation in the context of congenital heart disease is rare and is almost exclusively diagnosed postoperatively. For patients undergoing surgical intervention, preoperative knowledge of the diagnosis and appropriate perioperative management can be life-saving. We present the rare case of an infant with tetralogy of Fallot who was preoperatively diagnosed with long QT syndrome and discuss the implications of this diagnosis for his perioperative management.     

Medicolegal problems in the management of cardiac arrhythmias in children

Malpractice actions against pediatricians treating patients with arrhythmias have been recurrent in four general areas. Optimal medical management may not be widely recognized. Cases illustrating the following concepts are presented. Intravenous verapamil therapy in babies may cause apnea, hypotension, and bradycardia; continued episodes of atrial flutter in a child may cause sudden death; quinidine may be related to the death; children with "familial seizure disorders" may in fact have the long QT interval syndrome. The QT interval must be measured on the ECG in patients with unexplained seizures; "supraventricular tachycardia with aberration" is uncommon in children. Rapid heart rates with QRS complexes that are different from the sinus complexes are likely to be ventricular tachycardia. These situations must be recognized as potential problems and must be treated appropriately.     

Deadly proposal: a case of catecholaminergic polymorphic ventricular tachycardia

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare adrenergically mediated arrhythmogenic disorder classically induced by exercise or emotional stress and found in structurally normal hearts. It is an important cause of cardiac syncope and sudden death in childhood. Catecholaminergic polymorphic ventricular tachycardia is a genetic cardiac channelopathy with known mutations involving genes affecting intracellular calcium regulation. We present a case of a 14-year-old boy who had cardiopulmonary arrest after an emotionally induced episode of CPVT while attempting to invite a girl to the school dance. Review of his presenting cardiac rhythm, induction of concerning ventricular arrhythmias during an exercise stress test, and genetic testing confirmed the diagnosis of CPVT. He recovered fully and was treated with β-blocker therapy and placement of an implantable cardioverter-defibrillator. In this report, we discuss this rare but important entity, including its molecular foundation, clinical presentation, basics of diagnosis, therapeutic options, and implications of genetic testing for family members. We also compare CPVT to other notable cardiomyopathic and channelopathic causes of sudden death in youth including hypertrophic cardiomyopathy, arrhythmogenic right ventricular dysplasia, long QT syndrome, short QT syndrome, and Brugada syndrome.     

Incidence and significance of primary abnormalities of cardiac rhythm in infants at high risk for sudden infant death syndrome

Summary The exact relationship between cardiac arrhythmias and sudden infant death syndrome (SIDS) is uncertain. Several reports have implicated both ventricular and supraventricular arrhythmias in isolated cases, but there have been no studies of the incidence or type of arrhythmias that occur in populations at risk for SIDS. Of 1699 infants at high risk for SIDS, 60 (4%) were found to have a primary cardiac arrhythmia (i.e., not associated with disordered respiration or apnea). The incidence of atrial and ventricular premature beats, supraventricular tachycardia, and Wolff-Parkinson-White syndrome was similar to the incidence found in normal infants. Primary bradycardia (defined as a heart rate less than 60 for greater than 10 s not associated with abnormal respiration) was the most common arrhythmia, occurring with a frequency and severity not seen in normal infants. Thirty-two infants experienced periodic bradycardia. In 19 of these latter infants, there were symptoms associated with these bradyarrhythmias that necessitated treatment. Heart rates as low as 20 beats/min were recorded. One infant presented with an episode of ventricular fibrillation and on further evaluation was noted to have recurrent bradyarrhythmias. In no infant was there abnormal prolongation of the QT interval. Primary bradyarrhythmias are seen at an increased incidence in infants at high risk for SIDS and may play a causal role in this syndrome. Most symptomatic infants can be adequately controlled with sympathomimetic or parasympatholytic therapy. Other cardiac arrhythmias occur at a rate similar to that in normal infants and are therefore unlikely to play a major role in SIDS.     

Apnoea and seizures.

We report two infants with near miss sudden infant death syndrome events exhibiting seizure disorders after caffeine treatment, suggesting there is an infant subgroup diagnosed as near miss sudden infant death syndrome who have apnoea possibly with seizures whose seizure threshold may be lowered by central nervous system stimulants like caffeine.