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.     

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.     

Measures of cardiac repolarization and body position in infants

Sudden Infant Death Syndrome (SIDS) is the most common cause of death in children between 1 and 6 months of age. Recent data suggest that a prolonged QTc interval on the 12-lead electrocardiogram (ECG) is associated with SIDS. Prone body position during sleep is also known to be a risk factor for SIDS; this has prompted the American Academy of Pediatrics to promote the "Back to Sleep" campaign. We postulated that the QTc interval in infants might change as a function of body position, linking the observations relating body position and QTc interval to SIDS. We recorded ECGs in a group of infants in both the supine and prone position to determine if the QTc interval and QT dispersion differ between the 2 positions. Forty-seven standard 12-lead EGGs and high-amplitude, rapid-sweep 12-lead EGGs were performed on 45 healthy infants (mean age 26 +/- 40 days) in both the supine and prone positions. The infants were asleep in a quiet, restful state. The ECGs were reviewed by 2 investigators blinded to the position of the infants during recording. Measurements included the average QTc interval (using Bazett's correction) and QT dispersion (the difference between the longest and the shortest QT intervals on a standard 12-lead EKG). The study was designed to detect a 3% difference in QTc interval with 80% power and alpha = 0.05. All subjects had telephone or clinical follow-up at 1 year. The average QTc interval was 403 +/- 20 milliseconds (msec) in the supine position and 405 +/- 27 msec in the prone position (p = NS). The QT dispersion was 20 +/- 12 msec in the supine position and 22 +/- 13 msec in the prone position (p = NS). One infant in the study group died of SIDS at the age of 3 months. The EGG of this patient revealed a QTc interval of 382 msec in the supine position and 407 msec in the prone position; the QT dispersion was 34 msec in the supine position and 34 msec in the prone position. We found no difference in QTc interval or QT dispersion as a function of body position in healthy infants resting quietly. Prolongation of the QTc interval is unlikely to explain the increased risk for SIDS associated with prone body position in the general population of healthy infants, unless patients with long QT syndrome are somehow more influenced by body position than normal patients are.     

Congenital long QT syndrome in newborns]

The perinatal manifestations of the long QT syndrome are rare, but early diagnosis and therapy are necessary to prevent sudden death. CASE REPORTS: A long QT syndrome was diagnosed in two neonates who presented with foetal bradycardia. In one case, a mutation in the gene KCNQ1 was identified, and a long QT syndrome was diagnosed in the mother and two brothers of the neonate. On beta-blocker therapy, one infant became free of long QT syndrome related symptoms, but a sudden death of the second infant occurred. CONCLUSION: The long QT syndrome should be considered in the differential diagnosis of foetal bradycardia. Early treatment of the neonate and his family may prevent ventricular arrhythmias and sudden death.     

QTc interval prolongation in children with Ulrich-Turner syndrome

Introduction The Ullrich-Turner-Syndrome (UTS) is the most commonly occurring sex chromosome abnormality in females. Cardiac malformations are well known, but no data exist on specific electrocardiogram (ECG) patterns in children and adolescents. A prolongation of the QT interval on the ECG has been correlated to an increased risk for sudden cardiac death, and medical treatment is warranted in patients with long QT syndrome (LQTS). Moreover, several drugs of common use are contraindicated in LQTS because of their effects on myocardial repolarization.Methods The ECG tracings of 86 UTS patients [mean age (±SD): 11.0±3.6 years; mean height-SD: −2.6±1.0] were analyzed and compared to age-matched control groups of 75 boys (mean age: 11.3±3.5 years; mean height-SD: −1.9±1.0) and 62 girls (mean age: 10.1±3.2 years; mean height-SD: −2.5±0.9) with short stature.Results Eighteen UTS patients (20.9%) had an abnormally prolonged QTc >0.45 s in contrast to only one control subject (0.9%). The QTc interval of UTS patients was significantly prolonged compared to that of the controls (p<0.01) and normal values.Conclusions There is an increased prevalence of a long QT interval among UTS patients. This should be taken into account for the cardiovascular screening of such patients. Patients with UTS have an intrinsically prolonged QT interval and as such may be at higher risk for arrhythmias in the context of a QT-prolonging medication.R. Dalla Pozza and S. Bechtold contributed equally to this publication.     

Usefulness of electrocardiographic screening in a neonatal population

IntroductionCongenital long QT syndrome is a rare disease, but is responsible for nearly 10% of Sudden Infant Death Syndrome. It is characterized by an abnormal prolonged QT interval in the basal electrocardiogram (ECG) with life-threatening arrhythmias which occur in previously asymptomatic patients and are preventable with an appropriate treatment.AimsThe impact of introducing ECG-screening in newborns is studied and main ECG-measurements are described in our population.Material and methodsTwelve-lead ECG was carried out. Measurements: RR, PR and QT interval, heart rate corrected QT interval, R wave voltage in V1, AVR and AVL, Q wave in I and AVL, P amplitude and voltage, right bundle branch block and ST elevation (Brugada pattern) and delta wave. It was considered pathological: QTc >0.44 or <0.30 seconds; R >12 in V1 and >8 mm in AVR; R >7.5 mm in AVL; Q >25% QRS in I and AVL; Brugada pattern; delta wave.ResultsA total of 1061 healthy children were born in our hospital between 29 May 2007 and 12 December 2008, of which 50.3% were males. An ECG was performed on 1006 (94.8%). Five ECG were pathological (0.5%): 2 long QT interval, 2 Wolf-Parkinson-White, 1 pathological Q-wave. A second ECG confirmed except for 2 long QT. No structural heart disease was found.ConclusionsECG-screening in newborns is an innocuous, low-cost and parent-well-accepted test that allows us to diagnose asymptomatic but potentially lethal and preventable heart disease; main intervals and waves in our population are describes in this study.     

Prolonged QT syndrome and sedation: a case report and a review of the literature

Prolonged QT syndrome is the most common genetic arrhythmia syndrome, and the majority of patients are undiagnosed. The syndrome is characterized by abnormally long ventricular repolarization (QT interval) on electrocardiogram, which may manifest as syncopal episodes, arrhythmias, or sudden death. Arrhythmias may be precipitated by stress or medications. There are few randomized controlled trials examining the safety of typical sedation medications in the patient with prolonged long-QT syndrome. This case describes the management of sedation in a patient with prolonged long-QT syndrome and then reviews the current literature regarding commonly utilized sedation medications.     

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.     

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.     

Syncope with prolonged QT interval.

Four children with syncope had a prolonged QT interval on the electrocardiogram. Neurologic studies were negative. One patient had associated deaf mutism, one had a family history of sudden death and prolonged QT interval, and two had ventricular arrhythmias while being monitored in the hospital. Treatment with propranolol hydrochloride eliminated the syncope in all patients, although the ECGs remained abnormal.     

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.     

Sinus tachycardia in term infants preceding sudden infant death

The quantities of sinus tachycardia in 24-h recordings of the electrocardiogram from 16 full-term infants (37 weeks gestation) who were subsequently victims of the sudden infant death syndrome (SIDS), from 230 randomly selected age-matched full-term survivors and from 64 full-term survivors matched for age and birth weight were measured by computer and manual analysis techniques. Of 16 infants dying of SIDS, 7 had elevated levels of sinus tachycardia (>95th centile in controls) (P<0.01). Although high levels of sinus tachycardia might be of value in identifying infants at high risk of SIDS, these encouraging findings must first be validated by further prospective studies.Abbreviations IHR instantaneous heart rate - SIDS sudden infant death syndrome - ECG electrocardiogram     

A mitochondrial DNA polymorphism associated with cardiac arrhythmia investigated in sudden infant death syndrome

AIM: Long QT syndrome (LQTS) has been shown to be the cause of death in some cases originally diagnosed as sudden infant death syndrome (SIDS). Such cardiac arrhythmias have also been noted in families with mitochondrial disease, and studies indicate that mitochondrial disease could be involved in SIDS. This makes the mtDNA polymorphism T3394C interesting, as a previous study has shown it to be associated with electrocardiographic (ECG) changes after exercise in a family with LQTS, where some members harboured a KCNH2 mutation. SUBJECTS: A total of 245 SIDS cases and 176 control cases. METHODS: DNA was prepared from blood/tissue samples. Polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) were performed to search for the mtDNA polymorphism and KCNH2 mutation. Differences were confirmed by sequencing. RESULTS: The T3394C polymorphism was found in 3 pure SIDS cases (1.5%), 2 borderline SIDS cases (4.4%), 1 case of explained death (1.6%) and 2 living control cases (1.8%) (p = 0.62). The KCNH2 mutation was not found in cases or controls. CONCLUSION: The mtDNA polymorphism studied was found in a small number of SIDS cases and the frequency did not differ statistically from control subjects, making an association with increased SIDS risk unlikely.     

The QT interval in aborted sudden infant death syndrome infants.

The QT interval was measured in 12 normal and 7 aborted sudden infant death syndrome (SIDS) infants in rapid eye movement (REM) and quiet sleep at monthly intervals through the age of 4 months. An accuracy of better than 2 msec was assured by high resolution of the digitized signal and calibration of each QT measurement with an accurately generated time code. In contrast to current speculations, the QT index was significantly smaller in the infants with aborted SIDS than in the normal infants in both REM and quiet sleep (P less than 0.05). In addition, as in normal infants, the QTc was smaller in REM than in quiet sleep (P less than 0.01). Although these results offer no support for the hypothesis that SIDS results from prolongation of the QT interval, they suggest that aborted SIDS infants have a functional abnormality in the autonomic nervous system.     

QTc interval prolongation in children with Turner syndrome: the results of exercise testing and 24-h ECG

Background  Turner syndrome (TS) is the most common sex chromosome abnormality in females. Recently, a prolongation of the rate-corrected QT (QTc) interval in the electrocardiogram (ECG) of TS patients has been reported. A prolonged QTc interval has been correlated to an increased risk for sudden cardiac death, and medical treatment is warranted in patients with congenital long QT syndrome (LQTS). Additionally, several drugs of common use are contraindicated in LQTS because of their effects on myocardial repolarization. The importance of the QTc prolongation in TS patients is not known at present. Materials and methods  Eighteen TS patients with a prolonged QTc interval (group 1) and 11 TS patients with a normal QTc interval (group 2) (mean age 12.6±3.1 vs. 11.8±2.1 years, respectively) were tested. The QTc interval was calculated during exercise testing and during 24-h ECG recordings. Results  None of the patients experienced adverse cardiac events during the tests. The mean QTc interval decreased from 0.467 to 0.432 s in group 1 and from 0.432 to 0.412 s in group 2. During the 24-h ECG, the maximum QTc interval was significantly prolonged in group 1 (0.51 vs. 0.465 s, p<0.05, respectively). We conclude that exercise testing and 24-h ECG recording provide valuable information about the cardiac risk in the single TS patient with a prolonged QTc interval. This helps in counseling these girls, as clear therapeutic guidelines are currently lacking. All authors state that there is no conflict of interests.     

Travel and changes in routine do not increase the risk of sudden infant death syndrome

We investigated the relationship between travel and changes in routine and the sudden infant death syndrome (SIDS) among 485 SIDS cases compared with 1800 randomly selected control infants. There was no increased risk of SIDS with travel. Special events, such as christenings, were not associated with an increased risk of SIDS. However, visits to and by friends or relatives were associated with a significantly reduced risk of SIDS after controlling for potential confounders (odds ratios = 0.70; 95% confidence interval = 0.52, 0.96). These findings may indicate less social support in SIDS cases.     

Altered cardiac repolarization during exercise in congenital aortic stenosis

Summary The incidence of sudden death in children with congenital aortic stenosis (CAS) varies between 4 and 20%. In several syndromes sudden death is associated with a long QT interval in the electrocardiogram (ECG). The aim of the study was to evaluate the cardiac repolarization in CAS during stress.We included 40 children and young persons, 20 with CAS and 20 healthy controls. All underwent echocardiographic study and treadmill stress test. The QT and relative RR intervals were measured in leads II and V6 at rest and during exercise at preselected heart rates. Mean values of QT were compared by analysis of variance, Student'st-test, and linear regression method.No statistically significant differences in the resting ECG were found between the two groups, whereas during exercise the mean QT of the CAS group was significantly longer than in the controls (p<0.05), except at a heart rate of 140±5. Our study demonstrates that patients with CAS have transiently altered cardiac repolarization when there are sudden variations in heart rate.Such a defect could predispose patients with CAS to fatal arrhythmias and sudden death.     

Role of vagotony in sinus node dysfunction in children with symptomatic congenital long QT syndrome

The present study examined chronotropic dysfunction and the role of vagotony in congenital long QT syndrome, sinus node function and the effects of parasympathetic blockade. Six patients with congenital long QT syndrome were studied. The four males and two females, aged 1–15 years, had episodes of syncope and malignant ventricular arrhythmias. Congenital long QT syndrome was defined as a corrected QT interval greater than 0.45 s, T wave alternans and the age at diagnosis. The sinus heart rate measured from a 24 h electrocardiograph was abnormally low (< 50 min) in three patients (1, 4 and 5 years old) and did not increase sufficiently with the administration of atropine in five of the six patients with congenital long QT syndrome. From intracardiac electrophysiological studies, the corrected sinus node recovery time was prolonged in three patients and the total sinoatrial conduction time was prolonged in two patients. In most patients who had an abnormally long sinoatrial conduction time and corrected sinus node recovery time, these values returned to normal following atropine administration. In one patient, the corrected sinus node recovery time was prolonged paradoxically by atropine. Sinus node dysfunction in congenital long QT syndrome was affected by vagotony associated with a right sympathetic nerve system abnormality.     

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.     

Sudden infant death syndrome and post perinatal mortality in Norwegian birth cohorts 1967-1980

The well established effects of maternal age and birth order in sudden infant death syndrome (SIDS) formed the basis for a comparison with other categories of post perinatal death in an attempt to shed some light on the etiologic roles played by ante and postnatal factors. A total of 826,162 children, born 1967 through 1980 and recorded at the Medical Birth Registry of Norway was at risk to die during the post perinatal period (ages 7 through 364 days). Out of the 3,582 infants who died, 1,062 were considered SIDS. Strong effects of maternal age (negative) and birth order (positive) were found in the SIDS group, but not to the same extent in the non-SIDS group or the group of congenital malformations. Likewise, the excess risk in children of unmarried mothers was higher in the SIDS group. The suggested effects of postnatal factors in the causation of SIDS may seem promising from a preventive point of view. The strength of the effects of maternal age and birth order necessitate adjustment for these variables in future epidemiological studies of SIDS.