High‐Rate Atrial Pacing as an Innovative Bridging Therapy in a Neonate with Congenital Long QT Syndrome

Re, Tanel; Jk, Triedman; Ep, Walsh; Mr, Epstein; Jm, DeLucca; Je, Mayer; Sb, Fishberger; Jp, Saul

doi:10.1111/j.1540-8167.1997.tb00840.x

Cited by 23 publications

(7 citation statements)

References 17 publications

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“…23 LQTS with AV conduction disturbances has been reported often in infants or young children with a major QTc prolongation, but without any positive familial history, [23][24][25][26][27][28] as in our case. Indeed, the fast atrial rate, which characterizes pediatric sinus rhythm, can lead to functional AV block in the setting of dramatic prolongation of ventricular repolarization as the P wave falls within the T wave.…”

Section: Discussionmentioning

confidence: 81%

“…This form mainly affects neonates and seems to be associated with a worse prognosis. 24,28,29 Electrophysiological studies have confirmed the location of such blocks at the ventricular level associated with major prolongation of the refractoriness in the ventricular muscle. 25,29 In contrast, our results provide evidence for an infra-Hisian block location in the His-Purkinje system rather than at the ventricular level.…”

Section: Discussionmentioning

confidence: 89%

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Homozygous SCN5A Mutation in Long-QT Syndrome With Functional Two-to-One Atrioventricular Block

Lupoglazoff

Cheav

Baroudi

et al. 2001

Circulation Research

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Abstract-Heterozygous mutations in genes encoding cardiac ionic channel subunits KCNQ1, HERG, SCN5A, KCNE1, and KCNE2 are causally involved in the dominant form of long-QT syndrome (LQTS) while homozygous mutations in KCNQ1 and KCNE1 cause LQTS with or without congenital deafness. In addition, two homozygous HERG mutations have been associated with severe LQTS with functional atrioventricular conduction anomalies in young children. A 2:1 atrioventricular block (AVB) with a major QTc prolongation (526 ms) was evidenced in a 5-year-old boy referred for syncope and seizure. LQTS was diagnosed and beta-blocking therapy initiated leading to normal atrioventricular conduction. Electrophysiological study provided support that location of the AVB was infra-Hisian. DNA analysis was performed in the proband and in asymptomatic family members. A novel missense mutation, V1777M, in the early C-terminal domain of SCN5A was identified. The proband was homozygous while the parents and two siblings were heterozygous carriers. Homozygote and heterozygote expression of the mutant channels in tsA201 mammalian cells resulted in a persistent inward sodium current of 3.96Ϯ0.83% and 1.49Ϯ0.47% at Ϫ30 mV, respectively, which was dramatically reduced in the presence of tetrodotoxin. This study provides the first evidence for a homozygous missense mutation in SCN5A and suggests that LQTS with functional 2:1 AVB in young children, a severe phenotype associated with bad prognosis, may be caused by homozygous or heterozygous compound mutations not only in HERG but also in SCN5A. T he congenital long-QT syndrome (LQTS) is a potentially lethal cardiac disease caused by mutations in specific ion channels. Heterozygosity for a mutation in the potassium channel genes HERG (LQT2) and KCNE2 (LQT6) causes defects in the rapid component of the delayed rectifier I Kr , whereas mutations in KCNQ1 (LQT1) and KCNE1 (LQT5) cause defects in the slow component of the delayed rectifier I Ks . 1 Mutations in SCN5A cause a persistent cardiac sodium current that is responsible for LQT3. 2 This form has been associated with a lower rate of cardiac events but a higher rate of lethal events. 3 Homozygosity for mutations in KCNQ1 and KCNE1 have been associated with the recessively inherited Jervell and Lange-Nielsen syndrome, in which QT prolongation is associated with a bilateral neurosensitive deafness. 4 -6 Nevertheless, several LQT1 recessive variants without deafness have also been described. 7,8 Recently, homozygosity for HERG mutations associated with atrioventricular (AV) conduction disturbances have been reported. 9,10 We describe the first case of an LQTS patient with functional 2:1 AV block (AVB) due to a homozygous missense mutation in SCN5A. Materials and Methods Clinical DataThe proband of a 9-member family was referred for syncope. The father originated from Senegal and the mother from Guinea without any known consanguinity. Both parents and the 7 children underwent clinical evaluation and cardiovascular examination, including a 12-lead ECG (ECG...

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Section: Discussionmentioning

confidence: 81%

Section: Discussionmentioning

confidence: 89%

Homozygous SCN5A Mutation in Long-QT Syndrome With Functional Two-to-One Atrioventricular Block

Lupoglazoff

Cheav

Baroudi

et al. 2001

Circulation Research

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“…(A) Non-pause dependent torsade de pointes in a neonate 47. There is sinus tachycardia with marked T wave alternans.…”

Section: Resultsmentioning

confidence: 99%

Arrhythmias in the congenital long QT syndrome: how often is torsade de pointes pause dependent?

Viskin

Fish

Zeltser

et al. 2000

Heart

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Objective-To determine the frequency and predictors of pause dependent torsade de pointes among patients with the congenital long QT syndrome and spontaneous ventricular tachyarrhythmias. Design-The literature on the "congenital long QT" was reviewed. Articles with illustrations demonstrating the onset of spontaneous polymorphic ventricular arrhythmias in the absence of arrhythmogenic drugs were included. Results-Illustrations of 62 spontaneous episodes of torsade de pointes among patients with congenital long QT syndrome were found in the literature. The majority (74%) of documented arrhythmias were "pause dependent"; 82% of these pauses were longer than the basic cycle length by > 100 ms. Age and sex correlated with the mode of arrhythmia initiation. Arrhythmias in infants (< 3 years old) were not pause dependent, while female sex correlated with pause dependent torsade. Using multivariate analysis, age was the only independent predictor of the mode of onset of torsade de pointes. Conclusion-Available data suggest that the majority of spontaneous arrhythmias in the congenital long QT syndrome are pause dependent. Torsade de pointes that is not preceded by pauses appears to be limited to patient subgroups with severe forms of the disease, like symptomatic infants. These findings have important implications regarding the use of cardiac pacing for arrhythmia prevention. (Heart 2000;83:661-666)

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“…In addition hypokalaemia lowers the threshold for arrhythmias in the long QT syndrome and rapidly increasing the serum potassium improves repolarisation; in fetuses suspected of having the long QT syndrome maternal serum potassium should be more than 4 nmol/L. Potassium supplements may have to be given, and sometimes spironolactone 17 . In our case the maternal serum potassium was normal (4.1 nmol/L) at the end of the first trimester in spite of hyperemesis gravidarum.…”

Section: Discussionmentioning

confidence: 58%

Prenatal diagnosis and successful preterm delivery of a fetus with long QT syndrome

Manning¹,

Anthony²,

Östman‐Smith³

et al. 2000

BJOG

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A 35 year old primigravid woman with no significant medical or family history presented to her midwife at 24 weeks having had a normal anomaly scan at 20 weeks. At this visit the midwife was unable to identify the fetal heart rate but attributed this to an anterior placenta. During a routine check at 28 weeks the general practitioner was again unable to detect a fetal heart beat and referred her for immediate assessment to the local obstetric hospital. Ultrasound scan demonstrated a normally grown, active fetus but with a heart rate that varied from 60 to 110 beats per minute (bpm). Referral was made to a tertiary centre.Scanning by a paediatric cardiologist identified normal cardiac anatomy, 2:l second degree heart block resulting in a ventricular rate of 55 bpm, and episodes of nonsustained ventricular tachycardia. Subsequent scans carried out twice weekly demonstrated that the ventricular rate varied between 55 and 70 bpm in the presence of atrioventricular block with an atrial rate between 110 and 140 bpm. Short runs of ventricular tachycardia (at approximately 200 bpm) were observed but the fetus remained active with no development of hydrops. The cardiothoracic ratio was approximately 50%. Anti-Ro antibody testing of the woman was negative. There was no family history of the long QT syndrome and both parents had a normal Qt, on their 12-lead electrocardiograms.At 31 weeks she reported to her local hospital with a reduction in fetal movements over the previous 24 hours. The scan showed frequent and more prolonged ventricular arrhythmias and she was transferred to a unit with cardiac facilities. On arrival the scan showed a persistent sinus bradycardia fetal movement seen or felt; there was again no evidence of hydrops.In view of the possibility of fetal distress manifested by a slowing of the atrial rate from 110 to 85bpm and a lack of fetal movement, a decision was made for urgent delivery by caesarean section under general anaesthetic. This was performed with a cardiac surgeon standing by in the adjacent cardiac operating theatre for immediate insertion of an epicardial pacemaker.A live male infant weight 1.7 kg with Apgar scores of 8 at one minute and 9 at five minutes was delivered by emergency caesarean section. On delivery the heart rhythm was very irregular with a rate of 60-70 bpm.There was complete atrioventricular block with an underlying ventricular rate of 60 bpm and frequent multifocal ventricular ectopic beats progressing to couplets and triplets; there was torsade morphology and a swinging electrical axis.While the umbilical vein catheter was being inserted, there was sustained monomorphic ventricular tachycardia of 246 bpm which was terminated by two intravenous injections of lignocaine 1 mgkg. Five minutes later ventricular ectopic beats started to re-appear and a lignocaine infusion at 20 mg/kg/min was started. The serum potassium was 2.8 nmol/L and after correction of the acidosis and hypokalaemia, sinus rhythm appeared at a rate of 140 bpm with a long QT interval.Once stabilised, the bab...

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High‐Rate Atrial Pacing as an Innovative Bridging Therapy in a Neonate with Congenital Long QT Syndrome

Cited by 23 publications

References 17 publications

Homozygous SCN5A Mutation in Long-QT Syndrome With Functional Two-to-One Atrioventricular Block

Homozygous SCN5A Mutation in Long-QT Syndrome With Functional Two-to-One Atrioventricular Block

Arrhythmias in the congenital long QT syndrome: how often is torsade de pointes pause dependent?

Prenatal diagnosis and successful preterm delivery of a fetus with long QT syndrome

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