Implantable cardioverter defibrillator therapy in children with long QT syndrome

Primary prevention with the implantable cardioverter-defibrillator in high-risk long-QT syndrome patients

Aims

Prospective data regarding the role of implantable cardioverter-defibrillator (ICD) for the primary prevention of sudden cardiac death in patients with long QT syndrome (LQTS) is scarce. Herein, we explore the prospective Rochester LQTS ICD registry to assess the risk for appropriate shock in primary prevention in a real-world setting.

Methods and results

We studied 212 LQTS patients that had ICD implantation for primary prevention. Best-subsets proportional-hazards regression analysis was used to identify clinical variables that were associated with the first appropriate shock. Conditional models of Prentice, Williams, and Peterson were utilized for the analysis of recurrent appropriate shocks. During a median follow-up of 9.2 ± 4.9 years, there were 42 patients who experienced at least one appropriate shock and the cumulative probability of appropriate shock at 8 years was 22%. QTc ≥ 550 ms [hazard ratio (HR) 3.94, confidence interval (CI) 2.08-7.46; P < 0.001) and prior syncope on β-blockers (HR 1.92, CI 1.01-3.65; P = 0.047) were associated with increased risk of appropriate shock. History of syncope while on β-blocker treatment (HR 1.87, CI 1.28-2.72; P = 0.001), QTc 500-549 ms (HR 1.68, CI 1.10-2.81; P = 0.048), and QTc ≥ 550 ms (HR 3.66, CI 2.34-5.72; P < 0.001) were associated with increased risk for recurrent appropriate shocks, while β-blockers were not protective (HR 1.03, CI 0.63-1.68, P = 0.917). LQT2 (HR 2.10, CI 1.22-3.61; P = 0.008) and multiple mutations (HR 2.87, CI 1.49-5.53; P = 0.002) were associated with higher risk for recurrent shocks as compared with LQT1.

Conclusion

In this prospective ICD registry, we identified clinical and genetic variables that were associated appropriate shock risk. These data can be used for risk stratification in high-risk patients evaluated for primary prevention with ICD.

Implantation of Cardioverter-Defibrillator in Children With Long-QT Syndrome: Assessment of Indications, Efficacy, and Safety Based on 10-Year Experience

PURPOSE

to assess specificities of course of the long-QT syndrome in children before and after implantation of cardioverter-defibrillator (ICD), and optimization of indications to ICD-therapy.

MATERIALS AND METHODS

We included in this study 48 children with long-QT syndrome from 44 unrelated families (28 boys and 20 girls), who underwent ICD implantation at the mean age 11.8±3.8 years. Mean duration of follow-up after implantation was 5.2±2.8 years. Data from these children were compared with those from 59 children of comparable age and gender with long-QT syndrome from 46 unrelated families receiving antiarrhythmic therapy (β-adrenoblockers). We assessed clinical and electrocardiographic characteristics of the disease obtained at initial visit and their dynamics thereafter.

RESULTS

Children with long-QT syndrome and ICD were mainly probands with interval QT longer than 500 ms, recurrent syncope and often history of sudden cardiac arrest requiring high doses of β-adrenoblockers for control of ventricular tachyarrhythmias.

CONCLUSION

ICD implantation is an effective and safe method both of primary and secondary prevention of sudden cardiac death in children with long-QT syndrome.

Clinical aspects of the three major genetic forms of long QT syndrome (LQT1, LQT2, LQT3)

BACKGROUND

A comprehensive report on the clinical course of the three major genotypes of the long QT syndrome (LQTS) in a large U.S. patient cohort is lacking.

METHODS

Our study consisted of 1,923 U.S. subjects from the Rochester-based LQTS Registry with genotype-positive LQT1 (n = 879), LQT2 (n = 807), and LQT3 (n = 237). We evaluated the risk of a first cardiac event (syncope, aborted cardiac arrest, or sudden cardiac death, whichever occurred first) from birth through age 50 years. Cox proportional hazards regression models incorporating clinical covariates were used to assess genotype-specific risk of cardiac events.

RESULTS

For all three genotypes, the cumulative probability of a first cardiac event increased most markedly during adolescence. Multivariate analysis identified proband status and QTc > 500 ms as predictors of cardiac events in all three genotypes, and males <14 years and females >14 years as predictors of cardiac events in LQT1 and LQT2 only. Beta-blockers significantly reduced the risk of cardiac events in LQT1 (HR: 0.49, p = .002) and LQT2 patients (HR: 0.48, p = .001). A trend toward beta-blocker benefit in reducing cardiac events was found in LQT3 females (HR: 0.32, p = .078), but not in LQT3 males (HR: 1.37, p = .611).

CONCLUSION

Risk factors and outcomes in LQTS patients varied by genotype. In all three genotypes, proband status and prolonged QTc were risk factors for cardiac events. Younger males and older females experienced increased risk in LQT1 and LQT2 only. Beta-blockers were most effective in reducing cardiac events in LQT1 and LQT2, with a potential benefit in LQT3 females.

"Homozygous, and compound heterozygous mutation in 3 Turkish family with Jervell and Lange-Nielsen syndrome: case reports"

BACKGROUND

Jervell and Lange-Nielsen syndrome (JLNS) isa recessive model of long QT syndrome which might also be related to possible hearing loss. Although the syndrome has been demonstrated to be originated from homozygous or compound heterozygous mutations in either the KCNQ1 or KCNE1 genes, additional mutations in other genetic loci should be considered, particularly in malignant course patients.

CASE PRESENTATIONS

Three patients were admitted into hospital due to recurrent seizures/syncope, intrauterine and postnatal bradycardia respectively; moreover all three patients had congenital sensorineural hearing-loss. Their electrocardiograms showed markedly prolonged QT interval. Implantable defibrillator was implanted and left cardiac sympathetic denervation was performed due to the progressive disease in case 1. She had countless ventricular fibrillation and appropriate shock while using an implantable defibrillator. The DNA sequencing analysis of the KCNQ1 gene disclosed a homozygous c.728G > A (p.Arg243His) missense mutation in case1. Further targeted next generation sequencing of cardiac panel comprising 68 gene revealed a heterozygous c.1346 T > G (p.Ile449Arg) variant in RYR2 gene and a heterozygous c.809G > A (p.Cys270Tyr) variant in NKX2-5 gene in the same patient. Additional gene alterations in RYR2 and NKX2-5 genes were thought to be responsible for progressive and malignant course of the disease. As a result of DNA sequencing analysis of KCNQ1 and KCNE1 genes, a compound heterozygosity for two mutations had been detected in KCNQ1 gene in case 2: a maternally derived c.477 + 1G > A splice site mutation and a paternally derived c.520C > T (p.Arg174Cys) missense mutation. Sanger sequencing of KCNQ1 and KCNE1 genes displayed a homozygous c.1097G > A (p.Arg366Gln) mutation in KCNQ1 gene in case 3. β-blocker therapy was initiated to all the index subjects.

CONCLUSIONS

Three families of JLNS who presented with long QT and deafness and who carry homozygous, or compound heterozygous mutation in KCNQ1 gene were presented in this report. It was emphasized that broad targeted cardiac panels may be useful to predict the outcome especially in patients with unexplained phenotype-genotype correlation. Clinical presentations and molecular findings will be discussed further to clarify the phenotype genotype associations.

Implantable cardioverter-defibrillator harm in young patients with inherited arrhythmia syndromes: A systematic review and meta-analysis of inappropriate shocks and complications

BACKGROUND

Implantable cardioverter-defibrillators (ICDs) are implanted with the intention to prolong life in selected patients with inherited arrhythmia syndromes, but ICD implantation is also associated with inappropriate shocks and complications.

OBJECTIVE

We aimed to quantify the rate of inappropriate shocks and other ICD-related complications to be able to weigh benefit and harm in these patients.

METHODS

We performed a systematic review and meta-analysis of inappropriate shock and/or other ICD-related complication rates, including ICD-related mortality, in patients with inherited arrhythmia syndromes, that is, arrhythmogenic right ventricular cardiomyopathy/dysplasia, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia, hypertrophic cardiomyopathy, dilated cardiomyopathy due to a mutation in the lamin A/C gene, long QT syndrome, and short QT syndrome. We searched MEDLINE and EMBASE from inception to May 30, 2014.

RESULTS

Of 2471 unique citations, 63 studies comprising 4916 patients with inherited arrhythmia syndromes (mean age of 39 ± 15 years) were included. Inappropriate shocks occurred in 20% of patients (crude annual rate of 4.7% per year), with a significantly higher rate in studies published before 2008 (6.1% per year vs 4.1% per year). Moreover, 22% experienced ICD-related complications (4.4% per year) and there was a 0.5% ICD-related mortality (0.08% per year).

CONCLUSION

ICD implantation carries a significant risk of inappropriate shocks and inhospital and postdischarge complications in relatively young patients with inherited arrhythmia syndromes. These data can be used to better inform patients and physicians about the expected risk of adverse ICD events and thereby facilitate shared decision making.

Device therapy in the setting of long QT syndrome

Congenital long QT syndrome (LQTS) is an inherited disorder of myocardial repolarization characterized by prolongation of the QT interval associated with life-threatening polymorphic ventricular tachycardia. The treatment of congenital LQTS involves antiadrenergic therapies: β-blockers and surgical left cardiac sympathetic denervation (LCSD) to decrease sympathetic input to the heart, cardiac pacing, and implantable cardioverter-defibrillator (ICDs). Although this article focuses on the role of device therapy for the treatment of LQTS, it also discusses the role of β-blockers and LCSD because they are concomitant with device therapy. After implantation, programming should be optimized to minimize the risk for inappropriate ICD therapies.

Induced pluripotent stem cell-based therapies for inherited arrhythmias: opportunities and challenges involved (Review)

The identification of induced pluripotent stem cell (iPSC) technology represents great potential for recapitulating complex physiological phenotypes, probing toxicological testing and screening candidate drugs, demonstrating novel mechanistic insights and, in particular, applying iPSC-based therapeutic strategies for inherited disorders. Inherited arrhythmias are caused by various genetic abnormalities and harbor similar clinical outcomes. Clinically, the poorest outcomes are fatal arrhythmias and sudden cardiac death. However, the current therapeutic options for inherited arrhythmias are inadequate and problematic. In this review, we summarize the advances of the iPSC technique in the field of inherited arrhythmias and discuss the possibility of iPSC‑based therapies for inherited arrhythmias. Additionally, we highlight the key challenges faced in the field of iPSC and the emerging strategies used to address these concerns before the novel technique can be used safely and efficiently in clinical practice. It is likely that the iPSC technique will present opportunities and further challenges in the future.

New iPSC for old long QT syndrome modeling: putting the evidence into perspective

Induced pluripotent stem cells (iPS cells or iPSCs) are typically derived by transfection of certain stem cell-associated genes into non-pluripotent cells, such as adult fibroblasts (typically adult somatic cells). Various diseases can be modeled through iPSC technology. The important implication of iPSCs to offer an unprecedented opportunity to recapitulate pathologic human tissue formation in vitro has generated great excitement and interest in the whole biomedical research community. Long QT syndrome (LQTS), an inherited heart disease, is characterized by prolonged QT interval on a surface electrocardiogram. LQTS presents with life-threatening cardiac arrhythmias, which can lead to fainting, syncope, and sudden death. The iPSC-derived cardiomyocytes from LQTS patients offer a potentially unlimited source of materials for biomedical study. They can be used to recapitulate complex physiological phenotypes, probe toxicological testing and drug screening, clarify the novel mechanistic insights and may also rectify gene defects at the cellular and molecular level. Despite the emerging challenges, iPSC technology has been increasingly recognized as a valuable and growing toolkit for modeling LQTS over other various models of human diseases.

Jervell and Lange-Nielsen syndrome in a father and daughter from a large highly inbred family: a 16-year follow-up of 59 living members

OBJECTIVE

To report the autosomal dominant inheritance of the Jervell and Lange-Nielsen syndrome in a highly inbred family, the initiation of Torsades de Pointes, and the natural history of the syndrome based on a 16-year follow-up of the kindred.

METHOD

A family tree was constructed that included 66 blood relatives from three successive generations. Electrocardiograms were obtained from 59 living members including the proband, four members from a nuclear family, and 54 from the extended family. Evoked response audiometry was recorded for the proband and the nuclear family. All 59 family members were followed up regularly for 16 years.

RESULTS

A total of 24 living members were affected--QTc: 480-680 ms. The proband had long QTc, bilateral high-tone sensorineural deafness, recurrent syncope, and Torsades de Pointes. The asymptomatic father had long QTc and unilateral high-tone sensorineural deafness that involved specifically the left ear. One asymptomatic sibling of the proband had long QTc and normal hearing. The mother and another sibling were asymptomatic; QTc and hearing were normal in both. A total of 21 affected members from the extended family had only long QTc, and all were asymptomatic. There were three congenitally deaf first cousins who had recurrent syncope and adrenergic-triggered sudden death. In all, seven of 10 parents had consanguineous marriage to a first cousin. Each affected offspring had at least one affected parent. The severely symptomatic proband who received only β-blocker therapy and the 23 affected members without antiadrenergic therapy, all remained asymptomatic throughout the 16-year follow-up period.

CONCLUSION

Jervell and Lange-Nielsen syndrome was inherited as autosomal dominant in this kindred. The majority of the affected members had a mild phenotype. The severity of auditory and cardiac phenotypes corresponded.

Repolarization syndromes

Repolarization syndromes, including early repolarization, Brugada, and short and long QT, have been implicated increasingly as causes of sudden cardiac death (SCD) despite no obvious mechanical cardiac abnormalities. So-called idiopathic ventricular fibrillation is now often reassigned to one of the aforementioned entities. Underlying causes are diverse; genetic mutation has been proven in many but not all cases. Although high-risk individuals generally can be identified, most of the potential victim pool is still unknown and cannot be discovered at this time. Awareness of these entities' existence, knowledge of family history, and 12-lead electrocardiography are the initial steps toward preventing SCD in this population. Underlying mechanisms for ventricular tachycardia/fibrillation in such individuals include phase 2 reentry, early after depolarization, and vortex reentry. For the time-being, although most forms of long QT syndrome can be treated with β-blockers, an implantable cardioverter-defibrillator remains the only definitive therapy for the prevention of arrhythmic death among high-risk populations.

Prospective evaluation of defibrillation threshold and postshock rhythm in young ICD recipients

BACKGROUND

Adaptation of implantable cardioverter defibrillator (ICD) systems to the needs of pediatric and congenital heart patients is problematic due to constraints of vascular and thoracic anatomy. An improved understanding of the defibrillation energy and postshock pacing requirements in such patients may help direct more tailored ICD therapy. We describe the first prospective evaluation of defibrillation threshold (DFT) and postshock rhythm in this population.

METHODS

We prospectively studied patients ≤ 60 kg at time of ICD intervention. DFTs were obtained using a binary search protocol with three VF inductions. Postshock pacing was programmed using a stepwise protocol, lowering the rate prior to each VF induction.

RESULTS

Twenty patients were enrolled: 11 had channelopathy, five congenital heart disease, and four cardiomyopathy. The median age was 16 years, median weight 48 kg. Twelve patients had a transvenous high-voltage coil; eight had pericardial +/- subcutaneous coil(s). Median DFT was 7 J (range 3-31 J); 19/20 patients had DFT ≤ 15 J and all patients <25 kg had DFT ≤ 9 J (n = 6). There was no difference in DFT between patients with transvenous versus pericardial +/- subcutaneous coils (median 7 J vs 6 J, P = 0.59). No patient with normal atrioventricular conduction prior to defibrillation required postshock pacing (n = 16). There were no adverse events.

CONCLUSIONS

These data suggest that many pediatric ICD patients have low DFTs and adequate postshock escape rhythm. This may help determine appropriate parameters for future design of pediatric-specific ICDs.

Outcome of implantable cardioverter defibrillator therapy for congenital heart disease

BACKGROUND

The use of implantable cardioverter defibrillator (ICD) therapy for congenital heart disease (CHD) has been increasing, but few studies have reported on the efficacy of ICD therapy in Japanese CHD patients.

METHOD

Twelve CHD patients (median age, 35 years) with first ICD implantation were examined. Median follow-up duration was 2.9 years. Demographic information, implant electrical parameters, appropriate and inappropriate discharge data and complications were recorded for all implants from 2003 to 2010.

RESULTS

Implant indication was primary prevention in two patients and secondary prevention in 10. Overall four patients received one or more discharges; three patients (25%) with secondary prevention received nine appropriate discharges. Inappropriate discharge attributed to sinus tachycardia occurred in two patients (16.7%). Only one patient experienced the late complication of skin erosion at the generator implantation site.

CONCLUSIONS

Patients with CHD experienced significant rates of appropriate discharges and lower complications. But given that the indications of ICD implantation were mostly for secondary prevention, the ratio of appropriate shocks might be lower than in previous studies. In the primary prevention patients, the benefit of ICD was not clear because no appropriate discharges were seen during follow up. Although ICD implantation for CHD is beneficial for preventing sudden cardiac death, careful decision making and a large, long-term prospective study is required for the determination of the efficacy of ICD therapy in Japanese patients with CHD.

High efficacy of beta-blockers in long-QT syndrome type 1: contribution of noncompliance and QT-prolonging drugs to the occurrence of beta-blocker treatment "failures"

BACKGROUND

Beta-blocker efficacy in long-QT syndrome type 1 is good but variably reported, and the causes of cardiac events despite beta-blocker therapy have not been ascertained.

METHODS AND RESULTS

This was a retrospective study of the details surrounding cardiac events in 216 genotyped long-QT syndrome type 1 patients treated with beta-blocker and followed up for a median time of 10 years. Before beta-blocker, cardiac events occurred in 157 patients (73%) at a median age of 9 years, with cardiac arrest (CA) in 26 (12%). QT-prolonging drugs were used by 17 patients; 9 of 17 (53%) had CA compared with 17 of 199 nonusers (8.5%; odds ratio, 12.0; 95% confidence interval, 4.1 to 35.3; P<0.001). After beta-blocker, 75% were asymptomatic, and cardiac events were significantly reduced (P<0.001), with a median event count (quartile 1 to 3) per person of 0 (0 to 1). Twelve patients (5.5%) suffered CA/sudden death, but 11 of 12 (92%) were noncompliant (n=8), were on a QT-prolonging drug (n=2), or both (n=1) at the time of the event. The risk for CA/sudden death in compliant patients not taking QT-prolonging drugs was dramatically less compared with noncompliant patients on QT-prolonging drugs (odds ratio, 0.03; 95% confidence interval, 0.003 to 0.22; P=0.001). None of the 26 patients with CA before beta-blocker had CA/sudden death on beta-blockers.

CONCLUSIONS

beta-Blockers are extremely effective in long-QT syndrome type 1 and should be administered at diagnosis and ideally before the preteen years. beta-Blocker noncompliance and use of QT-prolonging drug are responsible for almost all life-threatening "beta-blocker failures." beta-Blockers are appropriate therapy for asymptomatic patients and those who have never had a CA or beta-blocker therapy. Routine implantation of cardiac defibrillators in such patients does not appear justified.

Results of a multicenter retrospective implantable cardioverter-defibrillator registry of pediatric and congenital heart disease patients

OBJECTIVES

We sought to determine the implications of implantable cardioverter-defibrillator (ICD) placement in children and patients with congenital heart disease (CHD).

BACKGROUND

There is increasing frequency of ICD use in pediatric and CHD patients. Until recently, prospective registry enrollment of ICD patients was not available, and children and CHD patients account for only a small percentage of ICD recipients. Therefore, we retrospectively obtained collaborative data from 4 pediatric centers, aiming to identify implant characteristics, shock frequency, and complications in this unique population.

METHODS

Databases from 4 centers were collated in a blinded fashion. Demographic information, implant electrical parameters, appropriate and inappropriate shock data, and complications were recorded for all implants from 1992 to 2004.

RESULTS

A total of 443 patients were included, with a median age of 16 years (range 0 to 54 years) and median weight of 61 kg (range 2 to 130 kg), with 69% having structural heart disease. The most common diagnoses were tetralogy of Fallot (19%) and hypertrophic cardiomyopathy (14%). Implant indication was primary prevention in 52%. Shock data were available on 409 patients, of whom 105 (26%) received appropriate shocks (mean 4 shocks/patient, range 1 to 29 shocks/patient). Inappropriate shocks occurred in 87 of 409 patients (21%), with a mean of 6 per patient (range 1 to 60), mainly attributable to lead failure (14%), sinus or atrial tachycardias (9%), and/or oversensing (4%).

CONCLUSIONS

Children and CHD ICD recipients have significant appropriate and inappropriate shock frequencies. Optimizing programming, medical management, and compliance may diminish inappropriate shocks. Despite concerns regarding generator recalls, lead failure remains the major cause of inappropriate shocks, complications, and system malfunction in children. Prospective assessment of ICD usage in this population may identify additional important factors in pediatric and CHD patients.

Long QT syndrome: A therapeutic challenge

Congenital long QT syndrome (LQTS) is one of the most common cardiac channelopathies and is characterized by prolonged ventricular repolarization and life-threatening arrhythmias. The mortality is high among untreated patients. The identification of several LQTS genes has had a major impact on the management strategy for both patients and family members. An impressive genotype-phenotype correlation has been noted and genotype identification has enabled genotype specific therapies. Beta blockers continue to be the primary treatment for prevention of life threatening arrhythmias in the majority of patients. Other therapeutic options include pacemakers, implantable cardioverter defibrillators, left cardiac sympathetic denervation, sodium channel blocking medications and lifestyle modification.

A successfully novel ICD implantation and medical treatment in a child with LQT syndrome and self-limiting ventricular fibrillation

Beta-blocker is the first line drug therapy for congenital long QT syndrome. However, in some children this drug is ineffective. In a non-responder patient, Shimizu et al. used Mexiletine to suppress the ventricular arrhythmias, obtaining a good result. In the high risk patient, the ICD is necessary. However the implantation of a device in small children can have technical problems. We report a case of a child affected by long QT syndrome with recurrent episodes of syncope due to self-limiting torsade de point/ventricular fibrillation, successfully treated by an association of mexiletin and propanolol, and in whom an ICD was implanted with a new subcutaneous approach.

Successful parental use of an automated external defibrillator for an infant with long-QT syndrome

Congenital long-QT syndrome with 2:1 atrioventricular block presenting in the perinatal period is rare, has a poor prognosis, and leads to high risk for lethal ventricular arrhythmic events. An implantable cardioverter-defibrillator seems to be the most effective treatment in the prevention of arrhythmic sudden cardiac death in patients with long-QT syndrome. Technical limitations and risks associated with implantable cardioverter-defibrillators in asymptomatic infants is considered too great to justify use for primary prophylaxis against sudden cardiac death. In this case report we describe the first successful parental use of an automated external defibrillator prescribed for primary prophylaxis against sudden cardiac death in an infant with long-QT syndrome.

Sudden cardiac death without structural heart disease: update on the long QT and Brugada syndromes

The long QT syndrome (LQTS) and the Brugada syndrome (BrS) are the most common genetic causes of malignant ventricular arrhythmias and sudden cardiac death in young patients with normal cardiac morphology. To date, more than 250 different mutations in seven genes have been identified as causing LQTS, whereas the only gene identified to be linked to BrS is SCN5A. In both syndromes, gene-specific mutations have been shown to be associated with specific phenotypic expressions. Risk stratification in LQTS and BrS is based mainly upon a constellation of electrocardiographic findings and a history of prior symptoms. In patients identified as high risk for arrhythmic mortality, the implantable cardioverter defibrillator is the most effective treatment and has been shown to provide near-complete protection during long-term follow-up.