Short QT syndrome in pediatrics

Molecular Pathways and Animal Models of Arrhythmias

Arrhythmias account for over 300,000 annual deaths in the United States, and approximately half of all deaths are associated with heart disease. Mechanisms underlying arrhythmia risk are complex; however, work in humans and animal models over the past 25 years has identified a host of molecular pathways linked with both arrhythmia substrates and triggers. This chapter will focus on select arrhythmia pathways solved by linking human clinical and genetic data with animal models.

Molecular autopsy: Twenty years of post-mortem diagnosis in sudden cardiac death

In the forensic medicine field, molecular autopsy is the post-mortem genetic analysis performed to attempt to unravel the cause of decease in cases remaining unexplained after a comprehensive forensic autopsy. This negative autopsy, classified as negative or non-conclusive, usually occurs in young population. In these cases, in which the cause of death is unascertained after a thorough autopsy, an underlying inherited arrhythmogenic syndrome is the main suspected cause of death. Next-generation sequencing allows a rapid and cost-effectives genetic analysis, identifying a rare variant classified as potentially pathogenic in up to 25% of sudden death cases in young population. The first symptom of an inherited arrhythmogenic disease may be a malignant arrhythmia, and even sudden death. Early identification of a pathogenic genetic alteration associated with an inherited arrhythmogenic syndrome may help to adopt preventive personalized measures to reduce risk of malignant arrhythmias and sudden death in the victim's relatives, at risk despite being asymptomatic. The current main challenge is a proper genetic interpretation of variants identified and useful clinical translation. The implications of this personalized translational medicine are multifaceted, requiring the dedication of a specialized team, including forensic scientists, pathologists, cardiologists, pediatric cardiologists, and geneticists.

Prognostic Effect of Underlying Chronic Kidney Disease and Renal Replacement Therapy on the Outcome of Patients after Out-of-Hospital Cardiac Arrest: A Nationwide Observational Study

Background and Objectives: This study assessed the prognostic value of underlying chronic kidney disease (CKD) and renal replacement therapy (RRT) on the clinical outcomes from out-of-hospital cardiac arrest (OHCA). Materials and Methods: This retrospective study was conducted utilizing the population-based OHCA data of South Korea between 2008 and 2018. Adult (>18 years) OHCA patients with a medical cause of cardiac arrest were included and classified into three categories based on the underlying CKD and RRT: (1) non-CKD group; (2) CKD without RRT group; and (3) CKD with RRT group. A total of 13,682 eligible patients were included (non-CKD, 9863; CKD without RRT, 1778; CKD with RRT, 2041). From the three comparison subgroups, data with propensity score matching were extracted. The influence of CKD and RRT on patient outcomes was assessed using propensity score matching and multivariate logistic regression analyses. The primary outcome was survival at hospital discharge and the secondary outcome was a good neurological outcome at hospital discharge. Results: The two CKD groups (CKD without RRT and CKD with RRT) showed no significant difference in survival at hospital discharge compared with the non-CKD group (CKD without RRT vs. non-CKD, p > 0.05; CKD with RRT vs. non-CKD, p > 0.05). The non-CKD group had a higher chance of having good neurological outcomes than the CKD groups (non-CKD vs. CKD without RRT, p < 0.05; non-CKD vs. CKD with RRT, p < 0.05) whereas there was no significant difference between the two CKD groups (CKD without RRT vs. CKD with RRT, p > 0.05). Conclusions: Compared with patients without CKD, the underlying cause of CKD—regardless of RRT—may be linked to poor neurological outcomes. Underlying CKD and RRT had no effect on the survival at hospital discharge.

Effect of Heroin on Electrocardiographic Parameters

Fundamento

Atualmente, o vício em heroína é um problema de saúde preocupante, e as informações sobre os efeitos eletrocardiográficos da heroína são limitadas.

Objetivos

O objetivo do presente estudo é investigar os efeitos da dependência de heroína em parâmetros eletrocardiográficos.

Métodos

Um total de 136 indivíduos, incluindo 66 indivíduos que fumam heroína como grupo de estudo e 70 indivíduos saudáveis sem dependência de drogas como grupo de controle, foram incluídos no estudo. Indivíduos que injetam heroína foram excluídos. A avaliação eletrocardiográfica (ECG) dos usuários de heroína foi realizada e comparada com as do grupo controle. Além disso, os ECGs pré e pós-tratamento do grupo usuário de heroína foram comparados. Um valor de p<0,05 foi aceito como estatisticamente significativo.

Resultados

A frequência cardíaca (77,2±12,8 versus 71,4±11,2; p=0,02) foi maior no grupo usuário de heroína em comparação com o grupo controle. Os intervalos QT (341,50±25,80 versus 379,11±45,23; p=0,01), QTc (385,12±29,11 versus 411,3±51,70; p<0,01) e o intervalo do pico ao fim da onda T (Tpe) (65,41±10,82 versus 73,3±10,13; p<0,01) foram significativamente menores no grupo usuário de heroína. Nenhuma diferença foi observada entre os grupos com respeito às razões Tpe/QT e Tpe/QTc. Na análise de subgrupo do grupo usuário de heroína, os intervalos QT (356,81±37,49 versus 381,18±40,03; p<0,01) e QTc (382,06±26,41 versus 396,06±29,80; p<0,01) foram significativamente mais curtos no período pré-tratamento.

Conclusão

O vício em heroína afeta significativamente os intervalos de tempo QT, QTc e Tpe. Os efeitos de arritmia desses parâmetros já são conhecidos. Os parâmetros eletrocardiográficos desses indivíduos merecem mais atenção. (Arq Bras Cardiol. 2020; 115(6):1135-1141)

Aborted cardiac arrest during sport activity in a teenager diagnosed with short QT syndrome

Short QT syndrome is a malignant repolarisation disorder characterised by short QT intervals. We present a previously asymptomatic 14-year-old male patient with negative family history, who suffered a sudden cardiac arrest while playing basketball and diagnosed with short QT syndrome to make emphasis on the fact that although very rare patients with this syndrome may experience cardiac arrest during exercise.

Electrical storm in an acquired short QT syndrome successfully treated with quinidine

Short QT syndrome (SQTS) is a malignant heart disorder defined by the presence of ventricular arrhythmias causing syncope and sudden cardiac arrest. The prevalence in the pediatric population is 0.05%. Quinidine is an established agent for pharmacological prophylaxis in SQTS patients, but can also terminate an electrical storm.

Drug Testing in Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes From a Patient With Short QT Syndrome Type 1

Short QT syndrome (SQTS) predisposes afflicted patients to sudden cardiac death. Until now, only one drug-quinidine-has been shown to be effective in patients with SQTS type 1(SQTS1). The objective of this study was to use human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) from a patient with SQTS1 to search for potentially effective drugs for the treatment of SQTS1 patients. Patch clamp and single-cell contraction measurements were employed to assess drug effects. Ivabradine, mexiletine, and ajmaline but not flecainide, ranolazine, or amiodarone prolonged the action potential duration (APD) in hiPSC-CMs from an SQTS1 patient. Ivabradine, ajmaline, and mexiletine inhibited KCNH2 channel currents significantly, which may underlie their APD-prolonging effects. Under proarrhythmic epinephrine stimulation in spontaneously beating SQTS1 hiPSC-CMs, ivabradine, mexiletine, and ajmaline but not flecainide reduced the epinephrine-induced arrhythmic events. The results demonstrate that ivabradine, ajmaline, and mexiletine may be candidate drugs for preventing tachyarrhythmias in SQTS1 patients.

Long-term follow-up of implantable cardioverter-defibrillators in Short QT syndrome

BACKGROUND

Short QT syndrome (SQTS) is associated with sudden cardiac death and implantable cardioverter-defibrillator (ICD) implantation is recommended in this rare disease. However, only a few SQTS families have been reported in literature with limited follow-up data.

OBJECTIVES

In the recent study, we describe the outcome data of 57 SQTS patients receiving ICD implantation. This includes seven SQTS families consecutively admitted to our hospital between 2002 and 2017 as well as patients reported in published literature.

METHODS

Seven SQTS patients admitted to our hospital were followed up. Additionally, 7 studies out of a total of 626 researched articles were identified through systematic database search (PubMed, Web of Science, Cochrane Library, and Cinahl) and their data analyzed according to our model.

RESULTS

Complications during a median follow-up time of 67.4 months (IQR 6-162 months) were documented in 31 (54%) patients. Inappropriate shocks were seen in 33% due to T wave oversensing (8.7%), supraventricular tachycardia (19%), lead failure and fracture (21%). Further complications were infection (10%), battery depletion (7%) and psychological distress (3.5%). Appropriate shocks were documented in 19%. Three patients (5%) were treated with s-ICD due to recurrent complications of transvenous ICD.

CONCLUSION

ICD therapy is an effective therapy in SQTS patients. However, it is also associated with significant risk of device-related complications.

Electrocardiographic Assessment and Genetic Analysis in Neonates: a Current Topic of Discussion

Background:

Sudden death of a newborn is a rare entity, which may be caused by genetic cardiac arrhythmias. Among these diseases, Long QT syndrome is the most prevalent arrhythmia in neonates, but other diseases such as Brugada syndrome, Short QT syndrome and Catecholaminergic Polymorphic Ventricular Tachycardia also cause sudden death in infants. All these entities are charac-terized by well-known alterations in the electrocardiogram and the first symptom of the disease may be an unexpected death. Despite the low prevalence of these diseases, the performance of an electro-cardiogram in the first hours or days after birth could help identify these electrical disruptions and adopt preventive measures. In recent years, there has been an important impulse by some experts in the scientific community towards the initiation of a newborn electrocardiogram-screening program, for the detection of these electrocardiographic abnormalities. In addition, the use of genetic analysis in neonates could identify the cause of these heart alterations. Identification of relatives carrying the ge-netic alteration associated with the disease allows adoption of measures to prevent lethal episodes.

Conclusion:

Recent technological advances enable a comprehensive genetic screening of a large number of genes in a cost-effective way. However, the interpretation of genetic data and its translation into clinical practice are the main challenges for cardiologists and geneticists. However, there is im-portant controversy as to the clinical value, and cost-effectiveness of the use of electrocardiogram as well as of genetic testing to detect these cases. Our review focuses on these current matters of argue.

Neonatal arrhythmias: diagnosis, treatment, and clinical outcome

Arrhythmias in the neonatal period are not uncommon, and may occur in neonates with a normal heart or in those with structural heart disease. Neonatal arrhythmias are classified as either benign or nonbenign. Benign arrhythmias include sinus arrhythmia, premature atrial contraction, premature ventricular contraction, and junctional rhythm; these arrhythmias have no clinical significance and do not need therapy. Supraventricular tachycardia, ventricular tachycardia, atrioventricular conduction abnormalities, and genetic arrhythmia such as congenital long-QT syndrome are classified as nonbenign arrhythmias. Although most neonatal arrhythmias are asymptomatic and rarely life-threatening, the prognosis depends on the early recognition and proper management of the condition in some serious cases. Precise diagnosis with risk stratification of patients with nonbenign neonatal arrhythmia is needed to reduce morbidity and mortality. In this article, I review the current understanding of the common clinical presentation, etiology, natural history, and management of neonatal arrhythmias in the absence of an underlying congenital heart disease.