Device therapy in the setting of long QT syndrome

Case report: Torsade de pointes induced by the bigeminy result from retrograde ventriculoatrial activation in VVI pacing and resolved by intentional atrial pacing

Introduction

While pacing has been used for long QT syndrome (LQTs), the optimal pacing modality is controversial.

Case

We report a woman with bradycardia and a recently implanted single-chamber pacemaker experienced multiple syncope. No device dysfunction was found. Multiple Torsade de Pointes (TdP) induced by the bigeminy result from retrograde ventriculoatrial (VA) activation in VVI pacing were demonstrated in the scenario of previously unidentified LQTs. Replacement for a dual-chamber ICD and intentional atrial pacing eliminated the VA conduction and symptoms.

Conclusion

Pacing without atrioventricular sequence might be catastrophic in LQTs. Atrial pacing and atrioventricular synchrony should be highlighted.

Autonomic cardiac innervation: impact on the evolution of arrhythmias in inherited cardiac arrhythmia syndromes

The autonomic nervous system (ANS) is an essential component of arrhythmogenicity, especially in the absence of structural heart disease and channelopathy. In this article, the authors review the role and characteristics of ANS in various channelopathies. Some of these, such as most long QT syndromes and catecholaminergic polymorphic ventricular tachycardia, are highly dependent on sympathetic activation, while parasympathetic tone is an important factor for arrhythmias in other channelopathies such as Brugada syndrome or early repolarisation syndrome. Recent advances highlighting the subtle role of ANS in channelopathies are presented here, demonstrating that all is far from being so simple and straightforward and revealing some paradoxical behaviours of channelopathies in relation to discrete ANS imbalance.

Congenital Long QT Syndrome: A Clinician's Guide

Congenital long QT syndrome (LQTS) is a familial cardiac ion channelopathy first described over sixty years ago. It is characterised by prolonged ventricular repolarization (long QT on ECG), ventricular arrhythmias and associated syncope or sudden cardiac death. As the most closely studied cardiac channelopathy, over the decades we have gained a deep appreciation of the complex genetic model of LQTS. Variability in genetic expression and incomplete penetrance leads to a heterogenous phenotype that can be challenging to clinically classify. In recent times, progress has been made in diagnostic method, risk stratification and treatment options. This review has been written as a guide for the general cardiologist to understand the basic pathophysiology, diagnosis, and management priorities for the most encountered LQTS subtypes: LQT1, LQT2 and LQT3. This article is protected by copyright. All rights reserved.

[Congenital long QT syndrome]

Congenital long QT syndrome (LQTS) represents a group of heart diseases of genetic origin characterized by prolongation of the QT interval and an abnormal T wave on the electrocardiogram (ECG). They can have a dominant or recessive expression, the latter associated with sensorineural deafness. In both cases, its clinical presentation is associated with recurrent syncope and sudden death as a consequence of ventricular tachycardia, specifically Torsades de Pointes. Currently they are classified according to the specific genetic defect, being able to compromise around 16 genes and almost 2000 mutations. It should be suspected in individuals with related symptoms, electrocardiographic findings, and family history. Management is based on the reduction or elimination of symptoms, and concomitantly the prevention of sudden death (SD), in those children with congenital deafness, the management requires the application of the otolaryngologist specialist's own measures. The cardiovascular management implies the modification of lifestyles, mainly the prohibition of competitive sports, including swimming, avoiding exposure to loud sounds or triggers. The medications used include beta-blockers, and more rarely flecainide, ranozaline, and verapamil; invasive management consists of the implantation of a cardioverter defibrillator or even left sympathetic denervation, each with its own risks and benefits. In any of the cases, we must avoid the circumstances that increase the QT interval, as well as carry out the appropriate analysis of the benefits and risks of each possible invasive measure.

How to prevent SCD in the young?

Sudden cardiac death in the young (SCDY) is always a devastating event. The death is sudden and unexpected and often in a person who was thought to be healthy. In recent years our understanding of these tragic events have drastically improved; 10-20years ago we did not know how often SCD occurred in the young, and we had sparse knowledge on the role of inheritance. We have found that SCD corresponds to 7% of all deaths with an overall (highest possible) incidence rate of 2.8 per 100,000 person-years (autopsy rate of sudden death cases of 75%). This incidence rate is higher than in the Veneto region (1.0), in the Netherlands (1.6), and in the UK (1.8), but can be explained by differences in definition and methodological factors. Cause of death in SCDY also differs to some extent between countries. Recent data suggest that there are identifiable risk factors for SCDY such as symptoms, comorbidities and polypharmacy. SCDY is to some extent preventable and this can be achieved through several initiatives: 1. better OCHA treatment including readily available AEDs, 2. family screening on the families left behind, and 3. better diagnostics and treatment for patients at risk for SCDY.