Efficacy of flecainide in bidirectional ventricular tachycardia and tachycardia-induced cardiomyopathy with Andersen-Tawil syndrome.

Andersen-Tawil syndrome is a rare autosomal dominant genetic or sporadic disorder characterized by periodic paralysis, ventricular arrhythmias and dysmorphic features. Ventricular arrhythmias can include frequent premature ventricular complex, polymorphic ventricular tachycardia, and less frequently bidirectional ventricular tachycardia. Left ventricle function has been reported in only a few individual cases of Andersen-Tawil syndrome. A 14-year-old female patient was referred to our clinic from another center with documented arrhythmia and left ventricular systolic dysfunction. Andersen-Tawil syndrome was suspected and the diagnosis was confirmed after detection of a previously unreported mutation in children. We report the successful use of flecainide in bidirectional ventricular tachycardia and tachycardia-induced cardiomyopathy in a case of Andersen-Tawil syndrome associated with a novel mutation.

Marked reduction in paralytic attacks in a patient with Andersen-Tawil syndrome switched from acetazolamide to dichlorphenamide.

Andersen-Tawil syndrome is a rare, autosomal dominant, multisystem disorder for which the majority of cases are caused by pathogenic variants in the KCNJ2 gene. The syndrome is characterized by the clinical triad of episodic paralysis, cardiac conduction abnormalities, and dysmorphic facial and skeletal features. Treatment of Andersen-Tawil syndrome is primarily focused on management of cardiac arrhythmias and preventive management of paralytic attacks. Dichlorphenamide is approved by the US Food and Drug Administration for use in primary periodic paralysis based on several randomized, controlled trials but has not been studied in patients with Andersen-Tawil syndrome. Here, we report a case of the syndrome caused by a de novo pathogenic variant in the KCNJ2 gene (c.95_98del). The paralytic attack rate for this patient was better controlled with dichlorphenamide compared with acetazolamide, further supporting the use of dichlorphenamide in patients with Andersen-Tawil syndrome.

Successful treatment of arrhythmia with ß-blocker and flecainide combination in pregnant patients with Andersen-Tawil syndrome: A case report and literature review.

Andersen-Tawil syndrome (ATS) is a rare disorder characterized by a triad of ventricular arrhythmia (VA), dysmorphic features, and periodic paralysis. Due to the rarity of this condition, less is known about physiologic effect of pregnancy to ATS and arrhythmia. There is no established guideline for peripartum or postpartum treatment and prevention of arrhythmia in ATS; thus, the clinical management is challenging. We reported two KCNJ2-associated ATS patients who got pregnant and underwent vaginal birth safely. Both individuals had VA, micrognathia without periodic paralysis. ß-blocker plus flecainide could be an effective treatment combination when monotherapy failed to control arrhythmia. VA of two pregnant patients with ATS could be controlled by either physiologic changes associated pregnancy or the combination treatment of ß-blocker and flecainide.

"Electrifying dysmorphology": Potassium channelopathies causing dysmorphic syndromes.

Potassium channels are a heterogeneous group of membrane-bound proteins, whose functions support a diverse range of biological processes. Genetic disorders arising from mutations in potassium channels are classically recognized by symptoms arising from acute channel dysfunction, such as periodic paralysis, ataxia, seizures, or cardiac conduction abnormalities, often in a patient with otherwise normal examination findings. In this chapter, we review a distinct subgroup of rare potassium channelopathies whose presentations are instead suggestive of a developmental disorder, with features including intellectual disability, craniofacial dysmorphism or other physical anomalies. Known conditions within this subgroup are: Andersen-Tawil syndrome, Birk-Barel syndrome, Cantú syndrome, Keppen-Lubinsky syndrome, Temple-Baraitser syndrome, Zimmerman-Laband syndrome and a very similar disorder called Bauer-Tartaglia or FHEIG syndrome. Ion channelopathies are unlikely to be routinely considered in the differential diagnosis of children presenting with developmental concerns, and so detailed description and photographs of the clinical phenotype are provided to aid recognition. For several of these disorders, functional characterization of the genetic mutations responsible has led to identification of candidate therapies, including drugs already commonly used for other indications, which adds further impetus to their prompt recognition. Together, these cases illustrate the potential for mechanistic insights gained from genetic diagnosis to drive translational work toward targeted, disease-modifying therapies for rare disorders.

Usefulness of the intravenous flecainide challenge test before oral flecainide treatment in a patient with Andersen-Tawil syndrome.

Andersen-Tawil syndrome (ATS) is an inherited disorder characterised by the triad of ventricular arrhythmias (VAs), periodic paralysis and dysmorphic features. A 31-year-old woman diagnosed with ATS caused by a KCNJ2 mutation (p.R228ins) was urgently admitted to our hospital following an episode of syncope during exercise. Electrocardiography revealed frequent premature ventricular complexes and non-sustained ventricular tachycardias (VTs) with pleomorphic QRS patterns. During the intravenous flecainide test (30 mg), the frequent VAs were inhibited completely. After oral flecainide (100 mg) was started, VAs, except for a brief bigeminy, were suppressed during the exercise test. On 24-hour Holter recordings, the VAs decreased from 50 133 to 13 363 beats/day (-73%). Sustained VT and syncope were not observed during a 3-year follow-up period. Intravenous flecainide challenge test may be useful in predicting the efficacy of oral flecainide treatment for patients with ATS.

Can flecainide totally eliminate bidirectional ventricular tachycardia in pediatric patients with Andersen-Tawil syndrome?

Andersen-Tawil syndrome (ATS) is a disorder that causes episodes of muscle weakness (periodic paralysis), changes in heart rhythm, and developmental abnormalities. QT prolongation and ventricular arrhythmias, including bidirectional ventricular tachycardia (VT) and polymorphic VT, may occur. About 60% of all cases of the disorder arecaused by mutations in the KCNJ2 gene. A 13-year-old female patient was referred for frequent premature ventricular contractions. Suspicion of ATS due to dysmorphic findings, electrocardiogram changes, and periodic muscle weakness was genetically confirmed. Beta-blocker therapy was initiated as a first-line treatment for bidirectional VT and frequent polymorphic premature ventricular contractions. Despite proper treatment, the VT attacks were not brought under control. Flecainide was added to the treatment regime. The number of premature ventricular contractions was dramatically reduced with flecainide and the VT attacks completely disappeared. This patient is a rare example of ATS in our country. This article provides a description of successful management of rhythm disturbance in a patient with ATS.

[Andersen-Tawil syndrome. Efficacy of class IC drugs].

A case of a rare disease - Andersen-Tawil the syndrome (ATS) is presented. Diagnosis of ATS, 7-th molecular-genetic variant of long QT syndrome was made basing on the characteristic clinical picture (periodic stress induced syncopal states), data of ECG and its Holter monitoring (pronounced QT prolongation, bouts of polymorphic bidirectional ventricular tachycardia), typical dysmorphic features (low-set ears, small mandible, brachydactyly, fifth-digit clinodactyly). However mutation of the KCNJ2 gene typical for this variant was not detected. Problems of pathogenesis, diagnostics, and treatment of the disease are discussed with special stress on class IC antiarrhythmic drugs.

Altered stress stimulation of inward rectifier potassium channels in Andersen-Tawil syndrome.

Inward rectifier potassium channels of the Kir2 subfamily are important determinants of the electrical activity of brain and muscle cells. Genetic mutations in Kir2.1 associate with Andersen-Tawil syndrome (ATS), a familial disorder leading to stress-triggered periodic paralysis and ventricular arrhythmia. To identify the molecular mechanisms of this stress trigger, we analyze Kir channel function and localization electrophysiologically and by time-resolved confocal microscopy. Furthermore, we employ a mathematical model of muscular membrane potential. We identify a novel corticoid signaling pathway that, when activated by glucocorticoids, leads to enrichment of Kir2 channels in the plasma membranes of mammalian cell lines and isolated cardiac and skeletal muscle cells. We further demonstrate that activation of this pathway can either partly restore (40% of cases) or further impair (20% of cases) the function of mutant ATS channels, depending on the particular Kir2.1 mutation. This means that glucocorticoid treatment might either alleviate or deteriorate symptoms of ATS depending on the patient's individual Kir2.1 genotype. Thus, our findings provide a possible explanation for the contradictory effects of glucocorticoid treatment on symptoms in patients with ATS and may open new pathways for the design of personalized medicines in ATS therapy.

Kir 2.1 channelopathies: the Andersen-Tawil syndrome.

As a multisystem disorder, Andersen-Tawil syndrome (ATS) is rather unique in the family of channelopathies. The full spectrum of the disease is characterized by ventricular arrhythmias, dysmorphic features, and periodic paralysis. Most ATS patients have a mutation in the ion channel gene, KCNJ2, which encodes the inward rectifier K+ channel Kir2.1, a component of the inward rectifier IK1.IK1 provides repolarizing current during the most terminal phase of repolarization and is the primary conductance controlling the diastolic membrane potential. Thus, ATS is a disorder of cardiac repolarization. The chapter will discuss the most recent data concerning the genetic, cellular, and clinical data underlying this unique disorder.

Novel de novo mutation in the KCNJ2 gene in a patient with Andersen-Tawil syndrome.

Andersen-Tawil syndrome is a rare autosomal-dominant disease characterized by episodic muscle weakness, cardiac arrhythmias, and dysmorphic features. Mutations in the KCNJ2 gene (which encodes an inward-rectifying potassium channel protein, Kir2.1) have been reported to be responsible for this disorder. Reported here is a novel de novo mutation in the KCNJ2 gene in a patient with Andersen-Tawil syndrome. This mutation predicts the substitution of alanine for glycine at position 146 (Gly146Ala, c.437G > C) of Kir2.1 and is located at the extracellular pore loop region that serves as a principal ion-selective filter. The patient did not respond to acetazolamide, but experienced an improvement of the paralytic symptoms on treatment with a combination of spironolactone, amiloride, and potassium supplements.

Oral verapamil effectively suppressed complex ventricular arrhythmias and unmasked U waves in a patient with Andersen-Tawil syndrome.

Andersen-Tawil syndrome (ATS) is a rare, heterogeneous, autosomal dominant, or sporadic disorder characterized by the clinical triad of periodic paralysis, dysmorphic features, and ventricular arrhythmias such as bidirectional ventricular tachycardia (BVT). We present a case of an elderly patient with ATS whose symptomatic ventricular arrhythmias including BVT were effectively suppressed by oral verapamil therapy.

Flecainide suppresses bidirectional ventricular tachycardia and reverses tachycardia-induced cardiomyopathy in Andersen-Tawil syndrome.

Bidirectional ventricular tachycardia (BVT), although a rare arrhythmia in the general population, is frequently observed in patients with Andersen-Tawil syndrome and long QT interval. However, the pharmacologic treatment of this arrhythmia remains unknown. In the present study, we documented the favorable antiarrhythmic action of flecainide in a young woman with sustained BVT and Andersen-Tawil syndrome. She presented with incessant BVT that could only be terminated with flecainide. During sinus rhythm, a prolonged QT interval was observed. Genetic studies revealed a mutation in the K(+) channel gene KCNJ2. Over a 4-year follow-up period, recurrence of her arrhythmia occurred twice. The first episode was due to noncompliance and resolved with resumption of flecainide therapy. The second recurrence was associated with a tachycardia-induced cardiomyopathy and resolved when the dose of flecainide was increased from 200 to 300 mg daily. This report suggests that flecainide can be effective in controlling BVT associated with Andersen-Tawil syndrome and indicates that the left ventricular dysfunction is secondary to the arrhythmia and not due to an associated phenotypic manifestation of the disorder.