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  • Current treatment options for paroxysmal supraventricular ta

    2019-06-12

    Current treatment options for paroxysmal supraventricular tachycardias include AV Dynasore manufacturer blocking agents (verapamil, diltiazem, propranolol, and metoprolol), class IC anti-arrhythmic agents (propafenone and flecainide), and catheter ablation. The identification of frequent coexistence of clinical, spontaneous AVNRT and drug-induced type 1 Brugada pattern calls for greater vigilance in the use of certain anti-arrhythmic agents that are known to exacerbate the Brugada phenotype (verapamil, diltiazem, propranolol, and class IC agents), avoidance of Brugada pattern-inducing non-cardiac drugs (certain selective serotonin reuptake inhibitors, tricyclic antidepressants, and antipsychotic and antiepileptic agents), and possible need for standard preventive measures such as use of antipyretics during fever [75,76]. Quinidine sulfate is known to be a safe and effective treatment for patients with SQTS and AF [28]. Inappropriate ICD shocks due to Dynasore manufacturer T-wave oversensing and/or AF are common in patients with STQS. Careful ICD programming and use of quinidine sulfate in those cases are recommended [28]. There is an anecdotal report of dramatic suppression of AF by mexiletine as a relatively selective blocker of late Na current in a patient with type 1 LQTS [80]. Pulmonary vein isolation can be performed safely and effectively in patients with CPVT and AF with or without inappropriate ICD shocks [33,34].
    Disclosures
    Introduction
    Kv11.1 biogenesis and ER export
    Molecular mechanism of class 2 LQT2 mutations
    Conclusions
    Conflict of interest
    Acknowledgments BPD was supported by research funding from Gilead Scientific and Kentucky Science and Engineering Foundation (KSEF-3139-RDE-017).
    Introduction Long QT syndrome (LQTS) is a potentially life-threatening arrhythmia characterized by delayed myocardial repolarization that produces QT prolongation on ECG, and an increased risk of torsades de pointes (TdP)-triggered cardiac events, such as syncope, cardiac arrest, and sudden cardiac death (SCD) [1,2]. This syndrome, with an estimated incidence of 1/2000 and a mortality rate of 21% for symptomatic patients not receiving therapy within one year from the first syncope event [1,3], includes congenital and acquired (e.g., drug-induced) conditions. Molecular genetic studies have revealed that congenital LQTS is linked to mutations in genes encoding subunits of cardiac ion channels or adapter proteins that modify the channel functions. There are two types of inherited syndromes: autosomal dominant Romano-Ward syndrome [4] and autosomal recessive Jervell and Lange-Nielsen syndrome [5,6] that is usually associated with deafness [7]. In 1991, the Keating group reported for the first time that a single genetic locus on chromosome 11p15.5 was associated with LQTS within a single family [8]. Based on subsequent pioneering work [9–11], at least 15 types of genes have been found to be linked to 15 different types of LQTS (LQT1-15) to date. In 1996, Wang et al. confirmed that type 1 congenital LQTS (LQT1) is caused by mutations in the KCNQ1 (KvLQT1) gene, which is highly expressed in the heart and encodes a protein with structural features of a voltage-gated potassium channel [11]. Of the fifteen LQTS types, LQT1 is the most common and present in approximately 40–50% of all genotyped patients [12,13]. The KCNQ1 gene encodes the α-subunit of the slow component of delayed rectifier K+ current (IKs) channel (Kv7.1). This protein, together with the β-subunit KCNE1 and an adapter protein Yotiao, forms a macromolecular complex (i.e., the functional potassium ion channel IKs) [14,15]. The channel carries the major outward repolarizing K+ current during the plateau phase of cardiac action potentials (APs) and plays a critical role in maintaining repolarization reserve in the heart [16,17]. Mutations in KCNQ1 can cause dysfunction in the IKs channel, such as a delay in channel opening or a reduction in the duration for which it is open [8,16,18,19]. This results in a decrease in repolarizing K+ current or a loss-of-function during phase 3 of the cardiac AP, which eventually causes QT prolongation and serious arrhythmias.