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Genetically Determined Ventricular Arrhythmias
Published in Andrea Natale, Oussama M. Wazni, Kalyanam Shivkumar, Francis E. Marchlinski, Handbook of Cardiac Electrophysiology, 2020
Houman Khakpour, Jason S. Bradfield
Short QT syndrome, first described by Gussak et al.41 is one of the rarer channelopathies associated with atrial and ventricular fibrillation and SCD.42 SQTS patients present with recurrent syncope, atrial fibrillation, and SCD.
The QT interval
Published in Andrew R Houghton, Making Sense of the ECG, 2019
Although congenital long QT syndromes are well recognized, it is only since 2000 that congenital short QT syndrome has been recognized as a clinical entity. The congenital short QT syndromes appear to follow an autosomal dominant pattern of inheritance and mutations affecting the genes KCNH2, KCNQ1 and KCNJ2 (which are linked to potassium channels) and CACNA1C, CACNB2 and CACNA2D1 (which are linked to calcium channels) have so far been identified.
The QT interval
Published in Andrew R Houghton, David Gray, Making Sense of the ECG, 2014
Implantation of a cardioverter defibrillator forms the cornerstone of treatment, although this can be challenging in view of the very young age at which the condition is diagnosed in some individuals. Drug treatment (e.g. quinidine) to lengthen the QT interval may be possible, depending upon the subtype of short QT syndrome. The management of this condition is complex and requires the input of a cardiologist with a special interest in arrhythmias.
Precision medicine in cardiac electrophysiology: where we are and where we need to go
Published in Expert Review of Precision Medicine and Drug Development, 2020
Ashish Correa, Syed Waqas Haider, Wilbert S. Aronow
Short QT Syndrome (SQTS) is an extremely rare congenital arrhythmia syndrome characterized a very short QT interval (</=330 ms) in the context of a structurally normal heart and no electrolyte abnormalities [59]. The first presentation of these patients is often cardiac arrest. These patients also have a predisposition to develop AF. The diagnosis is made by an EKG finding of a QTc interval </=330 ms or </=360 ms and either a genetic mutation, a personal history of cardiac arrest or a family history of SCD or SQTS. Using candidate gene approaches, mutations in the KCNH2, gene that encodes the hERG potassium channel that in turn regulates the inward repolarizing IKr current, were identified as a cause autosomal dominant SQTS (called SQT1) [68,69]. Similarly, candidate gene approaches were used to identify mutations in KCNQ1 [70–72] (encoding the potassium channel that facilitates the IKs current) and in KCNJ2 [73] (encoding an inward-rectifier potassium channel); mutations at these loci cause SQT2 and SQT3, respectively. Unlike in LQTS where loss-of-function mutations in these genes prolong the QT interval, in SQTS gain-of-function mutations result in rapid repolarization, shortening of the QT interval and a predisposition to develop polymorphic VTs (Figure 4).
Disease modeling of cardiac arrhythmias using human induced pluripotent stem cells
Published in Expert Opinion on Biological Therapy, 2019
Wenbin Liang, Lilit Gasparyan, Wael AlQarawi, Darryl R. Davis
Short QT syndrome is a rare inherited cardiac condition characterized by an abnormally short QT interval that confers an increased risk of atrial or ventricular arrhythmias. It was first described in 2000 when Gussak et al. reported two cases of idiopathic short QT interval associated with atrial fibrillation in one case and sudden cardiac death in the other [95]. Patients with short QT syndrome can be asymptomatic but can present with syncope or sudden cardiac arrest [96]. Short QT syndrome is genetically attributable to mutations within genes underlying cardiac action potential repolarization [97]. Given the natural heterogeneity of repolarization throughout the ventricle needed to coordinate cardiac contraction, mutations that alter endocardial or epicardial repolarization give rise to transmural dispersion of repolarization which serves as a substrate for pro-arrhythmia [98]. Al-Battrawy and colleagues recently explored the ability of cardiomyocytes differentiated from dermal fibroblast iPSCs to profile the pro-arrhythmic potential of a gain of function mutation within IKr (KCNH2-p.N588K) [99]. In a manner consistent with previous studies using non-cardiac expression systems [98], the N588K mutation increased IKr and shortened action potential duration by increasing gene and protein expression of KCNH2. Similar to clinical experience [100], abnormal Ca+2 transients were corrected by quinidine while IKr (sotalol) and beta-adrenoceptor (metoprolol) blockade were ineffective.
A finite element model of myocardial infarction using a composite material approach
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2018
Seyyed M. H. Haddad, Abbas Samani
Heart diseases have attracted major attention in the medical community as they are the leading cause of death worldwide in all genders and ethnicities (WHO 2017). There is a wide spectrum of cardiac conditions such as rheumatic, hypertensive, ischemic, and inflammatory heart disease that can potentially hamper the critical heart role as a mechanical pump which pumps the blood to deliver oxygen and nutrients to the body. Substantial research efforts have been dedicated to various aspects of heart disease. Some of these efforts have been geared towards a greater understanding of various cardiac pathologies and gaining insight into their early and late stages of development. These efforts have been also directed towards developing effective methods of diagnosis, prognosis and more effective treatment of heart diseases (Drzewiecki et al. 1996; Jin et al. 2010; McCain and Parker 2011; Christy 2012; Marchesseau et al. 2013). To achieve these goals, a suite of tools have been developed including tools for mechanical modeling of pathological heart (Choi et al. 2011; Dou et al. 2012; Lee et al. 2013; Genet et al. 2015). In addition to providing insight into normal heart’s function (McCain and Parker 2011; Marchesseau et al. 2013), cardiac mechanics models can be employed to study how mechanical alterations arising from pathological changes in the heart lead to specific impediments in its overall function (Luo et al. 2007; Howard and Omens 2011; Schwarzl et al. 2012). For instance, a mechanical model of a canine left ventricle (LV) under ischemic states, including myocardial infarction (MI), was developed using finite element (FE) method by applying partial or complete loss of contractility in the LV’s ischemic region (Perl and Horowitz 1987). In a different study, short QT syndrome (SQTS) which is a cardiac arrhythmogenic disease was investigated using an electromechanical model of the LV (Adeniran et al. 2013). Analysis of 3D displacement field of the LV model obtained in that study confirmed dissociation between ventricular repolarization and abnormal end-systole mechanical characteristics observed in the clinic.