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Short QT syndrome is a recently recognized cause of cardiac rhythm disorders, including sudden cardiac death. Although the syndrome is rare, its potential lethality justifies routinely screening the electrocardiograms of patients with syncope or unexplained atrial or ventricular arrhythmias to look for this diagnosis. This review discusses recent a...
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... To avoid the errors in interpreting the sequence variants from NGS data, we need follow the recent published guidance from the American College of Medical Genetics and Genomics and the Association for Molecular Pathology [95]. Physicians should obtain accurate and complete clinical information, including patients and their family history, physical examination, and previous laboratory tests, and then testing the genetic variants of patients and their family members to distinguish mutations leading to arrhythmias and those benign or accidental variants, which are unique Table 3. Genetic basis of short QT syndrome [41]. to the individual [95]. ...
Introduction: Although thousands of potentially disease-causing mutations have been identified in a handful of genes, the genetic heterogeneity has led to diagnostic confusions, stemming directly from the limitations in our arsenal of genetic tools.
Areas covered: We discuss the genetic basis of cardiac ion channelopathies, the gaps in our knowledge and how Next-generation sequencing technology (NGS) and can be used to bridge them, and how induced pluripotent stem cell (iPSC) derived-cardiomyocytes can be used for drug discovery.
Expert commentary: Univariate, arrhythmogenic arrhythmias can explain some congenital arrhythmias, however, it is far from a comprehensive understanding of the complexity of many arrhythmias. Mutational screening is a critical step in personalized medicine and is critical to the management of patients with arrhythmias. The success of personalized medicine requires a more efficient way to identify a high number of genetic variants potentially implicated in cardiac arrhythmogenic diseases than traditional sequencing methods (eg, Sanger sequencing). Next-generation sequencing technology provides us with unprecedented opportunities to achieve high-throughput, rapid, and cost-effective detection of congenital arrhythmias in patients. Moreover, in personalized medicine era, IPSC derived-cardiomyocytes can be used as ‘cardiac arrhythmia in a dish’ model for drug discovery, and help us improve management of arrhythmias in patients by developing patient-specific drug therapies with target specificity.
... Thus, it was thought that the dial settings of isoflurane vaporizer to 4% and 5% 315 reduced the repolarization phase of ventricular muscle, leading to shortening of QT interval in SHR/Izm rats. In humans, several drugs, including digitalis, are known to induce shortening of QT interval[34], and a tall and peaked T-wave is a common feature in short QT syndrome[22]. However, to the best of our knowledge, there are no reports on the isoflurane-induced shortening of QT interval. ...
Isoflurane is a widely used anesthetic, but its effects with increase in inspired concentration on cardiovascular function have not yet been clarified in rodents. Additionally, there are only a few studies comparing isoflurane-induced cardiorespiratory effects between rat strains. Thus, we investigated the differences in cardiorespiratory responsiveness to increasing concentration of inspired isoflurane in SHR/Izm, WKY/Izm and Crl:CD(SD) rats, by increasing the setting values of vaporizer’s dial indicator. The rats were anesthetized with 1.5% isoflurane, and electrocardiograms, blood pressure, and respiratory rate were recorded simultaneously. Thereafter, the inspired concentration was increased stepwise to 2%, 3%, 4%, and 5%, and cardiorespiratory parameters were obtained at each concentration. Under anesthesia at more than 4%, although prolongation of the RR and PR intervals was observed in all strains, shortening of the QTC interval was found only in SHR/Izm rats. From frequency domain analysis of heart rate variability, an increase in LF/HF ratio and a decrease of HF components were observed in SHR/Izm and WKY/Izm rats, respectively, with 5% isoflurane anesthesia. Blood pressure and heart rate were remarkably reduced in SHR/Izm rats at higher concentrations, whereas the reduction was smallest in WKY/Izm rats among the three strains examined. Respiratory rate was inspired concentration-dependently decreased in all strains. These results suggested that SHR/Izm rats are more sensitive to suppressive effects of isoflurane anesthesia on cardiovascular function among these rat strains.
This chapter summarizes the structure, function, and dysfunction of various contractile systems, including muscle (skeletal, cardiac, smooth) and nonmuscle entities (actin, cilia). Motility requires a specific arrangement of proteins, along with proper chemomechanical transduction. Muscle innervation varies according to muscle type. Muscle contraction is based on a sliding filament model and cross-bridge hypothesis. Muscle activity is highly regulated by a variety of molecular factors. Inherited diseases of the muscle include Duchenne and Becker’s muscular dystrophy, channelopathies, metabolic disorders, and mitochondrial mutations. Cilia allow motility through the actions of microtubules and dynein.
This work was supported in part by U.S. National Institutes of Health grants R01 HL092217, R01 HL124935, and K08 HL130587. Both authors have reported that they have no relationships relevant to the contents of this paper to disclose.
Congenital short QT syndrome (SQTS) is a rare inherited channelopathy without structural heart disease. It is an autosomal dominant primary electrical disorder with a low degree of penetrance. It has a characteristic clinical-electrocardiographic-electrophysiological phenotype consisting of irregular palpitations due to the frequent episodes of paroxysmal atrial fibrillation, dizziness and/or sudden cardiac death (SCD). Affected individuals usually have a positive family history of syncope or SCD in first-or second degree young relatives (younger than 40 years of age) with autopsy negative SCD. Resting electrocardiograms (ECGs) have very short and uniform QT/QTc intervals (QTc interval ≤330 ms with the exception of the calcium-dependent variants 4 and 5), absent or minimal ST segments, interval from J point to T wave peak (Jp-Tp) measured in the precordial lead with the T wave of greatest amplitude.
