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The QT interval
Published in Andrew R Houghton, Making Sense of the ECG, 2019
Patients with long QT syndrome need careful risk assessment and will usually require anti-arrhythmic medication (commonly beta blockers). Those at high risk of ventricular arrhythmias will usually need an implantable cardioverter-defibrillator.
Nonclinical Safety Evaluation of Drugs
Published in Pritam S. Sahota, James A. Popp, Jerry F. Hardisty, Chirukandath Gopinath, Page R. Bouchard, Toxicologic Pathology, 2018
Thomas M. Monticello, Jeanine L. Bussiere
Cardiac arrhythmias, such as Torsades de pointes (TdP), is a specific and rare variety of ventricular tachycardia that can progress to ventricular fibrillation. Prolongation of the QT interval, observed on an electrocardiogram (ECG), precedes the onset of this serious and often life-threatening arrhythmia. A common cause of long QT syndrome is a block of the hERG (human ether-a-go-go-related gene) ion channel. The hERG ion channel is a major contributor to cardiac repolarization and several marketed drugs have been reported to block the hERG channel, resulting in acquired long QT syndrome and TdP (Redfern et al. 2002; Roden 1998). The potential for drug-induced hERG binding, therefore, is now routinely evaluated and screened in a high-throughput assay during lead optimization (Bowlby et al. 2008).
Cardiovascular medicine
Published in Shibley Rahman, Avinash Sharma, A Complete MRCP(UK) Parts 1 and 2 Written Examination Revision Guide, 2018
Shibley Rahman, Avinash Sharma
Romano-Ward syndrome is purely a cardiac electrophysiological disorder, characterised by QT prolongation and T-wave abnormalities on the ECG. It is in fact the most common form of inherited long QT syndrome, affecting an estimated 1 in 7000 people worldwide. Mutations in the KCNE1, KCNE2, KCNH2, KCNQ1, and SCN5A genes cause Romano-Ward syndrome.
Gastroparesis syndromes: emerging drug targets and potential therapeutic opportunities
Published in Expert Opinion on Investigational Drugs, 2023
Le Yu Naing, Matthew Heckroth, Prateek Mathur, Thomas L Abell
5-HT3 receptors differ from all other 5-HT receptors in that they are ligand-gated ion channels, whereas the others are G-protein linked receptors. Activation of 5-HT3 receptors inhibits gastric secretions, stimulates migrating motor complexes, and increases intestinal secretions, accelerating small bowel transit. They also stimulate gastric antral contractions and vagal afferent nerves initiating the vomiting reflex[31]. 5-HT3 receptor antagonists are potent antiemetics often used to treat the symptoms of Gp. They block serotonin both peripherally on vagal nerve terminals in the GI tract, as well as centrally in the area postrema and nucleus tractus solitarius. Available 5-HT3 receptor antagonists include ondansetron (Zofran), granisetron (Kytril), tropisetron (Navoban), dolasetron (Anzamet), ramosetron (Nasea), and palonosetron (Aloxi). Some of them have been associated with QT prolongation on EKG, and it is recommended that patients with congenital long QT syndrome need to be cautious with their use. For patients with significant electrolyte abnormalities, congestive heart failure, or those taking other medications that prolong the QT interval, monitoring with serial EKGs is recommended.
Histopathology of the Conduction System in Long QT Syndrome
Published in Fetal and Pediatric Pathology, 2022
Alexandra Rogers, Rachel Taylor, Janet Poulik, Bahig M. Shehata
Long QT syndrome (LQTS) is a cardiac channelopathy disorder that was first described by Jervell and Lange-Nielsen (JLNS) and by Romano and Ward in the late 1950s and early 1960s [1]. The two groups noted different inheritance patterns (autosomal recessive for Jervell and Lange-Nielsen, autosomal dominant for Romano and Ward), but both described an inherited disorder resulting in prolongation of the QT interval on surface electrocardiogram. LQTS is characterized by abnormal ventricular myocardial repolarization due to dysfunctional ion channel behavior, leading to increased risk of developing symptomatic ventricular arrhythmias. Clinically, LQTS may be asymptomatic or can present with syncope, seizures, torsades de pointes, ventricular fibrillation and/or sudden cardiac death. Severity of symptoms varies depending on mutation type (i.e. homozygous, heterozygous), patient gender, and LQTS subtype, amongst other factors [2,3]. LQTS may be congenital (inherited) or acquired. Inherited LQTS is estimated to affect between 1 in 7,000 up to 1 in 2,000 people, with causative mutations in at least 10 genes identified to date. Acquired LQTS, in contrast, typically occurs in the context of QT-prolonging disease states, QT-prolonging medications, or QT-prolonging electrolyte disturbances.
Torsade de pointe due to QT prolongation following erythromycin administration in a preterm infant
Published in Acta Cardiologica, 2022
Caroline Fobe, Benedicte Van Grambezen, Stéphane Moniotte, Christophe Vo, Anneliese Dussart, Olivier Danhaive, Fiammetta Piersigilli
Moreover, there are non-modifiable risk factors that increase the risk of erythromycin-associated arrhythmias, such as female gender, cardiovascular comorbidities, diabetes, hypoglycaemia, and obviously congenital long QT syndrome [21]. Congenital long QT syndrome prevalence is estimated to be approximately 1:2000 to 1:5000 due to the heterogeneity of the disease [27]. Seventeen genes are known to be related to LQTS and some of them have limited evidence for disease causation [28]. For this reason, LQTS screening should include the parents, as it is an inherited disease. In our case, parents’ ECGs were normal. There was no history of sudden death infant syndrome (SIDS) nor any episodes of unexplained syncope in the family. Genetic analysis of the infant identified a missense variant of uncertain significance (class 3) in TNN gene, which can not confirm or exclude the genetic aetiology of long QT syndrome.