Cardiac Channelopathies in the Pediatric Patient: Short QT Syndrome.

A novel variant in KCNQ1 associated with short QT syndrome

QT interval shortening in spontaneous reports submitted to the FDA: the need for consensus

Although structural heart disease remains the predominant substrate for ventricular arrhythmia, channelopathies including long QT syndrome (LQTS), short QT syndrome (SQTS), Brugada syndrome (BrS), catecholaminergic polymorphic ventricular tachycardia (CPVT), and early repolarization syndrome (ERS) are less common but important contributing entities. These etiologies require specific therapies potentially contrary to empirical management of arrhythmias associated with structural heart disease. Conventional therapy including antiarrhythmic drug therapy may not only fail to resolve unstable arrhythmias but worsen them. Additionally, channelopathy patients with implantable cardioverter defibrillators (ICD) and arrhythmic storms represent a major challenge, and the acute care team needs to be cognizant of unique circumstances that require specific acute therapies beyond empirical advanced life support algorithm recommendations.1 Successful and considered acute management of ventricular arrhythmias is contingent on a number of variables, including knowledge of the cardiac substrate or potential substrate; form, mechanism, and precipitants of ventricular arrhythmias; and acute effect of potential therapies. In the longer term, an understanding of the natural history of the channelopathy along with the efficacy of long-term therapy will lead to superior outcomes. This review will present the risk of ventricular arrhythmias associated with these uncommon entities, the evolving understanding of the mechanism of arrhythmia, and the mechanistic basis of therapies along with a clinical approach to summarize the evidence pertaining to acute and long-term management. Patients with a prolonged QT interval are at risk of sudden cardiac death (SCD) due to Torsade de Pointes (TdP; Figure 1). Most patients with congenital LQTS are asymptomatic and diagnosed incidentally on electrocardiogram screening or following family screening. However, syncope, aborted SCD, or SCD may be the first presentation. Most arrhythmic events in congenital LQT1 occur during physical or emotional stress, at rest or in association with sudden auditory stimulation in LQT2, and during sleep or rest in LQT3 …

To the Editor: I read with interest the recent report by Gaita et al1 of short-QT syndrome as a familial cause of sudden death. The authors enumerated other factors that shorten QT interval, such as increased heart rate, hyperthermia, hypercalcemia, hyperkalemia, acidosis, and altered autonomic tone.1 I would like to add another important and common, but underappreciated, cause of short QT interval, that is, administration of digitalis preparations. Because digitalis administration is such a common everyday occurrence in the management of patients with congestive heart failure and in those with atrial fibrillation or paroxysmal atrial tachycardia, its effect on the QT interval should be kept in mind when …

Disopyramide: Although potentially life-threatening in the setting of long QT, could it be life-saving in short QT syndrome?

Clinical and electrocardiographic characteristics of patients with short QT interval in a large hospital-based population

Background: Short QT syndrome (SQTS) is a rare inheritable channelopathy characterized by a shortened corrected QT interval on an electrocardiogram and a significant risk of atrial and ventricular arrhythmias, potentially leading to sudden cardiac death. Despite advancements in our understanding of SQTS, knowledge gaps persist due to its extreme rarity. This scoping review aims to summarize the available knowledge on its clinical presentations, genetic mutations, and management strategies, while identifying areas for further investigation. Methods: This scoping review was conducted across the PubMed, Scopus, and Cochrane databases and identified relevant case reports, case series, and available studies on SQTS. We focused on articles that reported clinical outcomes, genetic mutations, diagnostic criteria, and management strategies, while excluding studies on the secondary causes of short QT intervals. Results: SQTS is present across a wide age range, from asymptomatic individuals to those experiencing syncope, palpitations, or sudden cardiac arrest. Common genetic mutations include KCNQ1, KCNH2, and KCNJ2. Management strategies vary, with some patients receiving implantable cardioverter defibrillators for secondary prevention and others treated pharmacologically, primarily with hydroquinidine. Our findings highlight the rarity and clinical variability of SQTS, underscoring the need for optimized diagnostic criteria and individualized management strategies. Conclusions: This review emphasizes the need for continued research to better understand the genetic basis of SQTS, optimize diagnostic tools, and improve treatment approaches. Large-scale studies and the integration of genetic and clinical data are critical to addressing the gaps in SQTS management and improving outcomes for patients with this potentially life-threatening arrhythmic disorder.

ObjectivesThe short QT syndrome is a cardiac channelopathy characterised by accelerated repolarisation which manifests as a short QT interval on the ECG. The definition of a short QT interval is...

Short and long QT syndromes: does QT length really matter?

To the Editor: In a recent study on twins, IJzerman et al1 report an association between low birth weight and a short pre-ejection period at rest and during stress tests. They interpret their findings as evidence for an increased sympathetic nervous activity in low birth weight subjects. These data elucidate an important aspect in the regulation of the sympathetic system in low birth weight subjects. However, on the background of a study of our group, which examined muscle sympathetic nerve activity (MSNA) in low birth weight singletons,2 the interpretation of the results may have to be modified. In our study, sympathetic neural activity to the muscle vascular bed was determined by specific intraneural measurement. Under resting conditions, MSNA was lower in low birth weight subjects as compared with a control group with normal birth weight. Baroreflex function was also examined and showed normal functional properties. Additionally, sympathoexcitatory maneuvers (inspiratory apnea …

There are many cardiac arrhythmias and sudden cardiac death (SCD) related to channelopathies or ion channel disorders. Short QT syndrome (SQTS) is an inherited cardiac channelopathy principally caused by defective functioning of both potassium–calcium ion channel that lead to abnormal shortening of QT interval, and an increased risk of ventricular and atrial arrhythmias. Tall T waves in all lead electrocardiogram (ECG), peaked T waves, and narrow‐based T waves that are reminiscent of the typical “desert tent” T waves of hyperkalemia are frequently associated with SQTS. Diagnosis is based on patient's family history, evaluation of symptoms (palpitations and cardiac arrest), and 12‐lead ECG. It can be time challenging because of the wide range of QT interval in healthy subjects. Implantable cardioverter defibrillator (ICD) is the first‐line therapy in SQTS. Quinidine has the potential to be an effective pharmacological therapy for SQTS patients, especially in young children who are not feasible in ICD implantation, because of the ability to prolong QT interval.

Short QT syndrome (SQTS) is an inherited cardiac channelopathy characterised by an abnormally short QT interval and increased risk for atrial and ventricular arrhythmias. Diagnosis is based on the evaluation of symptoms (syncope or cardiac arrest), family history and electrocardiogram (ECG) findings. Mutations of cardiac ion channels responsible for the repolarisation orchestrate electrical heterogeneity during the action potential and provide substrate for triggering and maintaining of tachyarrhythmias. Due to the malignant natural history of SQTS, implantable cardioverter defibrillator (ICD) is the first-line therapy in affected patients. This review summarises current data and addresses the genetic basis and clinical features of SQTS.

The epidemiology of short QT interval remains unclear. We attempted to determine the incidence and clinical characteristics of short QT interval in a longitudinal cohort study. A total of 19,153 subjects (7,525 male, 11,628 female) were enrolled in the study and all available electrocardiograms (ECGs) were investigated longitudinally from 1958 through 2003. We defined short QT interval as QTc of less than 350 ms. Of the 19,153 subjects, two met the criteria of short QT interval and allowed for prevalence and incidence estimates for short QT interval as 0.01% and 0.39/100,000 person-years, respectively. Both cases had neither a family history of sudden cardiac death, nor a history of drug use that might have affected for QT interval. Case 1 was a female with history of ischemic heart disease. Case 2 was a 60-year-old male who exhibited a short QT interval for the first time when he was 26 years of age. He had sick sinus syndrome as an underlying heart disease. Of the 19,153 subjects in this study, none were identified as having the short QT syndrome, with associated high risk of ventricular tachyarrhythmia, atrial fibrillation, and sudden death. Two subjects were identified as having QTc of less than 350 ms, and allowed prevalence and incidence estimates to be made of short QT interval. There observations were suggestive of clinical relationships between short QT interval and organic or electrophysiological heart disease.

The aim: To present clinical cases of sudden cardiac death in patients with prolonged and shortened QT interval. Materials and methods: The study includes description of two different clinical cases with prolonged and shortened QT interval after sudden cardiac death. Verification of the diagnosis was performed using the criteria recommended by the European Society of Cardiology (ESC) and European Heart Rhythm Association (EHRA). Clinical case: Two clinical cases of syncopе with life-threatening arrhythmias, confirmed by electrocardiographic and clinical diagnostic criteria, indicating a change in the dispersion of the QT interval, are presented. The first case represents a patient with intermittent syncope. The patient had previously had attacks of sudden palpitations with fainting. The patient came after another episode of syncope. Further follow-up revealed clinical and electrocardiographic signs of ventricular tachycardia paroxysm. Than the prolongation of the QT interval is set. In this clinical case, verification of QT prolongation syndrome was established in the elderly. Another clinical case is associated with QT syndrome, which remains difficult to diagnose. Such cases have been described relatively recently. The clinical picture of the syndrome of short QT interval in the presented clinical case was characterized by the appearance of syncopal states. The patient showed changes in the adjusted QT interval <320 ms. The causes of syncope in a patient with a short QT interval were paroxysms of atrial fibrillation (AF) or ventricular arrhythmias. At the same time the anatomical structure of a myocardium remains normal and unchanged. The hereditary nature of the disease in the patient has been proven. Conclusions: Timely diagnosis of prolongation (LQTS) or shortening (SQTS) of the QT interval after ECG and Holter monitoring allows you to identify a group of patients with an increased risk of developing ventricular arrhythmias, syncope and sudden cardiac death. Implantation of a cardioverter-defibrillator is an effective and safe method of preventing sudden cardiac death in patients with long and short QT syndromes.

Short QT syndrome (SQTS) carries an increased risk for sudden cardiac death. However, only a short QT interval does not express the risk of ventricular arrhythmias. Thus, additional evaluation of the repolarization abnormality in SQTS patients is essential. In experimental models of SQTS, increased transmural dispersion of repolarization (TDR) and its electrocardiographic counterpart T-wave peak to T-wave end interval (TPE) appeared critical for induction of polymorphic ventricular tachycardia (PMVT). In a clinical study with acquired long QT syndrome patients, TPE/QT ratio > 0.28 indicated arrhythmia risk. We hypothesized that the TPE/QT ratio would be greater in SQTS patients than in control subjects. We compared the behavior of the electrocardiographic TDR in three seriously symptomatic SQTS patients of unknown genotype presenting baseline QTc values < 320 ms and in nine healthy age-matched control subjects. We determined QT and TPE intervals as well as TPE/QT ratio from 24-hour ECG recordings using a computer-assisted program. Diurnal average of TPE/QT ratio was 0.28 +/- 0.03 in SQTS patients and 0.21 +/- 0.02 in control subjects (P = 0.01). SQTS patients had also lesser capacity to change TPE intervals from steady-state conditions to abrupt maximal values than control subjects. SQTS patients have increased and autonomically uncontrolled electrocardiographic TDR. According to experimental SQTS models, the present results may in part explain increased vulnerability of SQTS patients to ventricular arrhythmias.