Shortening of the Short Refractory Periods in Short QT Syndrome

The Uncommon Phenomenon of Short QT Syndrome: A Scoping Review of the Literature

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.

Effects of Dexmedetomidine on Basic Cardiac Electrophysiology in Adults; a Descriptive Review and a Prospective Case Study

Dexmedetomidine (DEX) is a commonly used sedative agent with no or minimal effects on breathing. DEX may also be beneficial in myocardial protection. Since the mechanisms of cardiac effects are not well known, we carried out a descriptive review and examined the effects of DEX on myocardial electrical conduction in a prospective and controlled manner. For the review, clinical studies exploring DEX in myocardial protection published between 2020-2022 were explored. A case study included 11 consecutive patients at a median (range) age of 48 (38-59), scheduled for elective radiofrequency ablation of paroxysmal atrial fibrillation. A bolus dose of DEX 1 µg/kg given in 15 min was followed by a continuous infusion of 0.2-0.7 µg/kg/h. Direct intracardiac electrophysiologic measurements, hemodynamics and oxygenation were measured before and after the DEX bolus. Experimental studies show that DEX protects the heart both via stabilizing cardiac electrophysiology and reducing apoptosis and autophagy after cell injury. The clinical evidence shows that DEX provides cardiac protection during different surgeries. In a clinical study, DEX increased the corrected sinus node recovery time, prolongated the atrioventricular (AV) nodal refractory period and cycle length producing AV nodal Wenckebach retrograde conduction block. DEX has a putative role in organ protection against hypoxic, oxidative and reperfusion injury. DEX slows down the firing of the sinus node and prolongs AV refractoriness.