Congenital Long QT Syndrome (LQTS) is a hereditary cardiac channelopathy defined by delayed ventricular repolarization and an elevated risk of life-threatening ventricular arrhythmias. Recent echocardiographic studies using speckle-tracking and strain imaging have identified subtle abnormalities in ventricular and atrial mechanics among LQTS patients, including reduced global longitudinal strain, impaired diastolic function, enlarged left atrial volumes and a consistently negative electromechanical window. These findings challenge the traditional concept of LQTS as solely an electrical disease and support evolving evidence of a subclinical cardiomyopathic phenotype. Left atrial remodeling, although less studied, may represent an underrecognized component of LQTS with potential implications for arrhythmia vulnerability and diastolic dysfunction. This review summarizes current evidence on electromechanical and structural cardiac involvement in congenital LQTS, highlights its diagnostic and clinical implications, and outlines future directions for research in this evolving field.

Background: Endothelial dysfunction is a key feature of diabetic vascular disease and is associated with high-glucose-induced changes in endothelial energy metabolism and redox balance. Transglutaminase-2 has been implicated in vascular stress responses, but its contribution to endothelial adaptation to high glucose remains incompletely defined. Methods: EA.hy926 endothelial cells were cultured under normoglycaemic (NG) or high-glucose conditions and treated with LDN-27219 at 20 µg/mL (48.9 µM). Cellular reducing capacity, total protein content, mitochondrial respiration, MitoSOX Red fluorescence, and selected cytokine and adhesion-marker secretion were assessed. Results: High glucose shifted cells toward a more glycolytic basal phenotype, increased MitoSOX Red fluorescence, and reduced glycolytic stress responsiveness compared with NG conditions. LDN-27219 had limited effects under NG conditions but, under high-glucose conditions, reduced basal respiration, maximal respiration, ATP-linked oxygen consumption, and spare respiratory capacity, while partially restoring stressed extracellular acidification. LDN-27219 also reduced high-glucose-induced MitoSOX Red fluorescence, although this cannot be interpreted as definitive evidence of reduced mitochondrial superoxide production because mitochondrial membrane potential was not measured. No statistically significant changes were detected in the selected inflammatory or adhesion markers. Conclusions: LDN-27219 modifies endothelial bioenergetic and oxidant-associated fluorescence responses under high-glucose conditions.