Nutritional Factors and Arrhythmic Risk in Long QT Syndrome: A Narrative Review of Mechanistic and Clinical Evidence

Long QT syndrome (LQTS) is an umbrella term for a group of genetic cardiac channelopathies characterized by prolonged ventricular repolarization and increased risk of life-threatening arrhythmias. Although β-blockers and lifestyle modifications remain central to management, specific dietary components may influence repolarization and arrhythmic risk, particularly in genetically predisposed individuals. This review summarizes mechanistic and clinical evidence on the electrophysiological effects of selected nutrients, food constituents, and supplements-including grapefruit juice, licorice, over-the-counter products, and energy drinks. Gene-nutrient interactions and their impact on ion channel function, drug metabolism, and electrolyte balance are discussed. The second part of the review outlines genotype-specific considerations, such as potassium supplementation and dietary guidance for rare forms of LQTS, including Andersen-Tawil and Timothy syndromes. Clinical data are presented in tabular format to facilitate interpretation. By integrating mechanistic and clinical data, the review aims to support dietary counseling and inform clinical decision making in the management of LQTS.