RESUMEN
Congenital long QT syndromes (cLQTS) are relatively rare diseases in which QT interval is prolonged due to several mutations on ion channels involved in cardiac cell repolarization. This condition confers higher risk of malignant arrhythmias and sudden cardiac death, and it is widely accepted that substances that prolong QT interval should be avoided by these patients. Most of these substances are antibiotics and non-antibiotics drugs, but almost nothing is known about frequently consumed fruits and juices. We report the case of a patient with a previously asymptomatic cLQTS type 1 (cLQTS1) with unusual QT prolongation of 167 milliseconds (ms) related to the consumption of large amounts of citric juices (oranges and lemons). A literature review was done for better understanding of its influence on QT interval duration and to know the concentration of flavonoids on citric fruits.