Unmasking Long QT Syndrome in a Serviceman: Effects of Hypoglycemia and a Flight Duty Medical Examination

We report the case of a 29-year-old male soldier with a time in service above 10 years, found to have asymptomatic long QT syndrome (LQTS), a condition associated with increased risk of potentially fatal ventricular arrhythmias, during a flight physical. A review of his past medical history revealed a transient QT prolongation during an episode of hypoglycemia due to endogenous hyperinsulinism caused by an insulinoma, as an infantryman 7 years earlier; the resolution of the QT prolongation was spontaneous. He was evaluated and considered fit for duty by cardiology. Before returning to duty, he underwent a Whipple procedure for the resection of the insulinoma; there was no sequela or recurrence. Seven years later, he was noted to have QT prolongation on a resting electrocardiogram during a routine evaluation to obtain clearance for advanced schooling to become a helicopter pilot. Consequently, he underwent additional workup including genetic testing and was found to be heterozygous for a well-known pathogenic variant KCNQ1: c.1031C > T (p.Ala344Val), LQT1 locus, and additionally for a rare variant in the SNTA1 gene, SNTA1: c.1003_1021dup (p.Ala341Glufs*103), LQT12 locus. The clinical implication, management, and the medical retention determination are presented. We conclude that the stringent requirement for an electrocardiogram as part of medical evaluation for fitness for flight duties in the U.S. Military setting facilitated the detection of an otherwise occult LQTS in this asymptomatic young serviceman. Retrospectively, the LQTS was transiently unmasked during an episode of hypoglycemia. Hypoglycemia deserves more recognition as a potential cause of QT prolongation.