Chloe Leach, 21, died Sept. 30 at the Sugarmill Club in Hull.
Dr. Ian Scott, who performed the post-mortem, said Leach had an unusually large heart, The Daily Telegraph reported. She had been diagnosed with epilepsy, and Scott said she suffered from QT Syndrome, abnormal electrical activity in the heart.
Leach had consumed four Red Bulls and had also been drinking a cocktail that contains vodka and some caffeine. Scott testified that the caffeine probably triggered her QT Syndrome.
Scott said he thought at first Leach might have been using drugs but testing found only her anti-epilepsy medication.
Leach was a social work student at the University of Lincoln's Hull campus.