Cardiovascular Effects of Energy Drinks in Familial Long QT Syndrome: A Randomized Cross-Over Study

Background Caffeinated energy drinks may trigger serious cardiac effects. The aim of this study was to determine the cardiovascular effects of caffeinated energy drink consumption in patients with familial long QT syndrome (LQTS). Methods and Results From 2014–2016, 24 LQTS patients aged 16–50 years were recruited to a randomized, double-blind, cross-over study of energy drink (ED) versus control (CD) with participants acting as their own controls (one week washout). The primary study outcome was an increase in corrected QT interval (QTc) by > 20ms. Secondary outcomes were changes in systolic and diastolic blood pressure. In 24 patients with LQTS (no dropout), mean age was 29 ± 9 years, 13/24 (54%) were female, and 8/24 (33%) were probands. Intention to treat analysis revealed no significant change in QTc with ED compared with CD (12 ± 28 ms vs 16 ± 27 ms, 3% vs 4%, p = 0.71). The systolic and diastolic blood pressure significantly increased with ED compared to CD (peak change 7 ± 16 mmHg vs 1 ± 16 mmHg, 6% vs 0.8%, p = 0.046 and 8 ± 10 vs 2 ± 9 mmHg, 11% vs 3% p = 0.01 respectively). These changes correlated with significant increases in serum caffeine (14.6 ± 11.3 vs 0.5 ± 0.1 μmol/L, p < 0.001) and serum taurine (737 ± 199 vs -59 ± 22 μmol/L, p < 0.001). There were three patients with dangerous QTc prolongation of ≥50ms following energy drink consumption. Conclusion Caffeinated energy drinks have significant haemodynamic effects in patients with LQTS, especifically an acute increase in blood pressure. Since dangerous QTc prolongation was seen in some LQTS patients, we recommend caution in young patients with LQTS consuming energy drinks.