People with borderline high QT interval in ECG should not consume energy drinks

Dr KK Aggarwal

A clinical trial reports that energy drinks can prolong QTC interval in ECG and raise blood pressure in volunteers

Packed with caffeine and ingredients like guarana, taurine, ginseng, and B vitamins, these drinks promise to boost concentration, improve physical performance, and reduce fatigue.

In the largest randomized, controlled clinical trial on the subject to date, researchers from the University of the Pacific in Stockton, CA, along with collaborators from other institutions, identify how energy drink consumption affects the heart.

For the study, published in the Journal of the American Heart Association, lead study author Sachin A. Shah, a professor of pharmacy practice at the University of the Pacific, enrolled 34 adults aged 18 to 40. After an overnight fast, the volunteers consumed two 16-ounce bottles of either one of two energy drinks or a placebo, which contained carbonated water, lime juice, and cherry flavoring. The study was double-blinded.

The researchers then measured the ECG and blood pressure readings every 30 minutes for a total of 4 hours and found a significant change in the QTC interval. A QTc interval of 450 milliseconds (ms) in men and 460 ms in women is considered the maximum for a healthy heart rhythm.

With QT interval propagation, a person’s risk of experiencing life-threatening arrhythmia and sudden cardiac death increases.

While consumption of the placebo drink caused a maximum change in QTc interval of an average of 11.9 ms, the two energy drinks resulted in average maximum changes of 17.9 ms and 19.6 ms. Importantly, the researchers saw significant changes in the QTc interval length up to 4 hours after the volunteers had consumed the energy drinks.

According to FDA QTc prolongation over 10 ms prompting further investigation.

The researchers also found an average maximum change of 3.5 mmHg in diastolic blood pressure and 4.6 to 6.1 mmHg in systolic blood pressure when the study participants had consumed the energy drinks.

Caffeine in the energy drinks may have contributed to the change in blood pressure, but only to some extent. Other ingredients, particularly taurine, could also play a role.

None of the participants experienced QTc intervals over 500 ms. Clinically, a QT/QTc interval over 500 ms or a change over 30 ms warrants careful monitoring.