Energy drinks can change heart rhythm

Energy drinks may increase blood pressure and disturb the heart's natural rhythm, U.S. researchers suggest. Lead author Sachin A. Shah of the University of the Pacific in Stockton, Calif., and Dr. Ian Riddock of the David Grant Medical Center at Travis Air Force Base, Calif., analyzed data from seven previously published studies concerning how energy drinks might impact heart health. In the first part of the pooled analysis, the researchers examined the QT interval -- a measure of the time between the start of the Q wave and the end of the T wave in the heart's electrical cycle -- of 93 people who had just consumed one to three cans of energy drinks. The study found the QT interval was 10 milliseconds longer for those who had consumed the energy drinks. The QT interval describes a segment of the heart's rhythm on an electrocardiogram; when prolonged, it can cause serious irregular heartbeats or sudden cardiac death, Shah said. "Doctors are generally concerned if patients experience an additional 30 milliseconds in their QT interval from baseline," Shah said in a statement. QT prolongation is associated with life-threatening arrhythmias, Riddock said. In addition, the study also found that the systolic blood pressure, the top number in a blood pressure reading, increased an average of 3.5 points in a pool of 132 participants. "The correlation between energy drinks and increased systolic blood pressure is convincing and concerning, and more studies are needed to assess the impact on the heart rhythm," Shah said. "Patients with high blood pressures or long QT syndrome should use caution and judgment before consuming an energy drink. Since energy drinks also contain caffeine, people who do not normally drink much caffeine might have an exaggerated increase in blood pressure." The findings were presented at the American Heart Association Scientific Sessions in New Orleans.