A new generation of faster, wilder roller coasters can make the heart race up to 155 beats a minute and spur dangerous changes to heart rhythm in some people, according to a study released today.
One volunteer in the study, which took place on the Holiday Park Expedition GeForce roller coaster in Germany, experienced an episode of atrial fibrillation, and another experienced ventricular tachycardia -- both problematic changes in heart rhythm. The two volunteers recovered after a few seconds.
The changes could have been fatal if the participants had underlying cardiac conditions or if the irregularities had lasted longer, said Dr. Dariusch Haghi, a coauthor of the study and a cardiologist at University Hospital of Mannheim in Germany.
"I don't think healthy people should be worried at all," said Haghi, whose study was published in the Journal of the American Medical Assn. "If people have a serious heart condition or if they are unaware of their heart condition, this might be worrisome."
Dr. Jon Resar, a cardiologist at Johns Hopkins University in Baltimore, who was not involved in the study, likened the cardiovascular changes to effects seen in "very vigorous exercise."
"This is quite a stressor on the cardiovascular system," he said. "It's real brief in duration, but it could certainly precipitate. . . heart pain in individuals with blockages in coronary arteries."
David Mandt, a spokesman for the Alexandria, Va.-based International Assn. of Amusement Parks and Attractions, said the study reinforced the warnings that amusement parks have posted at most roller coasters for years: People with heart conditions and high blood pressure should not ride.
"We go to great lengths to make sure patrons understand that they need to be healthy to ride and experience attractions," said Mandt, whose group was not involved in the study.
Roller coasters rarely spur fatal cardiac events. Researchers with the U.S. Centers for Disease Control and Prevention logged seven such deaths from 1994 to 2004.
A smaller 1989 study of a tamer roller coaster found that riders' heart rates increased on average to 154 beats a minute, but it found no evidence of heart rhythm problems. The normal resting heart rate for an adult ranges from 60 to 90 beats.
Haghi and his colleagues wanted to update that study because newer roller coasters travel faster and tug on riders' bodies with more gravitational force.
The roller coaster in Haghi's study reached a top speed of about 75 mph and accelerated to 4.5 times the force of gravity during a four-second free fall. U.S. versions of this German roller coaster are the Superman Rides of Steel, according to the online Roller Coaster Database.
The study looked at 55 healthy volunteers. The largest increase in heart rate occurred during the first 30 seconds of the ascent, even though the speed was low, underscoring the key role of emotion and anticipation in quickening the pulse, Haghi said. During the ride, heart rate increased from an average of 89 beats a minute to 155.
Researchers measured blood pressure before and after the ride. They found an elevation equivalent to mild hypertension, but it did not present a problem for healthy individuals, Haghi said. Almost half the participants also saw an increase in the variability of their heart pattern, known as sinus arrhythmia. The change was simply a physiological response to excitement, Haghi said, and riders were not even aware of it.
The study may not reveal the true prevalence of cardiovascular problems prompted by roller coasters because it looked at only a small group of riders, cautioned Dr. Ori Ben-Yehuda, who directs the coronary care unit at UC San Diego Medical Center and was not involved in the study.
Ben-Yehuda said the levels of stress recorded in the study were probably less than some other popular activities.
"I have yet to see a patient come in with a heart attack after a roller coaster ride," he said. "We had three heart attacks during the last Rock 'n' Roll Marathon."