November 30, 2009

Exercise-linked heart irregularity no risk to healthy older adults

Healthy older adults free of heart disease need not fear that bouts of rapid irregular heartbeats brought on by vigorous exercise might increase short- or long-term risk of dying or having a heart attack, according to a report by heart experts at Johns Hopkins and the National Institute on Aging.

Researchers say that such fears surfaced after previous studies found that episodes of errant heart rhythms, more formally known as nonsustained ventricular tachycardia, more than double the chance of sudden death in people who have already suffered a heart attack.

In a study presented Nov. 16 at the American Heart Association’s annual Scientific Sessions in Orlando, Fla., the research team monitored for on average 12 years the medical records of 2,234 initially healthy men and women, ages 21 to 96, participating in the NIA’s Baltimore Longitudinal Study of Aging. In adults with no earlier signs of heart disease, researchers found no adverse effects resulting from brief episodes of exercise-induced ventricular tachycardia.

In the study, each volunteer participant had at least one exercise stress test performed before 2001. The test assesses the heart’s pumping ability, requiring participants, whose average age at testing was 52, to walk or jog on a treadmill at increasing speeds and inclines until they felt exhausted, about 10 minutes for most.

Eighty-one (roughly 4 percent) of the mostly older participants—65 of them men and 16 women—experienced short periods of rapid irregular heartbeats during exercise, at a rate hovering around 175 beats per minute and typically lasting from three to six heartbeats.

Researchers said that overall death rates were higher in the tachycardia group than in the nontachycardia group (at 29 percent and 16 percent, respectively). But when they adjusted their analysis to account for differences in age, gender and those who developed known risk factors for heart disease early on, they found no measurable increased risk between the tachycardia and nontachycardia groups of overall death, death from heart disease or suffering a heart attack.

Lead study investigator and cardiologist Joseph Marine said that the study results should “provide reassurance” among apparently healthy middle-age and older people that such short episodes of ventricular tachycardia provoked on exercise testing do not have long-term consequences to health.

“So long as a medical examination shows no underlying heart disease or other serious health condition, then people should continue to live a normal lifestyle, including a return to exercise after clearance from their physician,” said Marine, an associate professor at the Johns Hopkins School of Medicine and its Heart and Vascular Institute. “Our results suggest that brief, nonsustained ventricular arrhythmia during exercise testing should, generally, not cause undue alarm in patients or physicians.”

When suspicious about heart disease, care providers should investigate further for any signs of ischemia, arterial blockages, heart muscle disease or inherited risk of arrhythmia, Marine said. But if everything checks out negative for heart disease, then restrictions on exercise are not needed. Indeed, he said, regular exercise has long been known to cut down on the risk of developing heart disease.

Study co-investigator and Johns Hopkins cardiologist Gary Gerstenblith added that the latest study results should help physicians better triage which patients to treat after incidents of exercise-induced tachycardia.

“Most people who experience erratic heart rhythms during exercise and who have no underlying heart condition can be left alone; they do not need to be treated, and they can continue to exercise,” said Gerstenblith, a professor in the Johns Hopkins School of Medicine. “However, patients with erratic heartbeats who are later found to have underlying coronary heart disease should refrain from arduous exercise until consulting with their physician about treatment with drugs and/or an implantable device to improve their heart function and to decrease the risk of dying from a potentially fatal heart rhythm.”

Marine said that the next steps in the team’s research are to determine whether other arrhythmias brought on by exercise, such as atrial tachycardia, have any impact on future death or heart-attack rates or lead to other arrhythmias.

Funding support for the study was provided by the NIA.

In addition to Marine and Gerstenblith, researchers involved in the study were Grant Chow, of Johns Hopkins; Veena Shetty, of the Medstar Research Institute; Jeanette Wright and Samer Najjar, both of the NIA; and senior investigator Jerome Fleg, of the National Heart, Lung and Blood Institute.

Related Web sites

Joseph Marine

Gary Gerstenblith

Baltimore Longitudinal Study of Aging