A population-based study involving nearly 15,000 healthy adults shows that electrocardiography identifies people who may have up to a 5-fold higher risk for death from cardiovascular disease, according to an article in the February 18th issue of the Journal of the American College of Cardiology.

"It's really such a simple, inexpensive and noninvasive tool. I think electrocardiograms are not being used enough in the general population. They are routinely used for patients who go to cardiologists, but what this tells us is that also in the general population or people with risk factors, that the electrocardiogram is informative," said Jacqueline M. Dekker, PhD, lead author of the study.

Dekker, who is Dutch, worked with American colleagues to analyze data from the Atherosclerosis Risk In Communities (ARIC) study, which enrolled healthy individuals age 45 to 64 years who lived in 4 widespread American communities. The study population included 14,548 men and women who were white or African American.

The researchers focused on measurements of the QT interval. Elongated QT intervals are one sign of heart abnormalities linked with sudden death, but the ECG abnormality is also associated with risk for developing a variety of heart diseases.

In the current study, prolonged QT interval was a strong predictor of both new heart disease and death from cardiovascular disease. People in the top 10 percent of QT interval duration were twice as likely to develop coronary heart disease and five times as likely to die of cardiovascular disease as those in the lower 90 percent. The link was stronger in African-American participants than in whites.

"It's intriguing that we found this statistically significant difference between blacks and whites, but I'd say we need to see it again in another study because it could be chance. The relative risks that we saw in the white population were lower than I had seen in previous studies. If we had seen the same relative risks in the white population as seen in those earlier studies, then probably it wouldn't have been a significant difference," Dekker noted.

The study addressed questions about the best ways to measure QT intervals and how to correct measurements for the effect of different heart rates. The researchers found that a widely available computer program (NOVACODE) that automatically calculates the QT interval produced results that were just as useful as those from manual measurements. The results also supported a widely used formula (Bazett) for making heart rate corrections.

Dekker said the performance of automated measurement software in the current study means that it should be relatively simple and inexpensive for general practitioners to add electrocardiograms to their screening protocols.

In an editorial in the journal, Peter M. Okin, MD, wrote that this is an important study and that the findings "strongly support the value of careful, quantitative electrocardiography in the application of QTc (QT interval corrected for heart rate) prolongation for risk stratification in the general population."

Okin highlighted the large size and diversity of the study population: "One of the great strengths of this study is that there were adequate numbers of black and white men and women to establish that the predictive value of a prolonged QTc is independent of race and gender."

Bente Brendorp, MD, PhD, who was not part of the research team, commented that this study provides new information on using the QT interval to predict heart disease and death risk in the general population. Brendorp also noted "As mortality rate is rather low in population studies (compared with studies including patients with established cardiovascular disease), a longer follow-up period probably would have strengthened the results of the study."

Brendorp also suggested that more study is needed on the question of when computerized QT measurements can be substituted for manual measurement of electrocardiograms.