NEW YORK (Reuters Health) – Electrocardiography (ECG) helps predict cardiac events in asymptomatic older patients, a new report says. But an editorial argues that since one of the main effects is to reclassify patients to lower risk groups, the benefit doesn’t warrant routine screening.
The study and the editorial are both online today in the Journal of the American Medical Association.
Dr. Reto Auer at the University of California, San Francisco and colleagues analyzed data from the population-based Health ABC Study on 2,192 patients, ages 70 to 79, with no history of cardiovascular disease.
ECG done at the start of the study showed that 506 patients (23%) had major abnormalities and 276 (13%) had minor abnormalities, as classified by the Minnesota Code.
At a median of 8.2 years from their baseline ECG, 351 participants had coronary heart disease (CHD) events, including 96 who died as a result. These events included acute myocardial infarction, coronary death and hospitalization for angina or coronary revascularization, which investigators reported based on interviews, hospital record reviews, death certificates and other documents.
Both major and minor ECG abnormalities at baseline were associated with an increased risk of CHD. After adjusting for seven common cardiovascular risk factors, the hazard ratio for a CHD event was 1.35 for patients with a minor ECG abnormality at baseline and 1.51 for those with a major abnormality, compared to the risks in study subjects with a normal baseline ECG.
When the ECG results were added to traditional cardiovascular risk factors to predict risk of a CHD event, 13.6% of intermediate-risk participants were correctly reclassified, which the investigators reported to be an overall net reclassification improvement of 7.4%. Overall, 7.1% of patients were reclassified.
Patients who received at least one follow-up ECG four years into the study were also stratified into groups with baseline abnormalities only, persistent abnormalities, new-onset abnormalities, and no abnormalities.
Both new abnormalities and persistent abnormalities were associated with an increased risk of CHD events, with hazard ratios of 2.01 and 1.66, respectively.
The researchers call for randomized controlled trials to study whether ECG should be incorporated in routine screening of older adults
However, because the most significant effect of using ECG was to reclassify patients to a lower risk group, “Using the ECG in this way would not result in more patients receiving preventive treatment,” wrote Dr. Philip Greenland of Northwestern University Medical School in an editorial. “Rather, it likely would result in fewer patients receiving preventive therapies and possibly lowering costs of treatment and follow-up.”
Thus, although health-care costs might be lower, it is possible that fewer coronary heart disease events would be prevented by adopting the strategy, he believes.
“For the time being, in the absence of clear evidence of benefit and no clear implications for costs, the best advice is not to perform ECGs in asymptomatic patients, regardless of age,” Dr. Greenland wrote.