Both major and minor abnormalities on electrocardiogram signaled an increased risk of coronary heart disease within 8 years among elderly people in the general population, according to a report in the April 11 issue of JAMA.
Adding ECG abnormalities to traditional cardiovascular risk factors in a risk prediction model modestly but significantly improved the prediction of coronary heart disease events, said Dr. Reto Auer of the department of epidemiology and biostatistics, University of California, San Francisco, and associates.
To date, few studies have examined whether ECG abnormalities could improve risk prediction in older adults, and none have adequately adjusted for the presence of traditional cardiovascular risk factors. Predicting CHD with traditional risk factors is less accurate in the elderly than in other patient populations, the investigators noted.
Dr. Auer and colleagues examined the issue using data from the Health, Aging, and Body Composition (Health ABC) Study, a population-based cohort study of community-dwelling men and women who were aged 70-79 years at baseline in 1997-1998. For their secondary analysis of data from this study, the investigators assessed a random sample of 2,192 subjects living near Pittsburgh or Memphis, Tenn., who had no evidence of cardiovascular disease and who underwent standard ECG at baseline and again 4 years later.
The mean age of the study subjects was 73.5 years. Just over half were women, and 41% were black.
Major ECG abnormalities were defined as Q-QS wave abnormalities, left ventricular hypertrophy, Wolff-Parkinson-White syndrome, complete bundle branch block or intraventricular block, atrial fibrillation, atrial flutter, or major ST-T changes. Minor ECG abnormalities were defined as minor ST-T changes.
A total of 506 subjects (23%) showed major and 276 (13%) showed minor ECG abnormalities at baseline, for an overall incidence of 36%.
During a median follow-up of 8 years, 351 study subjects had CHD events, including 96 CHD deaths, 101 acute myocardial infarctions, and 154 hospitalizations for angina or coronary revascularization. There also were 506 deaths from non-CHD causes.
The rate of CHD events was 17.2 per 1,000 person-years among subjects with no ECG abnormalities. This was significantly lower than the rate among subjects with minor ECG abnormalities (29.3 per 1,000 person-years) and the rate among those with major ECG abnormalities (31.6 per 1,000 person-years), said Dr. Auer, who is also of the University of Lausanne (Switzerland), and associates.
After the data were adjusted to account for risk factors such as subject age, sex, total and HDL cholesterol levels, blood pressure, smoking status, and diabetes status, the hazard ratio for CHD events for subjects with minor ECG abnormalities was 1.35 and the hazard ratio for CHD events for subjects with major ECG abnormalities was 1.51, compared with subjects who had no ECG abnormalities at baseline, the researchers said (JAMA 2012;307:1497-1505).
The findings were similar when the data were analyzed by race. In both black and white participants, major and minor ECG abnormalities at baseline were associated with CHD events during follow-up.
Adding ECG data to a prediction model for the subgroup of subjects at intermediate cardiovascular risk resulted in reclassifying 8% of them as high-risk and 6% of them as low-risk.
A total of 1,670 study participants underwent a second ECG at 4 years; 416 of them had a persistent ECG abnormality and 208 had a new ECG abnormality. During a median follow-up of 6.4 years, 185 of these subjects had CHD events, including 57 who died from CHD.
Both new and persistent ECG abnormalities at 4 years were associated with an increased risk of CHD events. The absolute risk was 33.2 per 1,000 person-years in those with new abnormalities and 27.8 per 1,000 person-years in those with persistent ECG abnormalities.
The findings indicate that ECG screening may be useful in the elderly population – especially in view of the fact that 36% of the study population was found to have ECG abnormalities at baseline, a rate much higher than that in younger adults. ECG screening is already known to be safe, low cost, and widely available, Dr. Auer and associates said.
However, the benefit of such screening was small in this study, and these results must be validated in other cohorts as well as in prospective clinical trials, they added.
This study was supported by the National Institute on Aging, the National Institutes of Health, the National Institute of Nursing Research, the Swiss National Science Foundation, and the Swiss Heart Foundation. Dr. Auer’s associates reported ties to Amgen, Bayer, Boston Scientific, Cardiomems, Corthera, GE Healthcare, Medtronic, Novartis, Ono Pharmaceutical, Takeda, Trevena, and World Heart.