ECGs have limited predictive value for heart disease diagnosis

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Electrocardiogram (ECG) tests commonly given to people with suspected angina to predict the likelihood future of heart disease have limited accuracy, according to a study published online Nov. 13 in the British Medical Journal.

The authors suggested that alternative tests which add predictive value to that obtained from the patient's clinical history are needed to improve the chances of detecting people at higher risk of future heart disease and heart attacks.

Researchers from the London Chest Hospital studied 8,176 patients with suspected angina and no prior diagnosis of heart disease, referred by their doctor to one chest pain at six clinics.

All the patients were clinically assessed (data such as age, sex, ethnicity, duration of symptoms, description of chest pain, smoking status, history of hypertension and medications), as well as having an ECG done while resting.

Sixty percent of the patients had an exercise ECG performed and were split into two groups, one comprising 4 848 patients with a ‘summary’ result recorded and the other with 1,422 patients who additionally had ‘detailed’ exercise ECG data recorded. All patients were followed up for the next few years.

The researchers found that 47 percent of all coronary events that happened to people during the follow-up period occurred in patients who had a negative exercise ECG that did not indicate any heart problems. They found that a routine clinical assessment provided almost as much predictive information about future heart problems as having an ECG. The resting ECG showed no additional benefit to the information obtained from the history and exam.

The authors concluded that ECG tests are of limited value in identifying future coronary problems in patients with suspected angina and no prior diagnosis of heart disease, adding little to routine clinical assessment including the patient's history and an exam.

In an accompanying editorial, Beth Abramson, MD, director of St Michael's Hospital in Toronto, said that the findings are a reminder of “the importance of taking a detailed history and making a thorough physical examination, and that additional information from the ECG is helpful in some patients but does not predict risk in everyone.”