A study published on bmj.com finds that the electrocardiograms (ECGs) usually given to people with suspected angina have limited accuracy in their ability to predict the future likelihood of heart disease. Researchers from the London Chest Hospital emphasize that in order to improve the chances of detecting individuals at high risk of heart disease and heart attack, physicians must also use alternative tests that add predictive value to what is gathered from the clinical histories of patients.

About 2% of people in the UK experience angina – a common chest-pain symptom of coronary artery disease. To make sure that people with angina symptoms can be checked by a specialist within two weeks of referral, there are rapid-access chest pain clinics available for patients. Assessments usually consist of non-invasive ECGs during rest and exercise, but there is little data on the ability of these tests to predict future heart disease.

Further investigating this issue, the researchers studied 8,176 patients who had no earlier diagnosis of heart disease but had suspected angina. Doctors referred each patient to one of six chest pain clinics. A clinical assessment provided researchers with information on age, sex, ethnicity, duration of symptoms, description of chest pain, smoking status, history of hypertension, and medications. In addition, patients received an ECG while at rest.

Of the total sample, about 60% (4,848) of the patients had an exercise ECG performed and 1,422 of these also provided more “detailed” exercise ECG data. Patients were followed up for a median of 2.46 years.

The results demonstrated that patients who had a negative exercise ECG – indicating no heart problems – had some 47% of the coronary events that occurred in the follow-up period. The authors believe that this points to the limited accuracy in predicting the risk of future heart disease when using exercise ECGs. In addition, the researchers argue that a routine clinical assessment was able to provide almost the same amount of predictive information as an ECG when predicting future heart problems. Similarly, no additional benefit was provided by the resting ECG.

“Our study emphasises the importance of the clinical assessment for prognosis in patients with suspected angina,” conclude the authors. “The data show that the need to improve risk stratification cannot be met by the resting ECG whereas the incremental value of the exercise ECG is small. Alternative tests are needed but must be developed within cohorts from chest pain clinic because prognostic value depends on the population in which the test is applied.”

They add: “The limited incremental value of these widely applied tests emphasises the need for more effective methods of risk stratification in this group of patients.”

In an accompanying editorial, Beth Abramson (Director of St Michael’s Hospital in Toronto) writes that these findings point to “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.”

Incremental prognostic value of the exercise electrocardiogram in the initial assessment of patients with suspected angina: cohort study
Neha Sekhri, Gene S Feder, Cornelia Junghans, Sandra Eldridge, Athavan Umaipalan, Rashmi Madhu, Harry Hemingway, Adam D Timmis
BMJ (2008). 337:a2240
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Written by: Peter M Crosta