The post hoc analysis of the SCOT-HEART trial by Dr. Adamson MBChB, Ph.D. published in JAMA Cardiology showed that abnormal results of exercise electrocardiography (ECG) were strongly associated with coronary revascularization and increased risk of mortality from coronary heart disease. However, coronary computed tomography (CT) angiography was a more accurate predictor of 5-year coronary events compared with exercise ECG alone.
The exercise ECG has long been known to be the mainstay of evaluating chest pain in patients who are suspected to have coronary artery disease (CAD). However, this investigation provides limited sensitivity in detecting obstructive CAD especially in case of low pretest probability. Compared to exercise ECG, coronary CT angiography has been shown to have high sensitivity in the detection of obstructive CAD. The recent guidelines have supported a diminished role for exercise ECG in the assessment of obstructive CAD. However, the American College of Cardiology and American Heart Association guidelines recommended the exercise ECG test (non-invasive stress testing) as the initial diagnostic method for patients with intermediate pretest risk who presented with chest pain suspicious for CAD.
The SCOT-HEART ( Scottish Computed Tomography of the Heart) analysis was a multi-center, randomized clinical trial conducted in clinics across Scotland to compare the standard care and standard care plus coronary CT angiography in patients with a history of chest pain suspected for CAD. The post hoc analysis of this study was done among 3283 patients with a history of chest pain suspected for CAD who underwent the exercise ECG test. The participants were randomized in a 1:1 ratio into two groups to either receive standard care combined with coronary CT angiography or to receive standard care only. Death from coronary heart disease or nonfatal myocardial infarction at 5 years was considered as the primary endpoint of the study.
This study demonstrated that exercise ECG had a sensitivity of 39% and a specificity of 91% for
detecting any obstructive coronary artery disease in those who underwent subsequent coronary CT angiography. Also, abnormal results of exercise ECG test was associated with an increased risk of future myocardial infarction and coronary revascularization. The result of this study is also in line with the data from the original SCOT-HEART study. Interestingly, coronary CT angiography benefited the most those who had normal or inconclusive exercise ECG test. This study also demonstrated a robust association between abnormal exercise ECG test and a higher rate of coronary revascularization.
There are some limitations to consider while interpreting the results of this study. First, of the total participants of the SCOT-HEART study, 79% had a documented exercise ECG test and therefore included in the study which may cause the potential for selection bias. Second, patients with abnormal coronary CT angiography had a higher quality of care and received secondary preventive therapy which may result in a change in risk estimate of the post hoc analysis.
Finally, the results of this study demonstrated that coronary CT angiography may identify further undetected CAD and be more helpful in clinical decision making in comparison to the exercise ECG test.
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