CCTA and 5-Year Risk of Myocardial Infarction

The New England Journal of Medicine

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• Patients with stable chest pain referred to a cardiology clinic for evaluation were randomized to receive standard care alone or standard care plus coronary computed tomographic angiography (CTA) to evaluate the effect of CTA on outcomes at 5 years. The rate of death from coronary heart disease or nonfatal myocardial infarction at 5 years was 2.3% in the CTA group vs 3.9% in the standard care group (P=.004). The rates of invasive coronary angiography and coronary revascularization were higher in the CTA group than in the standard care group in the first few months of the study, but there was no difference in the rates of coronary angiography or coronary revascularization over 5 years. More preventive and antianginal therapies were initiated in the CTA group than in the standard care group.

• The use of CTA in addition to usual care for patients with stable chest pain resulted in a significant reduction in death from coronary heart disease and nonfatal myocardial infarction at 5 years without increasing the rates of coronary angiography or coronary revascularization.

 Cardiology

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James E Udelson MD

David Newby and the SCOT-Heart investigators now report on the 5-year long-term follow-up data of their trial, a randomized comparison of diagnosis and management based on coronary CT angiography (CCTA) results vs standard of care (mostly exercise ECG). Their initial results published in 2015 in The Lancet showed better diagnostic certainty of angina/CAD for the patients randomized to CCTA.1The follow-up reported in that paper (average, 1.7 years) showed a trend toward fewer fatal or nonfatal myocardial infarctions (MI) in the CCTA group. In the current paper, with much longer follow-up, the authors report a 41% reduction in coronary heart disease death or nonfatal MI, driven entirely by the MI component. Importantly, in contrast to many previous studies, the group randomized to CCTA did not have an excess of catheterizations or revascularizations. This is the first study to show an impact on outcomes within the context of a randomized trial of testing strategies.

The magnitude of reduction in MI is quite large and, in fact, exceeds that observed in many therapeutic trials. Mechanisms or explanations can be challenging to discern from randomized comparisons of diagnostic testing. It is unlikely that revascularization played a role, as the incidence was balanced across the groups and, in general, revascularization does not reduce MI risk in stable outpatients. More likely is the better use of medications such as aspirin and statins in the CCTA group, as the presence of CAD—even nonobstructive CAD—would have been more obvious in a greater number of patients compared with exercise ECG.

Should all patients with suspected CAD now have a CCTA as their initial test, with the expectation of better outcomes? The SCOT-Heart data are in contrast to those of the PROMISE trial, a randomized comparison of anatomic imaging with CCTA vs functional testing as the initial approach in such patients.2 In PROMISE, over 2 years of follow-up, no difference in outcomes was observed. Although patients in both trials had CCTA-based management as one randomization arm, the difference in the trials was the comparator arm. In SCOT-Heart, the comparator was predominantly exercise ECG (only ~10% of patients had an imaging stress test, nuclear, or echo), whereas, in PROMISE, the comparator was predominantly stress imaging (only ~10% of patients had exercise ECG). One might interpret the totality of results from these two trials as there is now little role for exercise ECG in outpatients with suspected CAD, and stress imaging or CCTA should lead to similar outcomes.

Another general message is the importance of aggressive preventive measures when CAD is suggested so that the testing results can drive management well beyond simply being used for diagnosis of CAD.