Computed Coronary Angiography (CTCA) has been advocated as a useful adjunct in the investigation of acute coronary syndromes (ACS) in the ED. Although we’ve made huge progress in the diagnosis of ACS through the use of biomarkers, notably high sensitivity troponins, we still don’t have a complete picture. Partly this is because we cannot see the anatomical lesions that might be contributing to chest pain/angina. CTCA in low/intermediate risk patients offers the potential to risk stratify patients and to perhaps identify those who are most likely to benefit from further interventions such as angiography and stenting.
This pathophysiological argument is quite strong and has led to the widespread adoption of CTCA in some health economies to further classify patients. On the one hand identifying those who may benefit from intervention, and on the other perhaps letting other patient go home early and to avoid any unnecessary interventions.
This trial was designed to assess whether CTCA will improve healthcare outcomes in patients with suspected ACS in the ED. The abstract is below, but as always we recommend you review the paper yourself.
A brief declaration from me on this one too. I was a member of the data monitoring committee for the project.
What type of study is this?
It’s a randomised controlled trial which is appropriate for an intervention. Interestingly, this is an RCT of a diagnostic test which is something we don’t see as often as we should. It would have been possible to test CTCA against a blinded gold standard diagnosis, but that’s not really what we want here. This paper is much more focused on patient outcomes and therefore an RCT approach is better.
Tell me about the patients.
This trial was conducted in 37 UK emergency departments. They recruited adult patients with symptoms of suspected ACS or those who had a provisional diagnosis of ACS. They also had to have one or more of previous coronary heart disease, raised levels of cardiac troponin, or abnormal electrocardiogram (ECG).
What did they do?
Patients were randomised between early CTCA or no CTCA planned. CTCAs were conducted on 64 slice scanners. Patients were then followed up for one year. Early CTCA was defined as within 72 hours of admission.
What about the outcomes?
The primary endpoint was time to the first event of all cause death or subsequent myocardial infarction following stent insertion at one year. Myocardial infarction was defined according to the 2012 universal definition of myocardial infarction. Key secondary endpoints were cause of death (coronary heart disease or cardiovascular death) and subsequent myocardial infarction.
Tell me the results
The trial recruited 1749 patients. Of those who received an early CTCA the primary outcome occurred in 5.8% of patients vs. 6.1% in the standard care arm. This was neither clinically nor statistically significant leading the authors to conclude that there was little evidence to support the routine use of CTCA in these patients.
In secondary outcomes there was a small reduction in the number of patients undergoing angiography in the CTCA group and a sightly shorter length of stay in hospital. However, there was no difference in the rates of coronary revascularisation.
So should we abandon CTCA?
The trial has some limitations as does every trial. The open nature of the interventions could introduce bias, and the changes to sample size (as a result of an initial overestimate of event rates) will also be noted as concerns. It is also interesting to look at the number of patients screened (16193) vs. the number recruited (1749) indicating that this is quite a subgroup of patients presenting with potential ACS in our departments. The number of patients who didn’t receive CTCA within 72 hours when they should have, or did receive a CTCA within 30 days when in the standard of care group is also quite high (9.6%), although reflective of real world practice (and therefore perhaps this has more external validity).
Some will argue that the reduced rate of invasive interventions is a reason to continue with CTCA and I can see how this might be used in some patients, but as a routine intervention for this quite large cohort of patients presenting to emergency departments the authors conclusions seem valid.
Clinical Bottom Line
The findings do not support the routine use of early CT coronary angiography in all intermediate risk patients with acute chest pain
Early computed tomography coronary angiography in patients with suspected acute coronary syndrome: randomised controlled trial https://pubmed.ncbi.nlm.nih.gov/34588162/
Troponin posts on St Emlyn’s https://www.stemlynsblog.org/?s=troponin