Is routine cardiac CT useful in suspected ACS?

Cardiac CT angiography (CCTA) in the ED does not reduce the duration or cost of an in-hospital stay in patients with a suspected ACS, research shows.

A UK study randomised 250 adults presenting to the ED in 2019 with suspected ACS to standard of care plus CCTA or standard of care alone. Patients had intermediate initial high-sensitivity cardiac troponin (hs-cTnT) concentrations 5 – 50 ng/L and were without ischaemic changes on ECG.

The study, published in Heart [link here], found no differences between the treatment arms in the primary outcome of mean hospital length of stay (7.53 v 8.14 hours; p=0.13).

The finding was similar for those patients with ≥25% stenoses (8.8 v 9.2 hours; p= 0.609) although in patients with <25% stenoses, LOS was significantly shorter in the standard of care plus CCTA arm than standard of care alone (6.64 v 7.5 hours; p=0.021).

The study also found the mean cost of inpatient hospital stay was not significantly different between the two treatment arms (£1285 vs £1108; p=0.68).

“In our study, healthcare costs were not higher with a CCTA strategy than with SOC, which in turn suggests that the increased cost of CCTA must be offset by other saving, likely reflecting the expedited discharge of patients found to have little or no atheroma,” it said.

However there were significantly more referrals for cardiology outpatient clinic review and cardiac CT-related outpatient referrals in the SOC arm than the CCTA+SOC arm (60 vs 40; p=0.01).

There was similar use of invasive coronary angiography (5.6% v 4.8%; p>0.99) and coronary revascularisation (4.0% v 3.2%; p>0.99) while post-discharge 12-month MACE follow-up data were also similar in both arms (7 v 8; p=0.78).

The investigators suggested two possible reasons why CCTA may have failed to impact on the main outcome events.

“First, while the finding of little or no CAD gave clinicians the confidence to discharge patients early (as reflected in shorter LOS when the CCTA result was available compared with SOC in these patients), the converse was also true–the finding of at least mild CAD appeared to compound the ambiguity that had arisen from the finding of intermediate initial hs-cTnT concentrations, leading to neither expedited nor delayed discharge,” they said.

“The second reason may be that the protocol left the interpretation of the CCTA result and subsequent management to the discretion of the clinicians responsible for these patients. While this is reflective of real-world practice, it may have resulted in a lower rate of discharge than might have been achieved with a more didactic protocol.”

“Our findings complement recent RCTs that have evaluated different cohorts of patients with ACS and together suggest that CCTA may not be useful when managing suspected ACS,” they concluded.

However an Editorial in the journal [link here] said the study revealed no downside to CCTA and a number of plausible benefits.

“The most obvious advantage of cardiac CT is that it can provide reassurance given its high negative predictive value.”

“We believe this trial complements existing data showing CT to be a safe and effective way to identify coronary artery disease in acute chest pain syndromes. What remains to be determined is the optimal approach to patient selection for CT and the best management strategy for its diagnostic findings.”

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