Hospital clinicians should look out for coronary artery calcium (CAC) in non-contrast CT scans, regardless of referral indication or cardiovascular history, Australian cardiologists say.
The advice follows a retrospective study which found 61% of patients admitted to hospital for non-cardiac indications had visible CAC on non-gated CT, including 26% of patients with no known CV risk factors.
The 280 patients, who had no known history of coronary artery disease, were seen by Concord Repatriation General Hospital between 2011 and 2017.
Despite the lack of history, half the cohort experienced a major adverse cardiac event (MACE) within median 3.5 years’ follow-up, and half of those, within 18 months, University of Sydney cardiologist, Dr Christopher Yu and his team wrote in Open Heart.
Perhaps unsurprisingly, patients with visible CAC had a higher risk of MACE than those without (hazard ratio: 3.2 after adjusting for age, sex and CV risk factors). The finding persisted with both absolute CAC score and CAC score at or above the 50th percentile, the authors wrote.
“The fact that incidental visible CAC was independently predictive of MACE in an acute inpatient population, with half of the MACE events occurring within 18 months of discharge, indicates that intervention to reduce the risk of CV events may be temporally relevant in these populations,” they said.
However, greater efforts to report and assess CAC in these patients are needed to initiate preventative measures.
Incidental CAC “is known to be under-reported despite being in field of view [of non-contrast, non-gated CT scans] and having the potential ability to identify patients at risk who could benefit from risk-factor control and improve primary prevention of coronary events”, the authors wrote.
In fact, previous studies found up to 70% of outpatients and 63% of inpatients had incidentally visualised CAC.
“Traditionally, CAC has been identified using ECG-gated CT scan,” however, it is easily spotted on non-gated CT, Dr Yu and colleagues said, reporting “excellent interobserver reliability between two readers for both visual CAC and CAC scores”.
These simple visual assessments could help identify patients at increased risk of cardiac events and “facilitate commencement of primary prevention therapy”, Dr Yu and colleagues suggested.
“Future studies are needed to prospectively evaluate the prognostic role of incidentally identified CAC on non-gated CT scan of the chest among hospital inpatients.”