Results document low radiation from cardiac CT angiography
MUNICH – The perivascular fat attenuation index, a new measure of coronary plaque inflammation using data collected by a conventional coronary CT scan, identified an elevated risk for future cardiovascular death that was independent of standard risk factors in both derivation and validation studies with prospective data from more than 3,900 patients.
Dr. Charalambos Antoniades
Patients with a high fat attenuation index (FAI) in the perivascular fat surrounding their right coronary artery had a five- to ninefold higher risk of cardiac mortality during 4-6 years of follow-up than did those with lower scores, after adjustment for conventional risk factors and standard findings from the coronary CT, Charalambos Antoniades, MD, said at the annual congress of the European Society of Cardiology.
The FAI is a “powerful, novel technology for cardiovascular disease risk stratification. It has striking prognostic value for cardiac death and nonfatal MI over and above other risk scores and state-of-the-art interpretation of coronary CT angiography,” said Dr. Antoniades, professor of cardiovascular medicine at the University of Oxford (England). He also highlighted that the data he reported suggested a protective effect in patients with a high FAI who received treatment with aspirin or a statin, and he suggested that FAI might be a way to better target an anti-inflammatory agent such as canakinumab (Ilaris), which showed cardiovascular protective effects in the CANTOS trial (N Engl J Med. 2017 Sep 21;377[12]:1119-31).
Another key feature of the FAI analysis is that it uses data collected by “any standard” coronary CT angiogram, Dr. Antoniades said. He is a founder of, shareholder in, and chief scientific officer of Caristo Diagnostics, the company developing the software that uses coronary CT data to calculate the FAI.
Dr. Antoniades and his associates derived the FAI using data collected from 1,872 patients who underwent planned coronary CT angiography at a clinic in Erlangen, Germany, during 2005-2009. The researchers correlated FAI scores with cardiovascular disease outcomes during a median follow-up of 72 months. They then validated the FAI using data collected from 2,040 patients who underwent a planned coronary CT exam at the Cleveland Clinic during 2008-2016 and then had a median follow-up of 54 months. The researchers called this overall post-hoc analysis of prospectively collected CT and outcomes data the Cardiovascular Risk Prediction using Computed Tomography (CRISP-CT) study.
Using the derivation data, FAI measurements taken from fat around the proximal right coronary artery that met or exceeded the specified cutoff value of –70.1 Hounsfield units were tied to a 9.04-fold greater rate of cardiac death during follow-up, compared with patients with a lower FAI, and after adjustment for several demographic, clinical, and CT-angiography variables. When the researchers ran this analysis using data from the validation patients and the same cutoff value they found that an elevated FAI linked with a 5.6-fold higher rate of cardiac death. Concurrently with Dr. Antoniades’ talk the results appeared in an online article that was later published (Lancet. 2018 Sep 15;392[10151]:929-39).
Calculating a patient’s FAI offers the prospect for “better use of CT information,” Dr. Antoniades said during the discussion of his report. After a coronary CT scan and conventional data processing, about half the patients have no finding that warrants intervention, but about 10% of these patients actually have an inflamed coronary plaque that is at high risk for rupture that could trigger a cardiac event. The FAI provides a way to use coronary CT angiography to identify these at-risk patients, he explained.