Oikonomou EK, et al. - Given that the novel imaging biomarker—the perivascular fat attenuation index (FAI)—captures coronary inflammation by mapping spatial changes of perivascular fat attenuation on coronary computed tomography angiography (CTA), researchers investigated whether the perivascular FAI could predict clinical outcomes. Findings suggest that the perivascular FAI provides a quantitative measure of coronary inflammation that improves cardiac risk prognosis and restratification beyond what is seen with current state-of-the-art assessment in coronary CTA. Increased risk of cardiac mortality was evident with high perivascular FAI values (cutoff ≥–70.1 Hounsfield units). This suggests the utility of FAI in guiding early targeted primary prevention and intensive secondary prevention in patients.

Methods

• Researchers conducted the Cardiovascular RISk Prediction using Computed Tomography (CRISP-CT) study.
• Outcome data was gathered prospectively from two independent cohorts of consecutive patients undergoing coronary CTA in Erlangen, Germany (derivation cohort) and Cleveland, OH, US (validation cohort), for post-hoc analysis.
• Around the three major coronary arteries—the proximal right coronary artery, the left anterior descending artery, and the left circumflex artery—they performed perivascular fat attenuation mapping.
• In Cox regression models, adjusted for age, sex, cardiovascular risk factors, tube voltage, modified Duke coronary artery disease index, and number of coronary CTA-derived high-risk plaque features, the prognostic value of perivascular fat attenuation mapping for all-cause and cardiac mortality was assessed.

Results

• Between 2005 and 2009, coronary CTA was performed on 1,872 participants in the derivation cohort (median age 62 years [range 17–89]).
• Between 2008 and 2016, coronary CTA was performed on 2,040 patients in the validation cohort (median age 53 years [range 19–87]).
• The derivation cohort was followed-up for a median period of 72 months (range 51–109) vs 54 months (range 4–105) in the validation cohort.
• High perivascular FAI values around the proximal right coronary artery and left anterior descending artery (but not around the left circumflex artery) in both the cohorts were predictive of all-cause and cardiac mortality and had strong correlation with each other.
• Findings suggest the usefulness of the perivascular FAI measured around the right coronary artery as a representative biomarker of global coronary inflammation (for prediction of cardiac mortality, hazard ratio [HR] 2.15, 95% CI 1.33–3.48; p=0.0017 in the derivation cohort, and 2.06, 1.50–2.83; p < 0.0001 in the validation cohort).
• In the derivation cohort, they identified the optimum cutoff for the perivascular FAI of -70.1 Hounsfield units (HU) or higher, above which there is a steep increase in cardiac mortality (HR 9.04, 95% CI 3.35–24.40; p < 0.0001 for cardiac mortality; 2.55, 1.65–3.92; p < 0.0001 for all-cause mortality).
• The validation cohort supported this cutoff (HR 5.62, 95% CI 2.90–10.88; p < 0.0001 for cardiac mortality; 3.69, 2.26–6.02; p < 0.0001 for all-cause mortality).
• In both cohorts, perivascular FAI enhanced risk discrimination, leading to significant reclassification for all-cause and cardiac mortality.