Abstract Body (Do not enter title and authors here):
Introduction:
Rates of progression of atherosclerosis have been derived from populations with established atherosclerotic cardiovascular disease and on plaque modifying therapies. However, the rate of atherosclerosis progression in populations with no history of MACE, risk factors or risk modifying interventions is not known. The aim of this study is to determine the rate of progression in healthy populations on serial CCTA.

Aim:
To determine whether in this population, the rates of progression can be classified in slow, intermediate, and rapid.

Methods:
NATURE-CT retrospectively selected 205 participants from two sites in Los Angeles. Subjects underwent at least two CCTA scans, the initial scan showing CAC ≤100, absence of MACE, not placed on lipid modifying therapy in the first and last scan, and at least 2 years apart. Patients with diabetes, familial hypercholesterolemia or chronic kidney disease were excluded. FDA cleared automated software Cleerly Labs (Cleerly.Inc, NY, NY) which quantified percent atheroma volume PAV% from CCTA. Annual change in PAV% is presented by tertile in this lipid-modifying naïve cohort to understand slow, intermediate and rapid plaque progression rates among subjects.
Results:
There were 205 subjects with a mean age of 54.9±10.2 years and 72% (148) were male. Average time between serial CCTA scans was 4.9±2.2 years. Annual change in PAV% was less than 0.075% in the first tertile (mild progression), between 0.075% and 0.275% with intermediate progression (2nd tertile) and those with greater than 0.275% in a rapid group (3rd tertile). The median and interquartile range [IQR] for annualized change in PAV% for slow progression was 0.03 (0.0, 0.05), intermediate progression was 0.17 (0.12, 0.20) and 0.46 (0.35, 0.67) for rapid progressors. The moderate and rapidly progressing subjects were more likely to be male, have higher BMI, triglyceride levels, and baseline plaque. Rapid progressors were more likely to have LAP present.

Conclusions:
Rates of atherosclerosis progression can be classified in slow, intermediate, and rapid progressors, based on a population with low plaque burden in the first scan, no lipid-modifying interventions, and no events. The presence of low-attenuation plaque correlates rapid progression of atherosclerosis and may offer a justification for plaque directed treatment if confirmed with further studies.