Abstract Body (Do not enter title and authors here): Introduction
Oxidized phospholipids (OxPL) are carried by apolipoprotein B-100-containing lipoproteins (OxPL-apoB) including lipoprotein(a) [Lp(a)]. Both OxPL-apoB and Lp(a) have been associated with calcific aortic valve disease (CAVD).

Aims
We aimed to evaluate the independent associations between OxPL-apoB, Lp(a) and the prevalence, incidence, and progression of CAVD.

Methods
OxPL-apoB and Lp(a) were evaluated in the Multi-Ethnic Study of Atherosclerosis (MESA) and a participant-level meta-analysis of four randomized trials of participants with established aortic stenosis (AS). In MESA, the association of OxPL-apoB and Lp(a) with aortic valve calcium (AVC) at baseline and 9.5 years was evaluated using multivariable ordinal regression models. In the meta-analysis, the association between OxPL-apoB and Lp(a) with AS progression (annualized change in peak aortic valve jet velocity (V_max)) was evaluated using multivariable linear regression models.

Results
In MESA, both OxPL-apoB and Lp(a) were independently associated with prevalent AVC (OR (95% CI) per SD: 1.19 (1.07-1.32) and 1.13 (1.01-1.27), respectively) with a significant interaction between the two (p<0.01). Both OxPL-apoB and Lp(a) were associated with incident AVC at 9.5 years when evaluated independently (interaction p<0.01). The OxPL-apoB*Lp(a) interaction demonstrated higher odds of prevalent and incident AVC for OxPL-apoB with increasing Lp(a) levels. Mediation analyses demonstrated that Lp(a) partially mediated the association between OxPL-apoB and AVC. In a 2x2 analysis, the greatest risk for both prevalent and incident AVC was observed when Lp(a) and OxPL-apoB were both above the 80^th percentile (Figure). In the meta-analysis, when analyzed separately, both OxPL-apoB and Lp(a) were independently associated with faster increase in V_max, but when evaluated together, only OxPL-apoB remained significant (ß 0.07, 95% CI 0.01-0.12, Figure).

Conclusions
OxPL-apoB is an independent predictor of the presence, incidence and progression of AVC and established AS, particularly in the setting of elevated Lp(a) levels and may represent a novel therapeutic target for CAVD.