Biochemically, the AA/EPA Ratio is an index of two polyunsaturated fatty acids (PUFAs). Arachidonic acid (AA) is an omega-6 PUFA that serves as a substrate for eicosanoids often associated with inflammatory and platelet-activating signaling; EPA is an omega-3 PUFA that yields less inflammatory or pro-resolving mediators. The ratio thus functions as a shorthand for the relative abundance of pro- versus anti-inflammatory lipid substrates. Historically the AA/EPA relationship emerged from nutrition and inflammation research as a useful marker of systemic lipid signaling. AA and EPA compete for the same enzymatic pathways (cyclooxygenase and lipoxygenase), so their relative levels influence production of prostaglandins, leukotrienes, thromboxanes and related mediators that affect vascular tone, clotting tendencies, and immune cell behavior.

Higher AA/EPA ratios indicate relatively more AA versus EPA and are associated with greater potential for pro-inflammatory eicosanoid production, altered platelet reactivity, and vascular signaling patterns. Lower ratios indicate relatively more EPA versus AA and are associated with a lipid profile that favors less inflammatory or more pro-resolving mediator production. Interpretation should always be made alongside other Cardio Zoomer markers (inflammation, lipids, redox markers) and clinical context, since diet, metabolism, genetics, and recent events can shift fatty acid levels.

Cardio Zoomer includes the AA/EPA Ratio to assess lipid-derived inflammatory balance alongside hs-CRP, oxidized lipids, redox markers, and lipid subfractions. This ratio helps identify whether relative fatty-acid signaling may be contributing to vascular stress or inflammatory patterns, aiding clinicians in prioritizing which biological domains to explore further for personalized cardiovascular assessment.