Heart failure with preserved ejection fraction (HFpEF) is an increasingly common form of heart failure (HF) that is best understood as a systemic, multiorgan syndrome rather than a disease of left-ventricular filling alone. This review has three specific aims: first, to synthesize genetic and molecular pathways that are most relevant to non-ischemic HFpEF; second, to distinguish HFpEF-enriched mechanisms from evidence extrapolated from ischemic cardiomyopathy or HFrEF; and third, to consider translational implications for populations with high consanguinity, including the Kingdom of Saudi Arabia. The available evidence indicates that chronic inflammatory signaling involving CCL2, CCL5, TLR3, PTGS2/COX-2, IL-6/JAK/STAT3, NF-kB, and NLRP3 acts upstream of endothelial dysfunction, nitric-oxide/cGMP/PKG impairment, mitochondrial reactive oxygen species generation, and fibroblast activation. Extracellular-matrix regulators including ASPN, COL1A1, and MMP2 then amplify collagen deposition and myocardial stiffness, whereas mitochondrial genes and proteins such as ATP5C1 contribute to impaired oxidative phosphorylation, reduced ATP reserve, defective fatty-acid oxidation, and blunted mitophagy. Protein-quality-control pathways involving HSP90AA1, CCT2/CCT5, PSMA3, and stress-responsive STAT3 further link metabolic stress to proteotoxic injury. Epigenetic mechanisms, including DNA methylation and microRNAs such as miR-155, miR-1297, and miR-4649-3p, add a regulatory layer that may improve risk stratification but remains insufficiently validated for routine clinical use. In high-consanguinity settings, recessive cardiomyopathy variants can cluster in families and contribute to earlier NIHF presentations; however, population-level HFpEF-specific variant frequencies remain limited, and findings from HFrEF or dilated cardiomyopathy should be interpreted as candidate pathway evidence rather than definitive HFpEF markers. Translationally, SGLT2 inhibitors, mineralocorticoid-receptor antagonism, biomarker panels, and structured genetic evaluation provide the most clinically actionable bridge from molecular mechanisms to precision HFpEF care.
