Having mechanistic insights into early post-myocardial infarction (MI) is key to developing specific diagnostic and therapeutic strategies for early detection and intervention in heart failure with reduced ejection fraction (HFrEF). The study here aims to understand molecular event/s specific to early progression of HFrEF. We hypothesize that unbiased systemic screening of proteins and phosphoproteins in relevant left ventricular (LV) tissues can illuminate pathophysiological processes and underlying mechanisms implicated in HFrEF. We performed mass spectrometry-based multiplexed and label-free quantification for protein and phosphoprotein analysis respectively on LV tissues of normal (healthy pigs), normally perfused region (control) and viable myocardium surrounding the MI region (peri-infarcted) of HFrEF pig models. With over 3000 proteins quantified in the multiplexed experiments, network analysis of differentially-regulated proteins (mapped unto the human UniProt accession numbers) in the different LV regions highlighted extracellular matrix (ECM) organization as the main significant network involved in early HFrEF. ECM has been proposed to contribute to overall LV remodelling process in post-MI; and to further focus on the signalling events that may lead to this, we performed phosphoprotein pathway analysis based on confident differentially-regulated phosphosites in the different LV regions. With a total of over 14,000 phosphosites identified and mapped to over 3000 proteins, preliminary analyses revealed phosphorylation changes in cytoskeletal remodeling mediated by Rho GTPase effectors and PKA, and adrenergic signalling. Detailed network and pathway analyses of the phosphoproteins will be carried out to confirm this initial finding, which will subsequently shed light unto mechanistic details for further experimental validation. Understanding and scrutinizing the molecular events at both the protein and phosphorylation levels using this HFrEF pig LV tissues can potentially elucidate potential diagnostic and therapeutic target/s to reverse the underlying LV remodelling.