Aims: Cardiomyopathy (CMP) with a reduced ejection fraction develops in a dose-28 dependent manner in one- third of subjects with a long-term history of heavy daily alcohol consumption. Ethanol alters heart transduction signals including excitation- contraction sarcomeric coupling, causing diastolic and systolic left-ventricular (LV) dysfunction. Titin is a giant structural sarcomeric filament macro protein involved in contractile heart function and contributes to cardiac myocyte elastic recoil, a key factor for diastolic LV filling. We evaluated whether titin expression is affected by chronic high-dose ethanol 35 consumption in alcoholic CMP. Methods and Results: We analyzed a total of 30 heart samples from human organ 37 donors: 20 from high alcohol consumers (10 without CMP and 10 with CMP) and 10 healthy controls. Patient evaluation comprised daily and lifetime ethanol consumption, chest X ray, 2-D echocardiography and LV histology. CMP was assessed by functional 40 and histological criteria. Titin activity was evaluated by specific immunohistochemical 41 (IHC) and transcript expression (rtPCR) assays. Titin IHC expression was clearly present in sarcomere areas of myocytes. Compared to healthy donors (82.58±3.36), alcohol consumers showed a significantly lower cardiac titin expression (71.29±3.16; 13.67±3.83% decrease; p=0.04), being significantly lower in alcohol consumers with CMP (62.31±4.18; 24.54±5.06% decrease, p<0.0009), compared to both their counter-parts without CMP (80.27±2.62; 2.80±3.17% decrease 47 vs. controls; p<0.0030 vs. alcoholic CMP). Titin transcript levels confirmed similar patterns of expression.