Abstract Funding Acknowledgements Type of funding sources: None. Background In advanced stages of dilated cardiomyopathy (DCM), both atrial function and left ventricle (LV) myocardial mechanics are blunted. Left atrial reservoir strain (LASr) is a sensitive parameter for left atrial (LA) function evaluation. Our study aimed to find a correlation between LASr depression and rotational parameters damage in patients with DCM, using 4-Dimensional automated LA and LV quantification. Methods We enrolled 75 patients with DCM and narrow QRS and 30 healthy volunteers. The evaluation consisted of clinical examination, laboratory tests, 12 leads electrocardiography. All participants underwent a complete transthoracic echocardiogram to determine cardiac structure and function according to the current guidelines. Measurement of LA and LV strain was performed using 4D Auto-quantification software. The study evaluated LASr by 4D Auto Atrial Quantification. 4D LV Quantification measured twist and torsion. Results 1. We divided the patients into two groups: 27 with DCM and atrial fibrillation (AF) and 48 with DCM and sinus rhythm (SR). 2. Mean values of LASr were 10.20 in patients with DCM and 30.36 in the healthy volunteers’ group. (P<0.0001). Rotational parameters were LV twist=1.66, LV torsion=0.44 in DCM patients, LV twist=10.1, and LV torsion=1,73 in the healthy group. (P<0.0001). In DCM patients with AF, mean values were lower ( LASr =9.52, LV twist=0.97, LV torsion=0.28, LV torsion=0.4) than in patients with SR (LASr=10.59, LVtwist=1.93, LV torsion=0.5) 3. A correlation was found between LASr and LV twist (r=-0.8), between LASr and torsion (r=-0.78), in patients with AF, and also in those with DCM and SR ( r=-0.74 for the twist, r=-0.73 for torsion). Conclusions 1. LASr reduction was related to rotational damage of the left ventricle in DCM patients. 2. LASr, LV twist, and LV torsion were lower in cases with AF. 3. LA function is a parameter of chronic increased LV filling pressure. The correlation between LASr decrease and anomalies of twist and torsion may suggest a link between increased LV filling pressure and rotational dysfunction in patients with dilated cardiomyopathy phenotype.