Objectives: The aim of the this study was to investigatethe relationship between the degree of mitral regurgitation(MR), left ventricular (LV) dysfunction determined bystrain (S)/strain rate (SR) imaging and plasma brain natriureticpeptide (BNP) levels.Materials and methods: This is an observational crosssectionalstudy which included 31 consecutive patients(15[48.4%] male) who had applied to our outpatient clinicsand diagnosed as mitral regurgitation and 25 (12[48.0%] male) healthy persons as control subjects. Themitral regurgitation patients were divided into two groups:those with moderate MR (n=14[45.2%]) and those withsevere MR (n=17[54.8%]), and maximum strain / strainrate measurements of left ventricular wall segments andplasma brain natriuretic peptide levels were determined inthese two groups and controls.Results: S/SR values of all wall segments of left ventriclewere found to be decreased in patient with severe MRwhen compared with the control subjects and patientswith moderate MR (p<0.001).Conclusions: Although left ventricle functions with conventionalechocardiography in patients with mitral valveregurgitation were normal, subclinic deteriorations ofleft ventricle were detected in patients with severe mitralvalve regurgitation. J Clin Exp Invest 2012; 3 (4): 451-456Key words: strain/strain rate, echocardiography, mitralregurgitation, left ventricular functions