Abstract Student ID：N9816002 Title of thesis：The Differences between Outflow Volume of Left and Right Ventricle in Maltese Breed Dogs with Mitral Regurgitation Total page：75 Name of Institute: Graduate Institute of Department of Veterinary Medicine, National Pingtung University of Science and Technology Graduate date：June, 2012 Degree Conferred：Master Name of student：Shih-Yung Yeh Adviser：Chiang-Hua Chiang The contents of abstract in this thesis： Mitral regurgitation is the most common acquired valvular heart disease in the dog. Most previous studies assessed the structure and function of valves on Doppler echocardiographic examination in mitral regurgitation, and they seldom offered the information about the differences of outflow blood between the left and right ventricles. Clinically, Maltese is the most common species with mitral regurgitation so this study collects 81 Malteses for assessment, including the control group (n = 23) and the experimental group (n = 58). According to the clinical signs and the value of physical examination of New York Heart Association (NYHA), the experimental group (n = 58) with mitral regurgitation can be classified to grade Ⅰ (n = 15), grade Ⅱ (n = 17), grade Ⅲ (n = 14) and grade Ⅳ (n = 12). This study focuses on analyzing the correlation and the differences of stroke volume and cardiac output between left and right ventricles. The results indicate that there exists positive correlation between the differences of stroke volume among the both ventricles (RVSV－LVSV) and gradeⅠ～grade Ⅳ of NYHA ( r = 0.84, (P <0.01), and the result also exists the significant difference between the control group and gradeⅠ～grade Ⅳ of NYHA (P <0.05). We try to quantify the differences of the stroke volume between left and right ventricles divided into total five groups, including four groups of the experimental group 0.21-1.0 mL, 1.1-2.0 mL, 2.1-3.0 mL, > 3.1 mL and the control group <0.2 mL, and then, the results of comparing the maximum velocity of mitral regurgitation of these five groups with the degrees of mitral regurgitation of NYHA presents the significant difference (P <0.01). In conclusion, use this research model of intracardiac shunt to evaluate the differences of outflow among the both ventricles in dogs with mitral regurgitation is available. The both measuring methods, assess the differences of stroke volume between the left and right ventricle and estimate the degrees of mitral regurgitation of NYHA, can help estimate the degrees of heart failure which is caused by mitral regurgitation. Furthermore, there is high positive correlation between the differences of stroke volume among two ventricles and the maximum velocity of mitral regurgitation. Keywords: dogs, Doppler echocardiography, mitral regurgitation, stroke volume