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We have produced an eccentric roller type total artificial heart (ERTAH). As the first step in the development of this ERTAH, we conducted simulations such as a numerical simulation, a mock test, and an acute animal experiment using DeBakey roller pumps to analyze the left-right balance during its operation. The next step was redesigning the blood chambers to improve energy efficiency and implanting the ERTAH with an interatrial shunt into an animal for evaluation of the in vivo performance of the device. In the simulations, shunt flow through the bronchial arteries was approximately 500-600mlJmin, and the interatrial resistance was varied from 2.9-7.7 mmHg・min/liter. Redesigning the blood chambers resulted in the mock test in a 20% increase in energy efficiency, about a two-fold increase in cardiac output and improved durability compared to the previous type in the mock test. In the animal experiment the ERTAH operated with a left flow rate of 6.0 liters/min and a right flow rate of 5.4 liters/min. The interatrial shunt flow rate was 250-400m1Jmin. Creating an interatrial shunt is a useful method for balancing the blood flow between the left and right heart of the ERTAH. A decrease in friction resistance and the prevention of backward flow resulted in an increase in energy efficiency, cardiac output, and improved durability, in spite of downsizing the blood chambers., This work was supported in part by a Research Grant for Cardiovascular Disease 10C-2 from the Ministry of Health and Welfare, Japan.