In spite of the fact that patients with heart diseases requiring heart transplantation are increasing in the world, there are a lack of donors, which makes it hard to offer them these life-saving transplants. As a way to overcome this dilemma, we have researched the addition of the new biopump, which consists of the cultured embryonic cardiomyocytes grafted around the abdominal aorta and contracts spontaneously, which subsequently supports the function of the host heart. Ventricular tissues from ICR 14-day-old embryos were cultured and were injected to BALB/c nude mice (male, 8-week-old) subperitoneally around the abdominal aorta. At 3 and 7 days after implantation, action potential of the grafts was measured. Grafts were prepared for histological study. The grafts survived, showed vigorous angiogenesis, and contracted spontaneously. The cardiomyocytes in the grafts showed irregular arrangement, containing myofibrils with sarcomeres and intercalated disks. It was confirmed by immunohistochemistry that the cardiomyocytes in the grafts matured in accordance with normal development. The grafts were very quickly invaded by small vessels from the surrounding tissues showing the formation of new circulation. Embryonic cardiomyocytes have the ability to remodel the abdominal aorta into a spontaneous pulsating apparatus and to function as a vascular pump.