A heart beating moments after a successful transplantation!
Notice the aortic arch stitches.
During a cardiac transplantation procedure, the ventricles are excised, leaving the great vessels, right atrium, and left atrium of the recipient. The donor heart is then sewn to these areas.
Now, the transplanted heart fills with blood and pumps as any other normal heart. However, the transplanted heart is "denervated." This means that the nerves from the central nervous system that supplied connections to the original failing heart do not supply connections to the new transplanted heart. These nerves were divided upon removal of the patients own heart.
That being said, a defibrillator with small paddles is used to shock the heart to restart beating. The denervation of the organ makes it dependent on its intrinsic rate the heart increases its rate only after substances called catecholamines (adrenalin, for example) are released from the adrenal gland and circulated through the blood to the heart.
Video by @dr_wanderley