Abstract: A low velocity aortic cannula having a proximal end, a distal end, and a lumen therebetween for conducting blood, the distal end being adapted for insertion into the aorta during heart surgery to provide blood to the aorta. There is a diffuser at least partially blocking the distal end of the cannula, and a plurality of outlet openings in the side of the distal end of the cannula. In one embodiment the distal end of the cannula is closed with a cap, and the diffuser is a rounded cone extending generally upstream in the lumen. The outlet openings are located in the sidewall of the cannula. In a second embodiment of the invention, the diffuser has a helical configuration, and partially blocks the distal opening of the cannula. Additional openings are provided in the sidewall to permit flow. According to the method of this invention, an opening is formed in the aorta, the distal end of one of the embodiments of the cannula is inserted into the opening, and blood flow through the cannula is established.