An artificial heart, also known as a cardiac implant, was a device able to completely replace a heart in case of a major injury. Artificial hearts were more susceptible to weapon blasts, such as those caused by a compressed teryon beam, than the Human heart.
The procedure of replacing a cardiac implant is done conforming to VanDorens technique and has a mortality rate of 2.4%; any well-equipped medical facility can perform this procedure. Placing a cardiac implant is done by a medical team of six.
If necessary the surgeon can call for extra medical personnel.
Prior to the operation, a neural caliper is used to anaesthesize the patient after which the operation begins. The cardiac implant is placed via a mid line entry. When the operation is finished the patient has to stay in post-op for at least 4 hours. (TNG: "Samaritan Snare")
In 2365, Picard needed to have it replaced for maintenance reasons, so he traveled to Starbase 515, not wanting the crew to know by having the operation performed aboard the USS Enterprise-D, despite the fact that Doctor Pulaski was more than capable of performing the surgery. After a complication, she was required to perform the surgery anyway. (TNG: "Samaritan Snare")