Alexis Madrigal of The Atlantic displays some great pictures of the first totally artificial heart implanted 41 years ago.
To understand how far we've come, the newest devices being tested now are adapted left ventricular assist devices used as "destination" therapy that are about the size of a C-sized battery and are implanted entirely within the chest. The device is powered via a "plug-like" connection implanted behind the patient's ear. One such experimental device was recently implanted in a 15 year old boy with Duchenne muscular dystrophy in Rome.
Cooley DA, Liotta D, Hallman GL, Bloodwell RD, Leachman RD, Milam JD. Orthotopic cardiac prosthesis for two-staged cardiac replacement. The American Journal of Cardiology November 1969; 24(5), pp 723-730.
Farrar DJ, Bourque K, Dague CP, Cotter CJ, Poirier VL. Design Features, Developmental Status, and Experimental Results With the Heartmate III Centrifugal Left Ventricular Assist System With a Magnetically Levitated Rotor. ASAIO Journal
May/June 2007; 53 (3), pp 310-315.