My husband says the folks he treats who have pacemakers/defibrillators (sometimes they're a combination of both) who smoke cannabis have more electrical disturbances than those who don't--and they use up more battery power, too. He has to adjust those devices more frequently in his heavy-smoking patients.

They do have artificial hearts, Mad Sativa! There are several type of them and one has been pretty successful, but they're not generally a permanent solution. There's one called the Berlin heart that has been successfully implanted for, I think, more than 3 years in one patient and there's a modified version of the Jarvik-7 heart that's having some success. Usually artificial hearts are just bridging devices to buy more time for patients who're waiting for transplants. They also have ventricular assist devices that are implantable and do part of the job for the ventricles. Unless I'm mistaken, folks with those devices normally have to stay in the hospital because, even with the surgically implanted ventricular assist devices and artificial hearts, they're still real sick and need close monitoring and, as soon as possible, transplants.

Do a Google on "artificial heart" and you can read all about them. Pretty cool stuff!