Pacemakers and implanted defibrillators are both, uh, implanted inside your body. Typically they stick them in the front side of your left shoulder. They run th

Pacemakers and implanted defibrillators are both, uh, implanted inside your body. Typically they stick them in the front side of your left shoulder. They run the leads into a vein (or artery) and anchor them into the wall of the heart. They can implant basically under the fat layer or under the pectoral muscle. Beneath the fat layer is easier both from a surgery and recovery standpoint, but less secure. The downside of that is that it's possible for the device to flip over. They usually try to avoid securing the device to anything because that can lead to discomfort or pain if the device wants to move around, but they can if they have to. And yes, they do have to repeat surgery to replace the device when the battery gets low. The leads AIUI are usually a lifetime part (hopefully for all the right reasons). For defibrillators, battery life will be maximized if the device doesn't have to deliver shocks and can stick to just pacing. It turns out if they implant a defibrillator, you get a pacemaker for free.