Several answers. There are several answers to this. From the cardiologist, ep doctor or ct surgeon. First one meets the criteria for pacing. Next several companies have their reps hold the device with them and hospitals hold them. We use routine venous sheaths to access the vein and flexible wires to guide wires to the heart then through techniques position the leads and secure device or pacemaker to them.
Pacemakers. The device is generally a nonreactive metal like titanium along with computer components hermetically sealed inside the device. A battery usually lithium based is inside and the sealed electronic connections to the lead are protected by a silicone sleeve around the lead to keep body fluids from shorting and eroding the system.