There are multiple components, but all must be nontoxic, not cause immune sytem to react, sterilizable, and able to work in wet, warm and mobile environment.
Usually the case for the pacemaker
is made of titanium or a titanium alloy. The lead is also made of a metal alloy, covered with polyurethane or silicone
. Other components are sealed inside the case and are not exposed to react to the body.