An implantable medical device, IMD, comprises atrial and ventricular sensing units for sensing atrial or ventricular electric events. The fiber optic bundle is held by a high viscosity epoxy. The air pipe assembly includes a first pipe communicating with the connecting hole, a second pipe connected to the pump and communicating with the first pipe, and a third pipe communicating with the first pipe and the second pipe. Another association is created between the first installation scope and the second installation scope, and this third association is created within a third installation scope.