This chapter provides detail description of complications related to permanent pacemakers and intracardiac defibrillators. Some of the complications are mechanical and related to the presence of foreign body and its interaction with the valves and endomyocardium, for example, perforation, infection, and thrombosis, while others are related to the electrical pacing of the myocardium and conduction abnormalities, for example, dyssynchrony and TR. It is important to have a high index of suspicion to diagnose these complications, using the appropriate imaging modality. Based on the preceding review, it is clear that echocardiography plays an important role in the diagnosis of the device-related complications. Both 2D TTE and TEE provide extremely useful diagnostic information that is helpful in detecting the endocardial lead-related complications. Real time 3D echocardiography is a novel technique that can precisely track the intracardiac route of the lead and accurately detect most of the pacemaker/ICD lead-related complications. 9 self-explanatory and comprehensive images are included in this chapter. 84 references are given at the end of the chapter to facilitate further reading.