Cardiac pacemakers and implantable cardioverter-defibrillators (ICDs) are among the most significant modern applications in biomedical engineering. They play an essential role in managing cardiac rhythm disorders, improving patients’ quality of life, and reducing the risk of serious cardiac complications. Operating Principles and Main Components The heart relies on an internal electrical conduction system to regulate muscle contractions and pump blood throughout the body. When this system malfunctions, patients may experience abnormally slow heartbeats or rapid arrhythmias that can be life-threatening. In such cases, implantable cardiac devices monitor the heart’s electrical activity and intervene when necessary. A pacemaker consists of a pulse generator containing a battery and electronic circuits, electrodes that transmit electrical signals between the device and the heart, sensing and processing circuits, and wireless communication modules. The device continuously monitors the heart rate and delivers low-energy electrical impulses when the natural heartbeat fails to occur within a predetermined interval. An implantable cardioverter-defibrillator differs in its ability to detect certain dangerous ventricular arrhythmias and deliver a high-energy electrical shock to terminate them. This function helps prevent sudden cardiac death in patients who meet the clinical criteria for this treatment. Types of Cardiac Pacemakers Pacemakers are available in several types, depending on the patient’s condition and therapeutic requirements. A single-chamber pacemaker uses one lead positioned in either the right atrium or the right ventricle, while a dual-chamber pacemaker uses two leads to help maintain coordination between the atria and ventricles. Cardiac resynchronization therapy (CRT) devices are used in selected patients with heart failure to improve the coordination of ventricular contractions. In addition, leadless pacemakers have emerged as a modern alternative. These small devices are implanted directly inside the heart through a catheter, eliminating the need for traditional leads and a subcutaneous generator pocket, thereby reducing certain complications associated with these components. Clinical Applications and Medical Benefits Pacemakers are primarily used to treat bradycardia and certain types of cardiac conduction block. They help relieve symptoms such as dizziness and fainting caused by an insufficient heart rate. In contrast, implantable cardioverter-defibrillators are used in selected patients at risk of life-threatening ventricular arrhythmias. Cardiac resynchronization therapy can improve symptoms, exercise capacity, and reduce hospitalizations in appropriately selected patients. Furthermore, remote monitoring technologies allow device data, including battery status, lead performance, and detected arrhythmia episodes, to be transmitted to healthcare teams. This facilitates early detection of potential problems and improves clinical follow-up. The Role of Biomedical Engineering in Developing Cardiac Devices Cardiac implantable devices represent a clear example of integration between engineering and medicine. Biomedical engineers contribute to the design of electronic systems, development of sensing and stimulation algorithms, improvement of energy efficiency, and verification of device accuracy, performance, and safety. Device programming involves several important parameters, including the minimum pacing rate, electrical pulse amplitude, pulse width, sensing sensitivity, atrioventricular delay, and response to physical activity. These parameters are adjusted according to the patient’s needs and the assessment of the treating physician to achieve an appropriate therapeutic response while minimizing energy consumption. Challenges and Future Prospects Despite their significant benefits, these devices may present certain challenges, including infection, lead displacement or damage, battery replacement requirements, and the possibility of inappropriate shocks in some patients with ICDs. Protecting medical data and wireless communications is also essential, along with ensuring the availability of qualified professionals to program and monitor these devices. Current research focuses on developing multichamber leadless pacing systems, conduction system pacing techniques, and energy-harvesting technologies that use cardiac motion to generate power. Artificial intelligence is also being explored to analyze device data and identify patterns that may help predict the deterioration of certain cardiac conditions before complications arise. Conclusion Cardiac pacemakers and implantable cardioverter-defibrillators demonstrate the importance of engineering innovation in advancing healthcare and saving lives. With continued progress in medical electronics, wireless communication, and artificial intelligence, these devices are expected to become more accurate, efficient, and less invasive. Biomedical engineers remain essential to designing, testing, and improving these technologies in collaboration with cardiologists, ultimately enhancing patient safety and quality of life. Al-Mustaqbal University: First Among Private Universities in Iraq.