A pacemaker is a small, implanted device designed to treat bradycardia, a condition where the heart beats too slowly. It consists of a pulse generator, which contains the battery and electronic circuitry, and one or more flexible wires called leads. These leads deliver electrical impulses to the heart muscle to maintain a stable heart rhythm. The device constantly monitors the heart’s natural electrical activity and only delivers a pulse when necessary to ensure the heart rate remains above a programmed minimum.
Primary Categories of Pacemaker Complications
Lead and Device Failure
Mechanical failures can interrupt the electrical connection between the pulse generator and the heart muscle. Lead issues include a conductor fracture (where the internal wire breaks) or an insulation breach, which causes electrical current to leak away from the heart tissue. Lead dislodgment is another problem, often occurring soon after implantation, where the tip moves from its intended position. This movement can lead to a loss of contact or stimulate surrounding non-cardiac tissue.
Device-related mechanical issues primarily involve the pulse generator itself. The most common issue is the eventual depletion of the lithium-iodide battery, requiring the generator to be replaced. Less frequently, problems arise from a loose connection at the connector block where the lead plugs into the generator, causing intermittent pacing or sensing issues. Signals resulting from a lead fracture can sometimes be oversensed, leading the pacemaker to inappropriately withhold therapy.
Infection and Site Reaction
Infection is a risk with any implanted foreign body and can manifest in two primary ways. A localized pocket infection occurs at the incision site, often presenting with pain, redness, warmth, and swelling. In severe cases, the skin over the device may break down, leading to erosion and exposure of the pacemaker casing.
A more serious complication is a systemic infection, such as endocarditis, where bacteria colonize the leads inside the heart. Staphylococcus species are the most common pathogens. Once a biofilm forms on the leads, antibiotics alone are often insufficient, and the entire device, including the infected leads, must be removed.
Pacing Malfunctions (Sensing and Capture Errors)
Pacing malfunctions refer to errors in the device’s electrical performance related to sensing and capturing. Undersensing occurs when the pacemaker fails to detect the heart’s natural electrical activity, causing it to pace asynchronously when it should be inhibited. This malfunction can result from poor lead position or changes in the electrical properties of the tissue interface.
Oversensing happens when the device mistakenly interprets non-cardiac signals as a heart rhythm, such as skeletal muscle activity from the chest or electrical noise from a fractured lead. When these signals are oversensed, the device inappropriately stops pacing, resulting in long pauses. A third malfunction is failure to capture, meaning the electrical pulse is delivered but does not cause the heart muscle to contract. This can be due to lead dislodgment, high pacing thresholds, or metabolic disturbances like electrolyte imbalance.
Electromagnetic Interference (EMI)
Electromagnetic interference (EMI) occurs when external electrical or magnetic fields temporarily disrupt the pacemaker’s function. Although modern pacemakers are designed with shielding, exposure to strong sources can still cause issues. A strong magnetic field, such as from industrial equipment or antitheft devices, can cause the pacemaker to revert to a fixed-rate, asynchronous pacing mode.
In a healthcare setting, medical procedures like magnetic resonance imaging (MRI) or therapeutic radiation can pose a risk of EMI. Monopolar electrocautery, commonly used in surgery, is a frequent cause of temporary pacemaker inhibition. These external forces can lead to oversensing or transient loss of output, though the effect is often temporary and resolves once the interference source is removed.
Recognizing and Diagnosing Pacemaker Problems
When a pacemaker malfunctions, the patient may experience symptoms related to a slow or irregular heart rate. These include generalized fatigue, dizziness, and lightheadedness, indicating insufficient blood flow to the brain. More severe complications can cause syncope (fainting), particularly in patients who rely completely on the device for their heart rhythm.
Localized symptoms, such as pain, swelling, or heat at the implant site, suggest a pocket infection or hematoma. Systemic issues like fever and chills can point toward a lead infection that has spread into the bloodstream. Palpitations or a feeling of an irregular heartbeat can also occur if the device is pacing inappropriately.
The initial medical assessment often involves a 12-lead electrocardiogram (ECG) to check for abnormal pacing spikes or absent capture. A chest X-ray confirms the physical location and integrity of the leads, helping to identify fractures or dislodgment. The definitive diagnostic step is device interrogation, which uses a specialized programming wand to wirelessly retrieve detailed information on battery status, lead integrity, and recorded electrical events.
Long-Term Management and Monitoring
Pacemaker recipients require a routine schedule of care to ensure the device functions safely. Scheduled follow-up appointments monitor performance, typically occurring every three to six months. During these visits, the pacemaker is interrogated to assess battery life, check pacing and sensing thresholds, and adjust programming as needed.
Remote monitoring systems (telemetry) often supplement in-person visits by transmitting data wirelessly from the patient’s home to the clinic. This allows the care team to detect potential issues, such as battery decline or lead problems, between scheduled appointments. The pulse generator battery is designed to last approximately 7 to 10 years, depending on the amount of pacing required. When the battery reaches a predetermined elective replacement indicator, the generator is surgically replaced in a minor procedure, while the existing leads are usually left in place.