**MRI-compatible pacemakers** are specially designed cardiac devices that can safely undergo Magnetic Resonance Imaging (MRI) scans under specific conditions. Traditional pacemakers often pose risks during MRI due to strong magnetic fields and radiofrequency energy, which can interfere with device function or cause tissue heating. However, advances in pacemaker technology have led to the development of several types of MRI-compatible pacemakers, allowing patients with these devices to benefit from MRI diagnostics without compromising safety.
The main types of **MRI-compatible pacemakers** include:
1. **MRI-Conditional Pacemakers**
These pacemakers and their leads are specifically engineered and tested to be safe during MRI scans when certain protocols are followed. The entire system—device and leads—must be designed for MRI compatibility to ensure safety. For example, Medtronic’s EnRhythm MRI SureScan system was among the first to receive regulatory approval for MRI use, featuring specially designed leads (CapSureFix MRI SureScan) and a pacemaker that can be safely scanned under defined conditions. These devices require programming adjustments before and after the MRI and continuous monitoring during the scan. MRI-conditional pacemakers are typically compatible with 1.5 Tesla (T) MRI scanners, and some newer models support 3T scanners as well.
2. **Leadless Cardiac Pacemakers**
These are small, self-contained devices implanted directly into the right ventricle without leads (wires). Examples include the Nanostim and Micra systems. Because they lack leads, which are often the source of MRI-related complications, leadless pacemakers are inherently more compatible with MRI environments. Both Nanostim and Micra devices are approved for use in 1.5T and 3T MRI scanners under specific conditions, including device interrogation and programming before and after the scan, and patient monitoring during the procedure.
3. **Dual-Chamber and Single-Chamber MRI-Conditional Pacemakers**
MRI-compatible pacemakers come in various configurations depending on the patient’s cardiac needs:
– *Single-chamber pacemakers* stimulate one heart chamber, usually the ventricle.
– *Dual-chamber pacemakers* have leads in both the atrium and ventricle, coordinating their contractions more naturally.
Both types can be MRI-conditional if designed with MRI-safe hardware and leads. For example, Medtronic’s Advisa DR MRI and Advisa SR MRI SureScan systems are dual- and single-chamber pacemakers, respectively, designed for MRI compatibility.
4. **Biventricular (CRT) MRI-Compatible Pacemakers**
Cardiac resynchronization therapy (CRT) devices, also known as biventricular pacemakers, use three leads to stimulate both ventricles and sometimes the atrium to improve heart function in heart failure patients. Some CRT devices have been developed with MRI-conditional labeling, allowing patients with these complex devices to safely undergo MRI scans under strict protocols.
**Key considerations for MRI compatibility** include:
– The **entire system**—pacemaker and leads—must be MRI-conditional. If leads are abandoned (left in place but not connected) or epicardial (placed on the heart surface rather than inside chambers), the system is generally not MRI-compatible.
– Before an MRI, the device must be **interrogated and programmed** to an MRI-safe mode by a trained clinician.
– The MRI scan must be performed under **specific conditions**, such as limits on magnetic field strength (usually 1.5T or 3T), scan duration, and patient monitoring.
– After the MRI, the device must be **reprogrammed** to its normal settings and checked for proper function.
**Why MRI compatibility matters:**
Many patients with pacemakers eventually require MRI scans for unrelated medical issues, such as neurological or musculoskeletal conditions. Traditional pace
