Frequently Asked Questions

Frequently Asked Questions

What are the hazards posed by an MR scanner to a pacemaker or defibrillator?
Electromagnetic interference (EMI) produced during the MRI has the potential to induce several hazardous effects impacting the normal operation of implantable pacemakers and defibrillators. These include:

• Vibration
• Force and torque effects
• Device interactions with MR magnetic fields
• Unintended stimulation
• IPG/ICD heating
• Lead heating

What are the risks for a patient with an implantable device during an MRI?
Possible risks include:

• Mechanical forces causing rotational force (torque), device dislodgement
• High rate pacing beyond the pacemaker rate limit
• Inappropriate pacing leading to arrhythmia
• Oversensing leading to failure to pace
• Undersensing leading to inappropriate pacing
• Cardiac tissue damage
• Elevated thresholds and loss of capture
• Device malfunction or damage

What do I need to know about the current debate around MRI and device safety in the literature?
Despite theoretical and actual risks of MR scanning to patients with cardiac devices, the safety debate continues.

• Limited studies have documented safe procedures and no adverse events
• Patient safety cannot be guaranteed by extrapolating findings from limited studies that reported no adverse events. Safety is proven only by more rigorous scientific testing and regulatory review
• Clinicians must carefully balance the potential benefits and risks to patients
• Only the Revo MRI Pacing System is currently labeled MR-conditional for use in the MR environment
• All components of an implantable system need to be developed, tested, and proven safe and effective for current and evolving MRI technologies

Why is MR safety in patients with implanted cardiac devices so difficult to achieve?
A staggering combination of variables affects the magnitude of risk for patients, including:

• Type of imaging and MRI sequence
• Patient and device position within MRI scanner
• MRI scan duration
• Strength of RF field
• Target anatomy of scan
• Pacemaker and lead materials and design
• Length and anatomical orientation of pacing leads
• Blood flow in lead-tip region
• Patient factors and medical history

Can my patient have a partial extremity MRI?
Because a pacing, sensing, or ICD lead tip can heat regardless of anatomy being scanned, an MRI is not recommended for patients with implanted cardiac devices even for a partial extremity scan. The Revo MRI SureScan pacemaker system is designed to allow patients to undergo MRI under specified conditions for use. A complete system consisting of a Metronic Revo MRI SureScan IPG implanted with two CapSureFix MRI SureScan leads is required for use in the MRI environment. The Revo MRI SureScan Technical Manual provides the MR Conditions for Use to appropriately scan the Revo MRI pacemaker patient.

Can my patient have an MRI if the implantable cardiac device is programmed off?
Even when a device is programmed off, electromagnetic interference (EMI) produced during the MRI has the potential to induce several hazardous effects impacting the normal operation of implantable pacemakers and defibrillators. The Revo MRI SureScan pacing system is MR Conditional and, as such, is designed to allow patients to be safely scanned by an MRI machine when used according to the specified MRI conditions for use. When programmed to On, the MRI SureScan feature allows the patient to be safely scanned while the device continues to provide appropriate pacing.

Can my patient have an MR scan if the pacemaker generator has been removed but the lead(s) remains?
The effect of RF energy on the lead-tissue interface can be accentuated by the removal of the generator. The remaining lead may act like an antenna for RF energy, resulting in even more heating and tissue damage. Pacemaker manufacturers typically recommend that the safest strategy is to either remove the entire implantable cardiac device system or utilize an alternative imaging modality.

For additional information on the Revo MRI^™ SureScan^® Pacing System, please visit www.mrisurescan.com.

Hazards to Patient Safety

Electromagnetic interference (EMI) produced during the MRI has the potential to induce several hazardous effects on implantable cardiac devices:

Vibration

• Caused by gradient and static magnetic fields
• May cause patient discomfort and device damage

Force and Torque Effects

• Results from static magnetic fields acting on ferromagnetic components
• Can cause device damage and tissue injury in patients

Device Interactions With MR Magnetic Fields

Can cause device malfunctions during and after a scan, including:

• Unpredictable reed switch operations resulting in device reset
• Clock failure
• Device damage
• Failure to sense and pace

'Loop' created by pacing system acts as antenna for receiving gradient-induced voltages. This may result in:

• Arrhythmia
• Supply voltage collapse
• Oversensing
• Failure to pace

Unintended Stimulation

RF and gradient fields could induce voltage on the leads, resulting in:

• Inappropriate myocardial capture
• Erratic heart rate
• Life-threatening arrhythmia

Device Heating

• Gradient fields can heat a device at elevated slew rates
• May result in myocardial injury

Lead Heating

• May result from high-frequency RF energy from the MR environment
• May cause myocardial injury resulting in failure to capture or sense, and subsequent threshold changes