Models: SynchroMed® EL: All models beginning with 8626, 8627
Reference: August 2008 – Urgent: Medical Device Correction - –Important Information on Potential MRI Effects
SynchroMed EL pump performance has not been established for greater than 1.5 T horizontal, closed-bore MRI scanners. Patients should not have MRI using >1.5 T horizontal, closed-bore scanners. The magnetic field of the MRI scanner will temporarily stop the rotor of the pump motor and suspend drug infusion for the duration of the MRI exposure. The pump should resume normal operation upon termination of MRI exposure; however, there is the potential for an extended delay in pump recovery after exiting the MRI magnetic field. While extended delays in pump recovery are unlikely, reports have indicated that there is the potential for a two to twenty-four hour delay in return to proper drug infusion after completion of an MRI scan.
Prior to MRI, the implanting or follow-up physician should determine if the patient can safely be deprived of drug delivery. If the patient cannot be safely deprived of drug delivery, alternative delivery methods for the drug can be utilized during the time required for the MRI scan. If there is concern that depriving the patient of drug delivery may be unsafe for the patient during the MRI procedure, medical supervision should be provided while the MRI is conducted. Prior to the MRI scan, at an appropriate time as determined by the implanting or follow-up physician, the physician should confirm that the pump program settings are documented in case reprogramming is required after the scan.
Patients receiving intrathecal baclofen therapy (e.g. Lioresal® Intrathecal) are at higher risk for adverse events, as baclofen withdrawal can lead to a life threatening condition if not treated promptly and effectively. For complete product information, refer to the Lioresal Intrathecal (baclofen injection) Package Insert. For information on other drugs, please refer to the product labeling for the drug being administered.
Upon completion of the MRI scan, or shortly thereafter as defined by the implanting or follow-up physician, the pump must be interrogated using the clinician programmer in order to confirm that electromagnetic interference from the MRI has not affected the pump status. If interrogation using the clinician programmer shows that a “Pump Memory Error” occurred, the clinician must reprogram the pump in order for proper drug infusion to resume. A Pump Memory Error Alarm (double tone) will accompany a Pump Memory Error. Please notify Medtronic Technical Services at (800) 707-0933 if this occurs.
The SynchroMed EL pump does not detect or alarm for motor stalls. At an appropriate time as pre-determined by the implanting or consulting physician, a clinician should confirm that the SynchroMed EL pump has resumed proper drug infusion after an MRI by performing a pump roller study. If a pump roller study can not be performed, patients must be closely monitored for return of underlying symptoms to confirm the pump has resumed proper drug infusion after an MRI. The duration of monitoring depends on the drug and the delivery rate. Consult the patient’s providing physician for likely time period for return of symptoms in the event of a pump stoppage.
Testing on programmable pumps has established the following with regard to other MRI safety issues:
Specific Absorption Rate (SAR): Presence of the pump can potentially cause a two-fold increase of the local temperature rise in tissues near the pump. During a 20-minute pulse sequence in a 1.5 T (Tesla) GE Signa Scanner with a whole-body average SAR of 1 W/kg, a temperature rise of 1 degree Celsius in a static phantom was observed near the pump implanted in the “abdomen” of the phantom. The temperature rise in a static phantom represents a worst case for physiological temperature rise and the 20 minute scan time is representative of a typical imaging session. FDA MRI guidance1 allows a physiological temperature rise of up to 2 degrees Celsius in the torso, therefore the local temperature rise in the phantom is considered by FDA guidance1 to be below the level of concern. Implanting the pump more lateral to the midline of the abdomen may result in higher temperature rises in tissues near the pump.
In the unlikely event that the patient experiences uncomfortable warmth near the pump, the MRI scan should be stopped and the scan parameters adjusted to reduce the SAR to comfortable levels.
Time-Varying Gradient Magnetic Fields: Presence of the pump may potentially cause a two fold increase of the induced electric field in tissues near the pump. With the pump implanted in the abdomen, using pulse sequences that have dB/dt up to 20 T/ s, the measured induced electric field near the pump is below the threshold necessary to cause stimulation.
In the unlikely event that the patient reports stimulation during the scan, the proper procedure is the same as for patients without implants—stop the MRI scan and adjust the scan parameters to reduce the potential for nerve stimulation.
For magnetic fields up to 1.5 T, the magnetic force and torque on the SynchroMed pump will be less than the force and torque due to gravity. The patient may experience a slight tugging sensation at the pump implant site. An elastic garment or wrap will prevent the pump from moving and reduce the sensation the patient may experience.
The SynchroMed pump contains ferromagnetic components that will cause image distortion and image dropout in areas around the pump. The severity of image artifact is dependent on the MR pulse sequence used. For spin echo pulse sequences the area of significant image artifact may be 20-25 cm across. Images of the head or lower extremities should be largely unaffected.
Minimizing Image Distortion - Careful choice of pulse sequence parameters and location of the angle and location of the imaging plane may minimize MR image artifact; however, the reduction in image distortion obtained by adjustment of pulse sequence parameters will usually be at a cost in signal to noise ratio. The following general principles should be followed: