MRI Scan Procedure Protocol
After the Scan
2-15
battery depletion. In addition, prolonged exposure of a patient to the XOO mode chosen may be
deleterious to the patient’s health.
Manually exit MRI Protection Mode using the PRM after the scan (see Manual Exit from MRI
Protection Mode). After exit from MRI Protection Mode, check system integrity by running lead
impedance, pacing threshold, and intrinsic amplitude tests.
Upon exit from MRI Protection Mode, all parameters are immediately restored to pre-MRI
Protection Mode values with two exceptions. If PaceSafe Automatic Capture (RVAC) was
programmed on, this feature enters suspension upon entry of the device into MRI Protection
Mode. Upon exit from MRI Protection Mode, RV pace amplitude is set to two times the last
capture threshold determined by the RVAC feature before it entered suspension (output limited to
between 3.5 V and 5.0 V). After the next scheduled autothreshold test runs (within the next 21
hours) and is successful, the RV pace amplitude is set to the new capture threshold plus 0.5 V.
This behavior was designed to provide a safety margin against loss of capture during the
transient period between MRI completion and full body recovery from effects of the scanner
electromagnetic fields.
For details about the PaceSafe Automatic Capture feature, see the Reference Guide for the
pulse generator.
Restoration of function of the Minute Ventilation sensor is also delayed upon exit from MRI
Protection Mode. If MV is programmed to On or Passive at the time of entry into MRI Protection
Mode, upon exit from the mode, an automatic six-hour calibration of the sensor will begin. MV-
driven rate response is not available during this calibration period. If MV-driven rate response is
desired sooner, a manual calibration can be performed. Manual calibration is completed in five
minutes or less. For additional information about MV calibration, see the Reference Guide for the
pulse generator.
Time-out (automatic) Exit from MRI Protection Mode
If the MRI Protection Mode Time-out parameter was programmed to a value other than Off, the
pulse generator will exit MRI Protection Mode automatically after the selected number of hours,
and the system will return to previously programmed settings (for details about the resumption of
PaceSafe Automatic Capture and Minute Ventilation, see "After the Scan" on page 2-14).
Manual Exit from MRI Protection Mode
Manually exit MRI Protection Mode using the PRM after the scan.
Do not leave the pulse generator in MRI Protection Mode any longer than necessary following the
scan. MRI Protection Mode pacing is performed at a fixed, elevated rate. Some patients may
experience side effects during protracted pacing in this mode, including decreased exercise
capacity, acceleration of heart failure, and proarrhythmia.
• Interrogate the pulse generator using the wand (RF telemetry is disabled in MRI Protection
Mode)
• Select the Cancel MRI Protection Mode button from the MRI Protection Mode Programmed
screen (Figure 2–10 MRI Protection Mode Programmed (Cancel MRI Protection) on page 2-
16)
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