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Reference: N Engl J Med 2017 Dec 28;377(26):2555 (level 2 [mid-level] evidence)
- There is some concern that MRI scans in patients with non-MRI conditional cardiac implantable electronic devices may lead to tissue or device damage.
- A recent prospective cohort study evaluated adverse events and device changes in 1,509 patients with non-MRI conditional implantable cardioverter-defibrillators or pacemakers who had 2,103 MRI scans (1.5 Tesla).
- Adverse events immediately after the scan were rare, with the most common events being power-on reset in 0.4% of scans and premature scan termination in 0.3%. No long-term adverse events were reported, and device parameter changes were uncommon and did not require device reprogramming or lead or system revision.
The strong magnetic fields and high radiofrequency power of MRI scans are thought to have the potential to interact with implantable electronic cardiac devices, leading to tissue and device damage (J Am Coll Cardiol 2016). MRI conditional devices are designed to be compatible with MRI scans, but many patients have “legacy” non-MRI conditional devices that are considered to be a contraindication for MRI scans due to limited safety assessments. To evaluate the safety of MRI scans in these patients, a recent prospective cohort study examined 1,509 adults (median age 69 years) with a non-MRI conditional implantable cardioverter-defibrillator (ICD) (in 42%) or pacemaker (in 58%) who had 2,103 clinically indicated 1.5 Tesla MRI scans at a single center. Patients with ICD models before the year 2000 or pacemaker models before year 1996 were excluded, as were patients who were pacing-dependent and had an ICD without asynchronous pacing, had lead implantation ≤ 4 weeks previously, had permanent surgical epicardial or nonfunctional leads, or had a subcutaneous ICD system. Devices were temporarily reprogrammed before the scan to reduce potential complications. The scan region was head or neck in 52% of scans, abdomen or pelvis in 27%, thorax in 12%, and arm or leg in 9%.
Adverse events during or immediately after the MRI scan were rare. A power-on reset occurred during 9 scans (0.4%), of which generator function was restored in 8 instances, and 1 device with < 1 month of expected battery life needed to be replaced. The MRI was aborted during 7 scans (0.3%), due to arrhythmia in 2 instances, pulling sensation of device in 1 instance, reversion to inhibited pacing mode in a pacing-dependent patient in 1 instance (without clinical sequelae), and image artifacts in 3 instances. Device parameter changes such as changes from baseline in P-wave or R-wave amplitudes were observed immediately after the scan and also during the median 1-year follow-up of 958 patients, but these were uncommon and did not require device reprogramming or lead or system revision. A telephone follow-up was conducted in the 551 patients who did not have the median 1-year device assessment, of which 125 reported no device-related problems, 124 had died, and 302 could not be reached.
This prospective cohort study demonstrated that immediate adverse events may be rare in patients with non-MRI conditional ICDs or pacemakers who have 1.5 Tesla MRI scans, and found no additional adverse events or device parameter changes requiring reprogramming or revision at long-term assessments. Importantly, these results may not apply to MRI machines with different magnet strengths or to devices that did not undergo appropriate pre-scan reprogramming. They also may not apply to patients or devices that meet exclusion criteria; the patient’s cardiologist should be consulted. Consistent results were reported in a similar study that excluded thoracic MRI scans out of concern for a perceived increased risk of adverse events for scans of this region (N Engl J Med 2017b). Although the current study included thoracic MRI scans, they comprised only 257 scans, providing limited data for MRI scans of the thoracic region. Finally, the 426 patients (28% of those enrolled) who died or could not be reached at long-term follow-up adds uncertainty to the long-term outcomes in this study. However, given the low rate of immediate adverse events and lack of long-term adverse events, this study suggests that 1.5 Tesla MRI scans can be conducted safely in patients with non-MRI conditional ICDs or pacemakers.
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