1,3,15 These early successes led to a position statement by the European Society of Cardiology (ESC) in 2008 which considered the risks of MRIs in selected patients with implanted devices "acceptable" and set forth a protocol with careful selection criteria and best practices for safely performing MRI studies in these patients. Multiple studies using 1.5 Tesla MRI magnets have demonstrated that MRI scanning outside of the thorax could be completed safely in pacemaker patients with a low device complication rate and no deaths attributed to the MRI study. Following completion of the scan, reinterrogation and reprogramming of original settings is performed. 1,3,15,16 Continuous telemetry monitoring is utilized during the scan and supervised by a physician or nurse practitioner with expertise in device management and advanced resuscitation. Protocols typically involve device interrogation and reprogramming to an asynchronous pacing mode in pacemaker dependent patients, inhibited modes in non-pacemaker dependent patients, and disabling tachyarrhythmia detection and therapies in ICDs prior to the MRI study. This important gap in the accessibility of MRI imaging has given rise to major efforts from the clinical standpoint to enable patients with implanted devices to safely undergo MRI scans, in parallel with the development of MRI-conditional devices designed to be safe in the setting of MRI scans.īased on the relatively uncomplicated experience with MRI scans performed occasionally inadvertently on patients with implanted devices, since the early 2000s several centers have developed study protocols for those patients with an absolute clinical necessity for MRI scan. 14 This approach is clearly extreme, exposing the patient to the risks of two surgical procedures. 13 In fact, there are reports of devices being explanted and later reimplanted in patients deemed to have an absolute necessity for MRI scan. 6,10 Hence, since the early 1990s, implanted devices have been regarded as a near absolute contraindication to undergoing MRI scans and have prevented many patients from receiving an often optimal imaging test. 5-11 Multiple in-vitro studies have shown that the magnetic fields can exert mechanical forces upon the device generators, 12 cause electrical malfunction or noise that may be interpreted as cardiac activity, and significant heating of the lead-tissue interface from absorbed radiofrequency energy, leading to local myocardial damage and resultant decrease in lead functionality. 4 Early reports, though lacking in significant details, implicated MRI scans in the death of several patients with implanted devices. 3 However, there are major concerns that the static and gradient magnetic fields, and radiofrequency energy formed by MRI machines will interact with and cause malfunction of the device or permanent damage to the device, leads, or heart at the lead-tissue interface. 1,2 It is estimated that more than 50% of these patients will require magnetic resonance imaging (MRI) after device implantation. Over 2 million patients in the United States have implanted devices, including pacemakers and implantable cardioverter-defibrillators (ICDs).
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