永久性起搏器或植入式心脏复律除颤器（ICD）患者的磁共振成像（MRI）潜在风险包括编程改变，起搏异常和导线中的感应电流。在一系列1509名患有老一代起搏器或ICD的患者（例如，那些不特别符合食品和药物管理局规定的MRI-条件标准或“传统”设备的患者）中进行胸部或非胸部MRI检查以及随访1年，没有临床意义的事件。虽然这个和以前的报道令人放心，但是在MRI和成像过程中的患者监护之前和之后，可以使用除颤器和代码手推车，非MRI有条件的起搏器或ICD需要采取预防措施，包括设备编程。如果检查对于疾病的诊断或治疗是必要的和必要的，那么在非MRI有条件的永久起搏器或ICD的患者中可以进行MR成像，只要采取了特定的预防措施。
BACKGROUND Patients who have pacemakers or defibrillators are often denied the opportunity to undergo magnetic resonance imaging (MRI) because of safety concerns, unless the devices meet certain criteria specified by the Food and Drug Administration (termed "MRI-conditional" devices).
METHODS We performed a prospective, nonrandomized study to assess the safety of MRI at a magnetic field strength of 1.5 Tesla in 1509 patients who had a pacemaker (58%) or an implantable cardioverter-defibrillator (42%) that was not considered to be MRI-conditional (termed a "legacy" device). Overall, the patients underwent 2103 thoracic and nonthoracic MRI examinations that were deemed to be clinically necessary. The pacing mode was changed to asynchronous mode for pacing-dependent patients and to demand mode for other patients. Tachyarrhythmia functions were disabled. Outcome assessments included adverse events and changes in the variables that indicate lead and generator function and interaction with surrounding tissue (device parameters).
RESULTS No long-term clinically significant adverse events were reported. In nine MRI examinations (0.4%; 95% confidence interval, 0.2 to 0.7), the patient's device reset to a backup mode. The reset was transient in eight of the nine examinations. In one case, a pacemaker with less than 1 month left of battery life reset to ventricular inhibited pacing and could not be reprogrammed; the device was subsequently replaced. The most common notable change in device parameters (>50% change from baseline) immediately after MRI was a decrease in P-wave amplitude, which occurred in 1% of the patients. At long-term follow-up (results of which were available for 63% of the patients), the most common notable changes from baseline were decreases in P-wave amplitude (in 4% of the patients), increases in atrial capture threshold (4%), increases in right ventricular capture threshold (4%), and increases in left ventricular capture threshold (3%). The observed changes in lead parameters were not clinically significant and did not require device revision or reprogramming.
CONCLUSIONS We evaluated the safety of MRI, performed with the use of a prespecified safety protocol, in 1509 patients who had a legacy pacemaker or a legacy implantable cardioverter-defibrillator system. No long-term clinically significant adverse events were reported. (Funded by Johns Hopkins University and the National Institutes of Health; ClinicalTrials.gov number, NCT01130896 .).
