Methods:

The authors conducted a prospective nonrandomized study evaluating the accuracy and safety of 1.5 Tesla MRI in patients with pacemakers and ICDs, which are not MRI-conditional, at a single tertiary center. Patients with recently implanted leads (<4 weeks), epicardial leads, nonfunctional leads, subcutaneous ICD systems, or who were pacemaker dependent or had ICDs without an asynchronous pacing mode were excluded. Device parameters were measured prior to and minutes after the MRI. Programming was changed to asynchronous pacing for those with intrinsic heart rates <40 bpm and an inhibited mode for all others. Follow-up device interrogation was recommended at 6 months. MRI sequences were modified to limit specific absorption rates to <2.0 W/kg in the first 55 patients, but were not restricted in subsequent patients. Prespecified outcomes included generator failure, power-on reset, changes in pacing threshold or sensing requiring system revision or reprogramming, battery depletion, cardiac arrhythmia, inhibition of pacing, and inappropriate delivery of therapies such as tachycardia pacing or shock. Patient reported symptoms such as warmth at the device, and palpitations were also recorded. In patients who returned, lead and generator parameters were again recorded as no change (≤20%), expected change (20-50%), or notable change (>50%).