No long-term clinically significant adverse events were associated with MRI use in patients with legacy pacemakers or implantable cardioverter defibrillators, according to results published in The New England Journal of Medicine.
The researchers conducted a prospective, nonrandomized study to determine safety of MRI at 1.5 T in 1,509 patients (median age, 69 years; 36% women) with legacy pacemakers or ICDs, defined as not MRI-conditional, who underwent 2,103 MRI exams.
Pacing mode was changed to asynchronous in pacing-dependent patients and to demand mode for other patients, and tachyarrhythmia functions were disabled.
Outcomes of interest were adverse events, interaction with surrounding tissue and changes in variables indicating lead and generator function.
At a median follow-up of 1 year, there were no clinically significant adverse events reported, Saman Nazarian, MD, PhD, from the department of medicine (cardiology) at the University of Pennsylvania Perelman School of Medicine and the department of medicine (cardiology and epidemiology) at Johns Hopkins University, and colleagues wrote.
In 0.4% of MRI exams (95% CI, 0.2-0.7), the device reset to backup mode. This was transient in all but one case, in which a pacemaker with less than 1 month of battery life reset to ventricular inhibited pacing, could not be reprogrammed and was replaced, Nazarian and colleagues wrote.
Decrease in P-wave amplitude of at least 50% from baseline occurred in 1% of patients, according to the researchers.
At long-term follow-up, 4% of the patients had a decrease in P-wave amplitude, 4% had an increase in atrial capture threshold, 4% had an increase in right ventricular capture threshold and 3% had an increase in left ventricular capture threshold, none of which were clinically significant nor required device revision or reprogramming, the researchers wrote.
The study is consistent with the findings of the MagnaSafe registry and provides “complementary evidence that MRI scanning can be performed safely in patients with legacy devices, provided that an appropriate protocol is followed,” Nazarian and colleagues wrote. – by Erik Swain
Nazarian reports he receives consultant fees from and serves as the principal investigator for trials sponsored by Biosense Webster and St. Jude Medical, serves as an unpaid consultant for CardioSolv and receives consultant fees from Siemens. Two other authors report financial ties with Boston Scientific, Imricor, Medtronic and St. Jude Medical.