ICD detection, treatment of arrhythmias not impacted by MRI

Evidence is accumulating that MRIs do not induce clinically significant functional changes in non-MRI-conditional implantable cardioverter-defibrillators (ICDs), according to the authors of a recent study that followed the devices' performance for about two years after an MRI.

Non-MRI-conditional implantable cardioverter-defibrillators (ICDs) still appropriately treated tachyarrhythmias after MRI, a study found.

To evaluate whether non-MRI-conditional ICDs have preserved shock function of arrhythmias after MRI, researchers conducted a prospective cohort study at one location among 629 patients from February 2003 and January 2015. ICD interrogations were collected at baseline and immediately after 1.5-Tesla MRI scans. Clinical outcomes included arrhythmia detection and treatment, generator or lead exchanges, adverse events, and death. Results were published Jan. 31 by Annals of Internal Medicine.

All patients in the study had non-MRI-conditional ICDs. Median follow-up was 2.2 years from MRI to latest available ICD interrogation before generator or lead exchange in 536 of the 629 patients (85%). Of the 93 remaining patients, telephone follow-up and death certificates showed 45 had died, 18 were alive without device-related problems, and 30 were lost to follow-up. Overall, there were 4,177 arrhythmia episodes, and 97 patients received ICD shocks. Sixty-one patients (10%) had 130 spontaneous ventricular tachycardia or fibrillation events terminated by ICD shocks. A total of 210 patients (33%) had died (median, 1.7 years from MRI to death); three had cardiac arrhythmia deaths where shocks were indicated without direct evidence of device dysfunction.

The study authors found no direct evidence of ICDs failing to deliver therapy. They noted that there is a substantial patient population with non-MRI-conditional ICDs and that they are less able to access clinically indicated MRIs, likely because of perceived risks. The authors suggest that their study provides additional safety data for this patient population under a standardized imaging protocol of 1.5-Tesla MRI scans.

“Future multicenter studies and studies directly comparing non–MRI-conditional and MRI-conditional ICDs after MRI may be of interest to validate our findings,” the authors wrote. “In addition, continued data to establish MRI safety in patient populations not included in this study, such as those with epicardial and abandoned leads, subcutaneous ICDs, and more recently leadless pacemaker defibrillator systems, may contribute to further expanding access to MRI examinations for these groups.”