Implantable Defibrillator Shock Function After MRI

Quick Takes

  • In a single-center study of 629 patients with non–MRI-conditional ICDs undergoing 913 MRI examinations, there were no adverse events attributable to the MRI at a mean of 2.2-month follow-up.
  • Non–MRI-conditional ICDs appropriately treated detected tachyarrhythmias after MRI, and there were no serious adverse effects on device function.

Study Questions:

Do non–MRI-conditional implantable cardioverter-defibrillators (ICDs) have preserved shock function of arrhythmias after magnetic resonance imaging (MRI)?


The authors conducted a single-center observational study of 629 patients with non–MRI-conditional ICDs, who underwent 813 MRI examinations at a magnetic field strength of 1.5 Tesla. ICDs were interrogated after MRI. Clinical outcomes were assessed.


During a median follow-up of 2.2 years from MRI to latest available ICD interrogation before generator or lead exchange in 536 patients, 4,177 arrhythmia episodes were detected, and 97 patients received ICD shocks. Sixty-one patients (10% of total) had 130 spontaneous ventricular tachycardia or fibrillation events terminated by ICD shocks. A total of 210 patients (33% of total) are known to have died (median, 1.7 years from MRI to death); 3 had cardiac arrhythmia deaths where shocks were indicated without direct evidence of device dysfunction.


The authors conclude that non–MRI-conditional ICDs appropriately treated detected tachyarrhythmias after MRI and that there were no serious device malfunctions in follow-up.


The presented findings are consistent with prior evidence that 1.5-Tesla MRI scans do not induce clinically significant functional changes in non–MRI-conditional ICDs made at least since 2005. Patients with valid indications for MRI who have non–conditional-MRIs should not be denied the test except in the vast majority of circumstances. Further studies will be necessary to confirm these findings with epicardial and abandoned leads, subcutaneous ICDs, and leadless pacemaker defibrillator systems.

Clinical Topics: Arrhythmias and Clinical EP, Noninvasive Imaging, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Magnetic Resonance Imaging

Keywords: Arrhythmias, Cardiac, Defibrillators, Implantable, Diagnostic Imaging, Magnetic Resonance Imaging, Pacemaker, Artificial, Shock, Tachycardia, Ventricular, Ventricular Fibrillation

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