ICD maintains shock function after MRI

Stephen Padilla
20 Mar 2023
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The implantable cardioverter defibrillator (ICD) is a small device implanted under the skin in the chest, to help control life-threatening arrhythmias.

Non-magnetic resonance imaging (MRI)-conditional implantable cardioverter defibrillators (ICDs) are effective at treating detected tachyarrhythmias after MRI, with no serious adverse effects on device function seen, reports a study.

“Studies have shown that MRI does not have clinically important effects on the device parameters of non–MRI-conditional ICDs,” the researchers said. “However, data on non–MRI-conditional ICD detection and treatment of arrhythmias after MRI are limited.”

This prospective cohort study at a single centre in the US was conducted to determine if non-MRI-conditional ICDs have preserved shock function of arrhythmia following MRI. A total of 629 patients with the implanted device were consecutively enrolled from February 2003 to January 2015.

Using a prespecified protocol, 813 MRI examinations had been carried out at a magnetic field strength of 1.5 Tesla. The researchers then collected ICD interrogations after MRI and assessed the following clinical outcomes: arrhythmia detection and treatment, generator or lead exchanges, adverse events, and death.

Overall, the researchers detected 4,177 arrhythmia episodes during a median follow-up of 2.2 years from MRI to the latest available ICD interrogation before generator or lead exchange in 536 patients. Of these, 97 received ICD shocks. [Ann Intern Med 2023;doi:10.7326/M22-2653]

In addition, 61 patients (10 percent of total) experienced a total of 130 spontaneous ventricular tachycardia or fibrillation events, which were terminated by ICD shocks.

However, 210 patients (33 percent of total) were reported to have died during a median of 1.7 years from MRI. Of these, three had cardiac arrhythmia deaths in which shocks were indicated without direct evidence of device dysfunction.

This study was limited by its single-centre design, so data could not be generalized to other clinical settings and MRI facilities. Additionally, a subgroup of patients had no available ICD interrogations, and adjudication of the cause of death were reliant on death certificate data in a subset.

In an earlier study of an ICD system designed for full-body MRI at 1.5 Tesla, the findings showed that the system was safe and that the MRI scan had no negative impact on electrical performance or efficacy. [J Am Coll Cardiol 2015;65:2581-2588]

This 2015 study was conducted in 42 centres and enrolled 275 patients (mean age 60.4 years, 76 percent male). Ventricular pacing capture threshold and ventricular sensing amplitude, the efficacy endpoints, were achieved with minimal differences in the proportion of MRI and control patients who had a ≤0.5 V increase in ventricular pacing capture threshold (100 percent vs 98.8 perncet; p<0.0001) or a ≤50-percent decrease in R-wave amplitude (99.3 percent vs 98.8 percent; p=0.0001).

Thirty-four tachyarrhythmia or ventricular fibrillation episodes (20 induced; 14 spontaneous) occurred in 24 participants after MRI. There was no effect on sensing, detection, or treatment observed. [J Am Coll Cardiol 2015;65:2581-2588]

In another study, use of MRI was found to be lower among ICD patients than nonimplant counterparts. However, the burden of incident stroke, back and joint pain indicated the need for MR-conditional devices. [J Magn Reson Imaging 2016;43:115-127]

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