An Interchangeability Test Method for Developing IPG Impedance Equivalency Evidence for Cardiac Implantable...

Patients with cardiac implantable electronic devices (CIEDs) may receive replacement device components over time, resulting in mixed-manufacturer systems that pose unknown, potentially higher risk under MRI exposure. It is not clear how to efficiently evaluate whether adding a non-original implantable pulse generator (IPG) changes the system's radiofrequency (RF)-induced heating response. This study aimed to develop a least-burdensome RF safety evaluation method for MR Conditional labeling of CIEDs. Critical parameters were characterized and demonstrated as an IPG equivalency test method that supports leveraging existing single-manufacturer MR-Conditional labeling for mixed-manufacturer systems.

The transfer function model of the pacing lead was measured using the original system (Lead_A + IPG_A) or a third-party IPGs (Lead_A + IPG_B or IPG_C). Deposited power near the lead tip was compared for 50 Ω and open-end conditions, and lead or IPG impedances were measured at 64 and 128 MHz.

Lead tip heating was not significantly different between original and third-party IPGs configurations (p < 0.001). RF-induced heating responses were outside of measurement uncertainty when the lead was connected with a 50 Ω resistor and some open-end conditions. The results showed that small changes in IPG impedance (< 2.5 Ω) to the lead-IPG system impedance (> 80.2 Ω) may not significantly alter RF-induced heating, remaining within measurement uncertainties.

A simplified IPG impedance equivalency test has been developed to facilitate MRI access for patients with CIEDs that undergo IPG interchange. This test aids assessment of whether replacing an original IPG model with a different model may significantly increase RF-induced heating compared to the original system.