In Vitro Evaluation of Magnetic Resonance Imaging–Induced Temperature Changes of Epicardial Leads in an Innovative Perfused Phantom

Objectives: Magnetic resonance imaging (MRI) has become an essentially valuable and increasingly applied imaging modality in pediatric and adult congenital heart disease (CHD) patients. In pacemaker patients, MRI has the potential risk to induce lead heating resulting in tissue fibrosis and pacemaker malfunction. To date, various MRI-conditional pacemaker systems have been introduced; however, epicardial leads as frequently used in CHD patients are not approved for MRI scans. We therefore studied lead heating characteristics of epicardial leads in comparison to MRI-conditional endocardial leads in an in vitro phantom.

Methods: Using 3D-printing technique, we developed a heart phantom that allowed active perfusion simulating blood circulation cooling effect occurring in vivo. Moreover, lead implantation sites were filled with porcine myocardial tissue to provide a realistic experimental setting. Heating at the lead tip was studied in two MRI-conditional endocardial leads and compared with two epicardial leads with varying generator positions during six different MRI sequences in a 1.5 Tesla scanner.

Result: Both epicardial leads showed a temperature increase comparable to the endocardial MRI conditional leads (median and maximum increase according to sequence and position 1.0–7.2 vs. 1.0–8.7 and 7.8–11.9 vs. 13.5–18.7°C, respectively). A reproducible cooling effect by perfusion was observed with a mean decrease in temperatures of 27 to 30% for the endocardial leads. Epicardial leads were less influenced by the perfusion with a mean temperature reduction of 12%.

Conclusion: MRI-induced heating of epicardial leads without approved MRI compatibility was comparable to that of MRI-conditional leads in vitro. Our results indicate that by restricting applied SAR (<2W/kg), MRI-scans could be safely performed in pacemaker systems with epicardial leads which would allow patients with complex CHD and epicardial leads to benefit from MRI imaging during follow-up. However, additional research is required to firmly establish MRI conditionality. Perfusion is a relevant factor influencing lead heating that should be appreciated in future in vitro MRI compatibility studies.

Publication History

Article published online:
21 February 2021