SCMR 22nd Annual Scientific Sessions
The evolution of pacemaker/ICD safety in the magnetic field has triggered considerable interest in the possibility of more clinically routine use. However, several limitations to widespread adoption of this seemingly implausible concept just a few years ago still remain. Cardinal among them is the unresolved impact of the high magnetic field and radio-frequency amplitude, oscillatory forces, gradient strength and SAR on the electronics with possible high field damage on the capacitor, solenoid and other microcircuitry. However, given recent vendor refinements along with improved RF shielding/choke over the last 8-10 years, we hypothesized that the impact on such circuitry may be far less than expected.
Systematic interrogation of consecutive patients who underwent clinically indicated MRI were evaluated over 36 months. Routine interrogation was performed within 10 minutes of entry into the bore of a dedicated Cardiac MRI scanner (GE, 1.5T, Excite, Milwaukee, WI). As well, reinterrogation was performed within 10 minutes of departure of the scan (average 23±14min). At the time of interrogation pre and post MRI, a separate, repeat interrogation was performed within 5 minutes of each other such that 2 sets of pacemaker/ICD parameters were obtained pre and post MRI scan (total of 4 interogations). Statistics aimed at inter- and intra-study variations were made to discern intrinsic/ambient variability (baseline) from that of post CMR-RF effect. Under the assumption that any variation above the intrinsic could be reasonably assigned as an CMR-RF induced effect, differences were accordingly assigned.
No complications to either patient or device occurred during the performance of the MRI scan. All together, 520 patients representing 304 pacemakers and 216 ICDs underwent MRI scanning. This cohort was comprised of neurologic/neurosurgical (73%), orthopedic (10%) and cardiac (17%) cases. Avg MRI scan time;:33±21min. A cardiologist was present and guided the interrogation, configuration and reconfiguration of the pacemaker/ICDs as well as was present for the entire scan. There were no significant differences in common clinical metrics. More importantly, there was no difference in any PM/ICD parameter when compared in any order pre to post MRI scan (Figure 1).
Intrinsic variability and inherent changes triggered by the MRI environment are statistically and clinically negligible at baseline and do not exceed ambient variability post-MRI. Accordingly, we remove yet another of the few logical fears and apprehensions for primary pacemaker/ICD failure and destruction as we move towards a more uniform acceptance of this technology for clinically meaningful use and acceptance.