MRI "safe" for patients with abandoned leads, study challenges the established guidelines
Recent safety data, modified protocols and the advent of MRI conditional devices have led to increased use of MRI in the patients with implanted devices. However, the presence of abandoned leads remains an absolute contraindication. In the current issue of JAMA Cardiology, Schaller and colleagues have presented the results of a prospective registry that shows the safety of MRI at 1.5 tesla in these patients and questions the absolute contraindication for MRI in patients with abandoned leads.
An abandoned pacing lead, whether capped, uncapped, or fragmented, is an implanted lead that is no longer in electrical continuity with a pacemaker or defibrillator generator. The theoretical risk to the patient of an abandoned cardiac lead during MRI relates to the potential for myocardial thermal injury. It has been demonstrated that a cardiac lead in a dynamic magnetic field can absorb pulsed radiofrequency energy, and can conduct that energy to the lead-myocardial interface.
The current study assessed if the performance of an MRI in the presence of an abandoned CIED lead is safe and whether there are deleterious effects on concomitant active CIED leads. A total of 139 consecutive patients (110 men [79%]) with a mean (SD) age of 65.6 (13.4) years underwent 200 MRIs of various anatomic regions including the thorax. Repeat examinations were common with a maximum of 16 examinations for 1 patient. There was a total of 243 abandoned leads. The mean (SD) number of active leads was 2.04 (0.78) and 46% patients were pacemaker dependent. A transmit-receive radiofrequency coil was used in 41 patients (20.5%), all undergoing MRI of the brain.
Variation in pre- and post-MRI capture threshold of 50% or more, ventricular sensing 40% or more, and lead impedance 30% or more, as well as clinical sequelae such as pain and sustained tachyarrhythmia were considered significant. Long-term follow-up lead-related data were analyzed if available.
The key findings were:
1. There were no abnormal vital signs or sustained tachyarrhythmias.
2. No changes in battery voltage, power-on reset events, or changes of pacing rate were noted.
3. CIED parameter changes including decreased right atrial sensing in 4 patients and decreased left ventricular R-wave amplitude in 1 patient were transiently noted.
4. One patient with an abandoned subcutaneous array experienced sternal heating that subsided on premature cessation of the study.
The study represents an important contribution to the literature that addresses MRI with abandoned pacing leads, the last remaining obstacle to the performance and insurance coverage for MRI in patients with an implanted cardiac device.
The findings of this study thus suggest that the presence of abandoned CIED leads should not necessarily preclude MRI, regardless of the anatomic region being studied.
Source: JAMA Cardiology:. Published online February 17, 2021. doi:10.1001/ jamacardio. 2020. 7572