MRI safe for some ICD patients with left ventricular leads

With the right setting and monitoring, imaging via MRI is safe for patients with implantable cardioverter-defibrillators (ICD), according to a study published online Nov. 26 in Heart Rhythm.

The study looked at patients with coronary sinus left ventricular leads. Concerns about MRI use in this group of patients have included thermal damage to the coronary sinus, lead dysfunction or dislodgement and pro-arrhythmia, which has led to MRI imaging being discouraged. In some cases, however, MRI may still be medically necessary; therefore the research team sought to confirm the safety of imaging via MRI in patients implanted with this type of lead. 

Researchers scanned 40 patients at three different hospitals between 2005 and 2013. The patients were non-pacemaker dependent and all MRIs were medically necessary. Seth H. Sheldon, MD, of the division of cardiovascular diseases at the Mayo Clinic in Rochester, Minn., and colleagues ensured that each MRI was attended by specially trained pacing nurse or cardiologist, technicians, radiologists, and physicists. Patients were continuously monitored.

They performed the MRI with a 1.5 Tesla scanner with a specific absorption rate of less than 1.5 watts/kg, tailoring pulse sequences as needed. Patients whose heart rate synchronized to the scan had their imaging discontinued.

Of patients scanned, 78 percent had cardiac resynchronization with defibrillators, 18 percent had cardiac resynchronization with pacemakers and 5 percent had a dual chamber device with the coronary sinus left ventricular lead and the only ventricular lead. Scans occurred to the head/neck/spine in 83 percent of cases, lower extremities in 10 percent of cases, chest in 5 percent of cases, and abdomen in the remaining 2 percent.

Follow-up occurred per routine care post-MRI, however in 30 percent of cases, further follow-up occurred after 180 days.

Sheldon et al found no changes in impedance, pacing threshold, or coronary sinus left ventricular lead R wave sensing between pre- and post-MRI assessments. No significant changes occurred requiring intervention either. While one patient underwent lead revision more than three years after the MRI, they determined it was unrelated to the MRI.

No differences were noted between manufacturers: Devices by Boston Scientific, Medtronic and St. Jude Medical all performed equally as well following the MRI.

No lead dislodgement was seen post-MRI, nor were there differences in cardiac biomarkers.

Only one patient experienced a power-on reset, however, it neither interfered with the scan, nor was the patient adversely affected by it.

Sheldon et al wrote that their findings suggest MRIs are safe for these patients “under careful monitoring when performed with a 1.5T system keeping SAR [specific absorption rate] below 1.5.” These findings support previous reports.