Force and torque effects of a 1.5-Tesla MRI scanner on cardiac pacemakers and ICDs

Magnetic resonance imaging (MRI) is a widely accepted tool for the diagnosi s of a variety of disease states. However, the presence of an implanted pac emaker is considered to be a strict contraindication to MRI in a vast major ity of centers due to safety concerns. In phantom studies, the authors inve stigated the force and torque effects of the static magnetic field of MRI o n pacemakers and ICDs. Thirty-one pacemakers (15 dual chamber and 16 single chamber units) from eight manufacturers and 13 ICDs from four manufacturer s were exposed to the static magnetic field of a 1.5-Tesla MRI scanner. Mag netic force and acceleration measurements rr ere obtained quantitatively, a nd torque measurements were made qualitatively. For pacemakers, the measure d magnetic force was in the range of 0.05-3.60 N. Pacemakers released after 1995 had low magnetic force values as compared to the older devices. For t hese devices, the measured acceleration was even lower than the gravity of the earth (< 9.81 N/kg). Likewise, the torque levels were significantly red uced in newer generation pacemakers (<less than or equal to> 2 from a scale of 6). ICD devices, except for one recent model, showed higher force (1.03 -5.85 N), acceleration 9.5-34.2 N/kg), and torque (5-6 out of 6) levels. II I conclusion, modern pacemakers present no safety risk with respect to magn etic force and torque induced by the static magnetic field of a 1.5-Tesla M RI scanner. However, ICD devices, despite considerable reduction in size an d weight, may still pose problems due to strong magnetic force and torque.