RAPID VENTRICULAR PACING IN A PACEMAKER PATIENT UNDERGOING MAGNETIC-RESONANCE-IMAGING

Magnetic resonance imaging (MRI) generates potent electromagnetic forc es in the form of a static, gradient, or pulsed radiofrequency magneti c field that can result in pacemaker malfunction. This report document s a case of rapid cardiac pacing during MRI in a patient with a dual c hamber pacemaker. Although the mechanism of rapid cardiac pacing is un clear, it was directly related to radiofrequency pulsing. We postulate d that the lead acts as an antenna for radiofrequency energy that inte racts with the pacemaker's output circuit, thus, causing cardiac pacin g at a cycle length representing a multiple of the repetition time; or perhaps rapid pacing is related to induced currents generated between the MRI unit and the pacing lead.