To discuss: a) potential adverse effects of MRI on implanted pacemakers and defibrillator systems, b) selection of appropriate candidates with pacemakers and defibrillator systems for MRI, and c) methods to minimize potential risks of MRI in patients with pacemakers and defibrillator systems based on in vitro and in vivo testing of devices.

MRI is currently unavailable for millions of patients with implanted cardiac devices. Recent research, however, has demonstrated that certain devices can safely undergo MRI when a particular safety protocol is followed. The protocol begins by identification of patients with devices shown to be resistant to static and varying magnetic fields by previous in vitro and in vivo testing. Pacing mode is then changed to asynchronous for pacemaker dependent patients and demand for others. Magnet response and tachy-arrhythmia functions are disabled. Blood pressure, telemetry, oximetry, and symptoms are monitored. Specific absorption rate is limited to 2.0 W/kg for all sequences. Device interrogation is then repeated to ensure appropriate device function. In this exhibit, we will demonstrate methods for performance of MRI in patients with selected devices. Diagnostic questions can be answered in the majority of cases and may significantly alter patient care in an expanding proportion of patients.

A.L.,R.D.B.: Serve as scientific advisors for Guidant Inc.
H.R.H.: Serves as a scientific advisor for Medtronic Inc.