MRI can be safe in patients with pacemakers

MRI performed at an unlimited specific absorption rate is safe in patients with some permanent pacemakers or implantable cardioverter/defibrillator systems, as long as precautions are taken, according to a study from Israel.

The conventional wisdom has held that pacemakers are an absolute contraindication for MRI, mainly due to the presence of ferromagnetic components and the potential for electromagnetic interference. Practitioners are rethinking the ban since pacemaker devices are now smaller and have improved electromechanical interference protection.

"Consultation with a qualified cardiologist or electrophysiologist is strongly advised so that patients can be adequately screened and correctable physiologic abnormalities, such as hypoxia and electrolyte abnormalities, can be addressed prior to MRI," said Dr. Ariel Roguin, a senior lecturer in the cardiology department at Rambam Medical Center in Haifa, Israel, who spoke on the topic at the World Congress of Cardiology in Barcelona in September.

Special attention should be taken when the patient is pacemaker-dependent. The clinician must confirm that MRI is crucial to the management of the patient. The patient or a relative must sign a consent form that explains potential adverse reactions.

A physician or technician who is knowledgeable in device therapy and programming should be present throughout the examination, Roguin said. During the scan, high-quality ECG monitoring equipment, direct video visualization, audio communication, pulse oximetry, breathing monitoring, and resuscitation devices are essential.

Roguin presented details about 10 patients who had been scanned at Haifa. Six had pacemakers, and four had ICDs. In six patients, the brain was being investigated, while three underwent scans of the spine. Another patient had a knee scan. Two patients were pacemaker-dependent.

"During MRI, no device movement was felt by the patients and no episodes of inappropriate inhibition or rapid activation of pacing were observed," he said. "At interrogation, there were no significant differences between device parameters. Image quality was not influenced by the presence of the device."

Recent studies confirm that extrathoracic MRI of non-pacemaker-dependent patients can be performed with an acceptable risk-benefit ratio under controlled conditions, according to Dr. Luis Marti-Bonmati, chief of the MRI, CT, and abdominal radiology sections at Dr. Peset University Hospital in Valencia, Spain. Both MR and pacemaker-related precautions are essential, however.

"Several of the cardiovascular implants may be problematic for patients undergoing MR-both 1.5 and 3.0T-because of risks associated with magnet-related movements," he said. "We do not perform MR in these patients unless we know that the pacemaker is safe, the cardiologist is with us, and the clinical benefits are high."

Others are even less enthusiastic. It is important to remember the deaths that have occurred due to pacemakers, and it is not safe to routinely scan pacemakers, said Dr. Robert Herfkens, a professor of radiology at Stanford University's Lucas MRI Center in California.