While no definitive answer presents itself for this question, Edward Martin, MD, an invasive/noninvasive cardiologist at the Oklahoma Heart Institute in Tulsa, Okla., said that the presence of an implantable cardioverter-defibrillator (ICD) is complex than a the presence of a pacemaker when imaging a patient. Martin presented his lecture in a series “The Latest Advances in Cardiovascular MRI” at the Transcatheter Cardiovascular Therapeutics conference this week in Washington, D.C.
Martin said that 2.4 million U.S. patients have pacemakers, and 400,000 patients have an ICD. Also, there are 15,000 MRI systems implemented worldwide, and 80 million studies are being conducted on this modality.
The current concerns with MRI studies on patients with ICDs or pacemakers are: asynchronous pacing can be pro-arrythmic; experimental myocardial infarction can produce a lack of output, with resolution of continuous monitoring; and induced-currents may cause heating of lead-tissue may interface with a threshold check required post-scan.
Currently, the ICD needs to be shut off, or sub-threshold, and asynchronous programming during an MRI exam.
According to Martin, 17 deaths have occurred in patients with pacemakers who have gone through an MRI. Unfortunately, those deaths were unmonitored, therefore, there is no information on the deaths, Martin said.
Martin reviewed a prospective institutional review board-approved study of 61 MRI exams in 54 patients, most of whom were non-pacemaker dependent. The results showed no changes in battery volume, including the two patients with pacemakers. Out of 308 leads, 145 right atrial and 162 left ventricular and one in coronary sinus, there were 11 significant changes. The two patients with pacemakers required increased programming, and one patient died, but it was not related to their pacemaker.
Martin strongly recommends that patients, who are pacemaker-dependent to put the devices in the asynchronous mode when undergoing and MRI.
He noted additional complications of an increased force and torque and a saturation of the transformer.
Martin is conducting study results at Oklahoma Heart Institute, in which he started with 12 patients, and is now up to 16 patients. In one patient, they had to engage the power-on reset, because that patient’s defibrillator failed. Martin stressed that the department should conduct design for tests after a patient undergoes an MRI, because there was no other way to know the ICD had failed.
In conclusion, Martin said that the presence of ICDs presents a more complex issue for MRI studies than a pacemaker’s presence.