The availability of high-field-strength magnets, high-performance-gradient hardware, and ultrafast sequence technology in recent years has transformed cardiac magnetic resonance imaging (MRI) into a multifunctional tool. Cardiac MRI can provide three-dimensional analysis of cardiac anatomy, viability, motion, and function with high accuracy and reproducibility.1,2 Because of the complexity of cardiac anatomy and motion, cardiac MRI can be challenging and previously had been performed primarily at specialized centers. More recently, a comprehensive cardiac MRI exam has become a reliable clinical tool in a wide range of healthcare centers. In this article, we briefly outline imaging techniques and illustrate the various applications of cardiac MRI.
Communication between the surgeon and the MRI center is essential for efficient and accurate diagnosis. The examination will then be tailored to the specific clinical question. Instructing patients as to the nature of the examination will likely significantly improve the quality of the test. During the MRI examination, patients will need to perform multiple breath-holds of about 10- to 20-s duration. Patients with severe shortness of breath or who cannot lie flat on the MRI table are often poor candidates for cardiac MRI. Such patients should be discussed with the MRI center prior to referral. Overall, a directed examination requires about 20 to 30 min, whereas a comprehensive examination will require 45 to 60 min. There are no restrictions on eating or drinking before the MRI examination except if stress examinations are performed (see below).
Compatibility of a patient’s devices with the MRI scanner is a frequent issue and changes frequently with technology development. In general, all prosthetic cardiac valves are MRI compatible. Pacemakers and implantable cardioverters/defibrillators (ICDs) have previously been considered as strict contraindications to MRI. However, there have been recent reports at our institution and others of patients who have safely undergone MRI at 1.5 T magnetic field strength with certain types of these devices in place.3,4 In these instances, imaging information from other techniques, such as computed tomography or echocardiography, was incomplete. Currently, MRI scanning with pacemakers or ICDs in place remains investigational. Older devices manufactured before the year 2000 and certain manufacturers’ devices are less likely to be MRI compatible. Lower magnetic field strength (i.e., 1.5 T instead of 3 T) should also improve safety in conjunction with implanted devices. Thus, consultation with the MRI center should be performed when an MRI examination is deemed essential to patient care.
Coronary and other vascular stents are increasingly common. Most stents have not been explicitly tested by the manufacturer for MRI compatibility. Package labels from the manufacturer may indicate that MRI may be performed 6 weeks after implantation, with the rationale that the stent is endothelialized at that time and less likely to move in the magnetic field. Our approach is to evaluate these devices on a case-by-case basis. ...