ABSTRACT
Cardiovascular magnetic resonance (CMR) is widely reported as a safe modality, with no exposure limits, and thus is suitable for longitudinal studies. However, there are several conditions under which it would be unadvisable to scan a patient due to issues of safety. When evaluating safety issues associated with CMR studies of the heart, there are several approaches that can be taken to assess risk to the patient, including:
comparing the ratio of the number of scans without adverse events to the number of scans with adverse events,
sighting cases of patients who were scanned event-free with or without various implants, ranging from metallic eye liner to implantable cardiac devices (ICDs),
determining the risk on an individual basis. The first approach (i.e., sighting event rates) only gives us information
regarding the event rate for the scanned population (which could be refined for certain sub-populations, for example, those with ICDs). While this approach is generally unsatisfactory, it is nevertheless the criterion that is routinely used to assess the risk to patients undergoing procedures such as cardiac catheterization (where mortality is 1/1100). Use of the second approach (i.e., sighting anecdotal cases) can be countered as being
noninclusive, further it can be argued that even if some patients with ICDs were scanned event-free there may be known case of patients with such devices who have suffered adverse events. However, this method of assessing risk is commonly used to justify submitting patients to ionizing radiation. The third approach of assessing risk (i.e., on an individual basis) is commonly used in clinical practice to assess risk in complex cases. A question posed is ‘‘is the risk of using CMR to obtain a diagnosis substantially lower than the risk of not obtaining the diagnosis?’’ This approach is imperfect, since it relies on physician judgment and is often made from a standpoint of limited knowledge. Nevertheless, this is the approach that is routinely used and can be enhanced by educational programs and access to research data. To give physicians access to the latest information on contraindications for devices, a knowledge database is required. However, as knowledge increases, the list of devices and conditions that require consideration continues to grow. Thus, the process will always be imperfect because CMR technology and implantable devices are always changing. However, the number of resources available to physicians is increasing, including better patient records (searchable by computerized means) where the CMR compatibility of devices may be indicated and Internet web sites that provide up-to-date and searchable information on specific devices.
