Correct!
2. A previous CT of the abdomen and pelvis
A CT of the abdomen and pelvis would be the most useful examination, among those listed, to review to determine the etiology of the embolized metallic fragment because a major source for such fragments is fractured inferior vena cava filter struts that subsequently undergo embolization. It is unlikely that brain MRI could suggest a source for a metallic fragment embolization to the heart. Lumbar spine MRI could show the presence of an inferior vena cava filter or other subdiaphragmatic sources of metal, but the metallic nature of filters, as is the case with practically any metallic implant at MRI, will show extensive dephasing artifact that will obscure the metallic structure itself as well as surrounding anatomy. So, the presence of the filter may be noted at lumbar spine MR, but the morphology of the filter- intact and properly positioned versus fractured and improperly positioned- would be far better characterized at CT of the abdomen and pelvis than lumbar spine MR. Furthermore, the field of view of lumbar spine MRI is often restricted- considerably more so than CT of the abdomen and pelvis- and therefore may not demonstrate a subdiaphragmatic source for embolization of a metallic fragment to the heart. Reviewing prior chest radiographs may provide some indication of the time line for the development of the metallic fragment- if enough prior images are available, it may be possible to find a chest radiograph that does not show the metallic fragment and thereby determine a time window when the fragment must have been acquired. However, review of older chest radiographs is unlikely to be capable of showing the etiology of the fragment (although occasionally inferior vena cava filters can be partially seen at chest radiography). Echocardiography could show the fragment in the right ventricle in a manner similar to CT, as well as determine the dynamic impact of the fragment during the cardiac cycle, but it is unlikely echocardiography could reveal the source of the metallic fragment.
Review of the previous CT abdomen and pelvis showed an inferior vena cava filter with an irregular appearance and probable fractured struts (Figure 4), likely the source of the metallic fragment within the right ventricle.
Figure 4. Representative static images from the contrast-enhanced CT of the abdomen and pelvis shows the presence of an inferior vena cava filter (arrow, panel A). Note the asymmetry in the struts posteriorly and medially, with absence of at least one strut between the 4 o’clock and 6 o’clock position (arrowheads, panels B – C). More inferiorly, note how one strut extends medially beyond the confines of the inferior vena cava and appears to pierce the lateral wall of the abdominal aorta (arrowheads, panels E and F). Video of the CT of the abdomen and pelvis is one the right.
Based on the data thus far, which of the following represents the next most appropriate step for the evaluation of this patient? (Click on the correct answer to proceed to the seventh of eight panels)