To the Editor.—
The Mobin-Uddin vena caval umbrella filter for preventing recurrent pulmonary embolism does not require general anesthesia. However, this distinct advantage is offset by the filter's distressing tendency to migrate. The latest report (Edwards Laboratories, written communication, Oct 1, 1971) states that 571 implantations have been followed by six reported cases of migration. Whether all migrations have been reported is not known. Of the five instances investigated, two occurred immediately after implantation, and the other three instances 4, 36, and 48 hours later. Three of the five patients died.When a vena caval umbrella filter migrates and threatens to embolize, it may be worthwhile attempting to push the loose filter down with a second and, by so doing, trap the loose filter. In the following case, implanting a second filter apparently prevented catastrophic migration of the initial filter into the pulmonary artery.
Report of a Case.—