Vena cava umbrella filter: experimental, hemodynamic and embolization studies.

The Mobin-Uddin umbrella filter was placed into the inferior vena cava of mongrel dogs. Studies on hemodynamics and embolization were performed using blood flow and pressure determinations, cineangiography, and radiopaque emboli. Initially flow and pressure remained unaffected by the filter. At 70 minutes flow was only one fourth of the initial IVC flow. Immediately after positioning of the filter emboli up to 6 mm in diameter bypassed the filter, and smaller emboli passed through the perforations in the filter. Thrombus formation on the surface of the umbrella was already noted within one hour. At autopsy after two hours all the perforations were occluded by thrombus on both sides of the filter, and one week later the infrarenal vena cava was completely occluded by firm organized thrombus below and above the filter.