A multisheathed catheter (12) includes an umbrella (18) positioned on its exterior sheath (16). In use, the umbrella (18) should be positioned within the pulmonary artery. The umbrella (18) has a meshwork (22) through which blood and plasma pass freely therethrough, but which is capable of catching emboli and other foriegn matter before they travel to the lungs. Detection equipment, including a two-dimensional ultrasound probe (44), differential sensors (54 and 56), and chemical sensors (44), are positioned to detect when an embolus has been caught in the umbrella (18). A conduit (64) transports lysing agents (66) such as TPA or heparin to the trapped embolus. In addition, the umbrella (18) can be closed on a trapped embolus using cords (34) and the embolus can be broken apart using ultrasonic probes (70) or can be removed by suction after it is drawn inside the lumen of the catheter (12).