Transesophageal pulmonary artery flow detection of pulmonary embolism
Description
Each year more than one hundred thousand people die when blood clots, or emboli, which usually form in the legs, break loose, pass through the heart and block circulation in the lungs. At present, pulmonary angiography is the only reliable method of demonstrating pulmonary emboli. Pulmonary angiography, however, is an invasive, one-time procedure which is performed only to confirm a strong suspicion of pulmonary embolism. We have demonstrated that ultrasonic pulmonary artery flow-velocity signal patterns change with the passage of an embolus. In order to use this flow-velocity signal pattern change, a microcomputer-based continuous-wave Doppler embolism detection device was developed which, with a transesophageal probe, continuously monitors these flow signal patterns at the level of the pulmonary artery for the passage of emboli. In a series of acute canine procedures, the probe is positioned to receive the best pulmonary artery flow signal. Emboli are injected into the femoral vein and the resulting flow patterns recorded. The detection device in its present form detects the flow-pattern changes caused by emboli having volumes of approximately 3 cc., with a success rate greater than 70 percent. There are limitations in the pulmonary artery flow-velocity signal quality, which may be caused by the probe's distance from the pulmonary artery and by vessel wall movement. Further research is needed to determine the practical usefulness of this device in detecting pulmonary embolism