EFFICACY OF THROMBOLYTIC THERAPY IN PULMONARY-EMBOLISM DETERMINED BY MION-ENHANCED MRA - AN EXPERIMENTAL-STUDY IN RABBITS

RATIONALE AND OBJECTIVES. This study determined whether contrast-enhan ced magnetic resonance angiography could he used as a noninvasive imag ing technique to determine the therapeutic effect and endpoint in thro mbolysis of acute pulmonary embolism in an animal model. METHODS. New Zealand white rabbits (n = 18) were anesthetized and mechanically vent ilated. Single (n = 12 emboli) or dual (n = 12 emboli in 6 animals) pu lmonary emboli were created by injecting autologous thrombi through a right internal jugular venous approach. Three-dimensional time of flig ht (TOF) magnetic resonance angiograms were obtained after intravenous administration of 2 mg Fe of a long circulating monocrystalline iron oxide. Animals then received 5000 IU heparin and 1.3 mg recombinant ti ssue plasminogen activator/kg intravenously, and magnetic resonance an giography was repeated 30 minutes and 60 minutes after initiation of t hrombolytic therapy. RESULTS. MION-enhanced magnetic resonance angiogr aphy accurately detected pulmonary emboli in all rabbits, Thrombolysis during the observation period was successful in 8 of the 18 animals. In animals with a single embolus, the revascularization rate was 50% ( 6 of 12 emboli), The rate was 33% (4 of 12 emboli) in animals with mul tiple emboli. Magnetic resonance angiography allowed determination of thrombus resolution or thrombus persistence. CONCLUSIONS. It was feasi ble to diagnose pulmonary embolism accurately in this experimental stu dy and to monitor thrombolysis of pulmonary emboli by MION-enhanced ma gnetic resonance angiography.