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Efficacy of thrombolytic therapy in pulmonary embolism determined by MION-enhanced MRA: an experimental study in
Rationale And Objectives:
This study determined whether contrast-enhanced magnetic resonance angiography could be used as a noninvasive imaging technique to determine the therapeutic effect and endpoint in thrombolysis of acute pulmonary embolism in an animal model.
Methods:
New Zealand white rabbits (n = 18) were anesthetized and mechanically ventilated. Single (n = 12 emboli) or dual (n = 12 emboli in 6 animals) pulmonary emboli were created by injecting autologous thrombi through a right internal jugular venous approach. Three-dimensional time of flight (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 tissue plasminogen activator/kg intravenously, and magnetic resonance angiography was repeated 30 minutes and 60 minutes after initiation of thrombolytic therapy.
Results:
MION-enhanced magnetic resonance angiography 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 multiple emboli. Magnetic resonance angiography allowed determination of thrombus resolution or thrombus persistence.
Conclusions:
It was feasible to diagnose pulmonary embolism accurately in this experimental study and to monitor thrombolysis of pulmonary emboli by MION-enhanced magnetic resonance angiography.