Efficacy of thrombolytic therapy in pulmonary embolism determined by MION-enhanced MRA: an experimental study in rabbits.
OBJECTIVE
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.
Frank
H
H
Second Department of Internal Medicine, University of Vienna, Austria.
Loewe
R
R
Loewe
C
C
Oberhuber
G
G
Schwaighofer
B
B
Huber
K
K
Weissleder
R
R
D000208:Acute Disease; D000818:Animals; D003287:Contrast Media; D004195:Disease Models, Animal; D004353:Drug Evaluation, Preclinical; D052203:Ferrosoferric Oxide; D005343:Fibrinolytic Agents / Q000627:therapeutic use*; D006493:Heparin / Q000627:therapeutic use*; D007501:Iron; D018810:Magnetic Resonance Angiography / Q000295:instrumentation / Q000379:methods*; D010087:Oxides; D017395:Plasminogen Activator Inhibitor 1 / Q000097:blood; D011655:Pulmonary Embolism / Q000097:blood / Q000175:diagnosis* / Q000188:drug therapy*; D011817:Rabbits; D011994:Recombinant Proteins / Q000627:therapeutic use; D012189:Retrospective Studies; D015912:Thrombolytic Therapy; D013997:Time Factors; D010959:Tissue Plasminogen Activator / Q000097:blood / Q000187:drug effects / Q000627:therapeutic use*
D003287:Contrast Media; D005343:Fibrinolytic Agents; D010087:Oxides; D017395:Plasminogen Activator Inhibitor 1; D011994:Recombinant Proteins; D006493:Heparin; D007501:Iron; D010959:Tissue Plasminogen Activator; D052203:Ferrosoferric Oxide