Purpose: To evaluate the feasibility of bedside Technetium99-methoxy-isobutyl-isonitrile (99mTc-MIBI) cardiac imaging to assess perfusion after thrombolytic therapy (TT) for myocardial infarction (MI).
Methods: We studied 9 patients (mean age 59 +/- 9 years) submitted to TT with 100 mg of rt-PA in 90 minutes within the 6 hours of the onset of MI with subsequent angiography. 99mTc-MIBI was injected intravenously in a doses of 740 MBq immediately before TT start. Imaging was performed in three moments: study 1--as soon as the TT finished, study 2--3-18 hours after TT; study 3--7-10 days after TT. A perfusion score was established in each study and then compared to determine the perfusion patterns after TT. We compared through linear regression, the perfusion score with left ventricle ejection fraction, and with CKMB enzymatic peak.
Results: All patients had a patent infarct related artery. The perfusion score of study 1 varied from 12 to 22, mean 15.8 +/- 3.7, and correlated with ejection fraction (r = 0.9, p < 0.01) and peak CKMB (r = 0.78, p = 0.03). Four (44%) patients presented perfusion score improvement in study 2 (varied from 12 to 23, mean 16.8 +/- 4.3) and 8 (88%) in study 3 (varied from 12 to 28, mean 19.0 +/- 4.3).
Conclusion: Bedside 99mTc-MIBI cardiac imaging is useful to quantify myocardial area under risk before TT, and to identify the late (7 to 10 days) benefit of TT.