A non-invasive, quantitative method to demonstrate the early effects of therapy in acute pulmonary embolism

The objective of this study was to quantify the changes in pulmonary perfus ion due to therapy for pulmonary embolism (PE). To this end, seven consecut ive patients (five men, two women: mean age 64 +/- 10 years) were studied. After basal pulmonary arteriography had demonstrated the presence of massiv e PE, patients were injected intravenously with 4 mCi of technetium-99m-lab elled human albumin microspheres and were treated soon thereafter with a 2- h infusion of either alteplase 100 mg (five patients) or heparin 1,750 IU/h (two patients). Then, a second pulmonary arteriography study was obtained, and soon afterwards a single-photon emission tomographic (SPET) perfusion scan was performed. Immediately thereafter, a second intravenous injection of 4 mCi of Tc-99m-labelled microspheres was administered, followed by a se cond SPET scan. At the end of the study, the perfusion changes due to thera py were quantified by subtraction of the images of the two SPET studies; th e reperfused areas could be visualised and the volumes of reperfusion quant ified. This study demonstrates the validity of a newly devised, relatively rapid and noninvasive method for quantification of the early effects of the rapy on pulmonary perfusion in patients presenting with acute PE.