Chest
Volume 97, Issue 3, March 1990, Pages 554-561
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Clinical Investigations
Natural Course of Treated Pulmonary Embolism: Evaluation by Perfusion Lung Scintigraphy, Gas Exchange, and Chest Roentgenogram

https://doi.org/10.1378/chest.97.3.554Get rights and content

Perfusion lung scintigrams, pulmonary gas exchange data, and chest roentgenograms were obtained in 33 patients during acute embolism and over the following six months in order to assess their clinical usefulness in monitoring the effect of therapy. To this purpose, the measurement of pulmonary gas exchange and the presence of chest x-ray findings were compared with perfusion lung scintigraphic abnormalities both at diagnosis and after 7, 30, and 180 days during treatment. More than 50 percent of the pulmonary arterial tree was obstructed at diagnosis, and a large part of perfusion recovery was complete within the first month. All of the gas exchange parameters were abnormal at diagnosis, and the rate of their improvement was related to that of perfusion recovery. Interestingly, PaO2st (ie, PaO2 corrected for hyperventilation) and V˙E tended to return to normal during the first month as a consequence of the progressive recovery of perfusion, whereas oxygen and carbon dioxide gradients and physiologic dead space showed the persistence of some abnormalities six months after diagnosis. Significant correlations were observed between the number of ULSs evaluated on the perfusion lung scintigram (and considered an index of the severity of pulmonary embolization) and all of the gas exchange parameters at diagnosis (correlation coefficients averaged from 0.41 to 0.73) and after 7 and 30 days. The enlargement of the right descending pulmonary artery and particularly the “sausage” sign and the Westermark sign were significantly associated with a higher degree of gas exchange impairment and with a more severe embolization. In conclusion, this study demonstrates that perfusion lung scintigraphy has a primary role in monitoring the recovery of patients with pulmonary embolism under treatment. Moreover, the chest roentgenogram may help in this purpose. A second major result is that the simple measurement of some gas exchange parameters may allow the assessment of functional recovery of these patients, thus giving additional information about the effect of therapy.

Section snippets

MATERIALS AND METHODS

Our study was performed in 33 nonconsecutive patients (17 men and 16 women; mean age, 57 ± 14 years) who were admitted to our ICU with a diagnosis of pulmonary embolism. In 21 of them (64 percent), the diagnosis of pulmonary embolism was initially made on the basis of the presence of multiple, large segmental defects on the perfusion lung scintigram.12, 13 According to McNeil,14 in patients who showed “multiple large (segmental or greater) perfusion defects, pulmonary embolism is very likely.”

RESULTS

Mean values (± 1 SD) of ULSs and of pulmonary gas exchange parameters in the acute phase of pulmonary embolism are reported in the following tabulation:

No. of ULSs11.3 ± 2.6
pH7.45 ± 0.03
PaO2, mm Hg63 ± 10
PaO2st, mm Hg52 ± 14
PaCO2, mm Hg34 ± 5
P(A-a)O2, mm Hg59 ± 15
P(a-A)CO2, mm Hg10 ± 4
VE, L/min12 ± 4
VD/VT%45 ± 10

At this time, the mean number of ULSs was 11.3 ± 2.6, showing that the fraction of the pulmonary arterial tree obstructed by emboli was 63 percent on the average (18 segments

DISCUSSION

The recovery of pulmonary perfusion after embolism may be influenced by several factors, such as prompt and adequate treatment, recurrence of emboli, and underlying pulmonary pathologic abnormalities. Therefore, an accurate follow-up of patients, both in the early stages after embolization and later on, is clinically helpful.

Previous reports show that perfusion lung scintigraphy, owing to its simplicity and safety, still remains the most suitable technique to assess the severity of embolization

ACKNOWLEDGMENTS

We thank Dr. M. Miniati and Dr. G. Viegi for critical review of the manuscript, and Dr. C. Marini and G. Di Ricco for having performed the pneumoangiography. We also thank G. Maltinti (University of Pisa) and P. Pisani (CNR institute of Clinical Physiology) for their helpful technical assistance.

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    Supported in part with funds from CNR (National Research Council) Cardiorespiratory Group and Ministry of Public Education of Italy.

    Manuscript received Decemher 14; revision accepted August 22.

    Dr. A. Giannella-Neto was partially supported by funds from the bilateral cooperation between CNR and CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico) of Brazil.

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