Prognostic factors in restoration of pulmonary flow after submassive pulmonary embolism: a multiple regression analysis.

Defects as evaluated by lung perfusion scans may persist even 6 months after pulmonary embolism (PE), when treatment is withdrawn. The aim of this study was to evaluate the effect of several potential factors on the resolution of lung perfusion defects, both during the first days and at 6 months, when patients were discharged. In a retrospective follow-up cohort study we included 102 patients with PE, diagnosed lung from a ventilation/perfusion (V'/Q') scan, following Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) criteria, together with a phlebographic study of lower extremities or angiography. Lung perfusion scan was performed at diagnosis, and in two follow-up evaluations, at 7-10 days and at 6 months. Potential factors studied were: age; sex; presence of underlying cardiac or pulmonary disease; venous insufficiency; alveolar-arterial pressure difference for oxygen; delay in diagnosis; abnormalities in electrocardiogram or chest radiograph; and the size of defects as shown in lung perfusion scans. All factors were studied with regards to the size of the defects at the two follow-up evaluations, through a univariate statistical analysis and two multiple stepwise regression analysis. Multivariate statistical analysis selected four factors: size of defects at diagnosis; prior cardiopulmonary disease; delay in diagnosis; and sex, as synergistic variables to predict defect size at 7-10 days. On the other hand, the defect size at 7-10 days was the only variable selected as a predictor of the size of defects at 6 months. Resolution of pulmonary defects during the first days after diagnosis of pulmonary embolism is influenced by the initial defect size, prior cardiopulmonary diseases and sex. The size of residual defects at 6 months depends mainly on the size of defects at 7-10 days.