Clinical Outcome of Patients with Intermediate Probability Lung Scans During Six-Month Follow-Up

A retrospective review of a consecutive series of patients with intermediate probability (IP) ventilation/perfusion lung scans was performed to evaluate: the frequency of documented thromboem-bolic (TE)disease, either pulmonary embolism (PE)or deep-venous thrombosis (DVT), at time of presentation; the prevalence of new diagnoses of TE disease during 6-mo follow-up; and occurrence of mortality during the same follow-up interval. Methods: Radiologie and clinical records for all patients who had ventilation/perfusion lung scans reported as IP or indeterminate during a 7-yr period were reviewed. TE disease at presentation or during follow-up was identified from results of pulmonary angiography, chest CT, lower extremity Doppler ultrasound and venography, and repeat lung scans. Occurrence of mortality and cause of death were determined by medical record review. Results: Of 164 patients studied, 36 (22%) had TE disease confirmed at initial presentation (PE = 19; DVT only = 17), and four others (2%) developed evidence of TE disease during follow-up, two with PE and two with DVT. Prevalence of TE disease was significantly greater in patients with matching perfusion/chest radiographie abnormalities and ventilation/perfu sion mismatches (0.5-1.5 segmental equivalents) than in those with various patterns of matching ventilation/perfusion defects (31% versus 14%, p < 0.01). Twenty-eight patients (18%) died during follow-up, but recurrent PE was implicated in only one death in a patient with angiographically-confirmed PE at initial presentation. Among the 116 patients who did not receive long-term anticoagu-lation after their initial lung scans, 22 (19%) died, none of whom had PE confirmed or suspected as a contributing cause. Conclusion: The prevalence of new or recurrent TE disease is low in patients with IP lung scans who are appropriately evaluated and managed after their initial presentation. No evidence of significant mortality second ary to untreated PE was found in the study group. Key Words: ventilation/perfusionlung scan; pulmonary embolism; deep venous thrombosis; clinical outcom