Ventilation/Perfusion Scan in the Diagnosis of Acute Pulmonary Embolism

Abstract

Pulmonary embolism (PE) is a relatively common and potentially fatal disorder, for which treatment is highly effective and improves patients’ survival. The accurate and expeditious diagnosis of acute PE can be difficult because of nonspecific clinical, laboratory, and radiographic findings [26, 48]. In 1975 it was estimated that 600 000 cases of PE occur in the United States annually and approximately 10% of patients with PE die within 1 h of the event [5]. For those who survive beyond the 1st h following PE, anticoagulation with heparin or thrombolytic agents is an effective therapy [1, 5]. Mortality in patients with PE who are not treated has been reported to be as high as 30% [5]. In contrast, correct diagnosis and appropriate therapy significantly lowers mortality to between 2.5% and 8% [1, 2]. Although anticoagulant therapy is effective in treating PE and reducing mortality, it is not without some risk. The prevalence of major hemorrhagic complications has been reported to be as high as 10%–15% among patients receiving anticoagulant therapy [23, 25]. One study found heparin to be responsible for the majority of drug-related deaths in noncritically ill hospital patients [28]. Accurate diagnosis of PE is therefore essential not only to prevent excessive mortality but also to avoid complications related to unnecessary anticoagulant therapy.