Value of transthoracic echocardiography in the diagnosis of pulmonary embolism: results of a prospective study in unselected patients

Purpose Echocardiography is advocated as a useful diagnostic test for patients with suspected pulmonary embolism (PE), but its diagnostic accuracy is unknown. The present study was undertaken to determine prospectively the sensitivity and specificity of transthoracic echocardiography in the diagnosis of PE. Subjects and Methods We examined 110 consecutive patients with suspected PE. Study protocol included assessment of clinical probability, echocardiography, and perfusion lung scanning. Pulmonary angiography was performed in all patients with abnormal scans. As echocardiographic criteria to diagnose acute PE, we used the presence of any two of: right ventricular (RV) hypokinesis, RV end-diastolic diameter > 27 mm (without RV wall hypertrophy), or tricuspid regurgitation velocity > 2.7 m/s. Clinical estimates of PE served as pretest probabilities in calculating, after echocardiography, the post-test probabilities of PE. Results Pulmonary angiography confirmed PE in 43 (39%) of 110 patients. Echocardiographic diagnostic criteria for PE yielded a sensitivity of 56% and a specificity of 90%. For pretest probabilities of 10, 50, and 90%, the post-test probabilities of PE conditioned by a positive echocardiogram were 38, 85, and 98%, respectively. The post-test probabilities of PE conditioned by a negative echocardiogram were 5, 33, and 81%, respectively. Conclusions In unselected patients with suspected PE, transthoracic echocardiography fails to identify some 50% of patients with angiographically proven PE. Echocardiographic findings of RV strain, paired with a high clinical likelihood, support a diagnosis of PE, but a negative echocardiogram does not necessarily rule out PE, especially when this entity is strongly suspected on clinical grounds