Pulmonary embolism: diagnostic algorithms.

In 90% of cases the clinical suspicion of pulmonary embolism (PE) is raised by clinical signs and symptoms, while in only 10% of cases PE is suspected on the basis of electrocardiographic, arterial blood gas analysis or radiological findings. The combination of clinical signs and symptoms and the results of first-level diagnostic tests (electrocardiography, gas analysis and chest X-ray) allows a fairly accurate classification of patients with "clinical suspicion of PE" into three categories of clinical (or pre-test) probability: low, intermediate and high. The clinical diagnosis of PE is very often inaccurate making the use of additional tests, including imaging techniques, mandatory. The choice and the combination (= diagnostic algorithms) of second- and third-level diagnostic tests (D-dimer, venous ultrasound, echocardiography, lung scintigraphy, helical computed tomography and pulmonary angiography) depend primarily on the clinical conditions of patients and their pre-test probability. We propose two diagnostic algorithms: 1) a diagnostic algorithm for patients with clinically suspected PE and critical clinical conditions (unstable patients), 2) a diagnostic algorithm for patients with clinically suspected PE and non-critical clinical conditions (hemodynamically stable patients).