[Severe pulmonary embolism: value of clinical findings and complementary investigations]

Pulmonary embolism is severe when pulmonary arterial obstruction affects right heart haemodynamics and gas exchanges. The clinical signs are not very discriminating in the assessment of the severity of pulmonary embolism: shock, neurological signs and cyanosis are the most suggestive signs of severe embolism. Of the routine complementary investigations, normal blood gases does not exclude the diagnosis of even severe pulmonary embolism but when the pO2 is less than 50 mmHg the vascular obstruction is severe. The risk of haemorrhage due to thrombolysis, commonly used in severe pulmonary embolism, is greater after invasive investigations. This makes it preferable to resort to non-invasive investigation initially, echocardiography, spiral computed tomography or pulmonary scintigraphy, depending on which technique is available in an emergency. In a suggestive clinical setting, echocardiographic signs of right ventricular overload and visualisation of a thrombus in the right heart chambers or pulmonary artery on echocardiography or spiral computed tomography practically confirms the diagnosis of severe pulmonary embolism. Transoesophageal echocardiography is more sensitive than transthoracic echocardiography for the visualization of a thrombus in the pulmonary outflow tract, but is not always inoffensive in those patients in an unstable condition. Lung scintigraphy, when interpretable, provides the diagnosis of pulmonary embolism, shows the anatomic extension and allows follow-up of the outcome. However, the specificity of this investigation is problematic. Pulmonary angiography, coupled with catheterisation of the right heart, remains the reference investigation in the diagnosis of pulmonary embolism and its anatomical diffusion. It is reserved to situations in which echocardiography is difficult and scintigraphy is uninterpretable, notably in patients with previous cardiopulmonary disease.