Pulmonary embolism is nearly always a complication of deep venous thrombosis. The evaluation of risk factors for venous thromboembolism not only aids diagnosis but also guides decisions about the intensity of prophylactic measures. As both the extent and chronicity of pulmonary vascular obstruction vary widely, pulmonary embolism can produce widely differing clinical pictures. From the clinical, pathophysiological and therapeutical point of view, it is convenient to classify pulmonary embolism into four types: acute minor embolism (dyspnoea with or without pleuritic pain or haemoptysis), acute massive embolism (hemodynamic instability), subacute mas- sive embolism (mimicking heart failure or indolent pneumonia), and chronic thromboembolic pulmonary hypertension (slowly progressing dyspnoea). This classification is of importance not only for the rational diagnosis and differential diagnosis, but also for the institution of adequate therapy. Because the disease has many nonspecific manifestations but no pathognomonic symp- toms or signs, it is impossible to prove the diagnosis of pulmonary embolism alone on the basis of clinical presentation.

        Key words: Pulmonary embolism - Venous thrombosis - Pulmonary hypertension