1. Pulmonary embolism is a sudden blockage in the pulmonary arteries usually caused by blood clots.
2. Symptoms include sudden onset of unexplained dyspnea, hemoptysis, and pleuritic chest pain, though this classic triad is present in less than 20% of patients.
3. Classification is based on clinical presentation and investigations and includes massive, submassive, and minor/non-massive pulmonary embolism.