Pulmonary angiography is the definitive test for diagnosis of PE (Gill & Nahum 2000). It involves percutaneous catheterization and injection of contrast dye into a pulmonary artery branch (Gill & Nahum 2000). It is an expensive test and is associated with a significant risk of complications (e.g. hemorrhage, embolus, nerve injury). Relative contraindications include significant bleeding risk, allergy to contrast medium, and renal insufficiency (Gill & Nahum 2000). It is associated with a mortality rate of up to 0.5% (Newman 1989, Stein et al. 1992). Pulmonary angiography is most commonly used when ventilation-perfusion scanning is non-diagnostic but clinical suspicion remains high (Tapson et al. 1999). A negative pulmonary angiogram excludes clinically relevant PE (Gill & Nahum 2000, Tapson et al. 1999).