- PE will be diagnosed if there is a high probability V/Q scan (as per PIOPED Study criteria 66), an intraluminal filling defect in segmental or larger vessels on CTPA or a constant intraluminal filling defect or abrupt cut-off of vessels greater than 2.5 mm diameter on pulmonary angiography 8,10. Patients with non-definitive test results (e.g. low or intermediate probability V/Q scan, subsegmental PE on CTPA (~5% of PE patients 12) will not be included in order to have a strictly defined population of patients with definite PE.