Investigations

Investigations (1)

• ECG:
  • often normal except for sinus tachycardia (2)
  • atrial fibrillation is not uncommon
  • the classic S1,Q3,T3 with right axis deviation and right bundle branch block is uncommon
  • evidence of myocardial ischaemia
• chest radiography occasionally show reduced vascular markings (2)
• blood gases may show impaired gas exchange with arterial hypoxaemia and hypocapnia (2)
• pulmonary infarction causes an increased ESR
• D-dimer - this is a highly sensitive but nonspecific test for diagnosing pulmonary embolism. A d-dimer below a certain cut point rules out PE with a high predictive value, at least in patients with a low or moderate clinical probability (3)
• ventilation-perfusion scan (1):
  • demonstrate areas of ventilation-perfusion mismatch
  • emboli are frequently multiple
  • the lower lobes are more frequently involved than the upper part of the lungs
• CT pulmonary angiogram (CTPA) - generally performed for anybody with a clinically high risk for PE, or patients with low or moderate clinical risk and a positive D-dimer result. If a ventilation-perfusion scan is performed and the result is equivocal then CTPA should subsequently be performed (4)

Notes:

• there is study evidence that elevated troponin levels identify patients with acute pulmonary embolism at high risk of short-term death and adverse outcome events (5)
• study evidence revealed that CTPA was not inferior to V/Q scanning in ruling out pulmonary embolism (6), but significantly more patients were diagnosed with pulmonary embolism using the CTPA approach
• diagnostic evaluation should begin with clinical assessment using a validated prediction rule in combination with measurement of D-dimer when appropriate (1)

References:

1. Konstantinides SV, Meyer G, Becattini C, et al. 2019 ESC Guidelines for the diagnosis and management of acute pulmonary embolism developed in collaboration with the European Respiratory Society (ERS).
2. National Institute for Health and Care Excellence. Venous thromboembolic diseases: diagnosis, management and thrombophilia testing. Aug 2023 [internet publication].
3. Raja AS, Greenberg JO, Qaseem A, et al. Evaluation of patients with suspected acute pulmonary embolism: best practice advice from the Clinical Guidelines Committee of the American College of Physicians. Ann Intern Med. 2015 Nov 3;163(9):701-11.
4. Howard LSGE, Barden S, Condliffe R, et al. British Thoracic Society guideline for the initial outpatient management of pulmonary embolism (PE). Thorax. 2018 Jul;73 (Suppl 2):ii1-29.
5. Becattini C et al. Prognostic value of troponins in acute pulmonary embolism: a meta-analysis. Circulation. 2007 Jul 24;116(4):427-33
6. Anderson DR et al. Computed tomographic pulmonary angiography vs ventilation-perfusion lung scanning in patients with suspected pulmonary embolism: a randomized controlled trial. JAMA. 2007 Dec 19;298(23):2743-53