Investigations

These include: (1)

• chest radiography reveals elevation of the diaphragm and linear areas of atelectasis in the basal zones, but may be normal.
• ECG: the S1,Q3,T3 pattern may be found with or without right heart strain but often the cardiogram is unhelpful. (2) A normal ECG does not rule out a PE.
• blood gases, pulmonary function tests
• V/Q scan may show 'non-matching' defects characteristic of pulmonary embolism, but interpretation must take consideration of the radiological appearance. (3) A normal chest radiograph is usually required before V/Q scanning.
• pulmonary angiography, if performed within a few days of onset of the condition will usually demonstrate embolised zones if they are large enough. The diagnosis of acute PE is made on the evidence of a thrombus, either as amputation of a pulmonary arterial branch or a filling defect.
• Multidetector computed tomographic pulmonary angiography (CTPA) is now the diagnostic modality of choice for patients with suspected PE. CTPA allows appropriate visualization of the pulmonary arteries down to the subsegmental level. It has a sensitivity of 83% and a specificity of 96% in PE diagnosis. (4) CTPA can also detect right ventricular enlargement and other indicators of right ventricular dysfunction.(5)

Reference

1. NICE. Venous thromboembolic diseases: diagnosis, management and thrombophilia testing. NICE guideline NG158. Published March 2020, last updated August 2023
2. Rodger M et al. Diagnostic value of the electrocardiogram in suspected pulmonary embolism. Am J Cardiol. 2000 Oct 01;86(7):807-9, A10
3. Sostman HD et al. Acute pulmonary embolism: sensitivity and specificity of ventilation-perfusion scintigraphy in PIOPED II study. Radiology. 2008 Mar;246(3):941-6.
4. Stein PD et al. Multidetector computed tomography for acute pulmonary embolism. N Engl J Med. 2006 Jun 01;354(22):2317-27.
5. Becattini C et al. Multidetector computed tomography for acute pulmonary embolism: diagnosis and risk stratification in a single test. Eur Heart J. 2011 Jul;32(13):1657-63.