Population Covered By The Guidance
This pathway provides guidance on the imaging of haemodynamically unstable adult patients with suspected pulmonary embolism.
Lead Researcher: Sian Chin
Experts & Contributors: Ravinder Dhillon, Rachael O’Rourke, Mark Teh, Yuranga Weerakkody
Editorial Panel: Core Membership
Date reviewed: February 2019
Date Published: July 2019
Hampton's Hump
Bilateral Pulmonary Embolism
Bilateral Pulmonary Embolism
Image 2a and 2b (Computed Tomography): Axial and reconstructed images of bilateral pulmonary arterial emboli (arrows)
- Suspected PE in the setting of haemodynamic instability is immediately life threatening and requires urgent investigation and treatment
- CT pulmonary angiography (CTPA) is a highly sensitive and specific test which can directly demonstrate PE through filling defects within contrast filled pulmonary arteries down to the segmental level. Although CTPA involves ionising radiation, the urgency of the situation justifies its use as a first line investigation if it is immediately available and if the patient is stable following resuscitation
- ECG-synchronised CTPA provides better assessment of ventricular function
- Haemodynamic measurements should always be recorded during pulmonary angiography to estimate the severity of PE and assist in diagnosing alternative cardiopulmonary disorders
- If the patient remains unstable following resuscitation or if CTPA is not available, bedside transthoracic echocardiography (TTE) is the most useful test. It can demonstrate signs of acute pulmonary hypertension secondary to PE and also assess for cardiac causes of shock
- A negative bedside TTE cannot exclude PE
- Transoesophageal echocardiogram (TOE) may be considered in specific clinical scenarios. Presence of a mobile right heart thrombus often indicates bilateral central pulmonary emboli
- Treatment includes systemic thrombolysis or catheter directed thrombolysis. Alternatively, catheter thromboembolectomy or surgical embolectomy can be considered in patients with contraindications to thrombolysis
References are graded from Level I to V according to the Oxford Centre for Evidence-Based Medicine, Levels of Evidence. Download the document
- Thompson BT KC. Overview of acute pulmonary embolism in adults. UptoDate [cited 2018 August 17]. 2016 (Review article). View the reference
- Miniati M, Monti S, Pratali L, Di Ricco G, Marini C, Formichi B, et al. Value of transthoracic echocardiography in the diagnosis of pulmonary embolism: results of a prospective study in unselected patients. Am J Med. 2001;110(7):528-35 (Level III evidence). View the reference
- Pruszczyk P, Torbicki A, Kuch-Wocial A, Szulc M, Pacho R. Diagnostic value of transoesophageal echocardiography in suspected haemodynamically significant pulmonary embolism. Heart. 2001;85(6):628-34 (Level III evidence). View the reference
- Roy PM, Colombet I, Durieux P, Chatellier G, Sors H, Meyer G. Systematic review and meta-analysis of strategies for the diagnosis of suspected pulmonary embolism. BMJ. 2005;331(7511):259 (Level I evidence). View the reference
- Diel NL LA, Seppelt I. The use of echocardiography in diagnosis, risk stratification and management of pulmonary embolism: a retrospective single-centre analysis. Journal of the Intensive Care Society. 2014;15(3):5 (Level III evidence). View the reference
- Dogan H, de Roos A, Geleijins J, Huisman MV, Kroft LJ. The role of computed tomography in the diagnosis of acute and chronic pulmonary embolism. Diagn Interv Radiol. 2015;21(4):307-16 (Review article). View the reference
- Konstantinides SV, Torbicki A, Agnelli G, Danchin N, Fitzmaurice D, Galie N, et al. 2014 ESC guidelines on the diagnosis and management of acute pulmonary embolism. Eur Heart J. 2014;35(43):3033-69, 69a-69k (Guideline). View the reference
- Stein PD, Woodard PK, Weg JG, Wakefield TW, Tapson VF, Sostman HD, et al. Diagnostic pathways in acute pulmonary embolism: recommendations of the PIOPED II Investigators. Radiology. 2007;242(1):15-21 (Guideline). View the reference
- Stein PD, Fowler SE, Goodman LR, Gottschalk A, Hales CA, Hull RD, et al. Multidetector computed tomography for acute pulmonary embolism. N Engl J Med. 2006;354(22):2317-27 (Level II evidence). View the reference
- Coche E, Verschuren F, Keyeux A, Goffette P, Goncette L, Hainaut P, et al. Diagnosis of acute pulmonary embolism in outpatients: comparison of thin-collimation multi-detector row spiral CT and planar ventilation-perfusion scintigraphy. Radiology. 2003;229(3):757-65 (Level III evidence). View the reference
- Megyeri B, Christe A, Schindera ST, Horkay E, Sikula J, Cullmann JL, et al. Diagnostic confidence and image quality of CT pulmonary angiography at 100 kVp in overweight and obese patients. Clin Radiol. 2015;70(1):54-61 (Level III evidence). View the reference
- Patel S, Kazerooni EA, Cascade PN. Pulmonary embolism: optimization of small pulmonary artery visualization at multi-detector row CT. Radiology. 2003;227(2):455-60 (Level II evidence). View the reference
- Schoepf UJ, Holzknecht N, Helmberger TK, Crispin A, Hong C, Becker CR, et al. Subsegmental pulmonary emboli: improved detection with thin-collimation multi-detector row spiral CT. Radiology. 2002;222(2):483-90 (Level IV evidence). View the reference
- Zamboni GA, Guariglia S, Bonfante A, Martino C, Cavedon C, Mucelli RP. Low voltage CTPA for patients with suspected pulmonary embolism. Eur J Radiol. 2012;81(4):e580-4 (Level III evidence). View the reference
- Meinel FG, Nance JW, Jr., Schoepf UJ, Hoffmann VS, Thierfelder KM, Costello P, et al. Predictive Value of Computed Tomography in Acute Pulmonary Embolism: Systematic Review and Meta-analysis. Am J Med. 2015;128(7):747-59.e2 (Level I evidence). View the reference
- van der Bijl N, Klok FA, Huisman MV, van Rooden JK, Mertens BJA, de Roos A, et al. Measurement of right and left ventricular function by ECG-synchronized CT scanning in patients with acute pulmonary embolism: usefulness for predicting short-term outcome. Chest. 2011;140(4):1008-15 (Level III evidence). View the reference
- Garg K, Sieler H, Welsh CH, Johnston RJ, Russ PD. Clinical validity of helical CT being interpreted as negative for pulmonary embolism: implications for patient treatment. AJR Am J Roentgenol. 1999;172(6):1627-31 (Level IV evidence). View the reference
- Kim KI, Muller NL, Mayo JR. Clinically suspected pulmonary embolism: utility of spiral CT. Radiology. 1999;210(3):693-7 (Level III evidence). View the reference
- Marshall PS, Mathews KS, Siegel MD. Diagnosis and management of life-threatening pulmonary embolism. J Intensive Care Med. 2011;26(5):275-94 (Review article). View the reference
- Aviram G, Levy G, Fishman JE, Blank A, Graif M. Pitfalls in the diagnosis of acute pulmonary embolism on spiral computer tomography. Curr Probl Diagn Radiol. 2004;33(2):74-84 (Level IV evidence). View the reference
Pathway User Guide
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The relative radiation level (RRL) of each imaging investigation is displayed in the pop up box.
| SYMBOL | RRL | EFFECTIVE DOSE RANGE |
|---|---|---|
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None | 0 |
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Minimal | < 1 millisieverts |
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Low | 1-5 mSv |
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Medium | 5-10 mSv |
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High | >10 mSv |
Disclaimer
Status Of Recommendations Each pathway is designed to assist clinicians in situations when faced with a large array of possible diagnostic tests and examinations. However, it is recognised that diagnostic practice may differ from a particular pathway depending on local availability of equipment and expertise, as well as the experience of individual clinicians. Therefore each pathway is neither a rigid set of rules, nor a substitute for clinical assessment, and individual patient circumstances should always be considered.
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Echocardiogram
Echocardiogram
Most useful initial examination if CT is not immediately available or patient remains unstable despite resuscitation. It can detect signs of acute pulmonary hypertension due to PE and can also assess for cardiac differential diagnoses of shock
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- Bedside transthoracic echocardiography (TTE) is a useful test in suspected haemodynamically unstable PE:
- TTE can detect indirect signs of pulmonary hypertension and right ventricular overload such as:
- Increased right ventricular size
- Decreased right ventricular function
- Tricuspid regurgitation
- TTE can also detect a right heart thrombus in transit
- TTE can detect indirect signs of pulmonary hypertension and right ventricular overload such as:
- Transoesophageal echocardiogram (TOE) may allow direct visualisation of thrombus in the pulmonary arteries
- Reported sensitivity ranges from 60-70%. In the setting of haemodynamic instability, the absence of echocardiographic signs of right ventricular overload or dysfunction practically excludes PE as a cause of the instability
- Echocardiography may also assist in the differential diagnosis of shock by detecting pericardial tamponade, acute valvular dysfunction, severe global or regional LV dysfunction, aortic dissection and hypovolaemia
- Echocardiography is currently not recommended in the diagnostic approach to haemodynamically stable, normotensive patients
Computed Tomography Pulmonary Angiography (CTPA)
Computed Tomography Pulmonary Angiogram (CTPA)
Multidetector CTPA is a highly sensitive and specific test which can directly demonstrate PE through filling defects within contrast filled pulmonary arteries down to the segmental level
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- Computed tomography pulmonary angiography (CTPA) is the primary imaging modality for evaluating acute pulmonary embolism (PE) if there is no contraindication to contrast agents
- PE is demonstrated by the presence of a filling defect within contrast filled pulmonary arteries
- The Prospective Investigation of Pulmonary Embolism Diagnosis II (PIOPED II) trial reported a sensitivity of 83% and specificity of 96% using mainly 4-row MDCT without consistent use of bolus tracking contrast administration. Discordant CTPA and pre-test clinical risk stratification required further investigation. The negative predictive value of high risk patients with a negative CTPA was only 60% and the positive predictive value of patients at low risk with a positive CTPA was 58%. Relatively high rates (6%) of studies were non-diagnostic
- Modern MDCTs provide better resolution, sensitivity and specificity in detecting PE to segmental or sub-segmental levels with lower ionising radiation doses
- A systematic review of 49 studies with 13,162 patients found that increased right ventricular to left ventricular (RV/LV) diameter ratio measured on transverse CT images conferred the strongest risk for PE related mortality compared to other CT parameters
- ECG-synchronized CTPA provides better assessment of ventricular function. A prospective cohort study of 113 patients found both decreased right ventricular ejection fraction (RVEF) and increased RV/LV diameter ratio conferred high risk for PE related mortality in ECG-synchronised CTPA
- CT is also able to provide information on alternative diagnoses that may mimic PE
- Limitations:
- Radiation exposure
- Risk of contrast allergy and contrast induced nephropathy
- Subject to interpretive pitfalls such as respiratory motion artefact, streak artefact and problems related to patient body habitus