Recommendations on the diagnostic investigations to be employed in suspected PE

Recommendations in the diagnosis include:

• in suspected high-risk PE
  • emergency CT - if patient is stable and CT is immediately available or
  • bedside echocardiography - if patient is unstable or CT not immediately available
    • will usually indicate indirect signs of acute pulmonary hypertension and right ventricular overload if acute PE is the cause of haemodynamic instability
    • occasionally right heart thrombi in transit may be detected in transthoracic echocardiography
    • if available a trans-oesophageal echocardiogram can be done to allow direct visualization of a thrombus in the pulmonary artery (1)
      
      
• in suspected non-high-risk PE
  • initially the clinical probability of PE should be assessed either implicitly or using a validated prediction rule in order to select a suitable diagnostic strategy for hemodynamically stable patients
    • in high clinical probability
      • a normal D-dimer result does not safely excludes PE (even with a highly sensitive assay) hence D-dimer test is not recommended
      • multidetector computed tomography (MDCT) should be the first line test in these patients
      • if MDCT is negative further diagnostic investigations should be considered before withholding PE-specific treatment
    • in intermediate and low clinical probability
      • plasma D-dimer measurement is recommended preferably using a highly sensitive assay - a negative results excludes pulmonary embolism and the need for further testing in about 30% of patients (1,2)
      • in patients with positive D-dimer test, do a multidetector computed tomography (MDCT) to confirm PE (2)

Notes:

The task force for the diagnosis and management of acute pulmonary embolism of the European Society of Cardiology suggest that the severity of PE should be understood according to the PE-related early mortality risk rather than the anatomical burden and the shape and distribution of intrapulmonary emboli (1).

Hence the task force suggests that the currently used terms such as 'massive', 'sub-massive' and 'non-massive' be replaced with the estimated level of the risk of PE-related early death (during the acute phase in the hospital or within 30 days ) (1).

Initially the patients can be divided according to the haemodynamic stability to:

• high-risk PE
  • the patient is unstable haemodynamically and may present with
    • shock or
    • persistent hypotension - systolic blood pressure <90 mmHg or a drop of >40 mmHg for more than 15 minutes that was not triggered by new onset arrhythmia, hypovolemia or sepsis
  • is a life threatening condition
    • requires specific diagnostic and therapeutic strategies
    • short term mortality is >15%
      
      
• non-high-risk PE
  • the patient is haemodynamically stable
  • can be further divided according to presence of markers of RV dysfunction and/or myocardial injury into
    • intermediate risk PE - at least one RV dysfunction or one myocardial injury marker is positive
    • low risk PE - all checked RV dysfunction and myocardial injury markers are found negative, short term PE related mortality is <1% (1)

Note:

• principal markers used in risk stratification of non-high-risk PE are:
  • right ventricular dysfunction
    • RV dilatation, hypokinesis or pressure overload on echocardiography
    • RV dilatation on spiral computed tomography
    • BNP or NT pro-BNP elevation
    • Elevated right heart pressure at RHC
  • myocardial injury
    • cardiac troponin T or I positive
    • human fatty acid binding protein (H-FABP) elevation

References:

1. Torbicki A et al. Guidelines on the diagnosis and management of acute pulmonary embolism: the Task Force for the Diagnosis and Management of Acute Pulmonary Embolism of the European Society of Cardiology (ESC). Eur Heart J. 2008;29(18):2276-315.
2. Meyer G et al. Pulmonary embolism. BMJ. 2010;340:c1421