What is the role of transthoracic echocardiogram (TTE) in patients with suspected or confirmed pulmonary embolism (PE)?

Transthoracic Echocardiogram Indications in Pulmonary Embolism

Transthoracic echocardiography (TTE) is strongly recommended in patients with suspected high-risk pulmonary embolism presenting with shock or hypotension, but is not recommended as a routine diagnostic test in hemodynamically stable patients with suspected PE. 1

Role in High-Risk PE (with hemodynamic instability)

• In patients with suspected high-risk PE presenting with shock or hypotension, bedside TTE should be performed immediately as the absence of echocardiographic signs of right ventricular (RV) overload or dysfunction virtually excludes massive PE as the cause of hemodynamic instability 1
• TTE can provide immediate diagnostic information when CT is not immediately available or when the patient is too unstable to be transported for CT imaging 1
• In a highly unstable patient, unequivocal echocardiographic evidence of RV dysfunction is sufficient to prompt immediate reperfusion treatment for PE without further testing 1
• TTE can help in the differential diagnosis of shock by detecting other potential causes such as pericardial tamponade, acute valvular dysfunction, severe LV dysfunction, aortic dissection, or hypovolemia 1

Role in Non-High-Risk PE (hemodynamically stable)

• TTE is not recommended as part of the routine diagnostic workup in hemodynamically stable patients with suspected PE 1
• TTE has limited sensitivity (approximately 50-56%) for detecting PE in hemodynamically stable patients, making it inadequate as a screening test to rule out PE 2, 3
• TTE may be useful in the differential diagnosis of acute dyspnea when clinical and laboratory findings are ambiguous 1
• TTE is valuable for risk stratification in confirmed non-high-risk PE to identify patients at intermediate risk who might benefit from more intensive monitoring or treatment 1

Echocardiographic Findings in PE

• Key echocardiographic signs of RV pressure overload and dysfunction in PE include:
  • RV dilatation (RV/LV end-diastolic diameter ratio >0.9 or >1.0) 1
  • RV hypokinesia 1, 2
  • Abnormal motion of the interventricular septum (flattening or paradoxical motion) 1
  • Tricuspid regurgitation with peak systolic gradient <60 mmHg in acute PE 1, 2
  • Decreased tricuspid annular plane systolic excursion (TAPSE <16 mm) 1
  • "60/60 sign" (RV acceleration time <60 ms with tricuspid regurgitation pressure gradient <60 mmHg) 4
  • "McConnell sign" (RV free wall hypokinesia with preserved apical contraction) 4

Prognostic Value

• TTE is recommended for guiding therapeutic options in patients with PE at intermediate risk 1
• Evidence of RV dysfunction on TTE in normotensive patients with PE identifies those at intermediate risk who may benefit from more intensive monitoring 1
• The presence of right heart thrombi, detected in up to 4-18% of PE patients (higher in ICU settings), is associated with RV dysfunction and high early mortality 1
• Serial TTE can be used to monitor the effect of treatment and assess whether the selected management strategy is successful 5

Limitations of TTE in PE Diagnosis

• TTE has moderate sensitivity (56%) and high specificity (90%) for PE diagnosis, making it inadequate as a standalone test to rule out PE 2
• The absence of RV dysfunction does not exclude PE in hemodynamically stable patients 1
• Echocardiographic signs of RV overload may be present in conditions other than PE (e.g., COPD, right heart failure) 4
• Specific signs like the McConnell sign have high specificity (94-100%) but low sensitivity (19-25%) 4

Summary of Recommendations

• Recommended uses of TTE in PE:

  1. In suspected high-risk PE with shock or hypotension when CT is not immediately available 1
  2. For distinguishing cardiac vs. non-cardiac etiology of dyspnea when clinical and laboratory findings are ambiguous 1
  3. For guiding therapeutic decisions in patients with PE at intermediate risk 1

• Reasonable uses of TTE in PE:

  1. To search for thrombi in the right atrium, ventricle, or main pulmonary artery branches 1
  2. For risk stratification in non-high-risk PE 1

• Not recommended:

  1. As part of the elective diagnostic strategy in hemodynamically stable, normotensive patients with suspected PE 1