What is the role of echocardiogram (echo) in managing patients after a pulmonary embolism (PE)?

Role of Echocardiography in Managing Patients After Pulmonary Embolism

Echocardiography plays a crucial role in risk stratification and management decisions for patients after pulmonary embolism, particularly for identifying right ventricular dysfunction which is associated with a 2.29-fold increase in short-term mortality even in hemodynamically stable patients.

Immediate Post-Diagnosis Assessment

• Echocardiography should be performed immediately in patients with high-risk PE presenting with shock or hypotension, as the absence of right ventricular (RV) overload or dysfunction virtually excludes massive PE as the cause of hemodynamic instability 1
• In hemodynamically unstable patients with suspected PE, unequivocal signs of RV pressure overload on echocardiography are sufficient to justify emergency reperfusion treatment when immediate CT angiography is not feasible 2, 1
• Echocardiography helps in the differential diagnosis of shock by detecting other potential causes such as pericardial tamponade, acute valvular dysfunction, severe left ventricular dysfunction, aortic dissection, or hypovolemia 1

Risk Stratification in Hemodynamically Stable Patients

• Echocardiography 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
• Evidence of RV dysfunction on echocardiography is found in ≥25% of unselected patients with acute PE 2
• Systematic reviews and meta-analyses have shown that RV dysfunction on echocardiography is associated with an elevated risk of short-term mortality in hemodynamically stable patients 2
• Hemodynamically stable patients with acute PE who have RV dysfunction on echocardiography have a 2.29-fold increase in short-term mortality compared to those without RV dysfunction 3

Key Echocardiographic Parameters to Assess

• RV/LV diameter ratio ≥1.0 and tricuspid annular plane systolic excursion (TAPSE) <16 mm are the findings most frequently associated with unfavorable prognosis 2
• Other important parameters include:
  • Right ventricular dilatation and hypokinesis 1, 4
  • Abnormal interventricular septal motion 4
  • McConnell's sign (RV free wall hypokinesis with sparing of the apex) 4, 5
  • Tricuspid regurgitation with elevated pulmonary artery systolic pressure 4
  • Decreased S' velocity of the tricuspid annulus (<9.5 cm/s) 4
  • 60/60 sign (pulmonary acceleration time <60 ms with tricuspid regurgitation pressure gradient <60 mmHg) 4, 5

Special Considerations

• Echocardiography can identify right-to-left shunt through a patent foramen ovale and the presence of right heart thrombi, both of which are associated with increased mortality in patients with acute PE 2
• A patent foramen ovale increases the risk of ischemic stroke due to paradoxical embolism in patients with acute PE and RV dysfunction 2
• Right heart thrombi are detected in up to 4% of unselected PE patients and up to 18% in intensive care settings, and are associated with high early mortality 2, 1

Follow-up Echocardiography

• Right ventricular dysfunction may persist despite treatment with anticoagulation and almost complete resolution of perfusion defects on lung scan 6
• Follow-up echocardiography is useful to monitor the resolution of RV dysfunction and guide long-term management decisions 6
• Persistent RV dysfunction may indicate development of chronic thromboembolic pulmonary hypertension (CTEPH) 7

Differentiating Acute PE from Chronic Pulmonary Hypertension

• Key echocardiographic parameters that help distinguish acute PE from chronic pulmonary hypertension include:
  • Right ventricular free wall thickness (acute ≤5 mm, chronic >5 mm) 5
  • Tricuspid regurgitation pressure gradient (acute ≤46 mmHg, chronic >46 mmHg) 5
  • Right atrial enlargement (equal to left atrial size suggests acute, greater than left atrial size suggests chronic) 5

Pitfalls and Limitations

• Echocardiographic parameters have proved difficult to standardize, which may affect their prognostic value 2
• The positive predictive value for PE-related death is relatively low (<10%) in hemodynamically stable patients 2
• Echocardiography is not recommended as part of the routine diagnostic workup in hemodynamically stable patients with suspected PE due to its limited sensitivity 1
• Assessment may be challenging in patients with hyperinflated lungs due to COPD, but subcostal views can usually provide adequate visualization 7

Conclusion

• Echocardiography is essential for risk stratification in patients after PE diagnosis
• It helps identify patients with RV dysfunction who have higher mortality risk even when hemodynamically stable
• It guides decisions about level of care, monitoring intensity, and consideration of advanced therapies
• Follow-up echocardiography is valuable to assess resolution of RV dysfunction and screen for chronic complications