Echocardiographic Findings in Pulmonary Embolism
In suspected high-risk PE with hemodynamic instability, bedside transthoracic echocardiography (TTE) should be performed immediately to identify right ventricular (RV) overload and dysfunction, which can justify emergency reperfusion treatment when CT is unavailable or the patient is too unstable for transport. 1, 2
Primary Echocardiographic Findings
Classic Signs of RV Pressure Overload
The typical echocardiographic picture of hemodynamically significant PE includes the following findings 1:
- RV dilation and hypokinesis - The right ventricle becomes dilated with reduced contractility due to acute pressure overload 1
- Increased RV/LV diameter ratio >0.5 (or ≥1.0 for high-risk stratification) - Caused by interventricular septal bulging into the left ventricle 1, 2
- Dilated proximal pulmonary arteries - Reflects acute pulmonary hypertension 1
- Tricuspid regurgitation with increased jet velocity - Typically in the range of 3-3.5 m/s, though paradoxically may show only mild-moderate elevation (trans-tricuspid gradient <60 mmHg) despite severe PE 1
- Abnormal interventricular septal motion - The septum flattens or bows toward the left ventricle, creating a "D-shaped" left ventricle 1, 3
- Dilated inferior vena cava - Usually dilated and does not collapse on inspiration, reflecting elevated right atrial pressure 1
Specific Diagnostic Signs
McConnell's sign is a highly specific finding for acute PE: RV free wall hypokinesis with sparing of the apical segment, tested prospectively with 77% sensitivity and 94% specificity 1, 3. This regional wall motion abnormality distinguishes acute PE from other causes of RV dysfunction 1.
The 60/60 sign demonstrates severely disturbed RV ejection pattern (acceleration time <60 ms) with only moderate pulmonary hypertension (trans-tricuspid gradient <60 mmHg), which is 98% specific but only 48% sensitive for acute PE 1, 3.
Quantitative Parameters
- Tricuspid annular plane systolic excursion (TAPSE) <16 mm - Indicates RV systolic dysfunction and has prognostic value 2, 3
- Decreased S' velocity on tissue Doppler - Reflects impaired RV longitudinal function 3
- Pulmonary artery mid-systolic notching - Suggests elevated pulmonary vascular resistance 3
Direct Visualization of Thrombi
Right heart thrombi can be visualized in 4-18% of PE patients (higher in ICU settings), appearing as mobile masses in the right atrium, right ventricle, or inferior vena cava en route to pulmonary arteries 2, 4. These are associated with RV dysfunction and high early mortality 2.
Transesophageal echocardiography (TEE) may directly visualize thrombi in the main pulmonary arteries when transthoracic windows are inadequate 1, 5.
Clinical Application by Risk Category
High-Risk PE (Shock or Hypotension)
The absence of echocardiographic signs of RV overload or dysfunction virtually excludes massive PE as the cause of hemodynamic instability 1, 2. In highly unstable patients, unequivocal echocardiographic evidence of RV dysfunction is sufficient to prompt immediate reperfusion treatment without further testing 1, 2.
TTE serves critical roles in this setting 1, 2:
- Provides immediate diagnostic information when CT is unavailable
- Differentiates PE from other causes of shock (pericardial tamponade, acute valvular dysfunction, severe LV dysfunction, aortic dissection)
- Guides decision for thrombolysis or embolectomy
Non-High-Risk PE (Hemodynamically Stable)
TTE is NOT recommended as part of routine diagnostic workup in hemodynamically stable patients with suspected PE due to limited sensitivity 1, 2. A combination of RV/LV diameter ratio >0.5 and tricuspid regurgitant velocity >2.5 m/s showed only 81% specificity for PE diagnosis 1.
However, TTE remains valuable for 1, 2:
- Risk stratification - RV dysfunction identifies intermediate-risk patients who may benefit from intensive monitoring
- Prognostic assessment - RV dysfunction in normotensive patients confers 2.29-fold increased short-term mortality 2
- Differential diagnosis - When clinical and laboratory findings are ambiguous 2
Important Caveats and Pitfalls
Echocardiography cannot definitively confirm or exclude PE - It demonstrates the hemodynamic consequences rather than the thrombus itself 1. The sensitivity for PE diagnosis is only 50-60% with specificity of 80-90% 6.
Small or subsegmental PE may show normal echocardiography - When pressure overload is trivial, TTE findings may be entirely normal 5.
The degree of pulmonary hypertension may be paradoxically modest - The previously normal, non-hypertrophied RV cannot generate mean pulmonary arterial pressure exceeding approximately 40 mmHg acutely 7. This explains why tricuspid regurgitant velocities may suggest only mild-moderate elevation despite massive PE 1, 7.
Echocardiographic parameters are difficult to standardize - The positive predictive value for PE-related death is less than 10% in hemodynamically stable patients 2.
Serial echocardiography can monitor treatment response - Abnormalities resolve during recovery from PE, potentially more rapidly with thrombolytic therapy than heparin alone 7.