2D Echocardiography Findings in Pulmonary Thromboembolism
Key Echocardiographic Findings
The typical echocardiographic picture of hemodynamically significant pulmonary embolism includes right ventricular dilatation with hypokinesis, increased RV/LV diameter ratio (>0.5), interventricular septal bulging into the left ventricle, dilated proximal pulmonary arteries, and tricuspid regurgitation with jet velocities typically in the range of 2.5-3.5 m/s. 1, 2
Right Ventricular Changes
- RV dilatation and hypokinesis are the hallmark findings, with RV diameter typically increased to a mean of 4.2 cm (range 3.2-6 cm) in acute PE 3
- RV/LV diameter ratio >0.5 combined with tricuspid regurgitant flow velocity >2.5 m/s has 93% sensitivity for PE diagnosis 1
- RV free wall thickness ≤5 mm distinguishes acute PE from chronic pulmonary hypertension (where thickness is >5 mm) 4
- McConnell's sign (hypokinesis of RV free wall with sparing of the apex) is 77% sensitive and 94% specific for acute PE 1, 4
Pressure and Flow Patterns
- Tricuspid regurgitation jet velocity of 2.5-3.5 m/s corresponds to pulmonary arterial systolic pressure of 40-50 mmHg, reflecting the inability of the acutely overloaded RV to generate higher pressures 1, 3
- Tricuspid regurgitation pressure gradient ≤46 mmHg (velocity ≤3.4 m/s) suggests acute PE rather than chronic pulmonary hypertension 4
- Pulmonary artery acceleration time <60 ms with midsystolic notching and trans-tricuspid gradient <60 mmHg (the "60/60 sign") is 98% specific for acute PE 1, 4
- Disturbed flow velocity pattern in RV outflow tract with severely reduced ejection pattern (acceleration time <60 ms) is highly specific for acute PE 1
Additional Findings
- Interventricular septal bulging into the left ventricle due to RV pressure overload 1, 2
- Dilated inferior vena cava without inspiratory collapse 1
- Dilated proximal pulmonary arteries 1
- Right heart thrombi detected in 4-18% of PE patients, associated with high early mortality 2, 4
- Decreased tricuspid annular plane systolic excursion (TAPSE) <16 mm indicates poor prognosis 2
Clinical Indications for Echocardiography
Recommended Uses
- Immediate bedside TTE in suspected high-risk PE with shock or hypotension when CT is not immediately available, as absence of RV dysfunction virtually excludes massive PE as the cause 1, 2
- Differential diagnosis of acute dyspnea when clinical and laboratory findings are ambiguous 1, 2
- Risk stratification and guiding therapeutic decisions in confirmed intermediate-risk PE 1, 2
- In highly unstable patients, unequivocal echocardiographic evidence of RV dysfunction is sufficient to prompt immediate reperfusion treatment without further testing 2
Not Recommended
- Routine diagnostic workup in hemodynamically stable patients with suspected PE, due to limited sensitivity 1, 2
- Elective diagnostic strategy in normotensive patients with suspected PE 1
Prognostic Value
- RV dysfunction on echocardiography is found in ≥25% of unselected PE patients and confers a 2.29-fold increase in short-term mortality 2
- RV/LV diameter ratio ≥1.0 identifies patients at higher risk for adverse outcomes 2
- Right heart thrombi are associated with RV dysfunction and high early mortality 2
- Patent foramen ovale with right-to-left shunt is associated with increased mortality 2
Important Caveats
The acute RV cannot generate pulmonary arterial systolic pressure >60 mmHg; therefore, pressures exceeding this threshold suggest chronic or recurrent PE rather than acute presentation 1, 4. This distinction is critical for appropriate management decisions.
Echocardiographic parameters have proved difficult to standardize, and the positive predictive value for PE-related death is less than 10% in hemodynamically stable patients 2. Therefore, echocardiography should be integrated into a comprehensive diagnostic approach including clinical probability assessment, D-dimer testing, and definitive imaging 2.