What are the signs of pulmonary embolism on 2D (two-dimensional) echocardiography?

Echocardiographic Signs of Pulmonary Embolism

The most important echocardiographic signs of pulmonary embolism include right ventricular dilatation, right ventricular hypokinesia with sparing of the apex (McConnell's sign), interventricular septal flattening, and tricuspid regurgitation with moderate elevation of pulmonary arterial pressure. 1

Key Echocardiographic Findings

Right Ventricular Morphology and Function

• Right ventricular dilatation with RV/LV end-diastolic diameter ratio >0.6 or RV/LV end-diastolic area ratio >1.0 is consistent with significant pulmonary embolism 1
• Hypokinesis of the right ventricle, which may be global or limited to the mid-RV free wall with normal or hyperdynamic apex contraction (McConnell's sign) 1
• Regional right ventricular systolic wall motion abnormalities that spare the apical segment of RV free wall are 77% sensitive and 94% specific for acute pulmonary embolism 1, 2
• Decreased tricuspid annular plane systolic excursion (TAPSE) <16 mm indicates right ventricular dysfunction 3

Interventricular Septum

• Abnormal motion of the interventricular septum with flattening or bulging into the left ventricle due to right ventricular pressure overload 1
• Systolic flattening of the interventricular septum indicates right ventricular pressure overload 1, 4

Tricuspid Regurgitation and Pulmonary Pressure

• Tricuspid regurgitation with peak velocity typically in the range of 2.5-3.5 m/s 1
• In acute pulmonary embolism, pulmonary arterial systolic pressure is usually moderate (40-50 mmHg), as the normal right ventricle cannot generate pressures >60 mmHg acutely 1
• A severely disturbed RV ejection pattern with acceleration time <60 ms with only moderate elevation of pulmonary arterial systolic pressure (<60 mmHg) is 98% specific but only 48% sensitive for acute PE 1

Vena Cava and Pulmonary Arteries

• Dilated inferior vena cava with decreased inspiratory collapse (<40% of maximum expiratory diameter) 1
• Dilated proximal pulmonary arteries 1
• Disturbed flow velocity pattern in the right ventricular outflow tract 1

Diagnostic Value and Limitations

• Echocardiography has limited sensitivity (60-70%) but high specificity (80-90%) for diagnosing pulmonary embolism 1, 5
• A normal echocardiogram makes hemodynamically significant pulmonary embolism unlikely 1, 5
• In patients with suspected high-risk pulmonary embolism presenting with shock or hypotension, the absence of echocardiographic signs of RV pressure overload or dysfunction virtually excludes massive pulmonary embolism as the cause of hemodynamic instability 1
• Echocardiography cannot definitively confirm or exclude suspected PE but provides valuable information for risk stratification 1

Clinical Applications and Risk Stratification

• Echocardiography is recommended in suspected high-risk PE with shock or hypotension when CT is not immediately available 1, 3
• Echocardiography helps differentiate patients with non-high-risk PE into intermediate risk (evidence of RV dysfunction) versus low risk (no RV dysfunction) 1, 3
• Patients with moderate to severe RV dysfunction have worse outcomes and may benefit from more aggressive treatment strategies 1, 5
• Visualization of thrombi in the right heart chambers or pulmonary artery is rare but makes the diagnosis evident and indicates poor prognosis 1, 3

Common Pitfalls to Avoid

• Relying solely on echocardiography for diagnosis of PE in hemodynamically stable patients (CT pulmonary angiography is more sensitive) 1
• Misinterpreting chronic RV pressure overload as acute PE (pulmonary arterial systolic pressure >60 mmHg suggests a more chronic process) 1
• Overlooking that McConnell's sign (RV free wall hypokinesis with apical sparing), while specific, is not pathognomonic for PE and can be seen in other conditions 1
• Failing to recognize that echocardiographic signs of RV dysfunction may be absent in up to 50% of unselected patients with PE 1, 3

By systematically evaluating these echocardiographic findings, clinicians can better assess the likelihood of pulmonary embolism and stratify patients according to risk, which guides appropriate management decisions.