Echocardiographic Findings in Cor Pulmonale
The typical echocardiographic picture of cor pulmonale includes right ventricular dilation and hypokinesis, increased RV/LV basal diameter ratio >1.0, interventricular septal flattening with leftward bowing (D-shaped left ventricle), dilated inferior vena cava (>21 mm with <50% inspiratory collapse), elevated tricuspid regurgitation velocity (typically 2.9-3.4 m/s or higher), and dilated proximal pulmonary arteries (>25 mm). 1, 2, 3
Core Right Ventricular Findings
The right ventricle shows characteristic morphological changes:
- RV dilation with hypokinesis - The RV free wall becomes dilated and demonstrates reduced contractility 1
- RV/LV basal diameter ratio >1.0 - This reflects the degree of RV enlargement relative to the left ventricle 2, 3
- RV hypertrophy - Chronic pressure overload leads to increased wall thickness 4
A particularly specific finding is regional RV wall motion abnormality sparing the apex - hypokinesis affects the RV free wall but notably spares the apical segment, which is 77% sensitive and 94% specific for acute pulmonary embolism causing acute cor pulmonale 1.
Interventricular Septal Changes
The interventricular septum demonstrates pathognomonic alterations:
- Septal flattening or paradoxical motion - The septum bows leftward into the LV cavity, creating a D-shaped left ventricle 2, 3, 5
- Left ventricular eccentricity index >1.1 - This quantifies the degree of septal distortion in systole and/or diastole 3
This septal deformation occurs because elevated RV pressure causes the septum to shift toward the lower-pressure left ventricle, particularly during systole and early diastole 6.
Pulmonary Artery Findings
The pulmonary circulation shows multiple abnormalities:
- Dilated main pulmonary artery >25 mm 2, 3
- RV outflow tract acceleration time <105 ms with or without mid-systolic notching 2, 3
- Early diastolic pulmonary regurgitation velocity >2.2 m/s 2, 3
A severely disturbed RV ejection pattern (acceleration time <60 ms) combined with only moderate elevation of pulmonary artery systolic pressure (<60 mmHg trans-tricuspid gradient) is 98% specific for acute pulmonary embolism, though only 48% sensitive 1.
Inferior Vena Cava and Right Atrial Changes
Volume overload manifests as:
- IVC diameter >21 mm with decreased inspiratory collapse (<50% with sniff or <20% with quiet inspiration) 2, 3
- Dilated right atrium with end-systolic area >18 cm² 2
The IVC findings are particularly important as they reflect elevated right atrial pressure. An IVC that doesn't collapse appropriately suggests RAP of approximately 15 mmHg 3.
Doppler Assessment of Pulmonary Pressures
Peak tricuspid regurgitation velocity is the cornerstone measurement:
- Velocity 2.9-3.4 m/s suggests intermediate probability of pulmonary hypertension 2, 3
- Velocity >3.4 m/s indicates high probability of pulmonary hypertension 2, 3
- Velocity typically ranges 3-3.5 m/s in hemodynamically significant pulmonary embolism 1
Using the simplified Bernoulli equation (4V²) plus estimated RAP, systolic pulmonary artery pressure can be calculated. This correlates well with invasive measurements when technically adequate tricuspid regurgitation jets are obtained 7, 8.
Probability Assessment Algorithm
The 2022 ACR guidelines provide a structured approach 2:
High probability for PH:
- Peak TR velocity >3.4 m/s (regardless of other signs), OR
- Peak TR velocity 2.9-3.4 m/s PLUS ≥2 categories of echo signs (RV findings, PA findings, IVC/RA findings)
Intermediate probability for PH:
- Peak TR velocity 2.9-3.4 m/s without additional signs, OR
- Peak TR velocity ≤2.8 m/s PLUS ≥2 categories of echo signs
Low probability for PH:
- Peak TR velocity ≤2.8 m/s without additional echo signs
Important Clinical Caveats
A normal echocardiogram makes hemodynamically important pulmonary embolism unlikely 1. However, echocardiography alone cannot definitively confirm or exclude suspected pulmonary embolism - it demonstrates the hemodynamic consequences rather than the emboli themselves.
Acoustic windows are frequently limited in patients with chronic lung disease, which commonly causes cor pulmonale 4. Subcostal views are often most successful in these patients 8.
Right heart catheterization remains necessary for confirmation of pulmonary hypertension before initiating specific PH therapies in patients with intermediate or high echocardiographic probability 2, 4.
The echocardiographic grading correlates well with invasively measured mean pulmonary artery pressures, ranging from normal (15.7 mmHg) in Grade 0 to severely elevated (39.4 mmHg) in Grade III cor pulmonale 8.