RV/LV Diameter Ratio (CTPA)
Right-to-left ventricular short-axis diameter ratio on CT pulmonary angiography, a marker of right-heart strain in acute pulmonary embolism.
In acute pulmonary embolism, right ventricular dilatation on CTPA reflects acute pressure overload and right-heart strain. The RV/LV short-axis diameter ratio quantifies this and carries prognostic weight.
📐 Formula
RV/LV = RV short-axis diameter / LV short-axis diameter
🎯 When to Use
- Risk-stratifying patients with acute PE confirmed on CTPA.
- Identifying normotensive patients at higher risk of adverse outcome (intermediate-risk PE).
- Supporting decisions about monitoring intensity and reperfusion therapy.
⚙️ How It Works
- The maximal minor-axis (short-axis) diameter of each ventricle is measured between the endocardial border and the interventricular septum on axial (or reconstructed 4-chamber) CTPA images.
- The ratio is the RV diameter divided by the LV diameter.
- A reconstructed 4-chamber measurement is more accurate than a single axial slice but the axial ratio is widely used.
📊 Interpreting the Result
- RV/LV ≥ 1.0 indicates right ventricular enlargement and is associated with increased 30-day mortality and adverse clinical outcomes in acute PE.
- RV/LV < 1.0 confers a favourable short-term prognosis.
- The finding complements biomarkers (troponin, BNP) and the clinical PESI score in the ESC risk-stratification pathway.
⚠️ Limitations & Pitfalls
- Pre-existing chronic RV dilatation (chronic lung disease, prior chronic thromboembolic disease) reduces specificity.
- Axial slices may not capture the true maximal minor-axis diameter; 4-chamber reconstruction is preferred.
- A single ratio does not replace integrated clinical, biomarker and haemodynamic assessment.
📚 References
- Quiroz R, et al. Right ventricular enlargement on chest CT: prognostic implications in acute pulmonary embolism. Circulation. 2004;109:2401–2404.
- Kumamaru KK, et al. CT pulmonary angiography-based RV/LV ratio and outcome in acute PE. RadioGraphics / AJR, 2011–2013.
- Konstantinides SV, et al. 2019 ESC Guidelines for the diagnosis and management of acute pulmonary embolism. Eur Heart J. 2020;41:543–603.
⚕️ For clinical decision support only. Always verify calculations and apply clinical judgment.