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Cardiothoracic
Demonstration data

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.

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📐 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.