Simpson’s biplane method: explanation, clinical context and references
The biplane method of disks (the modified Simpson’s rule) estimates left ventricular end-diastolic and end-systolic volumes from apical 4-chamber and apical 2-ch views; the ejection fraction (LVEF) is then calculated as EF = [(EDV − ESV) / EDV] × 100%. In routine practice the machine may report volumes from each apical view and clinicians commonly average the two view-derived volumes to obtain a biplane estimate; alternatively, if a single, validated EDV and ESV are provided by the lab (already derived by biplane disk summation), those direct values can be used. Stroke volume equals EDV − ESV; cardiac output can be estimated as SV × heart rate, and cardiac index as CO divided by body surface area (BSA). LVEF thresholds used for clinical categorization commonly follow guideline conventions (HFrEF <40%, HFmrEF 41–49%, HFpEF >50%), but LVEF should always be interpreted in the clinical context, taking into account image quality, geometric assumptions and additional measures (volumes indexed to BSA, strain imaging, natriuretic peptides, clinical status).
References:
Lang RM, Badano LP, Mor-Avi V, et al. Recommendations for cardiac chamber quantification by echocardiography in adults: an update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging. J Am Soc Echocardiogr. 2015;28(1):1–39.e14. StatPearls — Left Ventricular Ejection Fraction (overview and Simpson’s biplane description). European Society of Cardiology — 2021 ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure (definitions of HFrEF/HFmrEF/HFpEF). Cleveland Clinic patient guidance on normal EF ranges and clinical interpretation. Normal LVEF ranges and categorizations may vary by source; always reference your local lab’s reporting conventions when using numeric cutpoints.