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    109 Stroke volume (SV)
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    109 Stroke volume (SV)

    Stroke volume: normal values, preload, afterload and contractility, measurement methods and causes of changes.

    Stroke volume (SV) is the volume of blood ejected by each ventricle with one heartbeat. It equals the end-diastolic volume (filling) minus the end-systolic volume (what remains after contraction). In a healthy adult at rest it is about 60–100 mL. Stroke volume is determined by preload (how much the ventricle fills), afterload (the resistance against which it ejects) and contractility. Multiplied by heart rate it gives cardiac output. The fraction of the filled volume that is ejected is the ejection fraction.

    HaemodynamicsHeart functionCardiac output
    Adult at rest≈ 60–100 mL
    Stroke volume index≈ 33–47 mL/m²
    FormulaSV = EDV − ESV
    Ejection fractionSV / EDV × 100%
    Stroke volume in an adult at rest: below about 60 mL low, about 60 to 100 mL normal, above 100 mL high as in athletes or high-output states Stroke volume (mL per beat) Low below ≈ 60 60 Normal ≈ 60–100 100 High above 100
    Figure 1. Stroke volume zones in an adult at rest. Values depend on body size; the stroke volume index (per m² of body surface) allows comparison between people.

    How it is measured

    Invasively, stroke volume is calculated from cardiac output measured by thermodilution or the Fick method, divided by heart rate. Non-invasively, it is measured by echocardiography (ventricular volumes, or the velocity–time integral of flow in the left ventricular outflow tract multiplied by its area), by cardiac MRI, by oesophageal Doppler or by arterial pulse contour analysis. In critically ill and surgical patients, the change in stroke volume after a fluid challenge shows whether fluid improves circulation.

    Clinical significance

    Low stroke volume

    Low preload (bleeding, dehydration, vasodilation), weak contraction (heart failure, myocardial infarction, cardiomyopathy), high afterload (severe hypertension, aortic stenosis), very fast heart rate, tamponade, valve regurgitation.

    High stroke volume

    Trained athletes (large, efficient heart with slow pulse), pregnancy, anaemia, hyperthyroidism, aortic regurgitation (large total stroke volume, part of which flows back).

    When to see a doctor

    Breathlessness, reduced exercise tolerance, swelling of the legs or fainting may indicate reduced stroke volume and need echocardiography.

    References

    1. Vincent JL. Understanding cardiac output. Crit Care. 2008;12(4):174. doi:10.1186/cc6975
    2. 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. doi:10.1016/j.echo.2014.10.003

    This article is for general information and does not replace a consultation with a doctor. Measurements must be interpreted by a physician together with symptoms and other tests.

    Published on 7 May 2024