113 Left ventricular Stroke Work Index (LVSWI)

Left ventricular stroke work index: formula, commonly quoted range and its prognostic value in cardiogenic shock.

The left ventricular stroke work index (LVSWI) describes the mechanical work the left ventricle performs with each beat to eject blood against arterial pressure, related to body surface area. It combines the volume of blood ejected (stroke volume index) and the pressure generated, so it reflects both pump function and afterload. LVSWI is lowest in patients with severe heart failure and cardiogenic shock. A low LVSWI, measured invasively or estimated by echocardiography, is associated with higher mortality in cardiac intensive care.

HaemodynamicsLeft ventricleCardiogenic shock

FormulaSVI × (MAP − PAWP) × 0.0136

Unitg·m/m² per beat

Commonly quoted range≈ 50–62 g·m/m²

Reference methodpulmonary artery catheter

Figure 1. LVSWI zones. The 50–62 g·m/m² range is the reference range commonly quoted for invasive haemodynamic monitoring; very low values occur in cardiogenic shock.

Calculation

LVSWI = SVI × (MAP − PAWP) × 0.0136

(SVI = stroke volume index in mL/m², MAP = mean arterial pressure, PAWP = pulmonary artery wedge pressure in mmHg; 0.0136 converts mL·mmHg into g·m.) A simplified version uses MAP alone (SVI × MAP × 0.0144). The invasive reference method uses a pulmonary artery catheter; an echocardiographic version uses stroke volume index, MAP and the E/e′ ratio as an estimate of filling pressure.

Clinical significance

Low LVSWI indicates that the left ventricle generates little work: heart failure with reduced function, myocardial infarction, cardiomyopathy, myocarditis, severe valve disease and especially cardiogenic shock. In cardiac intensive care patients, echocardiographic LVSWI fell as shock severity increased and was associated with in-hospital mortality. High LVSWI is seen when the ventricle works against high pressure (hypertension) or ejects a large volume.

Seek emergency care

for breathlessness at rest, chest pain, cold clammy skin, confusion or very low blood pressure.

References

Jentzer JC, Anavekar NS, Burstein BJ, et al. Echocardiographic left ventricular stroke work index: an integrated noninvasive measure of shock severity. PLoS One. 2022;17(3):e0262053. doi:10.1371/journal.pone.0262053
Vincent JL. Understanding cardiac output. Crit Care. 2008;12(4):174. doi:10.1186/cc6975

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 8 May 2024