2025 Pulmonary and Critical Care Medicine Fellows Course (INVITE ONLY)-SV Determination by Echocardiography Article

SV Determination by Echocardiography Article

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This article by Sattin et al. discusses the echocardiographic determination of stroke volume (SV) as a critical skill in critical care echocardiography (CCE), emphasizing its role in contextualizing two-dimensional (2D) cardiac abnormalities relative to hemodynamic status. Traditional basic CCE relies largely on qualitative 2D assessments, such as ventricular function and inferior vena cava size, but quantifying SV via Doppler measurements enhances clinical decision-making, providing a pragmatic indicator of cardiac contribution to shock states.<br /><br />The most accepted method to estimate SV noninvasively uses spectral pulsed-wave (PW) Doppler to measure the left ventricular outflow tract (LVOT) velocity-time integral (VTI) from apical five- or three-chamber views, combined with LVOT diameter (LVOTd) measurements from parasternal long-axis views. Stroke volume is calculated by multiplying the LVOT cross-sectional area (based on LVOTd squared times π) by the LVOT VTI. Since LVOTd is static in adults (~2 cm), changes in LVOT VTI primarily reflect changes in SV. Cardiac output can then be derived by multiplying SV by heart rate. The authors propose a streamlined workflow using LVOT VTI to rapidly evaluate whether 2D abnormalities impact hemodynamics, categorizing LVOT VTI into normal/elevated (≥22 cm), low (≤14 cm), or indeterminate (14–22 cm), guiding clinical interpretation and management.<br /><br />Clinical scenarios benefiting from SV measurement include distinguishing chronic compensated LV dysfunction from acute cardiac compromise, evaluating right ventricular failure's hemodynamic significance, and assessing hyperdynamic LV function states where volume status may be misleading. Serial LVOT VTI measurement is valuable for monitoring therapy response.<br /><br />Limitations include potential errors from improper Doppler alignment, aliased signals due to dynamic LVOT obstruction, and moderate to severe aortic insufficiency confounding SV estimates. Accuracy depends heavily on correct LVOTd measurement, as errors are squared in SV calculation. Training is feasible with focused instruction, with competency achievable after ~30–40 supervised examinations.<br /><br />In the presented case of septic shock with LV dysfunction and pericardial effusion, SV calculation revealed normal stroke volume, supporting a diagnosis of distributive shock rather than cardiogenic shock, thereby guiding appropriate vasopressor use without inotropes. The authors advocate incorporating SV measurement via LVOT VTI as a core component of CCE to enrich diagnostic precision and therapeutic guidance in critically ill patients.

Keywords

stroke volume

critical care echocardiography

LVOT velocity-time integral

Doppler echocardiography

hemodynamic assessment

left ventricular outflow tract

cardiac output measurement

shock differentiation

right ventricular failure

echocardiographic training