Doppler and volumetric echocardiographic methods for cardiac output measurement in standing adult horses.
Authors: McConachie E, Barton M H, Rapoport G, Giguère S
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary: Echocardiographic Measurement of Cardiac Output in Horses Monitoring cardiac output in critically ill adult horses remains clinically challenging because established methods require invasive procedures incompatible with clinical practice; McConachie and colleagues evaluated whether non-invasive echocardiographic techniques could reliably replicate lithium dilution cardiac output measurements across a range of haemodynamic states. Using eight healthy horses with experimentally manipulated cardiac outputs (16.6–63.0 L/min induced via dobutamine and romifidine infusions), the authors compared six echocardiographic methods against lithium dilution as a reference standard, with blinded image analysis to eliminate bias. Right ventricular outflow tract (RVOT) Doppler, Simpson's method, four-chamber area-length, and bullet methods demonstrated significantly lower bias (5.5–6.5 L/min) compared to left ventricular outflow tract Doppler and cubic methods (14.8–24.3 L/min), with superior performance maintained across both high and low cardiac output states. For practitioners, these findings suggest that RVOT Doppler and volumetric echocardiographic methods warrant integration into clinical assessment protocols for haemodynamic monitoring in critically ill horses, particularly as they avoid the invasiveness of established techniques and maintain accuracy across physiologically relevant ranges. Further validation in naturally occurring disease would strengthen the clinical utility of these approaches for real-world equine critical care.
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Practical Takeaways
- •Echocardiographic measurement of cardiac output is feasible in standing adult horses without invasive procedures, offering a noninvasive alternative for hemodynamic assessment in critical cases
- •Use RVOT Doppler, Simpson, 4-chamber area-length, or bullet methods for CO estimation; avoid LVOT Doppler and cubic methods which have unacceptably high error
- •These methods warrant clinical validation in critically ill horses before routine adoption in practice
Key Findings
- •Lithium dilution CO measurements ranged 16.6–63.0 L/min across manipulated hemodynamic states
- •RVOT Doppler, Simpson, 4-chamber area-length, and bullet echocardiographic methods had bias of 5.5–8.8 L/min versus lithium dilution
- •LVOT Doppler and cubic methods were significantly less accurate with bias of 14.8–24.3 L/min
- •Method of measurement significantly affected accuracy (P<0.001) but CO level and interactions did not