Transthoracic M-mode echocardiographic assessment of pulmonary vein-to-pulmonary artery ratio in healthy horses.
Authors: Caivano Domenico, Corda Andrea, Rishniw Mark, Giorgi Maria Elena, Parpaglia Maria Luisa Pinna, Conti Maria Beatrice, Porciello Francesco, Birettoni Francesco
Journal: PloS one
Summary
Transthoracic echocardiography is central to equine cardiac assessment, yet reference values for pulmonary vessel dimensions remain limited in horses despite their established diagnostic value in small animal cardiology. Caivano and colleagues prospectively examined 70 clinically healthy horses using modified right parasternal views to obtain M-mode measurements of right pulmonary vein (RPV) and right pulmonary artery (RPA) dimensions, calculating multiple ratio indices including RPV/RPA and normalisation to aortic diameter (Ao). The RPV/RPA ratio showed median minimum and maximum values of 0.51 and 0.60 respectively, with fractional dimensional change of 33% for the vein and 22% for the artery; importantly, neither bodyweight nor heart rate correlated significantly with any measured variables, suggesting these indices may be consistent across different horse types. Measurement reproducibility was excellent for both inter- and intra-observer comparisons, establishing M-mode echocardiography as a reliable technique for acquiring these parameters in clinical practice. Whilst this work provides essential baseline data for practitioners, further investigation in horses with left-sided cardiac disease (such as mitral regurgitation or dilated cardiomyopathy) is necessary to determine whether RPV/RPA ratios can effectively indicate volume overload and guide clinical decision-making in the way they do in canine patients.
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Practical Takeaways
- •Veterinarians now have a feasible echocardiographic technique to measure pulmonary vein and artery dimensions in live horses, enabling future comparison in disease states.
- •These baseline reference values (RPV/RPA ratios and vessel-to-aorta indices) provide a foundation for detecting abnormalities associated with cardiac diseases involving left ventricular overload.
- •The technique's good measurement reliability means it could become a standardised part of cardiac ultrasound assessment once clinical utility is established in diseased populations.
Key Findings
- •Right pulmonary vein-to-right pulmonary artery ratio (RPV/RPA) median values were 0.51 (minimum) and 0.60 (maximum) in healthy horses.
- •M-mode echocardiographic measurement of RPV and RPA was feasible in all 70 healthy horses with very good inter- and intra-observer reliability.
- •No significant correlations existed between bodyweight or heart rate and RPV/RPA variables (r² ≤ 0.04), suggesting measurements are independent of these factors.
- •Median RPV/Ao and RPA/Ao ratios were 0.18, 0.28, 0.35, and 0.46 respectively, providing reference values for healthy horses.