M-Mode Echocardiographic Measurements of Interventricular Septum, Left Ventricular Internal Diameter, and Left Ventricular Free-Wall Thickness in Normal Horses-A Meta-Analytical Study.
Authors: Marzok Mohamed, Kandeel Mahmoud, Babiker Hussein, Alkhodair Khalid M, Farag Alshimaa, Ibrahim Hussam, El-Ashker Maged, Alghuwainem Yousef, El-Khodery Sabry
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary A meta-analysis of fifteen published studies has consolidated reference ranges for M-mode echocardiographic measurements in healthy Thoroughbred and Standardbred horses, revealing considerable variation in how interventricular septum (IVS) thickness, left ventricular free-wall (LVFW) thickness, and left ventricular internal diameter (LVID) are reported across the equine literature. Using both fixed and random-effects statistical models, the researchers identified confidence intervals of 2.8–3.1 mm (fixed) and 4.7–7.5 mm (random) for IVS, 2.9–3.2 mm (fixed) and 4.2–6.7 mm (random) for LVFW, with substantially larger spreads for LVID measurements, indicating significant heterogeneity in study methodologies and potentially in horse populations studied. The marked heterogeneity (I-squared values exceeding 98% across parameters) suggests that differences in equipment, measurement technique, timing within the cardiac cycle, and horse demographics—rather than true biological variation alone—account for the wide ranges reported in the literature. For practitioners using echocardiography to screen for or diagnose cardiac disease, these findings underscore the critical importance of establishing individual baseline measurements and interpreting results within the context of each horse's history and clinical presentation, rather than relying on absolute reference values that may not be appropriate across all populations and imaging protocols.
Read the full abstract on PubMed
Practical Takeaways
- •M-mode echocardiographic reference values show substantial variation across studies; use breed-specific and institution-specific normative data when available rather than relying solely on this meta-analysis
- •When evaluating a horse for cardiac disease, interpret measurements in clinical context and compare to individual baseline or age-matched cohorts, as high heterogeneity limits applicability of pooled values
- •Standardization of M-mode echocardiographic measurement techniques across equine practitioners would improve comparability and clinical utility of cardiac assessments
Key Findings
- •Interventricular septum measurements ranged 2.8-3.1 mm (fixed effects) and 4.7-7.5 mm (random effects) in normal Thoroughbred and Standardbred horses
- •Left ventricular free-wall thickness ranged 2.9-3.2 mm (fixed effects) and 4.2-6.7 mm (random effects) with high heterogeneity (I-squared 98.08%)
- •Significant variation exists among published studies (Q statistic 925.3 for IVS, 886.6 for LVFW), indicating methodological or measurement differences
- •Meta-analysis of 15 studies demonstrates that individual horse cardiac assessments should be evaluated independently rather than against pooled reference values