Evaluation of doppler indexes of the lateral palmar digital artery in lame sport horses.

Overview

• This study investigated blood flow characteristics in the lateral palmar digital artery (LPDA) of horses with one lame forelimb using Doppler ultrasonography.
• Researchers aimed to determine if blood flow measurements differ between lame and sound limbs and whether those differences correlate with lameness severity.

Study Objective and Background

• The lateral palmar digital artery (LPDA) supplies blood to the forelimbs in horses.
• Typically, horses with lameness reduce the load on the affected limb while bearing weight.
• This altered weight bearing might change blood flow parameters, detectable using Doppler ultrasound.
• The goal was to assess if Doppler indexes such as peak systolic velocity (PSV), end-diastolic velocity (EDV), and resistive index (RI) differ between lame and sound forelimbs in horses with unilateral lameness.
• The study also aimed to evaluate whether these vascular changes correlate with how severe the lameness is.

Methods

• The study enrolled 27 lame horses and 15 healthy (sound) horses.
• Examinations were done while horses stood squarely and not sedated, ensuring natural weight distribution as much as possible.
• A single operator, blinded to lameness status and location, performed all pulsed-wave Doppler ultrasound imaging to measure:
• Peak systolic velocity (PSV): the maximum blood flow speed during heart contraction
• End-diastolic velocity (EDV): blood flow speed at the end of heart relaxation
• Resistive index (RI): a calculated value reflecting resistance to blood flow in the artery
• Measurements were taken from the LPDA in both forelimbs for comparison.

Key Findings

• No significant differences were found between lame and sound horses for EDV and RI values.
• PSV was significantly higher in lame horses compared to sound horses (P = 0.024), indicating faster peak blood flow velocity in the affected limbs.
• Differences in PSV between lame and sound limbs within the same horse (ΔPSV) were also significantly higher in lame horses (P = 0.002), suggesting the affected limb shows elevated PSV relative to the contralateral limb.
• There was no observed correlation between any Doppler index and severity of lameness, meaning blood flow changes do not predict how lame the horse is.

Interpretation and Implications

• The study suggests that horses shift weight off the lame limb, which might increase PSV values in the affected limb’s artery due to compensatory blood flow changes.
• However, since no correlation was found between Doppler indexes and lameness severity, PSV and other Doppler measurements are not reliable markers to gauge how severe a horse’s lameness is.
• The variability in PSV among lame horses implies that not all individuals respond in the same way, and other factors besides weight bearing reduction might influence LPDA blood flow.
• Future research could explore additional physiological or biomechanical influences on LPDA blood flow, potentially improving understanding or diagnostics of lameness.

Conclusion

• Doppler ultrasound can detect increased PSP in the lateral palmar digital artery of lame limbs, showing altered blood flow patterns.
• However, these measurements cannot reliably quantify or reflect the severity of lameness.
• Continued investigation is needed to clarify the mechanisms influencing LPDA blood flow changes in lame horses and to find better diagnostic tools for lameness assessment.