Measurements of right ventricular internal dimensions and their relationships to severity of tricuspid valve regurgitation in national hunt thoroughbreds.

This study examines the impact of tricuspid valve regurgitation (leakage of blood through the tricuspid valve of the heart) on the size of the right ventricular chamber in race-fit National Hunt Thoroughbreds. The research findings indicate that the severity of this condition is positively linked to the internal diameters of the right ventricle, suggesting a correlation between heart disease and the measurements of the right ventricle.

Research Methodology

• The study was performed on 394 Thoroughbred racehorses from four different training yards.
• Auscultation (listening to heart sounds) was used on every horse and the murmurs from tricuspid valve regurgitation (TR) were ranked on a scale of 1 to 6.
• Echocardiography, a procedure for visualizing the heart using sound waves, was employed. Specific focus was placed on long and short axis views of the right ventricle (RV), obtained from a right parasternal location.
• An m-mode image was taken of the RV just below the level of the tricuspid valve. This type of imaging provides a visual of the moving structures within the body.
• Colour flow Doppler (CFD) Echocardiography, a method for visualizing blood flow, was used on the tricuspid valve and right atrium. In cases where reverse blood flow was visible, pertinent recordings were taken.
• The severity of TR as determined by CFD was graded subjectively on a 1-9 scale.
• For assessment of repeatability, 5 horses were examined over five consecutive days, and images from 30 horses were measured twice.

Research Findings

• The researchers noted significant positive correlations between the severity of TR, as measured via CFD, and the internal diameter of the RV. This implies that the more severe cases of TR generally display larger right ventricle sizes.
• No significant associations were found between the grade of TR as determined by auscultation and right ventricle size. Meaning, the audible heart murmurs did not correlate with RV dimensions.
• In terms of the reliability and repeatability of RV measurements, it was found that only the M-mode-derived measurements had acceptable repeatability both intra-observer (the same observer measuring more than once) and day-to-day.

Conclusions

• The severity of TR measured via CFD was positively associated with both diastolic and systolic dimensions of the RV. Thus, an association between tricuspid valve regurgitation and right ventricle dimensions was demonstrable.
• However, the presence of a murmur (heard via auscultation) did not show a positive association with right ventricle size.
• M-mode and 2D echocardiography were found to be moderately reliable and repeatable methods for obtaining measurements of RV internal dimensions. Of them, M-mode was deemed the most reliable and repeatable method, especially for less-experienced operators.