Diagnostic value of two-dimensional echocardiographic measurements of the pulmonary artery diameter and the pulmonary artery distensibility index to detect pulmonary hypertension in horses.

This study investigates the use of two-dimensional echocardiography to diagnose pulmonary hypertension in horses, focusing specifically on measurements of the pulmonary artery diameter and the pulmonary artery distensibility index.

Research Objectives and Methods

• The study aimed to explore the potential of two-dimensional echocardiographic variables, specifically the pulmonary artery diameter (PAD) and the pulmonary artery distensibility index (PADI), in diagnosing pulmonary hypertension (PH) in horses.
• Three groups were analyzed for this study: 41 healthy horses; 82 horses with tricuspid regurgitation (TR) or pulmonic regurgitation (PR) with normal intracardiac pressure gradients; and 35 horses with TR or PR velocities indicating PH.
• The PAD and PADI of these groups were then compared. The researchers also determined cut-offs for diagnosing PH using these variables.
• In cases where TR or PR was absent, researchers utilized conditional inference trees to identify the best-predicting variable for PH.

Key Findings

• The study found that horses with PH exhibited larger end-diastolic cross-sectional PAD (5.8 ± 1.0 cm) and smaller PADI (15.4 ± 7.7%) compared to healthy horses (5.0 ± 0.6 cm, P<0.0001; 20.5 ± 4.4%, P<0.001) and horses with TR or PR but no PH (5.3 ± 0.6 cm, P=0.003; 18.8 ± 4.2%, P=0.005).
• Using the PAD measurements, PH prediction achieved a sensitivity of 36% and a specificity of 94% with a cut-off diameter of 6.0 cm. The PADI was somewhat more effective in predicting PH, with sensitivity of 43% and specificity of 92% when using a cut-off index of 13.7%.
• When TR was missing, PAD and the ratio of end-diastolic long-axis aortic diameter-to-PAD (AoD/PAD) were the most appropriate variables for diagnosing PH.

Conclusions

• The study concluded that measurements of the end-diastolic cross-sectional diameter of the pulmonary artery and the pulmonary artery distensibility index, using two-dimensional echocardiography, were moderately specific but relatively insensitive to diagnosing PH.
• Regardless of their limitations, these measurements could serve as additional indices for suggesting the presence of PH, particularly when TR or PR isn’t present, hence contributing to more comprehensive diagnostic techniques.