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Should we pay more attention to the right pulmonary artery for the diagnosis of pulmonary hypertension?

Journal of Veterinary Internal Medicine, 2025

Giovanni Grosso, Rosalba Tognetti, Oriol Domenech, Andrea Della Pina, Federica Marchesotti, Valentina Patata, Tommaso Vezzosi

Background
Pulmonary hypertension (PH) in dogs is a significant condition that often necessitates precise echocardiographic evaluation of pulmonary artery (PA) dimensions. Historically, the main pulmonary artery-to-ascending aorta ratio (MPA/AO) has been used as the key diagnostic parameter for PH in dogs. However, the diagnostic utility of right pulmonary artery (RPA) measurements has not been fully explored. This study aimed to assess and compare the diagnostic accuracy of MPA and RPA dimensions in detecting PH and to evaluate differences in PA variables between precapillary and postcapillary PH.

Methods
Study Design: Prospective, multicenter, observational study

Subjects: 404 dogs (136 controls, 268 with PH; 152 precapillary and 116 postcapillary PH)

Imaging Techniques:
-Echocardiography with MPA and RPA size measured via 2D and M-mode imaging
-Parameters normalized for body weight (BW) or indexed to the aortic annulus (Aod)
-Calculation of right pulmonary artery distensibility index (RPADi): ([RPAmax − RPAmin]/RPAmax) × 100

Statistical Analysis:
-Receiver operating characteristic (ROC) curves assessed diagnostic accuracy
-Intra- and interobserver variability evaluated using the coefficient of variation (CV)

Results
Diagnostic Accuracy:
-RPADi, RPAmin normalized for BW (RPAmin_N), and RPAmin/Aod exhibited the highest diagnostic accuracy for detecting PH (AUC = 0.975, 0.971, and 0.953, respectively).
-MPA/AO also demonstrated excellent accuracy (AUC = 0.926) but was inferior to RPAmin variables (P < .05).
-RPAmax variables had the lowest diagnostic accuracy among the parameters evaluated.

Precapillary vs. Postcapillary PH:
-No significant differences in MPA or RPAmin variables between the two subgroups.
-RPAmax variables were significantly higher in dogs with precapillary PH.

PH Severity:
-All PA variables were significantly higher in dogs with severe PH compared to mild or moderate PH cases (P < .05).
-RPADi and RPAmin variables progressively decreased or increased with worsening PH severity.

Measurement Variability:
-RPAmin variables had the lowest intra- and interobserver variability (CV% intraobserver: 1.5%, interobserver: 3.2%), making them the most consistent measures.

Limitations
The control and PH groups were not fully age- or body weight-matched.
The classification of precapillary and postcapillary PH relied on non-invasive methods rather than the gold standard of right heart catheterization.
Potential influence of body condition score and ascites on BW-based normalized parameters was not assessed.

Conclusions
RPAmin measurements (normalized or indexed) outperform MPA size in diagnostic accuracy and consistency for detecting PH in dogs.
RPADi remains a complementary parameter but exhibits higher variability than RPAmin variables.
Incorporating RPAmin measurements into routine echocardiographic evaluations could enhance the noninvasive diagnosis and monitoring of PH in dogs.

Comparison of the receiver operating characteristic curve of each pulmonary artery variable for the detection of pulmonary hypertension. The area under the curve of the right pulmonary artery distensibility index (RPADi, red line; AUC = 0.975) was not higher than the RPA minimum diameter (RPAmin) normalized for body weight (BW; RPAmin_N, orange line; AUC = 0.971; P = .67) and RPAmin-to-aortic annulus ratio (Aod; RPAmin/Aod, gold line; AUC = 0.953; P = .06); RPAmin_N performed better than main pulmonary artery (MPA) (MPA-to-ascending aorta ratio [MPA/AO, green line; AUC = 0.926; P = .002] and MPA normalized for BW [MPA_N, blue line; AUC = 0.880; P < .001], respectively); MPA performed better than RPA maximum diameter (RPAmax) (RPAmax normalized for BW [RPAmax_N, purple line; AUC = 0.814; P = .01] and RPAmax-to-aortic annulus [RPAmax/Aod, pink line; AUC = 0.803; P = .005]).


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