Arteriovenous Oxygen Content Difference: A Diagnostic Predictor for Pre-Selecting Invasive Treatment in Congenital Heart Disease-Related Pulmonary Arterial Hypertension

Aim: Patients with congenital heart disease-related pulmonary arterial hypertension (CHD-PAH) often require regular follow-up through invasive right heart catheterization (RHC) to assess disease progression and potential interventions. This study aims to evaluate the relationship between arteriovenous oxygen content difference (Ca−vO2) and RHC parameters to identify blood gas parameters that can aid in a clue about pre-selecting patients with CHD-PAH for follow-up RHC and potential surgical or percutaneous shunt closure. Methods: In this study, a total of 137 adult CHD-PAH patients were retrospectively enrolled between September 2019 and May 2024. The patients were divided into two groups based on their Qp/Qs ratio (<1.5 or ≥1.5). Key parameters such as Ca−vO2, 6-minute walk distance (6MWD), TAPSE, and IVC diameter were correlated with RHC parameters such as mean pulmonary artery pressure (mPAP), pulmonary vascular resistance (PVR) and pulmonary capillary wedge pressure (PCWP) and compared across groups with Qp/Qs <1.5 and ≥1.5. Statistical analysis included Pearson correlation, Logistic regression analysis, and receiver operator characteristic (ROC) curve to determine the predictors for shunt severity. Results: The study enrolled 80 patients with CHD-related PAH in the final evaluation, with a mean age of 41 ± 15 years. Ca−vO2 exhibits a significant positive correlation with RHC parameters, notably with mPAP (r = 0.524, p < 0.0001) and a negative correlation with Qp/Qs (r = −0.463, p = 0.04). Moreover, Ca−vO2 emerged as a significant diagnostic predictor with an optimal cutoff value of <4.3mmol/L (AUC = 0.71, sensitivity 88.8%, specificity 53.4%). Other non-invasive parameters such as 6MWD, TAPSE, and IVC diameter with AUCs of 0.87, 0.83, and 0.85 respectively, also demonstrated a strong predictive value. Conclusion: Ca−vO2 correlates well with CHD-PAH severity and can serve as a pre-selecting marker for invasive follow-up in CHD-related PAH. Other non-invasive measures such as 6MWD, TAPSE, and IVC diameter show stronger predictive value for assessing shunt severity.