Recruitment of major aorto-pulmonary collateral arteries across pulmonary hypertension groups and its clinical significance

Background & Aims Although the recruitment of major aorto-pulmonary collateral arteries (MAPCAs) has been reported in group 4 pulmonary hypertension (PH) and some other PH subgroups, the clinical impact of these collaterals remains unclear. In this single-center study, we aimed to evaluate the frequency, correlates, and clinical significance of MAPCAs across different PH groups. Methods Our study included 434 patients with PH enrolled in a single-center study. The diagnostic work-up for PH was based on the definitive criteria of the ESC/ERS 2015 and 2022 Pulmonary Hypertension guidelines, depending on the time of the first hemodynamic confirmation. Multiparametric risk scores (MRS) included ESC/ERS 2022, SPAHR, COMPERA (3 strata), REVEAL 2.0, REVEAL Lite 2.0, and the French Pulmonary Hypertension Network (FPHN) risk models at baseline evaluation. All patients underwent coronary angiography and MAPCA assessment during diagnostic right heart catheterization, with MAPCA recruitment graded from none (0) to severe (4). Results Across PH groups, the overall frequency of MAPCA recruitment was 70.5% in group 1, 53.3% in group 2, 15.9% in group 3, and 74.3% in group 4, whereas the prevalence of moderate to severe MAPCA was 30.4%, 20.0%, 6.8%, and 58.3%, respectively (p < 0.001). In group 1 PH, moderate to severe MAPCA recruitment was observed in 31.4% of patients with idiopathic pulmonary arterial hypertension (IPAH), 29.4% with PAH associated with connective tissue diseases, and 28.9% with PAH associated with congenital heart disease (p > 0.05). MAPCA grade was significantly associated with pulse oximetric saturation (%) (p = 0.03), brain natriuretic peptide (BNP) levels (p = 0.04), pulmonary arterial systolic and diastolic pressures (PASP, PAMP) estimated by Doppler echocardiography, invasively measured PASP and PAMP, right atrial mean pressure, pulmonary vascular resistance, and the pulmonary-to-systemic vascular resistance ratio (p < 0.001 for all). All MRS models demonstrated significant associations between risk status and MAPCA grades (p = 0.015 to <0.001). Moreover, higher MAPCA grades were associated with clinical deterioration requiring IV diuretics, add-on triple therapy, and parenteral prostacyclins (p < 0.05 for all), but not with overall survival (p > 0.05). Conclusions Our results highlight the frequency of MAPCA recruitment across different PH groups and PAH subgroups, beyond group 4 PH. These collaterals appear to be associated with pulmonary hemodynamic severity and multiparametric clinical risk status in PH patients. However, the clinical significance of MAPCAs remains to be determined.