198 Intrapulmonary shunt assessment in pulmonary arterial hypertension

Abstract

Abstract Aims Pulmonary arterial hypertension (PAH) is a rare, progressive disease with a poor prognosis. It is characterized by the presence of mean pulmonary arterial pressure (mPAP) ≥25 mmHg along with a pulmonary arterial wedge pressure (PAWP) ≤15 mmHg and pulmonary vascular resistance (PVR) >3 Wood units at right heart catheterization, in the absence of other causes of pre-capillary PH such as PH due to lung diseases, chronic thromboembolic PH, or other rare diseases. Hypoxaemia is a frequent finding in patients with PAH and could be related to ventilation–perfusion mismatch, reduced diffusing capacity, decreased cardiac output, or the opening of intrapulmonary (IP) or intracardiac shunt. Purpose of the present study is to detect IP shunts in PAH patients and its determinants. Methods and results We retrospectively enrolled 29 PAH patients, collecting clinical parameters, haemodynamic and blood gas analysis at baseline and after specific therapies at follow-up. Shunt fraction was calculated by the formula (Cc—Ca)/(Cc—Cv) during oxygen supplementation (FiO2 100%). Intracardiac defects were excluded by echo contrast examination. As expected, after treatments our results showed a significant decrease of PAPm (−7.2 ± 11.6 mmHg) and a significant decrease of PVR (−2.1 ± 3.9 WU). However, it was reported a statistically significant decrease in Hb value (−1.2 ± 1.7 g/dl), in SpO2 (−2.1 ± 3.8%) and in the alveolar–arterial oxygen gradient (a-ADO2) (+54.5 ± 113.1 mmHg). 6MWT and NYHA decreased at follow-up but not statistically significance was detected. IP shunt increase was detected at follow-up after specific treatments (delta Shunt +6.9 ± 6.5%). At multivariate analysis delta PVR remains the only independent determinants of delta Shunts with a significative increment of shunts when PVR are reduced by more than three WU. Conclusions Specific PAH treatments determine a decrease of PVR, but a reverse correlation with IP shunt was noticed. Increase of IP shunt could be not a favourable clinical feature. In fact high IP shunt fraction could determine hypoxaemia and the need of a chronic oxygen supply therapy. Although a not statistically significant decrease of 6MWT and NYHA was found, it is reasonable that a long-standing hypoxaemia could reduce the aerobic function capacity. Ours results unfortunately were deeply influenced by the loss of a great part of elective patients during the pandemic, with the most part of data coming from patients needing hospitalization. This could explain why the delta shunt fraction is higher than expected.