Small vessels, big problem: a dive into the pulmonary microcirculation in pulmonary hypertension and methods for evaluation.

Pulmonary microvascular dysfunction is central to the pathophysiology of pulmonary hypertension (PH), yet remains challenging to evaluate in clinical practice. This review outlines current and emerging methodologies for assessing the pulmonary microcirculation, including advanced imaging, computational modelling, and invasive haemodynamic techniques. Exercise right heart catheterisation, waveform analysis, and vasoreactivity testing provide indirect insights into microvascular health, while novel invasive approaches, such as pulmonary flow reserve and pulmonary microvascular resistance indices, offer the potential for more precise functional characterisation. Computational models incorporating CT-derived anatomical data and patient-specific haemodynamics may enhance early detection and phenotyping of PH. Although many of these tools remain in the research domain, their refinement and integration into clinical workflows could enable earlier diagnosis, personalised risk stratification, and monitoring of therapeutic response. Ultimately, translating these innovations into practice may allow for targeted interventions that address microvascular dysfunction at an earlier stage of disease progression.