Acute pulmonary vasoreactivity: a simple test revisited in the contemporary era - a narrative review

The acute vasodilator challenge during right heart catheterization (RHC) provides a deeper understanding of the pulmonary circulation by assessing vasoreactivity. The current criteria for a positive acute vasoreactivity test (AVT) are simplified to steady-state metrics, based on cutoff points derived from expert opinion. A positive AVT identifies a specific, but very rare, PH phenotype that may respond long-term to calcium-channel blockers. Growing evidence supports updating the role and criteria of AVT in pulmonary arterial hypertension, broadening its use to other PH groups, and potentially offering new insights for predicting risk and/or treatment outcomes. This study aims to revisit the uses, criteria, and goals of AVT in patients with PH beyond group 1 and to propose a new approach for phenotyping the pulmonary vascular response to the acute vasodilator challenge during diagnostic RHC. We propose a continuous multi-parameter criterion to evaluate the entire right ventricular afterload during AVT, such as the pulmonary vascular resistance-pulmonary arterial capacitance curve and alpha distensibility coefficient. AVT could assess the residual vasoreactive reserve of the pulmonary circulation as a provocative test for predicting risk outcomes and/or treatment responses.