Pulmonary Vascular Capacitance as a Predictor of Vasoreactivity in Idiopathic Pulmonary Arterial Hypertension Tested by Adenosine

BACKGROUND Acute pulmonary vasoreactivity testing has been recommended in the diagnostic work-up of patients with idiopathic pulmonary arterial hypertension (IPAH). Pulmonary arteriolar capacitance (Cp) approximated by stroke volume divided by pulmonary pulse pressure (SV/PP) is considered as an independent predictor of mortality in patients with IPAH. OBJECTIVES We sought to evaluate any differences in baseline and adenosine Cp between vasoreactive and non-vasoreactive IPAH patients tested with adenosine. PATIENTS AND METHODS Fourteen patients with IPAH and a vasoreactive adenosine vasoreactivity testing according to the ESC guidelines were compared with 24 IPAH patients with nonreactive adenosine test results. RESULTS There were no statistical significant differences between the two groups regarding NYHA class, body surface area, heart rate, and systemic blood pressure during right heart catheterization. Hemodynamic study showed no statistical significant differences in cardiac output/Index, mean pulmonary artery pressure, pulmonary vascular resistance, and baseline Cp between the two groups. There was a statistical significant but weak increase in adenosine Cp in vasoreactive group compared to non-reactive group (P = 0.04). Multivariable analysis showed an association between Cp and vasoreactivity (Beta = 2, P = 0.04, OR = 0.05 (95%CI = 0.003 - 0.9). CONCLUSIONS Cp could be considered as an index for the prediction of vasoreactivity in patients with IPAH. Prediction of long-term response to calcium channel blockers in patients with IPAH and a positive vasoreactive test by this index should be addressed in further studies.