Abstract: AIM: To investigate the acute hemodynamic responses to adenosine in patients with congenital heart disease (CHD) and severe pulmonary arterial hypertension (PAH). METHODS: Twenty-five patients with severe PAH secondary to left-to-right shunt CHDs underwent acute vasodilator test using IV adenosine infusion. Hemodynamic parameters were detected and analyzed. RESULTS: Only seven patients received the maximal dose 200 μg/(kg·min) of adenosine infusion without adverse effects. The tolerance dose of adenosine was (145±27) μg/(kg·min) in the other 18 patients. Both pulmonary artery pressure and systemic arterial pressure significantly decreased (P<0.05) after administration of adenosine, whereas the oxygen saturation of femoral artery blood, pulmonary vascular resistance, pulmonary-to-systemic flow ratio, mean pulmonary-to-aortic pressure and pulmonary-to-systemic vascular resistance ratio showed no significant changes. Mean pulmonary arterial pressure was >40 mmHg in all study patients. No significant difference was observed in the age and baseline hemodynamics between the patients with decreasing pulmonary vascular resistance and mean pulmonary-to-aortic pressure ratio >10% and the patients without these changes. CONCLUSION: Administration of adenosine induces synchronous decreases in pulmonary artery pressure and systemic arterial pressure but exerts no effect on pulmonary vascular resistance in patients with CHD and severe PAH.