Pulmonary arterial hypertension Pulmonary arterial hypertension with lack of acute response to NO challenge 2021-01-09T17:34:32Z A form of pulmonary arterial hypertension with lack of adequate hemodynamic response to NO challenge (adequate response is defined as a reduction of mean pulmonary artery pressure (mPAP) of at least 10 mmHg to reach an absolute value of mPAP 40 mmHg or less with an increased or unchanged cardiac output (CO) in response to inhaled nitric oxide at 10-20 ppm).