Adenosine for vasoreactivity testing in pulmonary hypertension: a head-to-head comparison with inhaled nitric oxide.

Background: APVT is an invasive method recommended for symptomatic patients with PAH that permits the identification of the minority of patients (<20%) that may benefit from long-term calcium channel blockers. Adenosine has been indicated in guidelines as a vasodilator agent of choice for APVT, although it has not been directly compared with iNO, the gold standard for this test. The objective of the study was to compare adenosine with inhaled nitric oxide (iNO) for acute pulmonary vasoreactivity testing (APVT) in pulmonary arterial hypertension (PAH), in order to determine the efficacy and safety of the first in the clinical setting.

Methods: The measurements of cardiac output, pulmonary and systemic resistance were done in the basal state and with a stepwise increase of the dose of each drug until either maximum dosage (adenosine: 500 microg/kg/min or iNO: 80 ppm) or side effects observed or a positive response were reached, according to current guidelines. The order of drugs used in each test was consecutively alternated during the study.

Results: Six of the 39 studied patients (15%) presented a positive response to iNO; none to adenosine (p = 0.047, McNemar's test). Twenty-three patients (59%) did not reach the maximum dose of adenosine due to side effects, including bronchospasm, thoracic pain and bradycardia.

Conclusions: APVT testing with adenosine was not able to detect PAH patients responsive to iNo and provoked frequent adverse effects. Adenosine should not be used as a vasodilator drug in APVT.