Relation between plasma nitrate and mean pulmonary arterial pressure in ventricular septal defect

Background-Nitric oxide (NO) is known to modulate myocardial contraction an d coronary tone, and its inhalation reduces pulmonary vascular resistance i n patients with pulmonary hypertension. Objectives-To evaluate the pathophysiological role of NO in patients with a ventricular septal defect (VSD). Patients-Twenty nine children with VSD, nine of whom had undergone VSD clos ure surgery, and 14 patients with Kawasaki disease. The mean age of the VSD patients was 3.1 years (range, 2 months to 9 years). Methods-Using high performance liquid chromatography, nitrate (a more stabl e NO oxidation product) was measured in plasma specimens of the patients un dergoing cardiac catheterisation. Results-Nitrate concentrations in the pulmonary artery bore a significant r elation to mean pulmonary artery pressure, pulmonary to systemic systolic p ressure ratio, and pulmonary to systemic flow ratio. Conclusions-The concentration of nitrate was in proportion to the increment in intravascular or cardiac pressure, indicating that endogenous NO is upr egulated as a compensatory homeostatic attempt to reduce pulmonary pressure and blood flow.