The co-occurrence of cyanotic congenital heart disease (CCHD) and PHEO/PGL has been reported, but the role of the hypoxic environment in the pathogenesis of PHEO/PGL remains unclear. Our aim was to compare plasma metanephrine and normetanephrine levels between patients with CCHD and patients with acyanotic congenital heart disease (ACCHD).We performed a cross-sectional study in a prospective cohort of 44 patients with congenital heart disease (CHD) (31 (70.5%) females) with a median age of 37.5 (31.0-55.6) years at the time of evaluation. Thirty-two (73%) patients had CCHD and 12 (27%) patients had ACCHD. Morning blood samples for plasma determination of metanephrine and normetanephrine were collected.Plasma normetanephrine levels were significantly higher in patients with CCHD compared to ACCHD (p = 0.002). Ten (31.3%) patients with CCHD had plasma normetanephrine levels elevated above the reference range, while all ACCHD patients had normal levels. Patients with lower oxygen saturation and higher proBNP had significantly higher normetanephrine levels (ρ = -0.444, p = 0.003 and ρ = 0.449, p = 0.002, respectively). No chromaffin cell tumors were detected.Increased plasma normetanephrine levels in patients with CCHD can be explained by the effect of hypoxia. Future research is needed to better understand the impact of chronic hypoxia in CCHD on increased sympathetic outflow, hyperplastic response of chromaffin tissue, and the role of somatic mutations in CCHD-PHEO/PGL pathogenesis related to hypoxia.
