Tetralogy of Fallot (TOF) is the most common cyanotic heart disease (CHD). The associated cardiac abnormalities disrupt oxygenation and depending on disease severity, infants with TOF syndrome are classified into two groups. Patients with normal oxygen saturation (SaO2 > 94%) are referred to as non-cyanotic TOF, whereas those with reduced oxygen saturation ( < 90%) are classified as cyanotic TOF. Despite low oxygen saturation, these patients often present with a relatively good clinical condition; however, significant postoperative complications may still occur. The optimal timing of surgical repair therefore remains controversial, with conflicting evidence regarding early versus delayed intervention.

The present study aims to evaluate the impact of preoperative hypoxemia on perioperative parameters in patients undergoing TOF repair and to explore whether the duration of hypoxemia is associated with postoperative complications and recovery.

This study was a single-center retrospective study conducted at Nantes University Hospital between January 2020 and December 2024 in children who had undergone corrective cardiac surgery for Tetralogy of Fallot. All presented data were extracted from the database of the pediatric intensive care and cardiac surgery unit.

A total of 176 patients were included, 70 in the normoxemic group (Median [range] SaO2, 97.0 [90.0–100.0]%) and 106 in the hypoxemic group (76.0 [54.0–88.0]%; P < 0.001), with an equal proportion of male and female. Patients in the hypoxemic group indeed exhibited elevated hemoglobin levels (Median [range] 17.9 [10.9–21.0] g/dl vs. 14.0 [13.9–24.5] g/dl) and increased hematocrit (Median [range] 56.8 [44.7–80.7]% vs. 41.8 [31.9–65.7]%), reflecting adaptive mechanisms to chronic hypoxemia. Hypoxemic patients are at increased risk of early postoperative complications ( e.g. , a prolonged duration of mechanical ventilation). However, paradoxically, prolonged hypoxemia appears to be associated with improved postoperative tolerance ( e.g. , no increased cardiac dysfunction and no increased bleeding) and even showed a more favorable postoperative course, in line with our clinical observations.

Prospective, multicenter, translational studies are needed to confirm these findings, refine management recommendations, and explore the protective mechanisms of prolonged hypoxemia at cellular and molecular levels.