Favorable Effects of Oxygen Inhalation in Patients After Bidirectional Glenn Procedure as Assessed by Cardiovascular Magnetic Resonance Flow Measurement.

Background: Home oxygen therapy (HOT) is used to adapt patients to the bidirectional Glenn (BDG) physiology. However, the precise cardiovascular effect of oxygen inhalation is still unknown. We used phase-contrast MRI to evaluate the cardiovascular effects of oxygen inhalation in young patients with BDG physiology. Methods and Results: The 56 sessions of cardiac MRI were performed in 36 patients with BDG circulation. Oxygen saturation (Sp02) and heart rate (HR) were monitored under both room air and nasal 100% oxygen inhalation, and the blood flow volumes of the ascending aorta (AA), superior vena cava (SVC), and inferior vena cava (IVC) were measured by phase-contrast MRI. Systemic-to-pulmonary collateral flow (SPCF) volumes were calculated by subtracting the sum of flow volumes through the SVC and IVC from the flow volume through the AA, and used for further comparative examination. Under nasal oxygen inhalation, SpO(2) significantly increased from 82% to 89%, while HR decreased from 115 to 110 beats/min. AA (5.0 vs. 4.9 L.min(-1).m(-2)), SVC (1.85 vs. 1.77 L.min(-1).m(-2)), and systemic blood flow volume (=SVC+IVC) significantly decreased (3.60 vs. 3.46 L.min(-1).m(-2)). In contrast, SPCF and the pulmonary -to-systemic blood flow ratio (Qp/Qs) remained unchanged. Conclusions; Oxygen inhalation improved arterial blood oxygenation and lowered HR in patients with BDG circulation without an increase in Qp/Qs. HOT would be protective of the cardiovascular system in patients with BDG circulation.