Partial pressure of oxygen is lower in the left upper pulmonary vein than in the right in adults with atrial septal defect

Kanji Iga MD, Chisato Izumi MD, Masahiko Matsumura* MD,

Shouji Kitaguchi MD, Yoshihiro Himura MD,

Hiromitsu Gen MD, Takashi Konishi MD

Abstract

Background. Right-to-left shunt at the atrial level is responsible for arterial hypoxemia in patients with atrial septal defect.

Objectives. This study investigated the mechanism of arterial hypoxemia in patients with atrial septal defect by measuring partial pressure of oxygen in both right and left upper pulmonary veins.

Subjects and Method. We prospectively measured partial pressure of oxygen in the femoral artery and right and left upper pulmonary veins during cardiac catheterization in 13 adults (mean age; 57.4-year-old) and 7 children (mean age; 7.6-year-old) with secundum atrial septal defect studied consecutively. Contrast echocardiography was performed to evaluate right-to-left shunt in all adults.

Results. Among children, there were no patients showing arterial hypoxemia and there was no difference of partial pressure of oxygen between the right and left upper pulmonary veins (right; 100±3.8 mmHg vs left; 100±7.8 mmHg: P=0.92). However, arterial hypoxemia was present in 11 patients of the 13 adults, although contrast echocardiography showed more than a moderate degree of right-to-left shunt in only 4 patients. Partial pressure of oxygen was lower in the left upper pulmonary vein than that of the right in all adult patients (right;91.6±13.8 mmHg vs left; 73.0±11.5 mmHg: P<0.0001).

Conclusion. Partial pressure of oxygen was low in the left upper pulmonary vein in comparison with that in the right in adults with atrial septal defect. Care must be taken in measuring pulmonary blood flow if partial pressure of oxygen in the left upper pulmonary vein is low enough to influence oxygen content. The decreased partial pressure of oxygen in the left upper pulmonary vein may contribute to arterial hypoxemia in adults with atrial septal defect in addition to right-to-left-shunt at the atrial level.