We describe pitfalls of a hitherto undetected patent foremen ovale during t
he conduct of an off-bypass coronary revascularization. Manipulation of the
heart resulted in right-to-left shunt and severe desaturation requiring in
stitution of cardiopulmonary bypass to close the patent foramen ovale and c
omplete the revascularization (C) 1999 by The Society of Thoracic Surgeons.