Onset of right-to-left shunting through a foramen ovale in a 70-year-old woman: successful surgical treatment.

A 70-year-old woman presented with disabling breathlessness. She was found to have severe arterial hypoxaemia due to isolated right-to-left shunting through a patent foramen ovale. In the absence of pulmonary hypertension or evidence of right ventricular dysfunction this is attributed to reduced right atrial compliance. The phasic nature of the shunt, which occurred only during atrial filling, supports this view. Surgical closure of the foramen abolished the hypoxaemia and her symptoms.