Totally implantable vascular access for long term chemotherapy.

Cyanosis attributable to right to left shunt in the carcinoid syndrome SIR,-Dr G W Stewart and colleagues (1 March, p 589) described an interesting case of pronounced arterial hypoxaemia in a patient with the carcinoid syndrome.In the absence ofpulmonary metastases they attributed the hypoxaemia to intrapulmonary shunting through microscopic arteriovenous fistulas.The data presented, however, do not exclude an alternative explanation-right to left shunting through a patent foramen ovale.Although right to left shunting through the foramen ovale is well recognised in patients with pulmonary hypertension,'"3 it may also occur in the presence of normal pulmonary artery and right heart pressures, apparently as a result of reduced right atrial compliance.4Thus though mean left atrial pressure may exceed mean right atrial pressure, during atrial filling right atrial pressure rises disproportionately, causing phasic shunting across the interatrial septum.Right atrial compliance